Practical electronics construction : techniques, equipment and projects 9780750667364, 0750667362

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Practical electronics construction : techniques, equipment and projects
 9780750667364, 0750667362

Table of contents :
Introduction
Tools - The main tools needed
Components
Circuit Development - The design and manufacture of boards
Enclosures, fixings and Hardware
Projects

Citation preview

Preface

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Preface

Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Burlington, MA 01803, United States. First edition 2005 Copyright © Keith Brindley 2005. All rights reserved. The right of Keith Brindley to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holders except in accordance with the provisions of the Copyright, Design and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 4LP. Applications for the copyright holders’ written permission to reproduce any part of this publication should be addressed to the publishers.

British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 7506 67362 For information on all Newnes publications visit our website at www.newnespress.com

Typeset and produced by Co-publications, Loughborough

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Preface

*VU[LU[Z Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

1.

Practical electronics construction . . . . . . . . . . . . 1

2.

Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.

Printed circuit boards . . . . . . . . . . . . . . . . . . . . . 73

5.

Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

6.

Housings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139



-H\S[ÄUKPUN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

8.

Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Component suppliers. . . . . . . . . . . . . . . . . . . . . . . . . . 221 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

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Preface PU[VHÄUPZOLKLSLJ[YVUPJKL]PJL0UMHJ[T`PU[LU[PVUPU^YP[PUNP[PZUV[ VUS`[VTHRL[OLQV\YUL`MYVTJPYJ\P[[VKL]PJLHZLHZ`HZWVZZPISL[V [YH]LYZLI\[[VTHRLP[M\UH[[OLZHTL[PTL0OVWL0»]LZ\JJLLKLK Running to keep up… 0ULSLJ[YVUPJZHZ^P[OTVZ[MHZ[TV]PUN[LJOUVSVNPLZ[OLYL»ZHS^H`Z[OL YPZR[OH[HIVVRZ\JOHZ[OPZVULJHUILJVTLV\[VMKH[L]LY`X\PJRS` ;OL^H`LSLJ[YVUPJZTV]LZ[OLZLKH`ZP[»ZUV[\UMHPY[VZH`[OH[HIVVR SPRL[OPZPZVUS`\W[VKH[LMVYHZSVUNHZ[OLPURPZ^L[:VH[[OPZWVPU[ 0»KSPRL[VPU[YVK\JLYLHKLYZ[VHJLU[YHS^LIZP[L! http://keithbrindley.members.beeb.net

^OLYL0^PSS[Y`[VRLLWYLSL]HU[PUMVYTH[PVUHIV\[[OLTL[OVKZHUK WYVJLZZLZJV]LYLKOLYL\W[VKH[L;OL^LIZP[LHSZVMLH[\YLZYLSL]HU[ SPURZ[VTHU\MHJ[\YLYZJVTWVULU[Z[VJRPZ[ZHUKV[OLYSPURZHZ0ZLLÄ[ 7YVQLJ[ZPU*OHW[LYHSSMLH[\YLWYPU[LKJPYJ\P[IVHYKJVWWLYMVPS[YHJR WH[[LYUZHUK[OLYLHYLSPURZVU[OL^LIZP[L[VHSSV^`V\[VKV^USVHK [OLZLPULSLJ[YVUPJMVYTH[Z[VV0UKLLK0»KNVHZMHYHZZ\NNLZ[PUN[OH[PM `V\PU[LUKJVUZ[Y\J[PUNHU`VM[OLWYVQLJ[ZOLYL`V\ZOV\SKSVVRVU[OL ^LIZP[L[VZLLPM[OLYLHYLHU`HS[LYH[PVUZVYV[OLYZ\NNLZ[PVUZYLNHYKPUN [OLWYVQLJ[ZILMVYL`V\Z[HY[(U`JVYYLJ[PVUZVYHS[LYH[PVUZ[V[OLJVWWLY MVPS[YHJRWH[[LYUZVYHU`[OPUNLSZL[VKV^P[O[OLWYVQLJ[Z^PSSIL MLH[\YLKVU[OL^LIZP[LHZZVVUHZ0JHUNL[[OLT[OLYL As you make it… ,SLJ[YVUPJZPUNLULYHSPZHMHZJPUH[PUNHYLH/V^L]LYNL[[PUNºPU[VP[»PU [OLÄYZ[WSHJLPZZVTL[PTLZKH\U[PUN0[PZT`HPT[OH[:[HY[PUN,SLJ[YVUPJZ *VUZ[Y\J[PVUNP]LZHZTHU`WLVWSLHZWVZZPISL[OLTLHUZ^OLYLI`[OL` JHUKVQ\Z[[OH[0U[OLTLHU^OPSLPM0JHUVMMLYHU`VULHZ\NNLZ[PVUPM [OL`PU[LUK[V[Y`P[PZ[OPZ!THRLP[M\U ;OH[^H``V\»SSSLHYUZVT\JOTVYL[OHU`V\L]LYJV\SKMYVTZ[\MM` [L_[IVVRZ0OVWL[OH[I`YLHKPUN[OPZIVVRHUKNL[[PUNPU[VWYHJ[PJHS LSLJ[YVUPJZJVUZ[Y\J[PVU[OH[`V\KVOH]LM\U

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Introduction

1 Introduction

;OPZIVVRPZHN\PKL[VHU`VUL^OV^HU[Z[VI\PSKHULSLJ[YVUPJKL]PJL 0[HZZ\TLZ]LY`SP[[SLWYPVYRUV^SLKNLHUKZVPU[YVK\JLZ`V\[V[OL ]HYPV\ZWYHJ[PJLZ[OH[`V\ULLK[VMVSSV^·^OL[OLY`V\^HU[[VI\PSK ZVTL[OPUNMVYWSLHZ\YLVYMVYLK\JH[PVUVYL]LUMVYWYVÄ[(SZV[OPZ IVVR[HRLZ[OLZ[HUJL[OH[P[TH[[LYZSP[[SL^OH[[OLWHY[PJ\SHYLSLJ[YVUPJ WYVK\J[PZ`V\^PZO[VI\PSK·[OLTVZ[PTWVY[HU[MHJ[PZ[OH[[OL WYHJ[PJLZ`V\MVSSV^HYLZPTPSHYPMUV[PKLU[PJHS^OH[L]LY[OLLSLJ[YVUPJ KL]PJLOHWWLUZ[VIL ,SLJ[YVUPJZPZPUWHY[H[OLVYL[PJHSLU[P[`HUK`V\JV\SKNV[V[L_[IVVRZ VY[VTHNHaPULZZJOVVSZJVSSLNLZVY\UP]LYZP[PLZVYLSZL^OLYL[VÄUK HUKSLHYU[OH[[OLVY`/V^L]LYP[PZHSZVPUH]LY`SHYNLWHY[HWYHJ[PJHS LU[P[`"HMHJ[[OH[·WHY[PJ\SHYS`PUYLJLU[`LHYZ·ZLLTZHSTVZ[[VOH]L ILLUV]LYSVVRLK;OLTHU`Z[\KLU[ZVMLSLJ[YVUPJZH[\UP]LYZP[PLZ^OV OH]LSP[[SLVYUVWYPVYL_WLYPLUJL^P[O[OLOHUKSPUNVMJVTWVULU[ZVY[OL I\PSKPUNVMJPYJ\P[ZH[[LZ[[V[OPZ :VHS[OV\NO^OH[`V\YLHKVU[OLWHNLZVM[OPZIVVRPZ[OLVY`P[PZ [OLVY`HIV\[[OLWYHJ[PJHSHZWLJ[ZVMI\PSKPUNLSLJ[YVUPJKL]PJLZ(Z Z\JOPUJS\KLKPU[OPZIVVRHYLOVWLM\SS`TVZ[VMWVZZPIS`HSS[OL WYHJ[PJHS[OPUNZ`V\ULLK[VRUV^HIV\[HUKILHISL[VKVILMVYL`V\ JHUTHRLHULSLJ[YVUPJKL]PJL 1

Starting Electronics Construction >OH[[OPZIVVRPZnotVU[OLV[OLYOHUKPZHIVVRHIV\[OV^ LSLJ[YVUPJZJPYJ\P[ZworkMVY[OH[ZLL[OPZIVVR»ZZPZ[LYIVVR!:[HY[PUN Electronics^OPJOPZ^YP[[LUHSZVI`TL>OH[`V\OH]LPUMYVU[VM`V\ UV^PZHIVVRVUS`HIV\[OV^[VconstructLSLJ[YVUPJKL]PJLZ0OVWL `V\LUQV`P[HUKNHPUZVTLRUV^SLKNLHIV\[OV^[VKVQ\Z[[OH[

What do you need to know about making an electronic device? ;OPZZLJ[PVUPZPU[LUKLKHZHZ\TTHY`VM[OL^OVSLIVVR0[^V\SKIL LHZ`[VTPZZ[OPZV\[HS[VNL[OLYI\[T`MLLSPUNPU^YP[PUNP[PZ[OH[`V\ ULLK[VZLL[OLIPNWPJ[\YLILMVYL`V\NVVU[VSVVRH[[OPUNZPUTVYL KL[HPS (UK[OLIPNWPJ[\YLPU[LYTZVMI\PSKPUNLSLJ[YVUPJZKL]PJLZPZZPTWS`H X\PJRV]LY]PL^VM^OH[HULSLJ[YVUPJKL]PJLPZHUKHSZV^OH[WHY[ZVMP[ ZOV\SK^L\UKLYZ[HUKPUVYKLY[OH[^LJHUI\PSKP[

So, what is an electronic device? >LJHUZ\TTHYPaLHULSLJ[YVUPJKL]PJLHUL_HTWSLVM^OPJOPZNP]LU PU-PN\YLHZILSV^

An electronic device invariably has three main features:

NUMBER 1 Electronic components. An electronic device is anything that incorporates electronic components of any description.

NUMBER 2 A printed circuit board. The electronic components which make up an electronic device are mounted upon a printed circuit board — (often called just a PCB), which is a means of holding all the components securely while at the same time making the necessary electrical connections between them all.

NUMBER 3 A housing. The printed circuit board, together with all the electronic components that it holds, will be housed in a box, or a module, or a case. In this way the electronic components are protected from damage.

So, what’s next? .P]LU[OH[HU`LSLJ[YVUPJKL]PJL`V\TPNO[JOVVZL[VI\PSKOHZ[OLZL [OYLLTHPUMLH[\YLZP[MVSSV^Z[OH[`V\ULLK[VRUV^HZT\JOHZ`V\JHU 2

Introduction

FIGURE 1.1 An example of an electronic device — note the electronic components, the printed circuit board, and the housing HIV\[[OLMLH[\YLZ(UK^L»SSSVVRH[[OLTUV^PUIYPLMILMVYLKL]V[PUN [OLYLZ[VM[OLIVVR[V[OH[W\YWVZL

Electronic components ;OLYLHYLTHU`JH[LNVYPLZVMLSLJ[YVUPJJVTWVULU[ZHUKLHJOJH[LNVY` PZKP]PKLKVM[LUPU[VZL]LYHSZ\IJH[LNVYPLZHUKMYVT[OLYLPU[VH T\S[P[\KLVMZ\IZ\IJH[LNVYPLZ@V\KVU»[ULLK[VRUV^HIV\[[OLT allI`HU`TLHUZI\[`V\KVULLK[VRUV^HIV\[[OLTVZ[JVTTVU JH[LNVYPLZHUK[OLPYTVZ[JVTTVUZ\IJH[LNVYPLZ@V\ULLK[VRUV^ OV^[VOHUKSL[OLZLJVTWVULU[ZZV[OH[`V\KVU»[KHTHNL[OLTHUKZV `V\ULLK[VRUV^^OH[KHTHNLcanILKVUL[V[OLT :VTLJVTWVULU[ZHYLLHZPS`KHTHNLKQ\Z[I`OVSKPUN[OLTHSP[[SL[VV YV\NOS`"ZVTLJVTWVULU[ZHYLKHTHNLKI`OLH["HUKJLY[HPUS`THU` JVTWVULU[ZHYLKHTHNLKPM`V\PUZLY[[OLTPU[VHJPYJ\P[PUJVYYLJ[S` [OL^YVUN^H`YV\UKZH`VY[VVMVYJLM\SS`[OLYLI`IYLHRPUN[OLPY JVUULJ[PVUWPUZ @V\HSZVULLK[VRUV^HIV\[^OPJO[VVSZ`V\ULLK[VOHUKSL[OLTHUK OV^[V\ZL[OLZL[VVSZJVYYLJ[S`

Printed circuit boards 4HRPUN[OLWYPU[LKJPYJ\P[IVHYKVU[V^OPJO[OLLSLJ[YVUPJJVTWVULU[Z VMHKL]PJLHYLTV\U[LKPZUV[H[YP]PHSQVI0UKLLK[OL^VYRPU]VS]LKPU KLZPNUPUNP[THRPUNP[[OLUH[[HJOPUN[OLJVTWVULU[Z[VP[YLWYLZLU[ZH THQVYWYVWVY[PVUVM[OLV]LYHSS[HZR/V^L]LYTHRPUNHWYPU[LKJPYJ\P[ IVHYKPZUV[HQVI^OPJOZOV\SKILY\ZOLKMVYHWVVYS`THKLWYPU[LK JPYJ\P[IVHYKPZHYLJPWLMVYKPZHZ[LY 3

Starting Electronics Construction ;OLWYPU[LKJPYJ\P[IVHYKPZ\ZLKMVY[^VTHPUW\YWVZLZ![VZ\WWVY[ [OLLSLJ[YVUPJZJVTWVULU["HUK[VJVUULJ[IL[^LLU[OLLSLJ[YVUPJ JVTWVULU[ZZV[OH[[OLJPYJ\P[[OL`HYL[VILJVUULJ[LKPU[VJHUIL MVYTLK(ZHYLZ\S[HWYPU[LKJPYJ\P[IVHYK[OH[JHUUV[Z\WWVY[[OL JVTWVULU[ZHKLX\H[LS`VYTHRLZPUJVYYLJ[JVUULJ[PVUZ^PSSWYL]LU[ [OLLSLJ[YVUPJKL]PJLMYVTM\UJ[PVUPUNJVYYLJ[S`:V`V\ULLK[VRUV^ HIV\[HSSHZWLJ[ZVMWYPU[LKJPYJ\P[IVHYKZ!OV^[VKLZPNU[OLT"OV^[V THRL[OLT"HUKOV^[VTV\U[[OLJVTWVULU[Z@V\ULLK[VRUV^^OH[ [VVSZ[V\ZL[VKV[OLZL[HZRZHUKOV^[V\ZL[OL[VVSZJVYYLJ[S` 0ZPTWS`JHUUV[Z[YLZZLUV\NOOV^PTWVY[HU[[OLWYPU[LKJPYJ\P[IVHYKPZ 0M[OLJPYJ\P[P[ZLSMPZ[OLIYHPUVMHULSLJ[YVUPJKL]PJL·[OH[TVUP[VYZ JVU[YVSZHUKZLUKZ[OLZPNUHSZ[OH[THRL[OLKL]PJL^VYR·[OLU[OL WYPU[LKJPYJ\P[IVHYKPZ[OLOLHY[[OH[RLLWZ[OL^OVSLKL]PJLNVPUNPU [OLÄYZ[WSHJL

Housings 6UJL[OLWYPU[LKJPYJ\P[IVHYKPZJVTWSL[L^P[OHSSLSLJ[YVUPJ JVTWVULU[ZPUWSHJL`V\OH]L[VJVUZPKLYOV^[VOV\ZLP[/V\ZPUNZ HYL\ZLK[VWYV[LJ[[OLJVTWVULU[ZPUZPKLHZ^LSSHZ[OLPYWYPU[LKJPYJ\P[ IVHYK/V\ZPUNZHSZV\Z\HSS`NP]LHSP[[SLL_[YHZWHJL[VHSSV^IH[[LYPLZ [VILOLSK^OLUULLKLKHZ^LSSHZWYV]PKPUNTV\U[PUNZWHJLMVYZVTL JVTWVULU[ZHUKJVU[YVSZUV[TV\U[LKVU[OLIVHYK;OL`HSZVWYV[LJ[ \ZLYZMYVTWV[LU[PHSS`OHYTM\S]VS[HNLZ[OH[TH`ILWYLZLU[PU[OLJPYJ\P[ ·THPUZ]VS[HNLZZH`3HILSSPUNVUHOV\ZPUN»ZMHJPUNWHULSZJHU PUKPJH[L^OH[]HYPV\ZJVU[YVSHKQ\Z[TLU[ZTH`ILTHKLI`[OL\ZLY(Z Z\JOHOV\ZPUNPZ[OLPU[LYMHJL·[LJOUPJHSS`]PZ\HSS`HUKHLZ[OL[PJHSS` ·^P[O[OLV\[ZPKL^VYSK 0UZOVY[PM[OLJPYJ\P[PZ[OLIYHPUHUK[OLWYPU[LKJPYJ\P[IVHYKPZ[OL OLHY[[OLU[OLOV\ZPUNPZ[OLIVK`[OLZRLSL[VUHUK[OLZRPUVMHU LSLJ[YVUPJKL]PJL /V\ZPUNZKVULYPNO[JHUTHRLHWYVK\J[H^PUULY"KVUL^YVUN[OL WYVK\J[PZHK\MMLY

What have we learned? ;VZ\TTHYPaL[OPZJOHW[LY^LVUS`ULLK[VYLTLTILYVUL[OPUN·HU LSLJ[YVUPJKL]PJLJVTWYPZLZ[OYLLTHPUWHY[Z;OLZLTHPUWHY[Z·[OL LSLJ[YVUPJJVTWVULU[Z[OLWYPU[LKJPYJ\P[IVHYKHUK[OLOV\ZPUN ·HYLOPNOS`KLWLUKLU[VULHJOV[OLY+LZPNULYZHUKTHRLYZVMgood LSLJ[YVUPJKL]PJLZ\UKLYZ[HUK[OPZKLWLUKLUJLHUK\ZL[OLTHPUWHY[Z [V[OLILZ[HK]HU[HNLVM[OLPYKL]PJLZ

4

Tools

2 Tools (Z^P[OHU`WYHJ[PJHS[LJOUVSVN`OH]PUN[OLYPNO[[VVSZMVY[OL[HZRPZ PTWVY[HU[0UKLLKZVTLVM[OL[VVSZHYLUV[Q\Z[PTWVY[HU[·[OL`HYL JYP[PJHS@V\ZPTWS`JHUUV[KVLSLJ[YVUPJZJVUZ[Y\J[PVU^P[OV\[[OLT:V ÄYZ[VMMPU[OPZJOHW[LYPZHOP[WHYHKLVM[OL[VVSZ`V\ULLKMVSSV^LKI` HUV[OLYVM[OL[VVSZ`V\ZOV\SKZLYPV\ZS`JVUZPKLYHS[OV\NO`V\could KV^P[OV\[[OLTH[HW\ZO

Tools you absolutely, positively, indisputably, and without a doubt need:

SOLDERING IRON — to solder components into place. The connecting lead of each component must be soldered into place on the printed circuit board. A specialized soldering iron must be used — one that is neither too big nor too powerful to harm either the component or the circuit board

MINIATURE SIDE-CUTTERS — to cut wire or component leads. While constructing an electronic device, there will be many wires to cut to size. Each component mounted on the printed circuit board needs its leads trimming close to the board after soldering

MINIATURE LONG-NOSED PLIERS — to form leads. Component leads are formed to the correct shape for mounting on a printed circuit board with small, long-nosed pliers. Larger components and many controls are attached with nuts and bolts, so a larger pair of long-nosed pliers is also needed

CONTINUED…

5

Starting Electronics Construction

…CONTINUED WIRE-STRIPPERS — to strip insulation from wires. Insulation must be removed from wires prior to soldering, and gripping the wire in your teeth before pulling the insulation off isn’t the best method. A good pair of wirestrippers solves the problem and keeps your dental bills as low as possible

SOLDER REMOVAL TOOLS — to err… remove solder. At some point or other, you will need to remove solder from a soldered joint, usually to take out a component you have accidentally put in the wrong place, or to replace a faulty component. Some type of solder-removal tool is required, allowing you to extract the component’s leads

DRILLS AND BITS — to err… drill holes. Every component lead goes through a hole in the printed circuit board. Each hole must be drilled. Components not mounted on the printed circuit board are usually mounted on the housing, usually with nuts and bolts, and holes for these must be drilled in the housing

SAFETY GOGGLES — to protect your eyes. Some of the processes involved in electronics construction may create potential hazards. You need to protect yourself! Goggles should be used when undertaking any process SPRLS`[VJYLH[LÅ`PUNKLIYPZZ\JOHZKYPSSPUNVY\ZPUNJOLTPJHSZ

Tools you don’t exactly need — but which make some jobs easier:

PLIERS — ordinary hand pliers FILES — HZTHSSZL[VMULLKSLÄSLZHUKHZLSLJ[PVUVMSHYNLYÄSLZ PUNCHES — for making some larger holes in housings VICE — to hold housings while working A STAND — to hold printed circuit boards.

6

Tools

The Tools >L»SSUV^[HRLHJSVZLYSVVRH[[OLTVZ[PTWVY[HU[VM[OVZL[VVSZSPZ[LK HUKUV[LHU`WHY[PJ\SHYH[[YPI\[LZ[OL`ZOV\SKOH]L

Soldering irons :VSKLYPUNPULSLJ[YVUPJZKVLZUV[OH]LHU`WHY[PJ\SHYYLX\PYLTLU[ZV[OLY [OHU[OLZVSKLYPUNPYVUZOV\SKUV[IL[VVWV^LYM\S6U[OLMHJLVMP[ [OPZTPNO[ZV\UKVKK[VHUL^JVTLYNP]LU[OH[[OLWYVJLZZVMZVSKLYPUN YLX\PYLZZVSKLY[VILTLS[LK[O\ZMVYTPUNHZVSKLYLKQVPU[I\[P[»ZX\P[L SVNPJHS^OLU`V\JVUZPKLYL_HJ[S`what`V\HYLZVSKLYPUN·LSLJ[YVUPJ JVTWVULU[Z;OLWYVISLTPZ[OH[LSLJ[YVUPJJVTWVULU[ZJHUIL KHTHNLKI`[VVT\JOOLH[·HUK[OLTVYLWV^LYM\S[OLZVSKLYPUNPYVU [OLNYLH[LYP[ZJHWHJP[`[VKLSP]LYOLH[ :VSKLYPUNPYVUWV^LYPZTLHZ\YLKPU^H[[ZHUKHYLHZVUHISL^H[[HNL MVYZVSKLYPUNLSLJ[YVUPJJVTWVULU[ZPZZVTL^OLYLIL[^LLUHUK ^H[[Z7YPJLZ]HY`IL[^LLUTVKLSZI\[`V\ZOV\SKL_WLJ[[VWH` IL[^LLUHIV\[‰HUK‰MVYHIHZPJZVSKLYPUNPYVUHS[OV\NOTVYL L_WLUZP]LZVSKLYPUNPYVUZ^P[OL_[YHMLH[\YLZL_PZ[ ([`WPJHSZVSKLYPUNPYVUPZZOV^UPU-PN\YL^OLYL`V\JHUZLLP[Z THPUWHY[Z·HOHUKSL[VOVSKP[HIP[[OLWHY[[OH[OLH[Z[OLQVPU[HUK [OLZVSKLYHUKHOLH[PUNLSLTLU[[OLWHY[[OH[OLH[Z[OLIP[(SZV ZOV^UPU-PN\YLPZHTHPUZSLHKHS[OV\NOUV[HSSZVSKLYPUNPYVUZ YLX\PYLTHPUZLSLJ[YPJP[`[VM\UJ[PVUHZ^L»SSZLLZVVU

FIGURE 2.1 A typical soldering iron — the main parts of which are (from left to right): the bit; the heating element; the handle. This particular soldering iron is mains-powered, so you can also see the mains lead exiting the handle at the right. 7

Starting Electronics Construction Soldering iron types ;OLYLHYLZL]LYHS]HYPHU[ZVMZVSKLYPUNPYVUZPU[LYTZVMOLH[PUNTL[OVKZ SPZ[LKILSV^ Mains-powered irons·[OLTVZ[JVTTVU;OLHK]HU[HNLVM[OLZLPZ[OH[

[OL`^VYR^OLYL]LYHTHPUV\[SL[PZH]HPSHISL;OLKPZHK]HU[HNLPZ [OH[[OL`KVOH]LHTHPUZSLHK^OPJOZVTLWLVWSLÄUKHSP[[SLÄKKS` PU\ZL)HZPJZVSKLYPUNPYVUZVM[OPZ[`WLOH]LUV[LTWLYH[\YLJVU[YVS HUKTLYLS`NL[HZOV[HZ[OL`JHU:VSKLYPUNPYVUZ^P[O[OLYTVZ[H[PJ JVU[YVSZHYLH]HPSHISLHUKL]LUJVTWSL[LZVSKLYPUNPYVUIHZLZ[H[PVU JVTIPUH[PVUZHYLJVTTVUZLLSH[LY@V\YI\KNL[KLÄULZ^OH[`V\I\` Rechargeable irons·^P[OIHZLZ[H[PVU9LJOHYNLHISLPYVUZOH]LPU[LYUHS

IH[[LYPLZ[OH[HYL\ZLK[VOLH[[OLLSLTLU[HUKIP[;OL`OH]LHIHZL Z[H[PVU[OH[PZTHPUZWV^LYLKPU[V^OPJO[OLZVSKLYPUNPYVUÄ[Z^OLUUV[ PU\ZL*VUULJ[PVUZPU[OLIHZLZ[H[PVUHUKZVSKLYPUNPYVUTH[LHUKZV [OLIH[[LYPLZHYLYLJOHYNLK^OLUL]LY[OLPYVUPZPU[OLIHZLZ[H[PVUHUK [OLIHZLZ[H[PVUPZWV^LYLKVMJV\YZL ;OLTHPUHK]HU[HNLVMYLJOHYNLHISLZVSKLYPUNPYVUZPZ[OLPYSHJRVMTHPUZ SLHKPU\ZL;OLTHPUKPZHK]HU[HNLPZ[OH[[OLIH[[LYPLZJHU»[WV^LY[OL LSLTLU[MVYSVUNLY[OHUQ\Z[HML^TPU\[LZH[H[PTL)`YLWSHJPUN[OL ZVSKLYPUNPYVUPU[V[OLIHZLZ[H[PVUHM[LYLHJOQVPU[PZZVSKLYLK[OV\NO ZV[OH[P[ZIH[[LYPLZYLJOHYNLWHY[PHSS`[OPZJHUILL_[LUKLKZVTL^OH[ -PN\YLZOV^ZHYLJOHYNLHISLZVSKLYPUNPYVU^P[OP[ZIHZLZ[H[PVU

FIGURE 2.2 Rechargeable soldering iron in use. To conserve batteries, the element only heats up when the button on the handle is pressed — heating rapidly to soldering temperature within seconds. In the background is the base station which recharges the soldering iron’s batteries. 8

Tools Gas-powered irons·[OL\S[PTH[LPUWVY[HIPSP[`-P[[LK^P[OZTHSSYLÄSSHISL

JOHYNLZVMI\[HULNHZ^OPJOSHZ[\W[VHYV\UKTPU\[LZVMJVUZ[HU[ \ZL[OLZLZVSKLYPUNPYVUZYLX\PYLUVLSLJ[YPJHSWV^LY-PN\YLZOV^ZH NHZZVSKLYPUNPYVUPU\ZL 7YPJLKIL[^LLUHYV\UK‰[V‰VYZV[OLZLZVSKLYPUNPYVUZHYL \ZLM\SMVYJLY[HPUH^R^HYKZVSKLYPUNQVIZ^OLYLLSLJ[YPJHSWV^LYPZ UV[H]HPSHISL;OL`[LUK[VILX\P[LWV^LYM\SWHY[PJ\SHYS`[OLTVYL L_WLUZP]LTVKLSZ[OV\NO^P[OJHYLJHUIL\ZLK[VNVVKLMMLJ[PU LSLJ[YVUPJZZVSKLYPUN

FIGURE 2.3 A gas-powered soldering iron. Small and portable, these can be recharged from lighter fuel butane gas containers. Low-voltage irons·MVYIH[[LY`WV^LYLKHWWSPJH[PVUZ6JJHZPVUHSS`

^OLU^VYRPUNVUHJHYZH`[OLYLHYLHWWSPJH[PVUZ^OLYLHSV^]VS[HNL ZVSKLYPUNPYVUTPNO[IL\ZLM\S:VTL=WV^LYLKZVSKLYPUNPYVUZHYL H]HPSHISLHUL_HTWSLPZZOV^UPU-PN\YL\Z\HSS`OH]PUNIH[[LY` JSPWZH[[HJOLK[V[OLWV^LYSLHK Soldering iron stations

>OPSL^L»YLVU[OLZ\IQLJ[VMZVSKLYPUNPYVU[`WLZP[»Z^VY[O[HRPUNH SVVRH[ZVSKLYPUNPYVUZ[H[PVUZ;OLZLHYLJVTWSL[L\UP[ZJVTWYPZPUN HZVSKLYPUNPYVUHZ[HUK[VOVSK[OLPYVU^OLUUV[PU\ZLHUKH JVU[YVSSPUNJPYJ\P[VMZVTLKLZJYPW[PVU([`WPJHSZVSKLYPUNPYVUZ[H[PVUPZ ZOV^UPU-PN\YL;OLJVU[YVSSPUNJPYJ\P[[`WPJHSS`JVU[YVSZ[OLWV^LY [V[OLZVSKLYPUNPYVULSLTLU[ZV[OH[[OLIP[Z[H`ZH[HJVUZ[HU[KLÄUHISL [LTWLYH[\YL>OPSLZ\JOZ[H[PVUZHYLL_WLUZP]LYHUNPUNMYVTHYV\UK ‰[VV]LY‰[OL`HYLL_JLSSLU[[VVSZPM`V\KVHJVUZPKLYHISL HTV\U[VMZVSKLYPUN 9

Starting Electronics Construction

FIGURE 2.4 A 12 V-powered soldering iron. The battery clips on the lead attach to a car’s battery for (relatively) portable power.

FIGURE 2.5 A soldering iron station, showing the iron itself in a stand, and the control knob to set bit temperature (Antex Electronics). Soldering iron bits (SVUNZPKL[OLPYVUP[ZLSM`V\ULLK[V[OPURHIV\[[OLIP[;OLIP[PZ[OL WHY[VM[OLPYVU[OH[JVTLZPU[VJVU[HJ[^P[O[OLWHY[Z[VILQVPULKZVPZ HMHPYS`JYP[PJHSWHY[VM[OLWYVJLZZ ([`WPJHSYHUNLVMIP[ZOHWLZPZZOV^UPU-PN\YLOPSL^L»YLVU[OLZ\IQLJ[VMJSLHUSPULZZ^OPJO^L»SSYL[\YU[VVM[LU [OYV\NOV\[[OLIVVR[OLV[OLYJVTWVULU[Z[OH[NV[VTHRL\WH ZVSKLYLKQVPU[OH]L[VILJSLHU·Q\Z[HZT\JOHZ[OLZVSKLYPUNPYVUIP[ [PW-VY[\UH[LS`[OLYLHYLWYVK\J[Z[OH[JHUOLSWOLYL[VV;OLJVWWLY Z\YMHJLZVM[OL[YHJRVUHWYPU[LKJPYJ\P[IVHYKZOV\SKILJSLHUHUKHZ [OL`V_PKPaL^OLUSLM[MVYTVYL[OHUQ\Z[HML^OV\YZHUKJVWWLYV_PKL JHUWYL]LU[HNVVKQVPU[MYVTILPUNTHKL[OL`ZOV\SKILJSLHULK TVYLVYSLZZPTTLKPH[LS`WYPVY[VZVSKLYPUN[OLQVPU[Z (NVVK[VVSMVY[OPZQVIPZHÄIYLNSHZZHIYHZP]LWLUJPS0[»ZHWYVWLSSPUN WLUJPS[`WLVMKLZPNU^P[OHUPU[LYUHSÄIYLNSHZZZ[PJRPUZ[LHKVMWLUJPS SLHK·ZLL-PN\YL0U\ZL`V\Y\I[OLLUKVM[OLÄIYLNSHZZZ[PJRVU [OLJVWWLY[YHJRHML^[PTLZYLTV]PUNHU`KPY[NYLHZLVYWYLÄUPZOLZ SLH]PUNJSLHUZOPU`JVWWLYYLHK`MVYZVSKLYPUN 14

Tools

FIGURE 2.11 An abrasive fibreglass pencil in use — note the residue, which is of fibreglass origins. (M[LYJSLHUPUN[OLJVWWLYZ\YMHJLJHYLZOV\SKIL[HRLU^OLUYLTV]PUN [OLYLZPK\HSK\Z[JYLH[LKPU[OLWYVJLZZ·P[isÄIYLNSHZZIHZLKHM[LYHSS ZVTH`PYYP[H[LZRPUL`LZVYPU[LYUHSVYNHUZ Abrasive scrubbing block

(UHS[LYUH[P]L[V[OLÄIYLNSHZZWLUJPSPZHUHIYHZP]LZJY\IIPUNISVJR ^OPJOWLYMVYTZ[OLZHTLM\UJ[PVU·ZJY\I[OLJVWWLY[YHJRWYPVY[V ZVSKLYPUN^P[O[OLISVJRPUHUHJ[PVUYLTPUPZJLU[VM\ZPUNHULYHZLY[V Y\IV\[WLUJPSTHYRZ-PN\YLZOV^ZZ\JOHZJY\IIPUNISVJR

FIGURE 2.12 An abrasive scrubbing block. 15

Starting Electronics Construction *VTWVULU[SLHKZ·^OPJOMVYTH[OPYKJYP[PJHSWHY[VMHZVSKLYLK QVPU[VUHWYPU[LKJPYJ\P[IVHYKULLK[VILJSLHUL]LY`IP[HZT\JOHZ [OLJVWWLY[YHJRHUK[OLZVSKLYPUNPYVUIP[»Z[PW4VZ[JVTWVULU[ZHYL Z\WWSPLK^P[O[PUULKSLHKZPL[OL`HYLJVH[LK^P[OTVS[LUZVSKLY[OLU JVVSLKMVY[\UH[LS`^OPJOTLHUZ[OH[HZPTWSLYLOLH[PUN[VZVSKLYPUN [LTWLYH[\YLYLTLS[Z[OLZVSKLY^OPJOOLSWZ[OLWYVJLZZVMZVSKLYPUN[OL QVPU[,]LUZVL_JLZZKPY[·WHY[PJ\SHYS`NYLHZL·VUHSLHKTH`Z[PSS WYL]LU[HNVVKQVPU[ILPUNTHKLZVPM`V\Z\ZWLJ[[OH[[VIL[OLJHZL `V\ZOV\SKJSLHU[OLSLHKWYPVY[VZVSKLYPUN0[»ZT\JOLHZPLY[VKV[OPZ ILMVYLZVSKLYPUN[OHU[Y`PUN[VJVYYLJ[[OLLMMLJ[ZVMP[HM[LY^HYKZ Chemical solvent cleaners

*OLTPJHSJSLHULYZZ\JOHZPZVWYVW`SHSJVOVSTH`IL\ZLM\SMVYJSLHUPUN WYPU[LKJPYJ\P[IVHYK[YHJRZVYJVTWVULU[SLHKZWYPVY[VZVSKLYPUN HZ[OL`KPZZVS]LNYLHZLKPY[HUKZVTLWYLÄUPZOLZ^OPJOTH`IL WYLZLU[;OL`JHUILW\YJOHZLKPUSPX\PKMVYTHS[OV\NOHLYVZVSVYWLU HWWSPJH[VYZHYLVM[LUT\JOTVYLJVU]LUPLU[ Heat shunt

;OLÄUHSZVSKLYPUNHJJLZZVY``V\TPNO[^HU[[VJVUZPKLYPU`V\Y HYTV\Y`PZHOLH[ZO\U[:VSKLYPUN·I`P[Z]LY`UH[\YL·YLX\PYLZOLH[ I\[[VVT\JOOLH[JHUKHTHNLZVTLLSLJ[YVUPJJVTWVULU[Z:VTL WLVWSL[OLYLMVYLSPRL[V\ZLHOLH[ZO\U[IL[^LLU[OLZVSKLYLKQVPU[HUK [OLJVTWVULU[IVK`[VOLSWLUZ\YL[OLOLH[H[[OLQVPU[PZZO\U[LKH^H` MYVT[OLJVTWVULU[P[ZLSM ;OLZPTWSLZ[MVYTVMOLH[ZO\U[PZHWHPYVMSVJRPUN[^LLaLYZ^OPJOHYL JSHTWLKVU[V[OLJVTWVULU[SLHK(Z[OLQVPU[PZOLH[LKOLH[PZZO\U[LK PU[V[OL[^LLaLYZYH[OLY[OHUWHZZPUNKV^U[OLJVTWVULU[SLHKPU[V[OL JVTWVULU[IVK` -PN\YLZOV^ZZ\JOHWHPYVM[^LLaLYZ

Take Note: Having said all that, I am duty-bound to say that I have never owned a heat shunt, I have never even used a heat shunt, and I don’t think I will ever use a heat shunt. All but a very few electronic components are fairly heat-resilient after all, and as long as the soldered joint is performed rapidly and without leaving the soldering iron in place on the joint too long, then excessive heat should not be a problem.

16

Tools

FIGURE 2.13 A heat shunt. Side-cutters (M[LY`V\YZVSKLYPUNPYVU[OLZPUNSLTVZ[PTWVY[HU[[VVSPU`V\Y[VVSIV_ PZHKLJLU[[VNVVKX\HSP[`WHPYVMTPUPH[\YLZPKLJ\[[LYZ(ZZPKLJ\[[LYZ areZVPTWVY[HU[P[»ZILZ[UV[[VZRPTWVU[OPZ[VVS·I\`[OLILZ[`V\ JHUHMMVYKKLJLU[X\HSP[`ZPKLJ\[[LYZHYLH]HPSHISLH[HYV\UK‰^OPSL goodX\HSP[`ZPKLJ\[[LYZHYLWYPJLKIL[^LLUHIV\[‰HUK‰¯ )LMVYL`V\IH\SRH[[OLWYPJLYLTLTILY[OH[[OLZPKLJ\[[LYZ`V\I\` ^PSSIL\ZLKL]LY`[PTL`V\ZVSKLYHWYPU[LKJPYJ\P[IVHYK[V[YPT[OL JVTWVULU[SLHKZHM[LYZVSKLYPUNQVPU[Z;OL`»SSIL\ZLKL]LY`[PTL`V\ J\[^PYLZ[VSLUN[OMVYPUZLY[PVUPU[VHWYPU[LKJPYJ\P[;OL`»SSIL\ZLK L]LY`[PTL`V\[YPT`V\Y[VLUHPSZ;OL`ZOV\SKnotIL\ZLKMVYJ\[[PUN [OPJR^PYLZVYTL[HSVYWY\UPUN[OLYVZLZVYJ\[[PUN[VLUHPSZPM`V\ OHKU»[HSYLHK`YLHSPaLK0^HZU»[ILPUNZLYPV\Z (UKÄUHSS`Q\Z[[VSHIV\Y[OLWVPU[HKLJLU[WHPYVMZPKLJ\[[LYZ^PSSSHZ[ HSPML[PTLPULSLJ[YVUPJZI\[HJOLHWWHPY^PSSWYVIHIS`SHZ[[PSS`V\ULLK [OLT -PN\YLZOV^ZHWHPYVMZPKLJ\[[LYZ[OH[OH]LSHZ[LKHSPML[PTLTPUL ;OL`^LYLL_WLUZP]LJVZ[PUNHYV\UK‰PU HUKH[[OL[PTL0^HZ `V\UNHUKMVVSPZOHUK[OV\NO[P[^HZHSP[[SLV]LY[OL[VWI\[UV^[OH[ 0»]LTH[\YLKHUK0»THNHPULYY¯`LZ^LSS¯0JLY[HPUS`YLHSPaL[OLPY ^VY[O0UHSSZLYPV\ZULZZ[OV\NO[OLTVUL``V\ZWLUKVU[OPZ[VVSPZ ^VY[OP[PU[OLSVUNY\U

17

Starting Electronics Construction

FIGURE 2.14 A good quality pair of miniature side-cutters. After your soldering iron, it’s the tool you’ll use the most in electronics. Long-nosed pliers 3PRLZPKLJ\[[LYZHTPUPH[\YLWHPYVMSVUNUVZLKWSPLYZPZHULZZLU[PHS[VVS MVY[OLI\PSKLYVMLSLJ[YVUPJZJPYJ\P[Z3PRLZPKLJ\[[LYZHSZVP[»ZWYL[[` PTWVY[HU[[VOH]LHKLJLU[[VNVVKX\HSP[`WHPY(UKPM`V\OH]LU»[ HSYLHK`N\LZZLKP[SPRLZPKLJ\[[LYZ[VV[OL`TH`ILL_WLUZP]L·KLJLU[ X\HSP[`SVUNUVZLKWSPLYZ^PSSJVZ[HYV\UK‰^OPSLHNVVKX\HSP[`WHPY ^PSSILWYPJLKIL[^LLUHYV\UK‰HUK‰(NHPUNL[[OLILZ[`V\JHU HMMVYK·[OL`^PSSIL^VY[OP[-PN\YLZOV^ZT`SVUNUVZLKWSPLYZ ^OPJO0IV\NO[HSVUN^P[OT`ZPKLJ\[[LYZPU MVYHYV\UK‰ ;OL`»YLZ[PSS^VYRPUNWLYMLJ[S`^OPJOPZTVYL[OHU0JHUZH`MVYT`ZLSM

FIGURE 2.15 Miniature long-nosed pliers are extremely useful tools to keep in your electronics toolbox. 18

Tools 3VUNUVZLKWSPLYZHYL]LY`\ZLM\SMVYMVYTPUNJVTWVULU[SLHKZWYPVY[V TV\U[PUN[OLJVTWVULU[PU[OLWYPU[LKJPYJ\P[IVHYK;OL`ZOV\SKUV[ IL\ZLKMVYHU`[OPUNOLH]PLY[OHU[OPZ·HUKZOV\SKKLÄUP[LS`notIL \ZLKMVY[PNO[LUPUNU\[ZVU[VSHYNLIVS[ZVY^VYRPUNVU[OLJHY;OL`HYL WYLJPZPVUPUZ[Y\TLU[Z^OPJOYLX\PYLHSP[[SLMVYL[OV\NO[PUOHUKSPUN

Wire-strippers 7YPU[LKJPYJ\P[IVHYKZHYLUV[\Z\HSS`JVTWSL[LLU[P[PLZHUK[OL`ULLK [VILJVUULJ[LK[V[OLV\[ZPKL^VYSK;OLLHZPLZ[HUKTVZ[WVW\SHY^H` [VKV[OH[PZ^P[OPU[LYJVUULJ[PUN^PYLZ^OPJOHYLUVYTHSS`PUZ\SH[PVU JV]LYLK[VWYL]LU[ZOVY[JPYJ\P[^P[O[OLPYULPNOIV\YZ,HJO^PYLOHZ[V ILZVSKLYLK[V[OLWYPU[LKJPYJ\P[IVHYKZVP[»ZULJLZZHY`[VYLTV]LH WPLJLVMPUZ\SH[PVUH[[OL^PYLLUKSLH]PUNHZOVY[SLUN[OVM\UPUZ\SH[LK ^PYL[OH[JHUILZVSKLYLK0[»ZWLYMLJ[S`WVZZPISL[VZ[YPWHZOVY[WPLJLVM PUZ\SH[PVUH^H`I`W\[[PUN[OLLUKVM[OL^PYLPU[V`V\YTV\[OIL[^LLU `V\Y[LL[OIP[PUNVU[OL^PYL^OPSLW\SSPUNP[IHJRV\[VM`V\YTV\[O 0UKLLK0\ZLK[VKV[OPZ]LY`[OPUNILMVYL0^VYLHOVSLPUT`MYVU[[LL[O HUKZ\MMLYLKTHU`L_WLUZP]LKLU[HSIPSSZ5V^0\ZLHWHPYVM^PYL Z[YPWWLYZHUK0^OVSLOLHY[LKS`YLJVTTLUK`V\KV[OLZHTL >PYLZ[YPWWLYZ^VYRPUL_HJ[S`[OLZHTL^H`[OH[MYVU[[LL[OKVPU[OH[ `V\PUZLY[[OL^PYLPU[V[OL^PYLZ[YPWWLYZQH^ZHUK`LZ[OL`HYLJHSSLK QH^Z^OLYL\WVU`V\ZX\LLaL[OL^PYLZ[YPWWLYZ»OHUKSLZ[VNL[OLYZV[OH[ [OL^PYLZ[YPWWLYZ»[LL[OJH[JO[OL^PYLIL[^LLU[OLT-\Y[OLYZX\LLaPUN VM[OLOHUKSLZMVYJLZ[OL[LL[OPU[V[OLPUZ\SH[PVUHUKZPT\S[HULV\ZS` W\SSZ[OLQH^ZIHJRZ[YPWWPUN[OLPUZ\SH[PVUMYVT[OL^PYL-PN\YL ZOV^ZHWHPYVM^PYLZ[YPWWLYZPUHJ[PVU

FIGURE 2.16 Using a pair of wire-strippers to strip the insulation from the end of a wire, prior to soldering to a printed circuit board. 19

Starting Electronics Construction :\JO^PYLZ[YPWWLYZHYLU»[[VVL_WLUZP]LHYV\UKH[LUULYHS[OV\NO`V\ JHUNL[T\JOTVYLL_WLUZP]LVULZ(Z^P[O[OLJHZLVM^PYLJ\[[LYZHUK SVUNUVZLKWSPLYZNL[[OLILZ[`V\JHUHMMVYK;OLILZ[^PYLZ[YPWWLYZ OH]LYLWSHJLHISLQH^Z\USPRLTLZVJHUILHS^H`ZTHPU[HPULK^P[OH NVVKZL[VM[LL[O;OLJOLHWLYVULZHYLQ\Z[[OYV^H^H`[VVSZ0»]LOLHYK thatZHPKHIV\[TLILMVYLHZ^LSS¯

Solder removal tools 0M`V\ZVSKLYLSLJ[YVUPJJVTWVULU[ZPU[VWYPU[LKJPYJ\P[IVHYKZ[OLU ZVVULYVYSH[LY`V\^PSSULLK[VKLZVSKLY[OLT[VYLTV]L[OLTMYVT WYPU[LKJPYJ\P[IVHYKZ0[NVLZ^P[OV\[ZH`PUN[OH[`V\^PSSH[ZVTLZ[HNL W\[HJVTWVULU[PU[OL^YVUNWSHJLHUKULLK[V[HRLP[V\[VY`V\^PSS ÄUK[OH[`V\OH]LHMH\S[`JVTWVULU[HUKULLK[VYLWSHJLP[ ;OLYLHYL[^V[VVSZ[OH[JHUOLSW`V\KV[OPZHUK`V\YZLSLJ[PVUVM^OPJO `V\I\`PZTLYLS`HTH[[LYVMJOVPJL;OLJOLHWLZ[PZKLZVSKLYPUNIYHPK ·SLUN[OZVMJVWWLYIYHPKLK^PYLZ[OH[H[[YHJ[TVS[LUZVSKLYH^H`MYVT HZVSKLYLKQVPU[ZPTWS`ILJH\ZLZVSKLYÅV^Z[VJV]LY[OLJVWWLY^PYL Z\YMHJLZPU[OLIYHPK-PN\YLZOV^ZKLZVSKLYPUNIYHPKPU\ZL·[OL IYHPKPZWSHJLKV]LY[OLQVPU[HUKHOV[ZVSKLYPUNPYVUIP[WYLZZLZVU[VW (Z[OLOLH[MYVT[OLPYVUIP[TLS[Z[OLZVSKLYP[PZH[[YHJ[LKVU[V[OLIYHPK H^H`MYVT[OLQVPU[6UJL[OLJVTWVULU[SLHKILJVTLZZ\MÄJPLU[S` MYLLVMZVSKLY[VILYLTV]LK[OLIYHPKHUK[OLZVSKLYPUNPYVUIP[HYL YLTV]LKHUK[OLSLHKJHUILL_[YHJ[LKMYVT[OLQVPU[OVSL

FIGURE 2.17 Desoldering braid in action. The braid is heated by the iron’s bit, which in turn heats the solder on the joint to melting point, whereupon the solder is attracted to the copper wires in the braid. 20

Tools 6UJL[OLIYHPKLUKOHZILLU\ZLK[VKLZVSKLYHQVPU[P[ILJVTLZ SVHKLK^P[OZVSKLYZVT\Z[ILJ\[VMMSLH]PUNMYLZOIYHPKMVY[OLUL_[ KLZVSKLYPUNVWLYH[PVU(ZZ\JOHSLUN[OVMKLZVSKLYPUNIYHPKVUS`OHZH SPTP[LKSPMLKLWLUKPUNVUOV^THU`QVPU[Z`V\KLZVSKLY+LZVSKLYPUN IYHPKJVZ[Z‰VY‰MVYHTL[YLVYZVHS[OV\NO`V\JHUI\`P[PUSVUNLY SLUN[OYLLSZPM`V\ULLK ;OLHS[LYUH[P]L[VVSMVYKLZVSKLYPUNW\YWVZLZPZHKLZVSKLYPUNW\TW JVTTVUS`JHSSLKHZVSKLYZ\JRLY;OPZ^VYRZZVTL[OPUNSPRLHIPJ`JSL W\TWPUYL]LYZL·`V\VWLYH[L[OLW\TW^OPJOPZZWYPUNSVHKLK[V W\ZOV\[HPY[OLUHWWS`[OLW\TW[VTVS[LUZVSKLYVUHQVPU[HUKYLSLHZL [OLWS\UNLY[VSP[LYHSS`Z\JR[OLTVS[LUZVSKLYH^H`MYVT[OLQVPU[PU[V [OLW\TW^OLYLP[YHWPKS`OHYKLUZ;OLUL_[VWLYH[PVUVM[OLW\TW MVYJLZV\[[OLOHYKLULKZVSKLYHUKWYPTLZ[OLW\TWYLHK`MVY[OLUL_[ KLZVSKLYPUNVWLYH[PVU-PN\YLZOV^ZHKLZVSKLYPUNW\TWPUWVZP[PVU V]LYHQVPU[HZ[OLQVPU[PZOLH[LK[VILJVTLTVS[LUI`HZVSKLYPUNPYVU IP[[PW;OLW\TWOHZILLUWYPTLKPLP[ZWS\UNLYOHZILLUW\ZOLKKV^U [OLW\TWIVK`HUKHZ[OLZVSKLYILJVTLZTVS[LU[OLI\[[VUJH[JO VU[OLKLZVSKLYPUNW\TWIVK`PZW\ZOLK[OLYLI`YLSLHZPUN[OLZWYPUN SVHKLKWS\UNLY^OPJOYL[\YUZ[V[OL[VWVM[OLW\TWIVK`

FIGURE 2.18 A desoldering pump in use. As the plunger returns to the top of the pump body, suction it creates sucks the molten solder on the joint inside the pump. >OPSLHSP[[SLTVYLL_WLUZP]L[OHUKLZVSKLYPUNIYHPKKLZVSKLYPUNW\TWZ SHZ[JVUZPKLYHIS`SVUNLY0UKLLKYLHSS`[OLVUS`WHY[VM[OLW\TW[OH[ TH`IL^VYUI`[OLKLZVSKLYPUNWYVJLZZPZ[OLW\TWUVaaSLK\L[V[OL YLWL[P[P]LHWWSPJH[PVUVM[OLOLH[VMZVSKLYPUN^OPJOUL]LY[OLSLZZ^PSS OH]LHUVWLYH[PUNSPMLVMTHU`[OV\ZHUKZVMVWLYH[PVUZ4VZ[KLZVSKLYPUN W\TWZOH]LHYLWSHJLHISLUVaaSLZVL]LUPM[OLUVaaSLis^VYU[OL 21

Starting Electronics Construction W\TWPZUV[ULJLZZHYPS`^YP[[LUVMM+LZVSKLYPUNW\TWZHYLH]HPSHISL MYVTHZSP[[SLHZ‰[V‰

Drills and bits ,HJOHUKL]LY`JVTWVULU[TV\U[LKVUHWYPU[LKJPYJ\P[IVHYKPU[OL JVU]LU[PVUHS^H`UV[L0ZH`JVU]LU[PVUHS^H`OLYL![OLYLareV[OLY TL[OVKZ^OPJOKVU»[UVYTHSS`HMMLJ[[OLPUKP]PK\HSLSLJ[YVUPJJPYJ\P[ I\PSKLYTVZ[UV[HIS`[OLZ\YMHJLTV\U[LKJVTWVULU[TL[OVK·ZLL WHNLOHZP[ZJVTWVULU[SLHKZNVPUN[OYV\NOOVSLZPU[OLWYPU[LK JPYJ\P[IVHYK;O\Z[OLWYPU[LKJPYJ\P[IVHYKOHZ[VILKYPSSLK^P[OOVSLZ MVY[OVZL]LY`ZHTLJVTWVULU[SLHKZ;OLOVSLZPaLPZHYV\UK TTNP]LVY[HRLH]LY`ZTHSSWLYJLU[HNL·KLWLUKPUNVU[OLHJ[\HS JVTWVULU[»ZSLHKZ^OPJOTLHUZ[OH[`V\YH]LYHNLWV^LYKYPSS[OH[`V\ \ZL[VKYPSSTHZVUY`VYZ[LLSPZUV[L_HJ[S`[OLILZ[[VVS[V\ZL7V^LY KYPSSZHYLNVVK^OLYL[OL[OPUNILPUNKYPSSLKPZOHYKHUK[OLOVSLZKVU»[ OH]L[VIL[VVHJJ\YH[LS`WVZP[PVULK 7YPU[LKJPYJ\P[IVHYKVU[OLV[OLYOHUKPZTHKLMYVTH[OPUHUKMHPYS` ZVM[Z\IZ[YH[LHUK[OLJVWWLY[YHJRPZI\[HML^TPJYVTL[YLZ[OPJR^OPSL [OLJVWWLYWHKZ`V\»SSILKYPSSPUN[OYV\NOHYLUV[[OH[T\JOIPNNLY[OHU [OLOVSLZYLX\PYLK[OLTZLS]LZ:VHKYPSSMVY[OL[HZRVMKYPSSPUNWYPU[LK JPYJ\P[IVHYKOHZML^WV^LYYLX\PYLTLU[ZI\[HJJ\YHJ`PZVMWYPTL PTWVY[HUJL :THSSOHUKOLSKSV^]VS[HNLKYPSSZJVTWSL[L^P[OTHPUZ[YHUZMVYTLY HYLH]HPSHISLMYVTTVZ[KVP[`V\YZLSMZ[VYLZHUK[OLZLHYLPKLHSMVY OHUKKYPSSPUNVMWYPU[LKJPYJ\P[IVHYKZ-PN\YL ZOV^ZZ\JOHKYPSS ILPUN\ZLK[VKYPSSOVSLZPUHWYPU[LKJPYJ\P[IVHYKWYPVY[VTV\U[PUNHUK ZVSKLYPUNVMJVTWVULU[Z

¬

FYI

š

Make sure you keep a couple of 1 mm and 1.5 mm drills in your toolbox at all times – it’s useful when one drill breaks (which they invariably do at the wrong time) to have another one ready to use. Oh, and make sure all your drills are sharp.

FIGURE 2.19 Using a hand-held low-voltage drill to drill holes in a printed circuit board. 22

Tools 3H[LYPU[OLIVVR^L»SSZLL[OH[SHYNLYWV^LYKYPSSZKVHJ[\HSS`OH]LH WSHJLPU[OLLSLJ[YVUPJZJPYJ\P[I\PSKLY»Z[VVSIV_MVYKYPSSPUNVMSHYNL OVSLZPUOV\ZPUNZMVYL_HTWSL)\[`V\doULLK[VOH]LHSV^]VS[HNL OHUKOLSKKYPSSMVY[OLÄULY[HZRZSPRL[OH[PU-PN\YL ;OL`HYLUV[ [OH[L_WLUZP]L·Z[HY[PUNH[HYV\UK‰HUKNVPUN\W[VHIV\[‰,]LU [OLJOLHWLZ[^PSSKV[OLQVILMMLJ[P]LS`OLU^VYRPUNVUHWYPU[LKJPYJ\P[IVHYKI`OHUKP[»ZUV[HS^H`ZLHZ` [VTV\U[HUKZVSKLYJVTWVULU[Z^P[OV\[[OLIVHYKTV]PUNHSVUN[OL ^VYRZ\YMHJLHZ`V\^VYR0M`V\OH]LHOV[ZVSKLYPUNPYVUPUVULOHUK HUKZVSKLYPU[OLV[OLYOHUK[OLSHZ[[OPUN`V\^HU[PZ`V\YWYPU[LK JPYJ\P[IVHYKZSPKPUNHSVUN[OLILUJOHUKMHSSPUN[V[OLÅVVY-HJLP[! `V\JV\SKKV^P[OH[OPYKOHUK(UHS[LYUH[P]LPZ[V\ZLHWYPU[LKJPYJ\P[ IVHYKZ[HUKPU[V^OPJO`V\YWYPU[LKJPYJ\P[IVHYKPZJSHTWLK;OLIVHYK JHUILYLWVZP[PVULKLHZPS`HUKL]LU[\YULKV]LY[VZ\P[ ([`WPJHSZ[HUKPZZOV^UPU-PN\YL^OPJOPZHTPUPH[\YL]PJL ^P[OHSL]LYVWLYH[LKZ\JRLYHYYHUNLTLU[VU[OLIV[[VT;OLZ\JRLY HSSV^Z[OL]PJL[VILJSHTWLK[VH^VYRZ\YMHJL^OPSL[OL]PJLOVSKZH WYPU[LKJPYJ\P[IVHYKZHMLS`SLH]PUN`V\YOHUKZMYLL[VPUZLY[HUKZVSKLY JVTWVULU[Z

FIGURE 2.20 A printed circuit board stand. 23

Starting Electronics Construction 4HU`V[OLY[`WLZVMZ[HUKHYLH]HPSHISLYHUNPUNMYVTHZPTWSLIV_[OH[ OVSKZHWYPU[LKJPYJ\P[IVHYK[VHT\S[PHYTLKHYYHUNLTLU[JVTWSL[L ^P[OTHNUPM`PUNNSHZZHUKJSPWZ[VOVSKV[OLYJVTWVULU[Z

IC insertion tool (Z`V\JVUZ[Y\J[LSLJ[YVUPJJPYJ\P[ZVUWYPU[LKJPYJ\P[IVHYKZ`V\^PSS JVTLHJYVZZPU[LNYH[LKJPYJ\P[Z0*Z·ZLLWHNL0U[LNYH[LKJPYJ\P[Z HYLJVTWVULU[Z[OH[JVU[HPUTHU`TPUPH[\YPaLKJVTWVULU[Z^P[OPU ;OL`HYLX\P[LZTHSSI\[\Z\HSS`OH]LTHU`YLSH[P]LS`MYHNPSLJVUULJ[PVU WPUZTVZ[JVTTVUS`PU[^VYV^Z·[OLdual-in-lineHYYHUNLTLU[ 0UZLY[PUNZ\JOPU[LNYH[LKJPYJ\P[ZPU[VHWYPU[LKJPYJ\P[IVHYKPZHSP[[SL [YPJR`HZ[OLYV^ZVMJVUULJ[PVUWPUZHYLHUNSLKZVTL^OH[H^H` MYVT[OL]LY[PJHSWSHULZVULLK[VILZWY\UNPUHZ[OL`LU[LY[OLPY JVYYLZWVUKPUNOVSLZPU[OLWYPU[LKJPYJ\P[IVHYK0[»ZWLYMLJ[S`WVZZPISL[V KV[OPZI`OHUK^P[OJHYLI\[HU0*PUZLY[PVU[VVSZ\JOHZ[OH[ZOV^UPU \ZLPU-PN\YLPZ^LSS^VY[O[OLJVZ[VM[LUSLZZ[OHU‰HUKTHRLZ [OL[HZRHIP[VMHKVKKSL 0U\ZL[OLPU[LNYH[LKJPYJ\P[PZW\ZOLKPU[V[OL[VVS^OPJORLLWZ[OL JVUULJ[PVUWPUZH[[OLJVYYLJ[HUNSLHUKKPZ[HUJL[OLU[OL[VVSPZ W\ZOLKKV^UVU[V[OLWYPU[LKJPYJ\P[IVHYK[VLUNHNL[OLPU[LNYH[LK JPYJ\P[PU[VP[ZJVYYLJ[WVZP[PVU

FIGURE 2.21 An integrated circuit insertion tool in operation. IC extraction tool .L[[PUNHUPU[LNYH[LKJPYJ\P[IHJRV\[VMHWYPU[LKJPYJ\P[IVHYKPZHU LX\HSS`[YPJR`[HZR/V^L]LY[OLYLHYLLX\HSS`JOLHWL_[YHJ[PVU[VVSZ ·VULPZZOV^UPU\ZLPU-PN\YL1\Z[OVVR[OL[VVSH[LHJOLUK VM[OLPU[LNYH[LKJPYJ\P[HUKW\SS6MJV\YZLPMHUPU[LNYH[LKJPYJ\P[PZ 24

Tools ZVSKLYLKKPYLJ[S`PU[VHWYPU[LKJPYJ\P[IVHYK`V\»SSULLK[VKLZVSKLYP[ ÄYZ[ZLLLHYSPLY/V^L]LY[OLPU[LNYH[LKJPYJ\P[ZOV^UPU-PN\YL OHZILLUPUZLY[LKPU[VHOVSKLY0U[LNYH[LKJPYJ\P[OVSKLYZWYV]PKLHW\ZO Ä[TL[OVKVMPUZLY[PUNPU[LNYH[LKJPYJ\P[ZZLL*OHW[LY

FIGURE 2.22 Using an extraction tool to pull out an integrated circuit — note the use of an integrated circuit holder, which means the integrated circuit itself is not soldered into the printed circuit board. Terminal pin pusher >OLUJVUULJ[PVUZHYLULLKLKVUHWYPU[LKJPYJ\P[IVHYKP[»ZJVTTVU [V\ZLW\ZOÄ[[LYTPUHSWPUZZLL*OHW[LYPU[OLWYPU[LKJPYJ\P[IVHYK 0[»Z[OLULHZ`[VZVSKLYHJVUULJ[PUNSLHK[V[OLWPUZLL*OHW[LYHZ YLX\PYLK/V^L]LY^OPSLP[»ZWVZZPISL[VW\ZO[OLZLWPUZPU[VWSHJLPUH WYPU[LKJPYJ\P[IVHYK\ZPUNWSPLYZZH`HNVVK[VVS[VI\`PZH[LYTPUHS WPUW\ZOLY·ZOV^UPU\ZLPU-PN\YL

FIGURE 2.23 Terminal pin pusher — just put the pin loosely in place in the printed circuit board, then push home firmly with the pusher. 25

Starting Electronics Construction Spot-face cutter >OLU\ZPUNZ[YPWIVHYK[VI\PSKHJPYJ\P[VUP[»ZPUL]P[HISL[OH[ZVTLVM [OLZ[YPWZULLK[VILIYVRLU·WHY[PJ\SHYS`^OLUZP[PUNHK\HSPUSPUL PU[LNYH[LKJPYJ\P[^OPJOOHZ[^VYV^ZVMWHYHSSLSWPUZ0U[OPZJHZLPM Z[YPWZHYLU»[IYVRLUIL[^LLU[OLYV^ZVMWPUZZOVY[JPYJ\P[IL[^LLU[OL WPUZ^PSSVJJ\Y )YLHRPUN[OLZ[YPWJHUILKVUL^P[OHZOHYWJYHM[RUPMLI\[[OPZPZ TLZZ`HUKHWV[LU[PHSS`KHUNLYV\ZTL[OVK)LZ[[VI\`HZWV[MHJL J\[[LY^OPJOPZH[VVS^P[OHYV[H[PUNJ\[[PUNLKNLZ-PN\YLZOV^ZH JVTTVU[`WL*OHW[LYZOV^ZOV^[V\ZLVUL

¬

FYI

š

While stripboard is fine for prototype work, I would not condone it for use in a final project. Always use printed circuit board to produce best end results.

FIGURE 2.24 A spot-face cutter, used to break strips in stripboard.

26

Components

3 Components ;OLYLHYLTHU`[`WLZVMJVTWVULU[Z\ZLKPULSLJ[YVUPJKL]PJLZ·[OL THPU[`WLZHYLSPZ[LKILSV^@V\ULLK[VRUV^^OH[LHJOVM[OLTHYL ^OH[[OLPYJPYJ\P[Z`TIVSZHYLOV^[OL`M\UJ[PVUOV^[VPKLU[PM`[OLT HUK^OH[[OLPY\UP[ZVMTLHZ\YLTLU[HUK]HS\LZHYL

Component types



RESISTORS



CAPACITORS



SEMICONDUCTORS



SWITCHES



INDUCTORS



CONNECTORS

;OLYLHYLV[OLY[`WLZVMJVTWVULU[ZI\[[OVZLSPZ[LKOLYLHUKKLZJYPILK PU[OPZJOHW[LYHYL[OLTVZ[PTWVY[HU[ 27

Starting Electronics Construction

Resistors ;OLYLZPZ[VYPZVULVM[OLTVZ[PMUV[theTVZ[JVTTVU`L[PTWVY[HU[ JVTWVULU[Z\ZLKPULSLJ[YVUPJZ0[ZWYPTHY`M\UJ[PVUPZ[VYLZPZ[[OLÅV^ VMLSLJ[YPJP[`PUHKLÄULKTHUULY ;VKV[OPZP[OHZHYLZPZ[HUJLZWLJPÄLKPU[OL\UP[VMVOTZUHTLKHM[LY [OLWO`ZPJPZ[6OT^OVKPKJVUZPKLYHISLLHYS`^VYRPU[V[OLX\HSP[PLZVM YLZPZ[HUJLHUKNP]LU[OLHIIYL]PH[PVU£:VHYLZPZ[VY»Z]HS\LPZNP]LU HZHU\TILYMVSSV^LKI`[OLVOTZZ`TIVSLN£6JJHZPVUHSS` [OLHIIYL]PH[PVU£PZJOHUNLK[V[OLHIIYL]PH[PVU9·ZPTWS`ILJH\ZL [OLHIIYL]PH[PVU£PZUV[HS^H`ZLHZPS`WYVK\JLKPU^VYKWYVJLZZPUN HWWSPJH[PVUZVUZVTLWLYZVUHSJVTW\[LYZ5L]LY[OLSLZZ`V\ZOV\SK RUV^[OH[[OL9Z[HUKZMVY£ =HS\LZVMYLZPZ[VYZYHUNLMYVTHMYHJ[PVUVMHUVOT[OYV\NO[VTHU` TPSSPVUZVMVOTZ>OLYL[OV\ZHUKZVMVOTZHYLZWLJPÄLKP[PZ\Z\HS[V \ZL[OL\UP[VMRPSVOTZHRPSVOTPZVOTZZV[OH[ZH`R£PZ\ZLK [VZWLJPM`VOTZVYR£ZWLJPÄLZVOTZ3PRL^PZL TPSSPVUZVMVOTZHYLRUV^UHZTLNVOTZZV[OH[ZH`4£PZ\ZLK[V ZWLJPM`VOTZHUKZVVU>P[ORPSVOTZHUKTLNVOTZP[OHZ ILJVTL\Z\HS[VKYVW[OLZ\WLYÅ\V\Z£[O\Z]HS\LZ^V\SKIL^YP[[LU RR4HUKZVVU 6UZVTLJPYJ\P[ZHUKL]LUPUZVTL[L_[ZVYSPZ[ZPUHULMMVY[[VKLJYLHZL [OLKPNP[ZHUKOLUJLZPaLVMSHILSZHUKJVTWSL_P[`VM[OLJPYJ\P[[OL VOTPJ\UP[PZ\ZLK[VPUKPJH[L[OLKLJPTHSWVPU[WVZP[PVU·ZV£ ^V\SKIL^YP[[LU9R^V\SKIL^YP[[LURHUK4^V\SKIL ^YP[[LU4 *VTTVUZ`TIVSZMVYHYLZPZ[VYPUJPYJ\P[ZHYLZOV^UPU-PN\YL;OL JVYYLJ[)YP[PZOZ[HUKHYKPZ[OLYLJ[HUN\SHYIV_ZOHWLVM-PN\YLH [OV\NO[OLaPNaHNNLKZOHWLVM-PN\YLIPZVM[LU\ZLKZV`V\T\Z[ ILH^HYLVMHUKILJVUÄKLU[^P[OIV[O

FIGURE 3.1 Resistor symbols commonly found in electronic circuits (a) correct British standard (b) zig-zag shape also used. 28

Components (WHY[MYVTHYLZPZ[VY»Z]HS\L·^OPJOPZI`MHY[OLTVZ[PTWVY[HU[ JYP[LYPVU·[OLYLHYLV[OLYPTWVY[HU[KPMMLYLUJLZ^OPJOKLÄULOV^^LSS HNP]LUYLZPZ[VY^VYRZPUHNP]LUJPYJ\P[!

• TOLERANCE ·YLZPZ[VYZHYLYHYLS`[OLL_HJ[]HS\LZWLJPÄLK ^OPJOT\Z[UV[ILL_JLLKLK([`WPJHSWV^LYYH[PUNMVYYLZPZ[VYZ\ZLKPU JVTTVULSLJ[YVUPJKL]PJLZPZ>·PUHSSI\[[OLTVZ[WV^LYO\UNY`VM JPYJ\P[Z[OPZ^PSS\Z\HSS`Z\MÄJL0UMHJ[SV^LYWV^LYYLZPZ[VYZLN> ^PSSWYVIHIS`KV·HUKHYLVMJV\YZLZTHSSLY STABILITY ·[OLHIPSP[`VMHYLZPZ[VY[VRLLWP[Z]HS\LV]LY[PTL +LZWP[LV[OLYJOHUNLZZ\JOHZOLH[O\TPKP[`[OH[JHUVJJ\YHYV\UKP[P[ ZOV\SKILHISL[VTHPU[HPUP[ZYLZPZ[HUJL]HS\LHZJSVZLS`HZWVZZPISL

Resistor types ;OLYL»ZHML^PTWVY[HU[[`WLZVMYLZPZ[VYJSHZZPÄLKI`OV^[OL`HYL JYLH[LK Carbon resistors ;OLYLHYLHJ[\HSS`[^VTHPU[`WLZVMJHYIVUYLZPZ[VYZI\[[OL`SVVR ZPTPSHYPMUV[PKLU[PJHS·ZLL-PN\YLZHUK

FIGURE 3.2 Carbon resistors — illustration. 29

Starting Electronics Construction

FIGURE 3.3 Photograph of carbon resistors. *HYIVUJVTWVZP[PVUYLZPZ[VYZHYLTHKLMYVTHTP_[\YLVMJHYIVUHUK JSH`*HYIVUJVUK\J[ZLSLJ[YPJP[`I\[JSH`KVLZUV[ZVI`TP_PUN[OL [^VYLZPZ[VYZHYLMVYTLK:[HIPSP[`HUK[VSLYHUJLVMYLZPZ[VYZTHKL[OPZ ^H`HYLUV[WHY[PJ\SHYS`NVVKI\[[OL`HYLJOLHW[VTHRLZVHYL]LY` JVTTVU *HYIVUÄSTYLZPZ[VYZHYLTHKLI`TV\SKPUNHSH`LYVMJHYIVUTH[LYPHS VU[VHUPUZ\SH[PUNYVK[OLUL[JOPUNHZWPYHS[YHJR[OYV\NO[OLJHYIVU[PSS [OLYLZPZ[HUJLPUJYLHZLZ;VSLYHUJLHUKZ[HIPSP[`HYLNVVK 4L[HSÄSTYLZPZ[VYZ ;OLZLHYLTHKLPUT\JO[OLZHTL^H`HZJHYIVUÄSTYLZPZ[VYZI\[ [VSLYHUJLHUKZ[HIPSP[`HYLT\JOIL[[LYZV[OL`HYL\ZLKPUJPYJ\P[Z^OPJO YLX\PYLNYLH[HJJ\YHJ`;OL`HYLOV^L]LYTVYLL_WLUZP]L-PN\YL ZOV^ZPSS\Z[YH[PVUZVMZVTLTL[HSÄSTYLZPZ[VYZ^OPSL-PN\YLZOV^ZH WOV[VNYHWO

FIGURE 3.4 Metal film resistors — illustration. 30

Components

FIGURE 3.5 Photograph of metal film resistors. >PYL^V\UKYLZPZ[VYZ >PYLPZ^V\UKHYV\UKHUKHSVUNHJLYHTPJMVYTLY[VTHRL[OLZL YLZPZ[VYZ;OL[OPJRULZZVM^PYLHUK[OLZPaLVM[OLMVYTLYKLÄUL[OL YLZPZ[HUJLVM[OLYLZPZ[VY>OPSLILPUNX\P[LL_WLUZP]LYLZPZ[VYZTHKL[OPZ ^H`OH]L[OLHK]HU[HNLVMOPNOWV^LYYH[PUN-PN\YLZHUKZOV^ PSS\Z[YH[PVUZHUKHWOV[VNYHWOVM^PYL^V\UKYLZPZ[VYZ

FIGURE 3.6 Wirewound resistors — illustration. Variable resistors — potentiometers 6M[LUPUHULSLJ[YVUPJJPYJ\P[[OLYLPZHYLX\PYLTLU[MVYHJVU[YVSRUVI VMZVTLZVY[]VS\TL[VUL]VS[HNLHUKZVVU=HYPHISLYLZPZ[VYZ\Z\HSS` JHSSLKpotentiometersVYQ\Z[potsJHUIL\ZLKMVY[OPZW\YWVZL;OL` MLH[\YLHYLZPZ[P]L[YHJR\Z\HSS`THKLMYVTHJHYIVUJVTWVZP[PVUTP_[\YL PUHJPYJ\SHYMVYTH[^P[OHYV[H[PUN^PWLYHYT^OVZLWVZP[PVUJHUIL 31

Starting Electronics Construction

FIGURE 3.7 Photograph of wirewound resistors. HKQ\Z[LK;OLYLHYL[^VTHPU[`WLZ·Z[HUKHYKWV[LU[PVTL[LYZMLH[\YPUN HJLU[YHSZOHM[[OH[JHUILH[[HJOLK[VHJPYJ\P[»ZMYVU[WHULSMVY\ZLY JVU[YVSHUKWYLZL[WV[LU[PVTL[LYZ^OPJOHYLTV\U[LKVUHWYPU[LK JPYJ\P[IVHYKHUKHYLHKQ\Z[LK^P[OHZJYL^KYP]LY[`WL[VVS;OLPY]HYPV\Z Z`TIVSZHYLZOV^UPU-PN\YL

FIGURE 3.8 Symbols of (a) standard and (b) preset potentiometers. 7V[LU[PVTL[LYZJHUILVMVULVM[^VTHPUNYV\WZlogarithmicVY logHUKlinearVYlin·^OPJOYLMLYZ[V^OL[OLY[OLYLZPZ[HUJLHSVUN [OL[YHJR]HYPLZPUHSPULHYTHUULYPL[OLYLZPZ[HUJL]HYPLZKPYLJ[S` HJJVYKPUN[V[OLWVZP[PVUVM[OL^PWLYHYTVYPUHSVNHYP[OTPJTHUULY PL[OLYLZPZ[HUJL]HYPLZSVNHYP[OTPJHSS`HJJVYKPUN[V[OL^PWLYHYT WVZP[PVU 4VZ[S`SPULHYWV[LU[PVTL[LYZHYL\ZLK/V^L]LYPUH\KPVJPYJ\P[ZPU WHY[PJ\SHY·^OLYL]VS\TLPZILPUNHKQ\Z[LKZH`·[OLUSVNHYP[OTPJ WV[LU[PVTL[LYZHYL\ZLK 32

Components ¬ FYI

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Volume is a logarithmic variant, in so far as a doubling in volume means a 3dB louder sound. So a sound of say 60dB is double the volume of a sound of 57dB. Similarly, a sound of 63dB is double the volume of the 60dB sound. To represent and control this with a potentiometer, the potentiometer must have a logarithmically scaled track. Logarithmic and linear scaled potentiometers can be used and will work in circuits requiring the use of the other type, but the characteristic of the potentiometer control as you turn it will not be correct.

+\HSNHUNWV[LU[PVTL[LYZHYLJVTTVUWHY[PJ\SHYS`PUH\KPVJPYJ\P[Z ^OLYLIV[OJOHUULSZVMHZ[LYLVHTWSPÄLYZH`ULLK[VILHKQ\Z[LK ZPT\S[HULV\ZS`;OLZLHYLX\P[LSP[LYHSS`THKLVM[^VWV[LU[PVTL[LYZ JV\WSLK[VNL[OLY^P[OHZPUNSLJVU[YVS[OH[YV[H[LZIV[O^PWLYZ[VNL[OLY 4VZ[WV[LU[PVTL[LYZHYLYV[HY`I\[ZVTL[PTLZ`V\^PSSZLL WV[LU[PVTL[LYZ[OH[VWLYH[LPUHSPUL:\JOZSPKLYWV[LU[PVTL[LYZ^VYRPU L_HJ[S`[OLZHTL^H`·^P[OHYLZPZ[P]L[YHJRHUKH^PWLYHYT :[HUKHYKWV[LU[PVTL[LYZHYLYLSH[P]LS`SHYNLHUK[OLZOHM[HSSV^ZMVYH JVU[YVSRUVI[VILÄ[[LKMVY\ZLYJVU[YVS:^P[JOTLJOHUPZTZJHUHSZV ILPUJVYWVYH[LKPU[V[OLIHJRVM[OLWV[LU[PVTL[LYIVK`^OPJOTLHUZ [OH[[OLJVU[YVSJHUIL\ZLKHZHUVUVMMZ^P[JOZH`H[[OLZHTL[PTL HZP[ILPUNH]VS\TLJVU[YVSMVYL_HTWSL7YLZL[WV[LU[PVTL[LYZHYL T\JOZTHSSLYHUKNL[[OLPYUHTLILJH\ZL[OL`HYL[`WPJHSS`ZL[ILMVYL [OLJVTWSL[LKLSLJ[YVUPJKL]PJLPZÄYZ[\ZLK[OLUYHYLS`[V\JOLKVY HKQ\Z[LKHNHPU(SSWV[LU[PVTL[LYZ·^OL[OLYZ[HUKHYKVYWYLZL[·OH]L [OYLL[LYTPUHSZ!VULMVYLHJOLUKVM[OLPU[LYUHSYLZPZ[VYHUKVULMVY[OL ^PWLYHYT0[»ZUV[HS^H`ZULJLZZHY`[V\ZLHSS[OYLL[LYTPUHSZPUHJPYJ\P[ [OV\NOHUKVM[LUVULVM[OL[LYTPUHSZPZSLM[\UJVUULJ[LK -PN\YL ZOV^ZPSS\Z[YH[PVUZVM]HYPV\ZWV[LU[PVTL[LYZ^OPSL-PN\YL ZOV^ZHWOV[VNYHWO

FIGURE 3.9 Potentiometers — illustrations: (a) front-panel fixing types — single- (top) and dualganged; (b) a preset potentiometer. 33

Starting Electronics Construction

FIGURE 3.10 Photograph of various potentiometers: single-gang, dual-gang, switched single-gang, together with preset potentiometers. 9LZPZ[VYJVSV\YJVKL 9LZPZ[HUJL]HS\LPZVJJHZPVUHSS`WYPU[LKU\TLYPJHSS`VUHYLZPZ[VY»ZIVK` I\[UVYTHSS`P[PZKLZPNUH[LKPU^OH[PZJHSSLK[OLYLZPZ[VYJVSV\YJVKL ;OLJVSV\YJVKLPZHJVSSLJ[PVUVMJVSV\YLKIHUKZUVYTHSS`MV\YIHUKZ HS[OV\NOÄ]LIHUKJVKLZL_PZ[[VVHYV\UK[OLYLZPZ[VYIVK`9LHKPUN MYVTSLM[[VYPNO[^P[O[OLÄYZ[IHUKILPUNJSVZLZ[[V[OLSLM[OHUKLKNLVM HYLZPZ[VY[OLIHUKZZPNUPM`!



BAND ·[OLÄYZ[KPNP[VM[OL resistor’s value



BAND ·[OLZLJVUKKPNP[VM[OL resistor’s value



BAND ·[OLÄN\YL[VT\S[PWS`[OL ÄYZ[[^VKPNP[ZI`



BAND ·[OLYLZPZ[VY»Z[VSLYHUJL

-PN\YLZOV^Z[OPZNYHWOPJHSS`;HISLNP]LZ[OLIHUKZ»YLZWLJ[P]L ]HS\LZ 34

Components

FIGURE 3.11 A resistor showing the four coloured bands that give its value according to the four-band resistor colour code detailed in Table 3.1.

;HISL ;OLMV\YIHUKYLZPZ[VYJVSV\YJVKL

  *VSV\Y Black Brown 9LK Orange Yellow Green Blue Violet Grey White .VSK :PS]LY None

Band 1 Z[ÄN\YL

Band 2 UKÄN\YL

Band 3 YKÄN\YL

Band 4 [VSLYHUJL

          · · ·

          · · ·

_ _ _ _ _ _ _ · · · _ _ ·

·   · · · · · · ·   

,_HTWSLZ\ZPUN[OLYLZPZ[VYJVSV\YJVKL ,_HTWSL·SL[»ZZH`[OLMV\YIHUKZVMHYLZPZ[VYHYL`LSSV^]PVSL[ VYHUNLZPS]LY;OLYLZPZ[VY]HS\LPZ`LSSV^]PVSL[T\S[PWSPLKI` VYHUNL^OPJOLX\HSZVOTZTVYL\Z\HSS`^YP[[LUR£ ^P[OH[VSLYHUJLVM— ZPS]LY ,_HTWSL·PM[OLMV\YIHUKZHYLNYL`YLKNYLLUNVSK[OLU[OL]HS\L PZNYL`YLK_NYLLU^OPJOPZVOTZTVYL \Z\HSS`^YP[[LU4£^P[OH[VSLYHUJLVM— NVSK 35

Starting Electronics Construction 7YLMLYYLK]HS\LZ 0UP[PHSS`^OLUJVUZPKLYPUN[OLYLZPZ[VYJVSV\YJVKL`V\TH`^LSS[OPUR [OH[P[»ZH]PY[\HSS`PTWVZZPISL[HZR[VYLTLTILYL]LY`ZPUNSL]HS\LVM YLZPZ[VY[VNL[OLY^P[OP[ZYLZWLJ[P]LJVSV\YJVKL*HSJ\SH[PUNL]LY` YLZPZ[VY»Z]HS\LMYVT[OLJVSV\YJVKL\UKLY[OLZLJPYJ\TZ[HUJLZ^PSSIL HSHIVYPV\Z[HZR/V^L]LYP[^V\SKILPTWVZZPISLMVYTHU\MHJ[\YLYZ[V THRLHUKMVYZ[VJRPZ[Z[VZ[VJRYLZPZ[VYZVMHSSWVZZPISL]HS\LZ·[OLYL ^V\SKZPTWS`IL[VVTHU`[VKLHS^P[OLMMLJ[P]LS`(ZYLZPZ[VYZHYLVUS` THKL[VJLY[HPU[VSLYHUJLZHU`^H`HUKHZJPYJ\P[KLZPNULYZOH]LH YLHZVUHISLJVTTHUKV]LY[OLJVTWVULU[Z[OL`ZWLJPM`MVY\ZL^P[OPU [OLPYJPYJ\P[ZP[OHZILJVTLUVYTHS[V\ZLYLZPZ[VYZVMVUS`JLY[HPU]HS\LZ ·[OLZLHYLJHSSLKWYLMLYYLK]HS\LZ;OL,Z[HUKHYKYHUNLVMWYLMLYYLK ]HS\LYLZPZ[HUJLZMVSSV^Z[OLZLYPLZ!   (ZHYLZ\S[`V\YQVIVMSLHYUPUN[OLJVSV\YJVKLPZTHKLZPNUPÄJHU[S` LHZPLY·ILJH\ZL[OLZL[^LS]L]HS\LZHYL[OLVUS`VULZ`V\ULLK[V RUV^(U`YLZPZ[VYZ`V\TPNO[\ZLVMOPNOLY]HS\LZMVSSV^PU[OPZ]LY` ZHTLZLYPLZTLYLS`I`OH]PUNHWHY[PJ\SHYT\S[PWS`PUNJVSV\YLKIHUKLN _$R_$4(M[LYVUS`HZOVY[^OPSL\ZPUN YLZPZ[VYZ`V\ZOV\SKÄUK[OH[`V\JHUHSTVZ[PUZ[HU[S`JHSJ\SH[LHU`UL^ YLZPZ[VY»Z]HS\LHUK`V\^VU»[L]LUULLK[VJHSJ\SH[LYLZPZ[VY]HS\LZ`V\ \ZLTVZ[YLN\SHYS`·`V\»SSRUV^[OLT 5V[L[OV\NO[OH[[OLYLHYLV[OLYWYLMLYYLK]HS\LYHUNLZVMYLZPZ[VYZ ·UV[HIS`[OL,YHUNL^OPJOHKKZHUL_[YH[^LS]L]HS\LZHIV]L[OL ,YHUNLZWHJLKPUIL[^LLU[OL,YHUNL]HS\LZ@V\^PSSYHYLS`PM L]LYLUJV\U[LY[OLTOV^L]LYHUK[OL[^LS]L]HS\LZVM[OL,YHUNL ^PSSTVZ[SPRLS`IL[OLVUS`VULZ`V\ULLK[VRUV^

:WLJPHSYLZPZ[VYZ ;OLYLHYLZL]LYHSV[OLY[`WLZVMYLZPZ[VYZ`V\TH`LUJV\U[LYPU`V\Y LSLJ[YVUPJ[YH]LSZ:VTLVM[OLZLHYLJV]LYLKLSZL^OLYLPU[OLIVVRI\[ MVYJVTWSL[LULZZ[OLTHPUVULZHYLSPZ[LKOLYL! Surface mount resistors·[OLYLOHZHS^H`ZILLUH[YLUK[VYLK\JL LSLJ[YVUPJKL]PJLZPUZPaL;OLSH[LZ[Z[LWPU[OPZ[YLUKPZ[V\ZLTPUPH[\YL JVTWVULU[Z[OH[HYLZVSKLYLKKPYLJ[S`[VHWYPU[LKJPYJ\P[IVHYK»ZJVWWLY [YHJRPL[OL`HYLTV\U[LKVU[OLIVHYKZ\YMHJLZLL-PN\YLYH[OLY [OHU^P[OJVTWVULU[SLHKZ[OH[NV[OYV\NO[OLIVHYK(ZZ\JOZ\YMHJL TV\U[YLZPZ[VYZHYLI`[OLPYUH[\YLL_[YLTLS`ZTHSSZV[OL`HYLUV[HZ Z\P[LK[VOHUKHZZLTIS`HUKZVSKLYPUNHZJVU]LU[PVUHSYLZPZ[VYZ^P[O SLHKZ/V^L]LY`V\TH`ÄUK`V\YZLSM^VYRPUN^P[O[OLTVJJHZPVUHSS` 36

Components

FIGURE 3.12 A typical surface mount resistor — colour coding or lettered markings may be used for component identification (but may not be...). Note that this is illustrated rather larger than full size — actual size is around 2 mm wide!

Thermistors·H[OLYTPZ[VYPZHYLZPZ[VY^OVZL]HS\LJOHUNLZHJJVYKPUN [VOLH[;OLZLHYL\ZLM\SPUHWWSPJH[PVUZ[OH[KL[LJ[OLH[Z\JOHZ LSLJ[YVUPJ[OLYTVTL[LYZ;OL`]HY`PUZPaLHUKZOHWLHJJVYKPUN[V JVUZ[Y\J[PVU[OL`HYLHJ[\HSS`THKL\ZPUNZLTPJVUK\J[VYTH[LYPHSZHUK [`WPJHSKL]PJLZHYLZOV^UPU-PN\YL;OLZ`TIVSMVYH[OLYTPZ[VYPZ ZOV^UPU-PN\YL

FIGURE 3.13 Typical thermistors.

FIGURE 3.14 Thermistor circuit symbol. 37

Starting Electronics Construction 3PNO[KLWLUKLU[YLZPZ[VY·SPRL[OL[OLYTPZ[VY[OLSPNO[KLWLUKLU[YLZPZ[VY VY3+9PZHYLZPZ[VYTHKLMYVTZLTPJVUK\J[P]LTH[LYPHSZ[`WPJHSS` JHKTP\TZ\SWOPKL0UZ[LHKVMP[ZYLZPZ[HUJL]HY`PUN^P[OOLH[OV^L]LY [OLSPNO[KLWLUKLU[YLZPZ[VY»ZYLZPZ[HUJL]HYPLZ^P[OHWWSPLKSPNO[-PN\YL ZOV^ZH[`WPJHSSPNO[KLWLUKLU[YLZPZ[VY·HKL]PJLRUV^UHZ[OL 697;OLJPYJ\P[Z`TIVSMVYHSPNO[KLWLUKLU[YLZPZ[VYPZZOV^UPU -PN\YL

FIGURE 3.15 The ORP 12 light dependent resistor.

FIGURE 3.16 Circuit symbol of a light dependent resistor.

*HWHJP[VYZ ;OLZLJVUKTVZ[JVTTVUJVTWVULU[\ZLKPULSLJ[YVUPJKL]PJLZPZ WYVIHIS`[OLJHWHJP[VY;OLIHZPJJVUZ[Y\J[PVUVMHU`JHWHJP[VYPZVM [^VTL[HS[OLYLMVYLJVUK\J[PUNWSH[LZZLWHYH[LKI`HUPUZ\SH[PUNSH`LY ^OPJOPZJHSSLK[OLdielectric;OLZPaLVM[OLTL[HSWSH[LZ[VNL[OLY^P[O [OL[`WLHUK[OPJRULZZVM[OLKPLSLJ[YPJKLÄULZ[OLJHWHJP[HUJLVM[OL JVTWVULU[*HWHJP[HUJLPZTLHZ\YLKPU\UP[ZVMfaradsUHTLKHM[LY [OLZJPLU[PZ[-HYHKH`HUKNP]LU[OLHIIYL]PH[PVU-/V^L]LY[OLMHYHK PZHUL_[YLTLS`SHYNL\UP[HUKJHWHJP[VYZ\ZLKPUTVKLYULSLJ[YVUPJ 38

Components JPYJ\P[ZHYLVUS`TPU\[LMYHJ[PVUZTPSSPVU[OZ[OV\ZHUKTPSSPVU[OZHUK TPSSPVUTPSSPVU[OZVMHMHYHK6ULTPSSPVU[OVMHMHYHKPZRUV^UHZH TPJYVMHYHKNP]LU[OLHIIYL]PH[PVU›-·›PZ[OL.YLLRSL[[LYT\^OPJO PZVM[LUKPMÄJ\S[[VWYVK\JLVUZVTLJVTW\[LYZ`Z[LTZZV[OLSL[[LY \PZVJJHZPVUHSS`\ZLKPUZ[LHKVUL[OV\ZHUKTPSSPVU[OVMHMHYHKPZH UHUVMHYHKU-HUKVULTPSSPVUTPSSPVU[OPZHWPJVMHYHKW- 0[»Z\ZLM\S[VILHISL[VZ^P[JOIL[^LLU[OL[OYLLTHPUZPaLZVM JHWHJP[HUJL\UP[ZHZMVYL_HTWSLVUL[OV\ZHUKWPJVMHYHKPZ[OLZHTL HZVULUHUVMHYHKHUKVUL[OV\ZHUKUHUVMHYHKZPZVULTPJYVMHYHK ;HISLZOV^Z[OLYLSH[PVUZOPWZIL[^LLU[OL[OYLLJVTTVU\UP[Z @V\YLHSS`ULLK[VILHISL[VZ^P[JOMYVTVUL[V[OLV[OLYLHZPS`ZVP[»Z ^VY[ONL[[PUN[VNYPWZ^P[OP[MHPYS`LHYS`VUPU`V\YLSLJ[YVUPJZJHYLLY -VY[\UH[LS``V\»SSNL[WSLU[`VMWYHJ[PJL[OLTVTLU[`V\Z[HY[[VOHUKSL JHWHJP[VYZ¯

;HISL 9LSH[PVUZOPWZIL[^LLU[OL[OYLLTHPUJHWHJP[HUJL\UP[ZPU TVKLYULSLJ[YVUPJZ 



TPJYVMHYHK›- UHUVMHYHKU- WPJVMHYHKW-

TPJYVMHYHK›- UHUVMHYHKU- WPJVMHYHKW-

  

  

  

,SLJ[YVS`[PJ]ZUVULSLJ[YVS`[PJ ;OLYLHYL[^VTHPUJH[LNVYPLZVMJHWHJP[VY·electrolyticHUKnonelectrolytic>OPSL[OPZZV\UKZ[YLTLUKV\ZS`JVTWSPJH[LKHUK^VYY`PUN HSSP[HJ[\HSS`TLHUZPUWYHJ[PJLPZ[OH[LSLJ[YVS`[PJJHWHJP[VYZHYL WVSHYPaLKHUKT\Z[ILPUZLY[LKPU[VHJPYJ\P[[OLYPNO[^H`YV\UK;OL` ^PSSILTHYRLK^P[OHWVZP[P]LHUKHULNH[P]L[LYTPUHSHUKT\Z[IL PUZLY[LKZV[OH[[OLWVZP[P]L[LYTPUHSPZH[HWVZP[P]LWV[LU[PHS^P[O YLZWLJ[[V[OLULNH[P]L[LYTPUHS5V[L[OH[ULP[OLY[OLWVZP[P]LUVY[OL ULNH[P]L[LYTPUHSULLK[VILH[HUHJ[\HSWVZP[P]LVYULNH[P]L]VS[HNL YLZWLJ[P]LS`·[OL`Q\Z[OH]L[VILmoreWVZP[P]LVYmoreULNH[P]L[OHU 39

Starting Electronics Construction [OLV[OLYYLZWLJ[P]L[LYTPUHS0M[OL`HYLPUZLY[LK[OL^YVUN^H`YV\UK [OLPUZ\SH[PUNSH`LYMVYTPUN[OLKPLSLJ[YPJJHUILKHTHNLKOLUJL^VU»[ ^VYRJVYYLJ[S`HUK[OLJHWHJP[VYTH`L]LUILJVTLHZOVY[JPYJ\P[ OLUJLJH\ZPUNWVZZPISLKHTHNL[V[OLJPYJ\P[PU^OPJOP[PZPUZ[HSSLK 5VULSLJ[YVS`[PJJHWHJP[VYZJHUILPUZLY[LKPU[VJPYJ\P[LP[OLY^H`YV\UK -PN\YLZOV^ZZVTL]HYPH[PVUZVMLSLJ[YVS`[PJJHWHJP[VYZ

FIGURE 3.17 Electrolytic capacitors.

,SLJ[YVS`[PJJHWHJP[VYZHYLHS^H`ZTHYRLKPUZVTL^H`·\Z\HSS`^P[OH Z`TIVS[VPUKPJH[L[OLWVZP[P]LJVTWVULU[SLHK:VTL[PTLZOV^L]LY WVZP[P]LPZTHYRLK^P[OHYPKNLKVYYPUNLKLUKVU[OLJVTWVULU[IVK` (_PHS]ZYHKPHS (UV[OLY^H`PU^OPJOJHWHJP[VYZHYLJH[LNVYPaLKOHZ[VKV^P[O[OLPY ZOHWLHUKPZZOV^UPU-PN\YL*HWHJP[VYZ^OPJOHYLSVUNHUK OH]L[OLPYJVTWVULU[SLHKZL_P[PUNMYVTVWWVZP[LLUKZVM[OLIVK`HYL RUV^UHZaxial-leadedJHWHJP[VYZ*HWHJP[VYZ^OLYLIV[OJVTWVULU[ SLHKZL_P[MYVTVULLUKVM[OLJHWHJP[VYIVK`HYLRUV^UHZradial-leaded JHWHJP[VYZ

5VULSLJ[YVS`[PJJHWHJP[VYZ ;OLYLHYLZL]LYHSJH[LNVYPLZVMUVULSLJ[YVS`[PJJHWHJP[VYPSS\Z[YH[LK PU-PN\YL4VZ[VM[OLTHYLRUV^UZPTWS`I`[OLZ\IZ[HUJL [OH[PZ\ZLK[VTHRL\W[OLPYKPLSLJ[YPJZ*VTTVUJHWHJP[VYZ HYLpolycarbonatepolyesterpolystyreneceramicmicaHUK polypropylene 40

Components

FIGURE 3.18 A variety of non-electrolytic capacitors. 9LHKLYZ^OVOH]LILLUWH`PUNH[[LU[PVUTPNO[IL^VUKLYPUN^O`P[»Z ULJLZZHY`[V\ZLLSLJ[YVS`[PJJHWHJP[VYZH[HSSPM[OL`»YLthatH^R^HYK [V\ZL>LSSPU[OLVY`P[KVLZU»[TH[[LY^OPJOJH[LNVY`VMJHWHJP[VY LSLJ[YVS`[PJUVULSLJ[YVS`[PJVY^OPJO[`WLVMKPLSLJ[YPJPZ\ZLKPUHU` NP]LUJPYJ\P[·HU-WVS`JHYIVUH[LJHWHJP[VYOHZL_HJ[S`[OLZHTL JHWHJP[HUJLHZHU-JLYHTPJJHWHJP[VYZVPUKLLKTH`[LJOUPJHSS` YLWSHJLP[/V^L]LY[OLTH[LYPHS\ZLKHZHJHWHJP[VY»ZKPLSLJ[YPJOHZ HULMMLJ[VU[OLJHWHJP[VY»ZIVK`ZPaLZOHWLHUKJVTWVULU[SLHKV\[ ZVHJHWHJP[VYVMVULKPLSLJ[YPJZPTWS`TH`UV[Ä[PU[V[OLZWHJLPUH WYPU[LKJPYJ\P[IVHYKHSSVJH[LK[VHJHWHJP[VYVMHUV[OLYKPLSLJ[YPJ(SZV PUHSSI\[HML^JHZLZP[^V\SKZPTWS`UV[ILWVZZPISL[VWYVK\JLHSHYNL ]HS\LJHWHJP[VYMYVTHUVULSLJ[YVS`[PJKPLSLJ[YPJ^P[OV\[[OLYLZ\S[HU[ JHWHJP[VYILPUNO\NL (UV[OLY[OPUN[VILHYPUTPUKPZ[OH[[OLKPLSLJ[YPJ\ZLKVMIV[O LSLJ[YVS`[PJHUKUVULSLJ[YVS`[PJJHWHJP[VYZJHUOH]LHZPNUPÄJHU[LMMLJ[ VU[OLJVTWVULU[WYPJL-VYL_HTWSLmicaJHWHJP[VYZZVTL[PTLZHSZV RUV^UHZZPS]LYLKTPJHHYLT\JOTVYLL_WLUZP]L[VWYVK\JL[OHUZH` WVS`JHYIVUH[LJHWHJP[VYZ -PUHSS`[OLKPLSLJ[YPJOHZHULMMLJ[VU[OLTH_PT\T]VS[HNLH JHWHJP[VYTH`IL\ZLKH[*HWHJP[VYZHYLYH[LKHSVUN^P[O[OLPYHJ[\HS JHWHJP[HUJL^P[OH^VYRPUN]VS[HNL·^OPJOMHPYS`VI]PV\ZS`0OVWL ZOV\SKUV[ILL_JLLKLK0[PZ\W[V[OLJPYJ\P[KLZPNULY[VZWLJPM`^OH[ [OLHJ[\HS^VYRPUN]VS[HNLVM[OLJHWHJP[VYPZ0[PZ\W[V[OLJVUZ[Y\J[VY VM[OLJPYJ\P[[VLUZ\YL[OH[JHWHJP[VYZVMH[SLHZ[[OPZ^VYRPUN]VS[HNLHYL \ZLK 41

Starting Electronics Construction Variable capacitors 3PRLYLZPZ[VYZHUK[OLPY]HYPHISLJV\U[LYWHY[ZWV[LU[PVTL[LYZJHWHJP[VYZ HYLH]HPSHISLPU]HYPHISLMVYTZOP[L @LSSV^ )SHJR .YLLU )S\L

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;HU[HS\T

       

7VS`JHYIVUH[L Polyester

  

     

     

Capacitor U\TILYSL[[LYJVKLZ (WHY[MYVTJVSV\YJVKPUNJHWHJP[VYZJHUHSZVILTHYRLK^P[OWYPU[LK SL[[LYZHUKU\TILYZ6M[LU[OLZLHYLMHPYS`ZLSML_WSHUH[VY`·HJHWHJP[VY THYRLK^P[O[OL[LYTWPZVI]PV\ZS`NVPUN[VILHUW-KL]PJL /V^L]LY[OLYLHYLZVTLUV[ZVVI]PV\Z]HYPH[PVUZ-VYL_HTWSLH W-JHWHJP[VYPZZVTL[PTLZTHYRLKU·^OPJOTLHUZ[OH[P[PZ U-^OPJOVMJV\YZLPZ[OLZHTLHZW-:VTL[PTLZHJHWHJP[VY TH`ILTHYRLK^P[OQ\Z[[OYLLU\TILYZ·ZH`0UZ\JOHJHZL[OL ÄYZ[[^VKPNP[ZPUKPJH[L[OLÄYZ[HUKZLJVUKKPNP[ZVM[OL]HS\L^OPSL [OL[OPYKKPNP[PUKPJH[LZ[OLT\S[PWSPLYPLU\TILYVMaLYVLZ[VHKKH[ [OLLUK:V[OLL_HTWSLVM[OLJHWHJP[VYWYPU[LK^P[O[OLU\TILY ^V\SKOH]LH]HS\LVMW-^OPJOPZU- ;VSLYHUJLZVMJHWHJP[VYZHYL\Z\HSS`UV[]LY`[PNO[6M[LU PZHU HJJLW[HISLÄN\YLHS[OV\NOZVTLJHWHJP[VYZ^P[O[VSLYHUJLZVM HYL H]HPSHISL6JJHZPVUHSS`[VSLYHUJLZHYLTHYRLKVUHJHWHJP[VY»ZIVK` ^P[OHSL[[LYZ\JOHZ1^OPJOTLHUZ VY2 ZVTL^OLYL HSVUNZPKL[OL]HS\LPUU\TILYZ

:LTPJVUK\J[VYZ ;OLYLHYLTHU`[`WLZVMJVTWVULU[^OPJOHYLNYV\WLK[VNL[OLYHUK RUV^UHZZLTPJVUK\J[VYZ>L»SS[HRLHSVVRH[ZVTLVM[OLTUV^ I\[P[»ZPTWVY[HU[[VYLTLTILY[OH[[OLJH[LNVY`PZO\NLHUK[OLYLHYL THU`TVYLZLTPJVUK\J[VYZ[OHU^LJHUWVZZPIS`OVWL[VJV]LYOLYL /V^L]LY[OLYLHYLZVTL[OH[HYLQ\Z[soPTWVY[HU[[OH[^LJHUUV[HMMVYK [VPNUVYL[OLT

44

Components +PVKLZ +PVKLZHYL[OLÄYZ[PTWVY[HU[JVTWVULU[PU[OLJH[LNVY`RUV^UHZ ZLTPJVUK\J[VYZ0UKLLK[OL`HYL[OLZPTWSLZ[ZLTPJVUK\J[VYKL]PJL ;OL`NL[[OLPYUHTLMYVT[OLIHZPJMHJ[[OH[[OL`OH]L[^VLSLJ[YVKLZ KP·VKLNLKKP[&6ULVM[OLZLLSLJ[YVKLZPZRUV^UHZ[OLanode![OL V[OLYPZ[OLcathode-PN\YLZOV^Z[OLZ`TIVSMVYHKPVKL^OLYL [OLHUVKLHUKJH[OVKLHYLTHYRLK-PN\YLZOV^ZZVTL[`WPJHS KPVKLIVK`ZOHWLZ·PU^OPJOJH[OVKLZHYLPKLU[PÄLKHZ[OLIHUKLKVY ZOHWLKLUKZ ;OLUHTLYLJ[PÄLYPZVM[LU\ZLKPUWSHJLVMdiode:[YPJ[S`ZWLHRPUNH YLJ[PÄLYPZHKPVKL[OH[PZ\ZLKPUOPNOWV^LYHWWSPJH[PVUZZH`HTHPUZ WV^LYZ\WWS`[OH[JVU]LY[ZTHPUZHS[LYUH[PUNJ\YYLU[[VHSV^]VS[HNL KPYLJ[J\YYLU[·[OLJVU]LYZPVUMYVTHS[LYUH[PUNJ\YYLU[[VKPYLJ[ J\YYLU[PZJHSSLKYLJ[PÄJH[PVU/V^L]LY[OL[^VUHTLZHYLV[OLY^PZL Z`UVU`TV\Z

FIGURE 3.22 The circuit symbol for an ordinary diode.

FIGURE 3.23 Some typical diode body shapes. -PN\YLHZOV^ZHKPVKL^OVZLHUVKLPZWVZP[P]L^P[OYLZWLJ[[VP[Z JH[OVKL(S[OV\NO^L»]LZOV^U[OLHUVKLHZWVZP[P]L^P[OHZ`TIVS HUK[OLJH[OVKLHZULNH[P]L^P[OH¶Z`TIVS[OL`KVU»[ULJLZZHYPS` OH]L[VILWVZP[P]LHUKULNH[P]L;OLJH[OVKLJV\SKMVYL_HTWSLILH[H ]VS[HNLVM=PM[OLHUVKL^HZH[HNYLH[LYWVZP[P]L]VS[HNLVMZH` =(SS[OH[ULLKZ[VVJJ\YPZ[OH[[OLHUVKLPZWVZP[P]L^P[OYLZWLJ[ [V[OLJH[OVKL 45

Starting Electronics Construction OLUHKPVKLPZYL]LYZLIPHZLKPLP[ZJH[OVKLPZWVZP[P]L^P[OYLZWLJ[ [V[OLHUVKLUVJ\YYLU[ÅV^ZHZZOV^UPU-PN\YLI6I]PV\ZS` ZVTL[OPUNOHWWLUZ^P[OPU[OLKPVKL^OPJO^LJHU»[ZLLKLWLUKPUNVU [OLWVSHYP[`VM[OLHWWSPLK]VS[HNL[VKLÄUL^OL[OLYJ\YYLU[JHUÅV^ VYUV[1\Z[L_HJ[S`^OH[[OPZZVTL[OPUNPZPZU»[ULJLZZHY`[V\UKLYZ[HUK OLYL >LULLKU»[RUV^HU`TVYLHIV\[P[OLYLILJH\ZL^L»YLVUS`JVUJLYULK ^P[O[OLWYHJ[PJHSHZWLJ[ZH[[OLTVTLU["HUKHSS^LULLK[VYLTLTILY PZ[OH[HMVY^HYKIPHZLKKPVKLJVUK\J[ZHSSV^PUNJ\YYLU[[VÅV^^OPSLH YL]LYZLIPHZLKKPVKLKVLZU»[>OPJO^H``V\ZOV\SKPUZLY[HKPVKLPU[V HWHY[PJ\SHYJPYJ\P[KLWLUKZ[V[HSS`VU[OLKPVKLHUK[OLJPYJ\P[(SS`V\ OH]L[VKVPZPUZLY[P[[OLZWLJPÄLK^H`YV\UK

FIGURE 3.24 Simple circuits for: (a) forward biased and (b) reverse biased diodes. OPSL[OLZLMV\YZ^P[JO[`WLZZOV^UPU-PN\YL H[VKHYL VI]PV\ZS`UV[[OLVUS`Z^P[JO[`WLZ[OL`MVYTI`MHY[OLTVZ[JVTTVU [`WLZ`V\^PSSJVTLHJYVZZPULSLJ[YVUPJZ

¬

FYI

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The switch types in Figure 3.49 are only the most common four. It’s possible to get switches with many more poles, and many more throw mechanisms, for specific purposes.

FIGURE 3.49 Four main switch types: (a) single-pole, single-throw (SPST); (b) single-pole, double-throw (SPDT); (c) double-pole, single-throw (DPST); (d) double-pole-double-throw (DPDT). 62

Components

Take Note The contacts of switches of all types have only limited voltage and current ratings, and you must make sure that you do not exceed these contact ratings when using switches. If the circuit a switch is used in is battery-powered, it is unlikely that contact ratings will be exceeded, but if the switch is to be used to switch mains power then contact ratings should be carefully checked before use.

Mechanics ;OLTVZ[JVTTVUTLJOHUPJZ\ZLKPUZ^P[JOLZPULSLJ[YVUPJZHYL!ZSPKL [VNNSLW\ZOHUKYV[HY`,_HTWSLZVMHSSHYLZOV^UPU-PN\YL,HJO [`WLTH`OH]LHU\TILYVMKL]PHU[ZHUKPZ\Z\HSS`H]HPSHISLPUHYHUNL VMZPaLZ[VV:^P[JOLZTH`HSZVILPUJVYWVYH[LK^P[OV[OLYM\UJ[PVUZ Z\JOHZHWV[LU[PVTL[LYZLLWHNLVYPUKPJH[VYZZLLWHNL (SZVLHJOTLJOHUPZT[`WLJHUOH]LTPUVY]HYPHU[ZPUVWLYH[PVU·MVY L_HTWSLW\ZOZ^P[JOLZJHUILW\ZO[VIYLHRVYW\ZO[VTHRLHUK Z^P[JOLKHJ[PVUVYmomentaryHJ[PVU·ZVP[»ZUV[OHYK[VZLL[OH[[OLYL HYLTHU`O\UKYLKZVMZ^P[JO[`WLZ[VJOVVZLMYVT

FIGURE 3.50 A range of switches, according to mechanism types, from left to right: slide, toggle, push, rotary.

63

Starting Electronics Construction Relays 9LSH`ZHYLQ\Z[Z^P[JOLZ[OH[HYLVWLYH[LKLSLJ[YVTLJOHUPJHSS`;O\Z ^OLYLHUVYKPUHY`Z^P[JOTH`ILVWLYH[LKI``V\W\ZOPUNHI\[[VU VYÅPJRPUNH[VNNSLHYLSH`PZVWLYH[LKI`TLYLS`HWWS`PUNHULSLJ[YPJ J\YYLU[[VHULSLJ[YVTHNUL[PJJVPS;OPZJ\YYLU[JYLH[LZHTHNUL[PJÄLSK [OH[ÅPJRZ[OLYLSH`»ZPU[LYUHSZ^P[JOTLJOHUPZT;OLHK]HU[HNLPZWYL[[` VI]PV\Z·HULSLJ[YVUPJJPYJ\P[JHUVWLYH[L[OLYLSH`H\[VTH[PJHSS` ^P[OV\[O\THUPU[LY]LU[PVU(JPYJ\P[Z`TIVSMVYHZPUNSLWVSLKV\ISL [OYV^YLSH`PZZOV^UPU-PN\YL

FIGURE 3.51

Circuit symbol of a single-pole, double-throw relay.

.LULYHSS`YLSH`ZHYLTV\U[LKVUHULSLJ[YVUPJJPYJ\P[»ZWYPU[LKJPYJ\P[ IVHYKZVHYLX\P[LZTHSS:L]LYHS]HYPHU[ZL_PZ[HUK\Z\HSS`P[PZZPTWS` HTH[[LYVMJOVVZPUN[OLYLSH`[VZ\P[PU[LYTZVMU\TILYVMZ^P[JOWVSLZ HUK[OYV^ZJVU[HJ[YH[PUNZJVPSVWLYH[PUN]VS[HNLHUKJ\YYLU[HUKZPaL (UL_HTWSLVMHYLSH`·HTPUPH[\YLWYPU[LKJPYJ\P[IVHYKTV\U[PUN YLSH`·PZZOV^UPU-PN\YL

FIGURE 3.52 A miniature, printed circuit board mounting relay. 64

Components 3V\KZWLHRLYZHUKV[OLYZV\UKV\[W\[KL]PJLZ 0UHUH\KPVJPYJ\P[P[»ZVM[LUYLX\PYLK[OH[^LJHUOLHY[OLH\KPVZPNUHS ;OL\Z\HS^H`[VKV[OPZPZLP[OLY^P[OHUPUI\PS[SV\KZWLHRLYVY\ZPUN LHYWPLJLZ 3V\KZWLHRLYZI\PS[PU[VLSLJ[YVUPJJPYJ\P[ZHYL\Z\HSS`MHZ[LULK[V[OL OV\ZPUNVM[OLJPYJ\P[HUKVUJLPUWSHJLHYLWYL[[`YVI\Z[/V^L]LY [OL`KVYLX\PYLZVTLWYLJH\[PVUZPUOHUKSPUN;OL`^VYRILJH\ZLH JVULVMZVTLTH[LYPHSPZ]PIYH[LKLSLJ[YVTHNUL[PJHSS`K\L[VHULSLJ[YPJ J\YYLU[WHZZPUN[OYV\NOHUH[[HJOLKJVPSVM^PYL[OH[PZZP[\H[LKPUH THNUL[PJÄLSK7YVISLTZJHUHYPZLILJH\ZL[OLJVULPZLHZPS`KHTHNLK VYZWSP[PMTPZOHUKSLK(JV\WSLVML_HTWSLZVMSV\KZWLHRLYZMVY\ZL^P[O LSLJ[YVUPJJPYJ\P[ZHYLZOV^UPU-PN\YL

FIGURE 3.53 Loudspeakers typically used in electronic circuits. :VTL[PTLZ^OPSLH\KPVZV\UKPZUV[V\[W\[[LKMYVTHJPYJ\P[ZVTLMVYT VMUVPZLPZ·ZH`HI\aaVYILLW;OLYLHYLZL]LYHSMVYTZVMKL]PJLZMVY KVPUN[OPZI\[VUS`[^VTHPUNYV\WZ!I\aaLYZHUKZV\UKLYZ )\aaLYZHYLNLULYHSS`LSLJ[YVTLJOHUPJHSVYWPLaVLSLJ[YPJZV\UKZV\YJLZ ^OPJO^OLUH]VS[HNLNLULYHSS`VMKPYLJ[J\YYLU[PZHWWSPLKHJYVZZ[OLPY [LYTPUHSZ]PIYH[LH[HÄ_LKMYLX\LUJ`JH\ZPUNHZV\UK;OL`JVTLPU ]HYPV\ZZOHWLZHUKZPaLZHUKHTWSP[\KLSL]LSZZVTLVM^OPJOHYLZOV^U PU-PN\YL;OLJPYJ\P[MLLKPUN[OLI\aaLYTLYLS`ULLKZ[VZ^P[JOH J\YYLU[[V[OLI\aaLY[VTHRLP[^VYR :V\UKLYZHYLTVYLSPRLSV\KZWLHRLYZPUVWLYH[PVUZVTLHYLZOV^UPU -PN\YLHUKYLX\PYLZVTLMVYTVMHS[LYUH[PUNJ\YYLU[ZPNUHSOPSLZ\JOTL[OVKZZLY]LK[OLPY W\YWVZLPU[OLPYKH`UVVULJHUKV\I[[OH[WYPU[LKJPYJ\P[IVHYKZHYL PUÄUP[LS`IL[[LY

Copper-clad printed circuit board :V^OH[L_HJ[S`PZHWYPU[LKJPYJ\P[IVHYK^OH[»ZP[THKLVMOV^»ZP[ THKLHUKOV^KV^LZL[HIV\[NL[[PUNP[& >LSS[OLWOV[VNYHWOPU-PN\YLZOV^ZHZTHSSWPLJLVMWYPU[LKJPYJ\P[ IVHYKKPYLJ[S`HZP[^V\SKILVI[HPULKMYVTHWYPU[LKJPYJ\P[IVHYK THU\MHJ[\YLYVYHZ`V\TPNO[I\`MYVTHULSLJ[YVUPJZJVTWVULU[ZZOVW ;OPZZTHSSWPLJL^V\SKOH]LILLUJ\[MYVTHT\JOSHYNLYZOLL[[`WPJHSS` HML^TL[YLZZX\HYL0UP[ZYH^Z[H[LSPRL[OPZ[OLWYPU[LKJPYJ\P[IVHYKPZ 74

Printed circuit boards

FIGURE 4.2 Raw printed circuit board, comprising a thin layer of copper on a insulating material baseboard. JHSSLKJVWWLYJSHKIVHYKHUKP[JVTWYPZLZH[OPUIHZLIVHYKHIV\[ TTVMPUZ\SH[PUNTH[LYPHSZ\JOHZYLZPUIVUKLKWHWLYVYTVYLSPRLS` ÄIYLNSHZZ^P[OHUL]LU[OPUULYSH`LYVMJVWWLYHIV\[TTVUVUL Z\YMHJLVYIV[OPMP[»ZKV\ISLZPKLKJVWWLYJSHKIVHYK-PN\YLZOV^Z HULUSHYNLKJYVZZZLJ[PVUVMH[`WPJHSWPLJLVMJVWWLYJSHKIVHYK

FIGURE 4.3 Enlarged cross-section of copper-clad printed circuit board ¬ FYI

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Apart from basic copper-clad printed circuit boards like this, industrial manufacturing often makes uses of double-sided copper-clad printed circuit boards (in which a circuit is made up from copper connections on both sides of the board) and multi-layered printed circuit boards (which comprise several internal layers of copper connections as well as those on one or both surface sides of the board) — typically these would be used in only the most complex of circuits, where space is at a premium!

75

Starting Electronics Construction ;OPZJVWWLYJSHKIVHYKT\Z[UV^IL[\YULKPU[VH\ZHISLWYPU[LK JPYJ\P[IVHYKZVZVTL^H`T\Z[ILMV\UK[VYLTV]LL_JLZZHYLHZVM JVWWLYSLH]PUNILOPUKVUS`[OVZLHYLHZ^OPJO^LULLK[VJVUULJ[[OL JVTWVULU[Z[V;OLHYLHZSLM[ILOPUKMVYT^OH[»ZJHSSLK[OLJVWWLY[YHJR VY[OLJVWWLYMVPS-PN\YLZOV^ZZ\JOHWYPU[LKJPYJ\P[IVHYK^OLYL [OLJVWWLY[YHJRVYMVPSPZJSLHYS`]PZPISL

FIGURE 4.4 Once the excess copper is removed from copper-clad board, the copper track or foil remains. 6UJLHWYPU[LKJPYJ\P[IVHYKOHZILLUJYLH[LKJVTWSL[L^P[OHJVWWLY [YHJRP[PZ[OLUHYLSH[P]LS`ZPTWSL[HZR[VKYPSS[OLOVSLZPU[OLWYPU[LK JPYJ\P[IVHYKMVY[OLJVTWVULU[SLHKZ[VÄ[[OYV\NOHUK[OLUZVSKLY [OLTPU )\[^LZOV\SKU»[NV[VVMHY[VVMHZ[>LZOV\SKYLHSS`Z[VWHUK[OPURMVY HTPU\[LHIV\[^OH[»ZQ\Z[ILLUZHPK:VTLOV^HWPLJLVMJVWWLYJSHK IVHYK^OPJOJVUZPZ[ZVMH[OPUSH`LYVMJVWWLYZ[\JRVU[V[OLZ\YMHJL VMH[OPUPUZ\SH[PUNIVHYKT\Z[OH]LHYLHZVMJVWWLYYLTV]LKSLH]PUN ILOPUKHJVWWLYMVPS^OPJOMVSSV^Z[OLMVPSWH[[LYUYLX\PYLKVU[OL WYPU[LKJPYJ\P[IVHYKMVY[OLWYVQLJ[1\Z[L_HJ[S`OV^KV^LYLTV]L[OL JVWWLY& +VU»[^VYY`[OLHUZ^LY»ZUV[X\P[LHZKPMÄJ\S[HZ`V\TPNO[PTHNPUL ·^LZPTWS`KPZZVS]LP[H^H`\ZPUNHUHJPK[`WLL[JOHU[ 76

Printed circuit boards )\[KVLZU»[[OLL[JOHU[KPZZVS]LH^H`[OLJVWWLYMVPS[VV&>LSSUV ·ILJH\ZLÄYZ[^LOH]L[VJVH[[OLHYLHZVMJVWWLY[OH[HYL[VTHRL\W [OLJVWWLYMVPS^P[OZVTL[OPUN^OPJO^PSSYLZPZ[[OLL[JOHU[WYL]LU[PUN [OLJVWWLY\UKLYULH[OMYVTILPUNKPZZVS]LK-PN\YLZOV^Z[OLPKLH

FIGURE 4.5 Coating the copper surface with an etch-resistant material means that the copper under the material is protected from attack from etchant. (M[LYL[JOPUN-PN\YL[OL\U^HU[LKJVWWLYOHZILLUKPZZVS]LKI\[ [OLJVWWLYMVPS\UKLY[OLL[JOYLZPZ[YLTHPUZ

FIGURE 4.6 Once the board of Figure 4.5 has been etched, only the copper underneath the etchresistant material remains. (M[LYYLTV]HSVM[OLL[JOYLZPZ[[OLWYPU[LKJPYJ\P[IVHYKPZYLHK`MVY KYPSSPUN-PN\YLJVTWVULU[PUZLY[PVU-PN\YLZVSKLYPUN-PN\YL  HUKÄUHSS`JVTWVULU[SLHK[YPTTPUN-PN\YL

77

Starting Electronics Construction

FIGURE 4.7 Holes are drilled through the board at relevant points, after the etch-resistant material has been removed.

FIGURE 4.8 Component leads are inserted through the drilled holes.

FIGURE 4.9 Component leads are soldered into position. 78

Printed circuit boards

FIGURE 4.10 Component leads are trimmed, leaving a neat soldered printed circuit board.

0UZ\TTHY`[OLZ[LWZ[VTHRPUNHWYPU[LKJPYJ\P[IVHYKHYL!

• OBTAIN VYKLZPNU[OLMVPSWH[[LYUMVY[OLJPYJ\P[ • APPLY L[JOYLZPZ[[VJVWWLYJSHKIVHYKPU[OLZOHWLVM[OL MVPSWH[[LYU

• ETCH H^H`[OL\U^HU[LKJVWWLY • REMOVE [OLL[JOYLZPZ[HUKKYPSS[OLJVTWVULU[SLHKOVSLZ • INSERT [OLJVTWVULU[SLHKZ • SOLDER [OLJVTWVULU[SLHKZ[V[OLIVHYK • TRIM [OLL_JLZZJVTWVULU[SLHKZ

3H[LYPU[OPZJOHW[LY[OLZLZ[LWZHYLKLZJYPILKPUM\SSHUK[OL]HYPV\Z TL[OVKZ[OH[`V\JHU\ZL[VJYLH[L`V\YV^UWYPU[LKJPYJ\P[IVHYKZHYL KL[HPSLK 79

Starting Electronics Construction Other boards ;OLYL»ZUVKV\I[[OH[WYPU[LKJPYJ\P[IVHYKZNP]LHT\JOIL[[LY^H`[V I\PSKJPYJ\P[ZHUKP[»Z[OL^H`YLJVTTLUKLK^OVSLOLHY[LKS`I`[OPZ IVVRHUKI`HU`VULLSZL^OVRUV^ZHU`[OPUNHIV\[IHZPJLSLJ[YVUPJZ HUK^OVZLYPV\ZS`^HU[Z[VOLSWWLVWSLSPRL`V\·[OLYLHKLY·[V\ZL [OLILZ[TL[OVKZ /V^L]LYWYPU[LKJPYJ\P[IVHYKZHYLU»[[OLonlyTL[OVKVMI\PSKPUN LSLJ[YVUPJJPYJ\P[Z:V^L»YLNVPUN[V[HRLHZOVY[IYLHRMYVTWYPU[LK JPYJ\P[IVHYKZ[VSVVRH[HJV\WSLVMV[OLYTL[OVKZ;OH[^H``V\»SSZLL [OLKPMMLYLUJLZHUKZLL^O`WYPU[LKJPYJ\P[IVHYKZHYLILZ[ Matrix board 4HKLMYVTHWSHPUIVHYKVMPUZ\SH[PUNTH[LYPHS^P[OOVSLZH[PUJO OVYPaVU[HSHUK]LY[PJHSKPZ[HUJLZTH[YP_IVHYKPZTLYLS`H^H`VM OVSKPUNJVTWVULU[ZVUHIVHYK(WSHPUWPLJLVMTH[YP_IVHYKPZZOV^U PU-PN\YL

FIGURE 4.11 A plain piece of matrix board. (Z^P[OWYPU[LKJPYJ\P[IVHYKZJVTWVULU[SLHKZHYLPUZLY[LK[OYV\NO[OL OVSLZVUTH[YP_IVHYKI\[[OLYL[OLZPTPSHYP[`LUKZ;OLYLPZUVJVWWLY VU[OL\UKLYZPKLVMHTH[YP_IVHYKHZ[OLYLPZVUHWYPU[LKJPYJ\P[IVHYK ZVHSSJVUULJ[PVUZIL[^LLUJVTWVULU[ZT\Z[ILTHKLI`LP[OLYILUKPUN JVTWVULU[SLHKZ[V[OLUL_[JVTWVULU[VYI`HKKPUNL_[YH^PYL[V KV[OLZHTL>OLYLJVTWVULU[SLHKZVY^PYLZQVPU[OLQVPU[T\Z[IL ZVSKLYLK

80

Printed circuit boards 6]LYHSSTH[YP_IVHYKPZ\ZLM\SMVYWYV[V[`WPUNHZPTWSLJPYJ\P[[VTHRL Z\YLP[^VYRZ0[JHUHSZVIL\ZLM\S^OLYL[OLJPYJ\P[PZILPUNKLZPNULK HZP[»ZI\PS[·P[»ZX\P[LLHZ`[VHKKL_[YHJVTWVULU[ZPMHJOHUNLPZ YLX\PYLKHUKP[»ZHSZVX\P[LLHZ`[VHKHW[[OLJPYJ\P[HZ`V\NV0UKLLK ^OLU\ZPUNTH[YP_IVHYK[OL^OVSLSH`V\[PZ\Z\HSS`KLZPNULKHZ`V\NV /V^L]LYP[»ZUV[[OLPKLHSJVUZ[Y\J[PVUTL[OVKMVYHÄUPZOLKLSLJ[YVUPJ JPYJ\P[HZP[PZOHYK[VYLWSPJH[LHUKPZ[YPJR`[V\ZLPM[OLJPYJ\P[PZ JVTWSL_ :[YPWIVHYK :[YPWIVHYKPZHZVY[VMJYVZZIL[^LLUTH[YP_IVHYKHUKWYPU[LKJPYJ\P[ IVHYKZVOHZHK]HU[HNLZMYVTIV[OTL[OVKZVMJVUZ[Y\J[PVU-VYH Z[HY[[OL\UKLYZPKLZOV^UPU-PN\YLOHZZ[YPWZVMJVWWLY[VTHRL JVUULJ[PVUZIL[^LLUJVTWVULU[Z(SZV[OLIVHYKPZWYLKYPSSLK^P[O OVSLZH[PUJOOVYPaVU[HSHUK]LY[PJHSKPZ[HUJLZQ\Z[HZ^P[OTH[YP_ IVHYK(ZHYLZ\S[P[»ZX\P[LLHZ`[VTHRLHZPTWSLLSLJ[YVUPJJPYJ\P[I` PUZLY[PUNJVTWVULU[ZHUKZVSKLYPUN[OLTPUWSHJL(SZVHZ[OLJVWWLY Z[YPWZHYLWYLKLÄULKHUK\USPRL[OLLHYSPLYTH[YP_IVHYKJVUZ[Y\J[PVU TL[OVKP[»ZWLYMLJ[S`WVZZPISL[VKLZPNUHSH`V\[VUWHWLYÄYZ[ZV[OH[ JPYJ\P[ZJHUILYLWSPJH[LKMHPYS`LHZPS`-VY[OPZYLHZVUZ[YPWIVHYKJPYJ\P[ SH`V\[ZHYLZVTL[PTLZNP]LUPULSLJ[YVUPJZTHNHaPULZHUKIVVRZ WHY[PJ\SHYS`MVYZPTWSLJPYJ\P[Z;OL`HYLUV[OV^L]LYPKLHS

FIGURE 4.12 A plain piece of stripboard, showing the strips of copper. Pre-drilled holes in the strips mean that component insertion is straightforward, if defined.

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Starting Electronics Construction

Hint When using stripboard it’s often the case that only a couple of holes on a copper strip are used to connect components – the rest of the copper strip is then unusable. Also, where components like dual-in-line integrated circuits are to be used, the copper strips of plain stripboard would directly connect the integrated circuit’s two rows of pins. The answer is to cut the copper strip, effectively splitting it into parts. A sharp knife such as a craft knife could be used to split the copper strip, but a purpose-made tool – the spot-face cutter – is best used. To use the spot-face cutter just position it onto a hole in a copper strip, then twist it backwards and forwards two or three times, until the copper strip has been cut away (shown in Figure 4.13).

FIGURE 4.13 Using a spot-face cutter to split a copper strip on a stripboard.

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Printed circuit boards

Making your own printed circuit boards 4HU`WLVWSL[HRLHK]HU[HNLVM[OL]HYPV\ZWYPU[LKJPYJ\P[IVHYKZLY]PJLZ [OH[LSLJ[YVUPJZTHNHaPULZVMMLY[OYV\NO^OPJO[OL`JHUW\YJOHZLYLHK` THKLWYPU[LKJPYJ\P[IVHYKZMYVT[OLTHNHaPULW\ISPZOLYJVTWSL[LHUK YLHK`[VI\PSK[OLPYWYVQLJ[ZVU[V0M`V\KVU»[MHUJ`THRPUN`V\YV^U IVHYKZ[OLZLZLY]PJLZHYLPKLHS

Hint: When electronics books and magazines give printed circuit boards for projects, they do so by printing what is called the foil patterns of the projects. It’s the foil pattern of any particular project, of course, which is the shape of the copper to be left on the printed circuit board when the excess areas are removed. When you make a project given in a book or magazine you have the foil pattern to create the printed circuit board. If you want to design and build any other circuit, you must design the foil pattern yourself.

6U[OLV[OLYOHUK`V\TH`IL[Y`PUN[VI\PSKHWYVQLJ[[HRLUMYVTH IVVRSPRL[OPZVULVY·ZPTWS`·`V\TH`SPRL[VOH]LH[Y`THRPUN `V\YV^U4HRPUN`V\YV^UWYPU[LKJPYJ\P[IVHYKZPZJLY[HPUS`TVYL YL^HYKPUN[OHUI\`PUN[OLTYLHK`THKL·I\[P[PZHSP[[SLTVYL JVTWSL_/V^L]LYP[»ZUV[OPUN[OLH]LYHNLUL^JVTLY[VLSLJ[YVUPJZ JHU»[OHUKSL"HZSVUNHZ`V\MVSSV^[OLML^ZPTWSLY\SLZ^OPJO^L»SSUV^ NP]L`V\

9PNO[MYVT[OL]LY`ILNPUUPUN·[OLMVPSWH[[LYU 3L[»ZHZZ\TL[OH[`V\OH]LHJPYJ\P[^OPJO`V\TH`OH]LKLZPNULK `V\YZLSMVYZVTLIVK`LSZLTH`OH]LKLZPNULKP[I\[`V\OH]LUVWYPU[LK JPYJ\P[IVHYKMVPSWH[[LYUMVYP[-PN\YLPZH[`WPJHSJPYJ\P[^OPJO `V\TH`YLJVNUPaLHZILPUNHT\S[P]PIYH[VYHUK^PSSKVUPJLS`MVYV\Y W\YWVZLZOLYL ([[OPZWVPU[`V\ULLKZVTLIHZPJ[VVSZ·HSSVM^OPJO`V\WYVIHIS` OH]LH[OHUK·WHWLYWSHPU[YHJPUNHUKNYHWOHWLUJPSHUKHY\IILY HUKHY\SLY@V\»SSHSZVULLKHZLSLJ[PVUVMVULVMLHJO[`WLVM[OL JVTWVULU[ZPU[OLJPYJ\P[LNVULYLZPZ[VYVULJHWHJP[VYVUL[YHUZPZ[VY VULPU[LNYH[LKJPYJ\P[L[JVY[OLPYWO`ZPJHSKPTLUZPVUZ;OPZPZILJH\ZL `V\ULLK[VRUV^OV^IPNLHJOJVTWVULU[PZZV[OH[^OLUKLZPNUPUN [OLMVPSWH[[LYU`V\RUV^^OH[KPZ[HUJL[VSLH]LIL[^LLUJVTWVULU[ SLHKOVSLZ 83

Starting Electronics Construction

FIGURE 4.14 A simple circuit which we’ll use to show how to design your own printed circuit boards. (S[OV\NO[OPZTH`ZLLTKH\U[PUNH[ÄYZ[KVU»[^VYY`ILJH\ZLPM`V\ KLZPNUTVYL[OHUQ\Z[HJV\WSLVMMVPSWH[[LYUZ`V\»SSILNPU[VYLTLTILY [OLZPaLZVMHSSI\[[OLTVZ[\U\Z\HSJVTWVULU[Z3H`L]LY`[OPUNV\[VU HKLZRVYJSLHU^VYRILUJO 5V^[OLKPMÄJ\S[IP[UV[YLHSS`!KLZPNUPUN[OLMVPSWH[[LYU>OH[`V\ OH]L[VYLTLTILYOLYLPZ[OH[[OLJVTWVULU[ZNVPU[VVULZPKLVM[OL WYPU[LKJPYJ\P[IVHYKI\[[OLJVWWLYMVPSTHRPUN[OLJVUULJ[PVUZPZVU [OLV[OLYZPKLVM[OLIVHYK )LNPUI`JOVVZPUNHJVTWVULU[MHPYS`JLU[YHS[V[OLJPYJ\P[^L»SSJOVVZL [YHUZPZ[VY;95V^KYH^P[ZHWWYV_PTH[LZOHWLHZ]PL^LKMYVTHIV]L VU[VHZOLL[VMWSHPUWHWLYHZPU-PN\YL 1\Z[HZ^L»]LKVULTHYR^OLYLP[ZJVUULJ[PVUSLHKZ^PSSLU[LY[OLWHWLY ºIVHYK»HUKSHILSP[;9PUV\YL_HTWSL(SZVPMP[»ZHU`[OPUNV[OLY[OHU HZPTWSLYLZPZ[VYVYJHWHJP[VY`V\ZOV\SKTHYR[OLSLHKZ[VVeIHUKc PMP[»ZH[YHUZPZ[VY 5V^KYH^HML^TVYLJVTWVULU[ZVU[V[OLWHWLYHSVUNZPKL[OLÄYZ[ ZPTPSHYS`THYRPUN[OLTHZ`V\NV-PN\YL+VU»[ILHMYHPK[V WVZP[PVU[OLTJSVZL[VNL[OLY"HZWHJPUNVMVUS`TTVYZVIL[^LLU JVTWVULU[ZPZUVYTHSS`PKLHS 84

Printed circuit boards

FIGURE 4.15 First steps: marking the first component onto plain paper. Also mark its leads — as it’s a transistor, the leads should be named e, b and c to show the emitter, base and collector.

FIGURE 4.16 Add further components to the layout, by marking them on the paper — they can be quite close. ([[OPZZ[HNL`V\TH`ÄUKP[OLSWM\S[VTVYLVYSLZZMVSSV^[OLNLULYHS WH[[LYUVM[OLJPYJ\P[KPHNYHT^OLUWVZP[PVUPUNJVTWVULU[ZHS[OV\NO [OPZPZI`UVTLHUZLZZLU[PHS·P[»ZWYVIHIS`Q\Z[LHZPLYMVYHUL^JVTLY [VKV

85

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FIGURE 4.17 Connections between component leads should be drawn in now. )\PSK\W[OLSH`V\[W\[[PUNPUTVYLHUKTVYLJVTWVULU[ZHUKTVYL HUKTVYLºJVUULJ[PVUZ» 9LTLTILY[OH[[OLÄUPZOLKWYPU[LKJPYJ\P[IVHYK^PSSOH]LP[ZMVPS WH[[LYUVU[OLV[OLYZPKL[VP[ZJVTWVULU[ZZV[YHJRZJHUHJ[\HSS`WHZZ \UKLYULH[OJVTWVULU[ZHZPU-PN\YL;OLYLPZHSZVUVYLHZVUH[HSS ^O`[^VVYL]LU[OYLL[YHJRZJHU»[WHZZ\UKLYULH[OHJVTWVULU[ZV SVUNHZ[OL[YHJRZKVU»[[V\JOLHJOV[OLYVY[V\JO[OLJVTWVULU[SLHK OVSLZ 0M`V\^LYL^VYYPLKHIV\[`V\YMVPSWH[[LYUILPUN\U[PK`UV^»Z`V\Y VWWVY[\UP[`[VJOHUNLHSS[OH[7SHJLHZOLL[VM[YHJPUNWHWLYV]LYHZOLL[ VMNYHWOWHWLYHUK[HWL[OL[^V[VNL[OLYHSVUN[OLLKNLZ 86

Printed circuit boards

FIGURE 4.18 As the copper will be on the other side of the board to the components, there’s nothing to stop you designing the printed circuit board so that copper tracks actually run beneath components. OLU[OLMVPSWH[[LYUPZJVTWSL[L`V\JHUWLLSVMM[OLWHWLYIHJRPUN HUKZ[PJR[OLWSHZ[PJ[V[OLJVWWLYJSHKIVHYK 5V^`V\LMMLJ[P]LS`OH]LHZ[LUJPSL_HJ[S`[OLZOHWLVM`V\YYLX\PYLK MVPSWH[[LYU;OLYL»ZUVULLK[V\ZLHÄULWHPU[IY\ZOUV^"Q\Z[WHPU[V]LY [OL^OVSLWSHZ[PJZOLL[^P[OHT\JOIYVHKLYIY\ZO(M[LY`V\»]LKVUL [OH[JHYLM\SS`WLLSVMM[OLWSHZ[PJHUK`V\»YLSLM[^P[O[OLMVPSWH[[LYUVM WHPU[LKYLZPZ[ *SL]LYLO&

0UR 7LUZHYLH]HPSHISLHZRH[`V\YSVJHSLSLJ[YVUPJZZ[VYL^OPJOHYLSVHKLK ^P[OZWLJPHSPURYLZPZ[HU[[V[OLJPYJ\P[IVHYKL[JOHU[

88

Printed circuit boards >P[O[OLZLWLUZP[PZX\P[LHULHZ`QVIZOV^UPU-PN\YL [VKYH^ [OLMVPSWH[[LYUKPYLJ[S`VU[V[OLJVWWLYJSHKIVHYK@V\^VU»[THRLH WLYMLJ[S`ULH[WYPU[LKJPYJ\P[IVHYK\ZPUN[OPZTL[OVKI\[P[KVLZHSSV^ HX\PJRHUKLHZ`YV\[L[VHZLTPHJJLW[HISLÄUPZOLKQVI-PUHSX\HSP[` OV^L]LYKLWLUKZ[V[HSS`VU`V\YHY[PZ[PJ[HSLU[VYH[SLHZ[OV^Z[LHK` `V\YOHUKPZ

FIGURE 4.19 Drawing copper foil pattern directly onto the copper surface of a copper-clad board using an etch-resistant ink pen.

Hint: In all these manual methods of applying resist it’s sometimes a bit tricky to estimate where on the copper board the component leads go, before filling in the connecting etch-resistant bits. A useful trick is to put your tracing paper copy of the foil pattern upside-down onto the copper (the pencilled connections are to go on the bottom of the board, remember), and using a sharp pointed instrument such as a scriber or a compass point, prick through the tracing paper into the copper at every component hole location. When you remove the tracing paper you will find a network of little holes, corresponding to each component lead hole. Now you can put on the resist (whichever method you choose) knowing where the positions are.

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Starting Electronics Construction Transfers 7YVIHIS`[OLILZ[TL[OVKVMWYPU[LKJPYJ\P[IVHYKTHU\MHJ[\YLMVY[OL HTH[L\YPZZOV^UPU-PN\YL^OLYL`V\JHUZLL[OH[Y\IKV^U [YHUZMLYZHYLILPUN\ZLKHZYLZPZ[MVYJVTWVULU[OVSLZ@V\JHUI\` [YHUZMLYZMVYHSSRPUKZVMZOHWLKOVSLZ[VV·MVYPU[LNYH[LKJPYJ\P[ZVY LKNLJVUULJ[VYZVYL]LUZWLJPHSS`ZOHWLKVULZMVY[YHUZPZ[VYZ

FIGURE 4.20 Rub-down transfers of all component shapes and sizes make an effective method of applying etch-resist. >OLUHSS[OLJVTWVULU[SVJH[PVUZHYLKVUL[OLJVUULJ[PVUZJHUIL THKL\ZPUNZ[YHPNO[SPULKVYJ\Y]LK[YHUZMLYZ\U[PS[OLYLZPZ[VU[OL JVWWLYOHZ[OLZHTLZOHWLHZ`V\YMVPSWH[[LYUKYH^PUN

Hint A word of caution here: be extremely careful as you do this job, because any small cracks or breaks in the transfer resist will mean that a corresponding crack or break will occur in the copper when the board is etched.

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FYI

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You don’t have to stick to just one manual method of resist application. It’s perfectly possible to combine two or more of these methods to good effect. For instance, you can use rub-down transfers to apply the component lead positions (particularly useful for integrated circuit positions) but use a resist pen, or paintbrush and paint, to make the other connections.

Hint If you make any mistakes at this stage they can be removed using the corner of a small piece of sticky tape – but once you have etched the board your mistakes are permanent.

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7OV[VNYHWOPJTL[OVK OH[»ZTVYLHZP[isHWOV[VNYHWOPJTL[OVK`V\JHUTHRLTVYL[OHU VULWYPU[LKJPYJ\P[IVHYKMYVTP[Q\Z[HZ`V\JHUNL[YLWYPU[ZVM`V\Y OVSPKH`ZUHWZ -PYZ[S``V\ULLKHM\SSZPaLKTHZ[LYJVW`VM[OLMVPSWH[[LYUVUÄST;OLYL HYL[^VTL[OVKZOLYL!^OLYL[OLTHZ[LYJVW`PZHULNH[P]LHZMYVTH JHTLYHÄST"VY^OLYLP[PZHWVZP[P]L)V[OTL[OVKZHYL\ZLKPUWYPU[LK JPYJ\P[IVHYKTHRPUNI\[[OLWVZP[P]LTL[OVKPZ[OLTVZ[WVW\SHYMVY UVV[OLYYLHZVU[OHUILJH\ZLP[»ZLHZPLY[VTHRLHWVZP[P]LTHZ[LY[OHUH ULNH[P]LVULZV^L»SSZ[PJR^P[O[OH[VUL

Hint: You can make a positive master from your foil pattern by laying a sheet of acrylic film (which you can get from drawing-office suppliers) over the tracing paper or magazine foil pattern. Now, using the rub-down transfer or dots and tape method described earlier, make up the foil pattern directly onto the acrylic film. When complete, this film is your master copy – so keep it safe!

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FYI

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If your foil pattern is taken from a magazine or book, and you have a computer with a scanner and printer, you can make your master copy a little more accurately. Simply scan in the magazine foil pattern, then print it onto some acetate film. You’ll need to check that the output size is the same as the source foil pattern and adjust as necessary. Note that some printers aren’t capable of printing onto acetate film, however. Later there is more information about using computers to aid electronics construction.

Hint If you are creating your own printed circuit board foil patterns for your own circuits, and you have a computer, then it might be worth looking at one or more of the many available programs for printed circuit layout. While these aren’t always the easiest programs to use, they can give very good results, and if you intend making several printed circuit boards over the years, they are often worth the learning curve you have to climb. See later for details.

9LZPZ[JVH[LKJVWWLYJSHKIVHYK ;OLJVWWLYJSHKJPYJ\P[IVHYK`V\ULLKUV^PZUV[Q\Z[VYKPUHY`IVHYK I\[OHZH[OPUSH`LYVMWOV[VNYHWOPJYLZPZ[ZVTL[PTLZZOVY[LULK[V photo-resistV]LY[OLJVWWLYHZPSS\Z[YH[LKPU-PN\YL^OPJO·Q\Z[ SPRLJHTLYHÄST·ULLKZ[VILL_WVZLK[VSPNO[@V\JHU»[Q\Z[L_WVZLP[ [VHU`VSKSPNO[HZ`V\KV^P[O`V\YJHTLYHÄST[OV\NO ;OLVUS`[`WLVMSPNO[^OPJO^PSSHMMLJ[[OLWOV[VYLZPZ[PZ\S[YH]PVSL[ OLUUL^L[JOHU[TH`[HRLVUS`Ä]LVY ZP_TPU\[LZ[VL[JOHWYPU[LKJPYJ\P[IVHYKWHY[PJ\SHYS`PM[OLL[JOHU[PZ OLH[LK^OLYLHZH[[OLLUKVMP[Z^VYRPUNSPMLL[JOHU[TH`[HRL[^LU[` TPU\[LZVYTVYL[VKV[OLQVI;OLU\TILYVMWYPU[LKJPYJ\P[IVHYKZH IH[JOVML[JOHU[^PSSZ\JJLZZM\SS`L[JOKLWLUKZVU[OLZPaLVM[OLWYPU[LK JPYJ\P[IVHYKHUK[OLHYLHVMJVWWLYMVPS[VILL[JOLKI\[`V\ZOV\SK YLHSPZ[PJHSS`L_WLJ[[VILHISL[VL[JO[^LU[`VYTVYLWYPU[LKJPYJ\P[ IVHYKZWLYIH[JO Hint Etching baths complete with heaters and agitators are (you guessed it!) expensive, but there’s nothing to stop an enterprising reader making one, from nothing more complicated than a plastic container, aquarium heater, and a toy motor with plastic propellor. Just make sure that nothing metal is inserted into the etchant – for obvious reasons!

([[OLV[OLYLUKVM[OLZJHSLHWSHZ[PJWOV[VNYHWOPJ[`WLKL]LSVWPUN[YH` VYZPTPSHYJHUILHKLX\H[LS`\ZLKHZHTHRLZOPM[L[JOPUNIH[O[VOVSK [OLMLYYPJJOSVYPKLK\YPUNL[JOPUNHZZOV^UPU-PN\YL)\[HZ`V\»SS OH]L[VRLLWYVJRPUN[OLIH[ONLU[S`[VHNP[H[L[OLL[JOHU[V]LY[OL WYPU[LKJPYJ\P[IVHYK[OPZTL[OVKPZMYH\NO[^P[OOHaHYKZ·P[»ZHSS[VV LHZ`[VZWSHZOZVTLVM[OLL[JOHU[

FIGURE 4.35 A makeshift etchant bath — an old ice-cream container, in which the etchant is manually agitated by rocking the tray gently. A good excuse to have some ice-cream! 102

Printed circuit boards /V^L]LY`V\JOVVZL[VKV[OPZQVIP[»Z^PZL[V^LHYVSKJSV[OLZVY V]LYHSSZHUKKV[OLQVIV\[ZPKLVYH[SLHZ[PUHU\UJHYWL[LK^VYRZOVW (SZV^LHYY\IILYNSV]LZILJH\ZLP[JHUKVZVTLWYL[[`NOHZ[S`[OPUNZ[V ÄUNLYZ·P[»SSJLY[HPUS`Z[VWHU`VUL»ZUHPSIP[PUNWYVISLTHZP[»SSSLH]LUV UHPSZH[HSS[VIP[L (M[LYL[JOPUN^HZO[OLIVHYK[OVYV\NOS`PU^H[LY[VNL[YPKVMHSS[YHJLZ VM[OLL[JOHU[(SZVTHRLZ\YL[OH[HU`L[JOPUNZVS\[PVUOHZILLULP[OLY ^HZOLKH^H`VYWYVWLYS`YL[\YULK[VP[ZSPKKLKJVU[HPULYHUKPZUV[SLM[ ^OLYLHU`VULVYL]LU`V\YJH[MVY[OH[TH[[LYJHUHJJPKLU[HSS`ZWPSSP[

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¬ FYI

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Make sure the drill bit (of whatever size you use) is perfectly sharp. A blunt drill increases drilling time, overworks your hand-held drill, and creates holes with burrs.

FIGURE 4.36 Hand-drilling a printed circuit board — rest the printed circuit board to be drilled on a block of wood. Hold the drill upright. 103

Starting Electronics Construction

Irresistible ([[OPZWVPU[[OLL[JOLKHUKKYPSSLKIVHYKZ[PSSOHZHJVH[PUNVMYLZPZ[ V]LY[OLJVWWLY[YHJRZVM[OLMVPSWH[[LYU+LWLUKPUNVU`V\YTL[OVK VMTHRPUN[OLWYPU[LKJPYJ\P[IVHYK`V\ULLK[VYLTV]L[OPZYLZPZ[WYPVY [VPUZLY[PUN[OLJVTWVULU[ZHUKZVSKLYPUN9LZPZ[YLTV]HSJHUILKVUL JOLTPJHSS`\ZPUNHZVS]LU[HZZOV^UPU-PN\YL

FIGURE 4.37 Removing etch-resist with a chemical.

Hint: Some types of photo-resist coated boards actually allow soldering direct to the resist – in fact, the resist acts as a solder flux. If the resist-coated board you buy has such a resist, there is no requirement – other than personal preference – to remove it.

:\JOZVS]LU[ZHYLUV[JOLHWZV`V\JHUJOVVZL[VYLTV]L[OLYLZPZ[ TLJOHUPJHSS`\ZPUNHUHIYHZP]LYLTV]HSISVJR-PN\YL^OPJO `V\Y\IV]LY[OLJVWWLY[YHJR[V[HRLVMM[OLYLZPZ[(UHS[LYUH[P]L[VH YLTV]HSISVJRPZ[OLÄIYLNSHZZWYVWLSSPUNWLUJPS[`WLVMHIYHZP]LJSLHULY ZOV^UPU-PN\YL  104

Printed circuit boards

FIGURE 4.38 Removing resist using an abrasive block.

FIGURE 4.39 An abrasive cleaner in the form of a fibreglass propelling pencil-type of holder can also be used to remove resist.

Component insertion (ZHY\SLVM[O\TIJVTWVULU[ZZOV\SKILPUZLY[LKHUKZVSKLYLK HJJVYKPUN[V^OL[OLY[OL`JHUILKHTHNLKI`OLH[:VWHZZP]L JVTWVULU[ZSPRLYLZPZ[VYZHUKJHWHJP[VYZZOV\SKILPUZLY[LKHUKZVSKLYLK ÄYZ[SLH]PUNHJ[P]LJVTWVULU[ZSPRLPU[LNYH[LKJPYJ\P[Z\U[PSSH[LY 105

Starting Electronics Construction 0UZLY[HUKZVSKLYVUS`HML^JVTWVULU[ZH[H[PTL·UVTVYL[OHU[OYLL VYMV\YH[VUJLMVYL_HTWSL;OPZTLHUZ[OH[JVTWVULU[ZHYLSLZZSPRLS` [VZSPWV\[VM[OLPYWVZP[PVUZILMVYLZVSKLYPZHWWSPLK 6UJLZVSKLYLKPU[VWVZP[PVUZ[YPTHSSSLHKZJSVZL[V[OLZVSKLYLKQVPU[ HZZOV^UPU-PN\YL;OPZWYL]LU[ZZOVY[JPYJ\P[ZVJJ\YYPUNIL[^LLU JVTWVULU[SLHKZ

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FYI

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The process of inserting components into a printed circuit board is often — particularly in industrial electronics manufacturing — called (for fairly obvious reasons) stuffing.

FIGURE 4.40 Trim all component leads down after soldering. Use your side-cutters for this task.

Soldering :VSKLYPUNVMJVTWVULU[ZPU[VHWYPU[LKJPYJ\P[IVHYKPZHJ[\HSS`X\P[LHU LHZ`QVII\[[OLYLisHIP[VMH[LJOUPX\L[VP[HUK`V\ULLK[VILH^HYL VM[OLWYVISLTZ[OH[PUJVYYLJ[ZVSKLYPUNJHUJYLH[L*OHW[LYJV]LYZ ZVSKLYPUNPUKLW[O

106

Soldering

5 Soldering ;OLZPUNSLTVZ[PTWVY[HU[WYVJLZZPULSLJ[YVUPJZPZZVSKLYPUN0[PZ ·X\P[LSP[LYHSS`·[OLNS\L[OH[OVSKZHSSV[OLYWYVJLZZLZ[VNL[OLY :VSKLYPUNPZ[OLTHPUTLHUZVM!

• HOLDING components in their positions on the printed circuit board

• CONNECTING components to other components in the circuit.

What is solder? :VSKLYPZHTL[HSSPJJVTWV\UK^OPJOWVZZLZZLZHYLSH[P]LS`SV^TLS[PUN WVPU[0[OHZILLU\ZLK[VQVPUTL[HSZMVY[OV\ZHUKZVM`LHYZZPUJL 9VTHU[PTLZH[SLHZ[/PZ[VYPJHSS`VULVM[OLTHPUJVUZ[P[\LU[ZVMZVSKLY OHZILLUSLHK0UKLLK[OL3H[PUUHTLVMSLHK·plumbum·NP]LZH JS\L[VVULVMZVSKLY»ZTHPU\ZLZPUWS\TIPUN[VQVPU^H[LYWPWLZHUK Ä[TLU[Z 0ULSLJ[YVUPJZZVSKLY»ZTHPU\ZLPZ[VQVPUJVTWVULU[SLHKZ[VWYPU[LK JPYJ\P[IVHYKZPU^OH[PZJHSSLKHZVSKLYLKQVPU[·VJJ\YYPUNIL[^LLU [OLJVTWVULU[SLHKHUK[OLJVWWLYMVPS[YHJRVM[OLWYPU[LKJPYJ\P[ IVHYK;OLJVWWLYMVPS[YHJRPU[\YUHSSV^Z[OH[ZVSKLYLKQVPU[[VJVUULJ[ [VV[OLYZVSKLYLKQVPU[ZHSZVMVYTLKI`V[OLYJVTWVULU[SLHKZHUK[OL JVWWLY[YHJRZV[OH[[OLJVTWSL[LLSLJ[YVUPJJPYJ\P[JHUILTHKL\W VU[OLWYPU[LKJPYJ\P[IVHYK(ZHI`WYVK\J[[OLYPNPKP[`VM[OLZVSKLYLK QVPU[ZTHRPUN\W[OLJPYJ\P[TLHUZ[OH[HSSJVTWVULU[ZHYLHSZVOLSK ZLJ\YLS`PUWSHJL 107

Starting Electronics Construction The components of solder ,_JLW[PUP[Z]LY`LHYSPLZ[\ZLZ^OLUW\YLSLHK^HZ\ZLKZVSKLYOHZ HS^H`ZILLUHTP_[\YLVM[^VVYTVYLZ\IZ[HUJLZ;OL9VTHUZHYL RUV^U[VOH]L\ZLKH[PUSLHKHSSV`[VQVPU[SLHK^H[LYWPWLZ;OPZPZ THPUS`ILJH\ZLH[PUSLHKHSSV`OHZHSV^LYTLS[PUNWVPU[[OHUSLHKP[ZLSM -VYL_HTWSLW\YLSLHKOHZHTLS[PUNWVPU[VM‡*^OLYLHZHUHSSV`VM  [PUHUK SLHKOHZHTLS[PUNWVPU[VM‡*·ZVP[»ZWVZZPISL[V QVPU[SLHKWPWLZ^P[OV\[HJ[\HSS`TLS[PUN[OLWPWLZ[OLTZLS]LZ (ZZVSKLYPUNOHZL]VS]LKHUK[OL\ZLZ[V^OPJOP[PZW\[OH]LJOHUNLK KPMMLYLU[ZVSKLYHSSV`ZOH]LILLUJYLH[LKMVYKPMMLYLU[W\YWVZLZ0UMHJ[ ZVSKLYPUNPZZ[PSSL]VS]PUN·HUKPZHJ[\HSS`PU[OLTPKKSLVMX\P[LHSHYNL L]VS\[PVUHY`Z[LW·HZ^LZOHSSZLLOLYL ;OL [PU SLHKZVSKLYHSSV`TLU[PVULKHSYLHK`PZRUV^UHZ [OLL\[LJ[PJJVTWVZP[PVUHUK[OLTLS[PUNWVPU[VM‡*[OLSV^LZ[ TLS[PUNWVPU[VMHU`[PUSLHKZVSKLYHSSV`PZJVYYLZWVUKPUNS`RUV^UHZ [OLL\[LJ[PJWVPU[0[»ZUV[OHYK[V\UKLYZ[HUK[OH[·W\YLS`PU[LYTZVM ZVSKLYPUNJVTWVULU[SLHKZ[VWYPU[LKJPYJ\P[IVHYKJVWWLYMVPS[YHJRZ PULSLJ[YVUPJZ·[OPZOHZPUL]P[HIS`ILLU]PL^LKOPZ[VYPJHSS`HZH]LY` \ZLM\SPMUV[[OLPKLHSZVSKLYHSSV` /V^L]LY[PTLZHYLJOHUNPUN-VYHZ[HY[[OL^VYSK»ZYLZV\YJLVM[PUPZ KLWSL[PUNYHWPKS`·VUS`HYV\UK`LHYZ»^VY[OH[J\YYLU[\ZHNLYH[LZ PZSLM[4VYLPTWVY[HU[[OV\NOPZ[OH[SLHKPZUV[L_HJ[S`]PL^LKHZH ZHMLZ\IZ[HUJLILPUNH[V_PJWVPZVUV\ZTL[HS-VY[OPZ[V_PJP[`YLHZVU [OL^VYSK»ZLSLJ[YVUPJZPUK\Z[Y`·HSVUN^P[OV[OLYPUK\Z[YPLZ[OH[ J\YYLU[S`\ZLSLHK·PZ\UKLYNVPUNHYL]VS\[PVUH[WYLZLU[[VJVTWSL[LS` HUKWLYTHULU[S`LSPTPUH[L[OL\ZLVMSLHKPUHU`VMP[ZWYVJLZZLZHUK JVTWVULU[Z :L]LYHSUL^ZVSKLYHSSV`ZOH]LILLUKL]LSVWLK[VYLWSHJL[OLVSK [PUSLHKHSSV`ZPU^OPJO]HYPV\ZV[OLYLSLTLU[Z·ZPS]LYIPZT\[OaPUJ JVWWLY·OH]LHSSILLU\ZLK^P[O[PU[VMVYT[OLZLUL^lead-freeZVSKLY HSSV`Z >OPSLILPUNPUOLYLU[S`ZHMLY[VIV[O\ZHUK[OLLU]PYVUTLU[[OLZL SLHKMYLLZVSKLYZHSSOH]LHTHQVYKPZHK]HU[HNLWYHJ[PJHSS`V]LY[OLVSK [PUSLHKHSSV`ZPU[OH[[OLUL^HSSV`ZOH]LOPNOLYTLS[PUNWVPU[ZHYV\UK ¶‡OPNOLY;OPZTLHUZ[OH[[OLPY]LY`\ZLTH`OHYT[OLLSLJ[YVUPJ JVTWVULU[ZILPUNZVSKLYLKHUK[OL`JHUILTVYLKPMÄJ\S[[V\ZLPU NLULYHS5L]LY[OLSLZZ[OLLSLJ[YVUPJZPUK\Z[Y`HPTZ[VILSLHKMYLLI` 

108

Soldering Effects of lead-free solder on us ;OL\ZLVMSLHKMYLLZVSKLYPZTPYYVYLKPU[OLUVUPUK\Z[YPHSHYLHZVM LSLJ[YVUPJZ[OH[YLHKLYZVM[OPZIVVR^PSSILTVZ[PU[LYLZ[LKPU·PU [OLOVTLZJOVVSJVSSLNLVY\UP]LYZP[`(SYLHK`SLHKMYLLZVSKLYZHYL H]HPSHISLVMM[OLZOLSMMVYWLYZVUHS\ZLHUK^LJHUL_WLJ[[OH[[PUSLHK ZVSKLYZ^PSSIL\UH]HPSHISL]LY`T\JOZVVULYYH[OLY[OHUHSP[[SLSH[LY

The good soldered joint >OH[L]LY[OLHJ[\HSZVSKLYHSSV`\ZLK[OLWYPUJPWSLZVMTHRPUNH ZVSKLYLKQVPU[HYL[OLZHTL:VSKLYPZHWWSPLK[VHOLH[LKHYLHVMTL[HS ^OLYL\WVU[OLZVSKLYHSSV`TLS[ZHUK^L[Z[OLTL[HS[VMVYTHQVPU[ 5V[L[OH[[OL[LYT^L[PZ\ZLKHUKPUZVTLYLZWLJ[ZTLHUZT\JO[OL ZHTLHZHSPX\PKZ\JOHZ^H[LY^L[[PUNHZ\YMHJL·P[ÅV^ZV]LY[OL Z\YMHJL >L[[PUNPUZVSKLYPUN[LYTZVU[OLV[OLYOHUK·\USPRL^H[LY^L[[PUN HZ\YMHJL·PZHWYVJLZZ^OLYL[OLZVSKLYJVTLZPU[VKPYLJ[TL[HSSPJ JVU[HJ[^P[O[OLTL[HSZ[VILZVSKLYLK[VNL[OLYPU[V[OLQVPU[([[OL Q\UJ[PVUIL[^LLU[OLZVSKLYHUK[OLTL[HSHZWLJPÄJJVTWV\UKVM IV[O[OLZVSKLYHUK[OLTL[HSPZMVYTLK·RUV^UHZHUPU[LYTL[HSSPJ JVTWV\UK·HUKVJJ\YZPUH]LY`[OPUSH`LYIL[^LLU[OL[^V :VTL[PTLZ[OLIVUKH[[OH[WVPU[PZJHSSLK[OLPU[LYTL[HSSPJIVUK 0U[LYLZ[PUNS`VUJL[OPZPU[LYTL[HSSPJJVTWV\UKIL[^LLUZVSKLYHUK TL[HSOHZILLUJYLH[LKP[JHUUV[ILYLTV]LK·`V\JHUUV[YLTV]L ZVSKLYMYVTTL[HSVUJLP[OHZILLU^L[[LK -PN\YLZOV^ZHJYVZZZLJ[PVUVMHZVSKLYLKQVPU[PSS\Z[YH[PUN[OL THPUKL[HPSZ-PN\YLZOV^ZHTPJYVZLJ[PVUVMHUHJ[\HSZVSKLYLK QVPU[PU^OPJOJHUILZLLU[OLZVSKLY[OLTL[HS·JVWWLY·HUK[OL PU[LYTL[HSSPJJVTWV\UKSH`LYIL[^LLU[OL[^V

¬ FYI

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Note that we are talking about soldering joints with copper. Don’t even think about trying to solder to aluminium — it just won’t work — if you need to make an electrical connection to aluminium, do it with a nut and bolt!

FIGURE 5.1 Wetting takes place when solder comes into intimate contact with the surface metal, to form an intermetallic compound at the junction between solder and metal. 109

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FIGURE 5.2 Micro-section through an actual soldered joint, where the intermetallic compound layer between solder on top and copper beneath is clearly visible. The bad soldered joint ;OLJVUKP[PVUMVYHNVVKZVSKLYLKQVPU[[V[HRLWSHJL·PSS\Z[YH[LK WYL]PV\ZS`PU-PN\YLHUKZOV^UWOV[VNYHWOPJHSS`PU-PN\YL ·PZ[OH[ZVSKLYJVTLZPU[VJVU[HJ[^P[OTL[HS[V^L[P[(U`[OPUN[OH[ WYL]LU[ZZVSKLYMYVTJVTPUNPU[VJVU[HJ[^P[OTL[HS[OLYLMVYLJHU^VYR [VWYL]LU[HNVVKZVSKLYLKQVPU[MYVT[HRPUNWSHJL ;OLJVU]LYZLVM[OLNVVKZVSKLYLKQVPU[PZVUL^OLYL[OLZVSKLYKVLZUV[ ^L[[OLQVPU[ZVKVLZUV[JVTLPU[VJVU[HJ[^P[O[OLTL[HS:\JOHIHK ZVSKLYLKQVPU[PZZOV^UPU-PN\YL

¬

FYI

š

Many conditions can occur that create a bad soldered joint, and there are many types of bad soldered joints, so it is not always easy to specify exactly what has gone wrong in the soldering process. However, the usual problem is that the metal surface is not clean. Any number of contaminants may prevent a good soldered joint from taking place — dirt, grease, metal oxide, being the main ones.

FIGURE 5.3 A bad soldered joint — where a layer of metal oxide on the surface of the metal has prevented wetting of the solder to the metal taking place. 110

Soldering 0UWYHJ[PJL[OLYLHYLZL]LYHSSL]LSZVM^L[[PUN^OPJOKVUV[THRLH NVVKQVPU[HUK[OLZLHYL^VY[OJVUZPKLYPUNHZ[OL`NP]LHJS\LHZ[V[OL WYVISLTZ[OH[^LJHUL_WLYPLUJLPUZVSKLYPUNLSLJ[YVUPJJPYJ\P[Z (SS[OL]HYPV\ZSL]LSZVM^L[[PUNHYLKLZJYPILK\UKLYULH[OHUK-PN\YL ZOV^Z[OLTHPUSL]LSZI`^H`VM]PZ\HSJVTWHYPZVU



NON-WETTING. 7YL[[`VI]PV\Z[V[OLL`L·ZVSKLYKVLZUV[ÅV^VU [V[OLTL[HSH[HSS0[^PSSUV[HKOLYL[V[OLWYPU[LKJPYJ\P[IVHYK»ZJVWWLYMVPS [YHJRH[HSS(JPYJ\P[I\PS[^P[OUV^L[QVPU[Z^PSSWYVIHIS`UV[^VYRH[HSS



PARTIAL WETTING. >OPSLUV[ÅV^PUNHUKJVTWSL[LS`^L[[PUN[OLTL[HS Z\YMHJLHWHY[PHSS`^L[QVPU[^PSSHWWLHY[VILZVSPK/V^L]LYP[PZ\UYLSPHISL HUKTH`LHZPS`IYLHRVMM^P[O[PTLVY]PIYH[PVU0U[LYLZ[PUNS`[OLJPYJ\P[P[ZLSM TH`^VYRPUP[PHSS`^OLUWHY[PHSS`^L[QVPU[ZHYLWYLZLU[I\[TH`UV[^VYRMVY more than a short time



DE-WETTING. :\JOQVPU[ZTH`HWWLHY[VOH]LILLUJYLH[LKWYVWLYS` I\[PU[OLJVVSPUNWOHZLHM[LYOLH[OHZILLUYLTV]LK[OLZVSKLYYL[YHJ[Z ·VM[LUSLH]PUNZTHSSZVSKLYIHSSZHYV\UK[OLQVPU[(ZPUWHY[PHS^L[[PUN[OL QVPU[TH`PUP[PHSS`JH\ZLHJPYJ\P[[V^VYRI\[^PSSIYLHRKV^UMHPYS`X\PJRS`

• TOTAL WETTING. .P]LZNVVKQVPU[ZVMJV\YZL^OPJO^PSSJYLH[LJPYJ\P[Z [OH[^VYRHUKJVU[PU\L[VKVZV5V[L[OLKPMMLYLUJLIL[^LLU[V[HSS`^L[ QVPU[ZHUKHSS[OLV[OLY^L[[PUN]HYPHU[Z([V[HSS`^L[QVPU[PZJVUJH]LPUHW WLHYHUJLHUK^PSSHJ[\HSS`ILX\P[LZOPU`[V[OLUHRLKL`L(SSV[OLY^L[[PUN ]HYPHU[ZVMQVPU[Z^PSSILJVU]L_PMUV[YV\UKLKHUKTH`ILK\SSPUHWWLHY HUJL[V[OLUHRLKL`L

Hint: As you can see here, one of the main causes (if not the main cause) of faults in electronic circuits, is bad soldering. Therefore, it makes sense to be able to solder well. Practise it before you attempt to build an electronic circuit till you are able to make good joints every time. Don’t bother using printed circuit boards for this, instead use a few bits of stripboard (see page 81 for details) – even just a couple of boards give you many holes and copper strips to practise with. By the time you’ve soldered a couple of handfuls of components and a few short lengths of lead to the stripboards, you’ll be a past master at the art of soldering!

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FIGURE 5.4 Four extremes of soldered joint: (a) non-wetting; (b) partial wetting; (c) de-wetting; (d) total wetting. Flux (Z^L»]LZLLUP[»ZLZZLU[PHS[OH[[OLTL[HS[VILZVSKLYLKPZJSLHU;OL WYVISLTPZ[OH[JVWWLY[OLTL[HS\ZLK[VTHRLJVWWLYJSHKWYPU[LK JPYJ\P[IVHYKZ[OH[^L\ZLPULSLJ[YVUPJZV_PKPaLZ(TPU\[LS`[OPU Z\YMHJLSH`LYVMJVWWLYV_PKLMVYTZVU[VWVM[OLJVWWLYJSHKSH`LYVM [OLWYPU[LKJPYJ\P[IVHYK[OH[THRLZ\W[OLJVWWLYMVPS[YHJRWH[[LYU]LY` YHWPKS`:VUVTH[[LYOV^^LJSLHU[OLJVWWLYZ\YMHJL[OLV_PKLSH`LY I\PSKZ\WILMVYL^LJHUNL[HZVSKLYPUNPYVU[VP[(UKJVWWLYV_PKL JHUUV[ILZVSKLYLK -\Y[OLYL]LY`[PTLHWYPU[LKJPYJ\P[IVHYKPZOHUKSLKP[WPJRZ\WKPY[HUK NYLHZLIV[OVM^OPJO^VYR[VWYL]LU[ZVSKLYMYVT^L[[PUN[OLIVHYK»Z JVWWLY[YHJR ;OLRL`[VTHRPUNZ\YL[OH[[OLJVWWLYPZYL[\YULK[VWYPZ[PULJVUKP[PVU PUVYKLY[OH[ZVSKLYJHU^L[P[PZHZ\IZ[HUJLJHSSLKÅ\_ -S\_LZHYLJOLTPJHSS`HJ[P]L·[OH[PZ[OL`^VYRVU[OLZ\YMHJL JVU[HTPUHU[ZJVWWLYV_PKLKPY[NYLHZLVU[OLJVWWLY[YHJRVM[OL WYPU[LKJPYJ\P[IVHYK[VKPZZVS]L[OLT;OPZVJJ\YZ^OLU[OLJVWWLYPZ OLH[LKI`HZVSKLYPUNPYVUPU[OLÄYZ[Z[HNLVM[OLZVSKLYPUNWYVJLZZ 6UJL[OLJVWWLYZ\YMHJLPZJSLHUZVSKLYJHUILHWWSPLK 112

Soldering ¬

FYI

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There are many types of flux, judged usually by the level of chemical activity they have. Generally, the fluxes used in the solder used for hand soldering are of low activity. They are typically made by distilling the sap (or resin) from pine trees. The residue is then dissolved in a solvent, making it easier to apply.

([ÄYZ[ZPNO[P[TPNO[ZLLT[OH[JVVYKPUH[PUNHSS[OPZOLH[PUN[OLJVWWLY HWWS`PUN[OLÅ\_^HP[PUN[PSS[OLJVWWLYPZJSLHUHWWS`PUN[OLZVSKLYPZ H[YPJR`TH[[LYILZ[SLM[[V[OLWYVMLZZPVUHSZHUK[OLPYPUK\Z[YPHSZVSKLYPUN WYVJLZZLZ/V^L]LY[OLreal[YPJRPZ[OH[P[JHUHSSILKVULI`OHUKPU HZPUNSLZTVV[OWYVJLZZI`HU`VULHZSVUNHZHML^ZPTWSLZ[LWZHYL MVSSV^LK 2L`[V[OL^OVSLWYVJLZZPZ[OH[TVKLYUZVSKLY\ZLK[VZVSKLYWYPU[LK JPYJ\P[IVHYKZI`OHUKHSYLHK`JVU[HPUZ[OLÅ\_ULLKLK[VJSLHULHJO QVPU[[VILZVSKLYLK ;OLZVSKLY\ZLKOHZJVYLZ\Z\HSS`MV\YVYZP_[OYV\NOV\[P[ZSLUN[O ^OPJOHYLÄSSLK^P[OÅ\_·HZPSS\Z[YH[LKPU-PN\YL+PHTL[LYVM[OL ^OVSLÅ\_JVYLKZVSKLYSLHKPZ\Z\HSS`HYV\UK[VTT

FIGURE 5.5 Cored solder, obtained in reels, appearing much like thin flexible wire. Flux is present in cores within the solder. 113

Starting Electronics Construction :VOV^KVLZP[^VYR&(M[LYHSSOH]PUN[OLÅ\_PUZPKL[OLZVSKLYSPRL[OPZ TLHUZ[OH[[OLÅ\_PZWYLZLU[LK[V[OLQVPU[[VILZVSKLYLKH[[OLZHTL [PTLHZ[OLZVSKLYPZYH[OLY[OHUILMVYLP[·^OPJO^V\SKZ\NNLZ[P[OHZ UV[PTL[VJSLHU[OLQVPU[/V^L]LY[OLÅ\_OHZHT\JOSV^LYTLS[PUN WVPU[[OHU[OLZVSKLYOHZZV[OLÅ\_TLS[ZHUKÅV^ZVU[V[OLQVPU[ ÄYZ[0[[OLYLMVYLOHZ[OL[PTL[VJVH[[OLTL[HSZ\YMHJLZVM[OLQVPU[HUK JSLHU[OLTILMVYL[OLZVSKLYTLS[ZHUKÅV^ZV]LY[OLQVPU[[VTHRL[OL ZVSKLYLKQVPU[HZZOV^UPU-PN\YL

FIGURE 5.6 The main stages of hand soldering a joint: (a) the soldering iron is applied to the joint, to heat it; (b) while maintaining the soldering iron’s position, cored solder is applied to the joint; (c) flux melts quickly and flows from the cored solder onto the joint’s metal surfaces, to clean them and protect them; (d) the solder melts, and flows over the joint’s metal surfaces. ¬ FYI

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This whole process, from first applying the soldering iron to the solder flowing over the joint surfaces, takes only a few seconds (depending mainly on the size of the joint and how powerful the soldering iron is). If a joint takes longer than just a few seconds to make, there’s a good chance the soldering iron isn’t powerful enough.

114

Take Note Throughout this chapter we look at processes involved in soldering various joints on printed circuit boards (ie, those circuit boards made from copper-clad board, with copper foil tracks). The processes – however – are actually identical whatever sort of circuit boards you use.

Soldering

Key points when soldering )LPUNHISL[V\ZLHZVSKLYPUNPYVUPZU»[[OLVUS`[OPUN`V\ULLK[VRUV^ ^OLUZVSKLYPUN;OL^OVSLWYVJLZZKLWLUKZVUZL]LYHSHZWLJ[Z!

When soldering



CLEAN all parts — copper printed circuit board track, component leads, soldering iron bit — before soldering



MAKE a reliable mechanical joint — before soldering



HEAT [OLQVPU[Z\MÄJPLU[S`·before HWWS`PUNZVSKLY

• APPLY the solder — keeping the soldering iron on the joint while the solder melts



REMOVE the soldering iron and allow [OLZVSKLY[VZVSPKPM`·before handling or moving the joint

• TRIM the excess component lead from [OLQVPU[VUJL[OLQVPU[OHZZVSPKPÄLKHUK JVVSLKZ\MÄJPLU[S`[VHSSV^OHUKSPUN

>LZOV\SKUV^JVUZPKLY[OLZLZP_HZWLJ[ZPUKL[HPS

Cleaning all parts >LHSYLHK`RUV^[OH[Å\_PZ\ZLKH\[VTH[PJHSS`^OLUZVSKLYPUN\ZPUN JVYLKZVSKLY[VOLSWJSLHU[OLQVPU[Z\YMHJLZHZWHY[VM[OLZVSKLYPUN WYVJLZZ/V^L]LYÅ\_JHUVUS`YLTV]LZVT\JOV_PKLNYLHZLVY KPY[0[»ZILZ[[VPTWYV]L`V\YJOHUJLZVMTHRPUNHNVVKZVSKLYQVPU[I` THU\HSS`JSLHUPUN[OLQVPU[Z\YMHJLZÄYZ[P[OH_PHSVYYHKPHS SLHKLKJVTWVULU[ZZ\JOHZYLZPZ[VYZHUKJHWHJP[VYZ[OLLHZPLZ[^H`[V KV[OPZPZ[VILUK[OLSLHKZZSPNO[S`HM[LYPUZLY[PVUPU[V[OLWYPU[LKJPYJ\P[ IVHYKHZZOV^UPU-PN\YL(ZHN\PKL[OLHUNSLVM[OLILUKKVLZU»[ ULLK[VILHUKZOV\SKU»[ILHU`TVYL[OHUQ\Z[HML^KLNYLLZ·ILUK [OLSLHKZVUS`HZMHYHZULJLZZHY`[VOVSK[OLJVTWVULU[PUWSHJL

FIGURE 5.12 After inserting a component into the printed circuit board, bend its leads slightly to hold it in place ready for soldering.

Take Note If you insert more than one component into a printed circuit board at a time before soldering, and bend their leads outwards to prevent them falling out, be careful that when you solder their joints solder doesn’t bridge between them, as shown in Figure 5.13. When angled leads like this are soldered, the joint contains much more solder than a lead which is perpendicular to the printed circuit board.

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FIGURE 5.13 Showing how solder can easily bridge between joints if angled component leads are used to hold components in place prior to soldering — take care when using this method to prevent such short circuits. Heat the joint -VYZ\JJLZZM\SZVSKLYPUN[OLTL[HSZ[VMVYT[OLZVSKLYLKQVPU[ZOV\SKIL WYLOLH[LK7YLOLH[PUNPZLHZPS`HJJVTWSPZOLK·HWWS`[OLZVSKLYPUN PYVUIP[[PW[V[OLQVPU[·[V\JOPUNIV[O[OLJVWWLY[YHJRHUK[OL JVTWVULU[SLHKHZZOV^UPU-PN\YL;OL[PTL`V\ZOV\SKWYLOLH[ [OLQVPU[KLWLUKZVU[OLZPaLVMTL[HS[VILOLH[LKHUK[OLWV^LYVM[OL ZVSKLYPUNPYVUI\[NLULYHSS`[OPZ^PSSILMVYUVTVYL[OHUHML^ZLJVUKZ ·IL[^LLUHIV\[[^VHUKLPNO[ZLJVUKZZH`@V\^PSSSLHYU[VQ\KNL [OLWYLOLH[[PTLYLX\PYLKI`QVPU[Z^P[OWYHJ[PJLI\[PUHU`JHZLP[»ZUV[ UVYTHSS`[OH[JY\JPHS

;OLMHJ[VYZ`V\ZOV\SKILHYPUTPUKHYL[OH[!

• IF `V\KVU»[WYLOLH[[OLQVPU[Z\MÄJPLU[S` [OLTVS[LUZVSKLYJVVSZ[VVX\PJRS`HUK`V\ run the risk of making a defective joint

• IF `V\WYLOLH[[OLQVPU[[VVT\JO`V\TH` KHTHNL[OLJVTWVULU[HUKTH`L]LUJH\ZL the copper track to lift from the printed circuit board.

120

Soldering

FIGURE 5.14 Pre-heating the joint to be soldered — apply the soldering iron bit tip to the joint’s metal surfaces.

(WWS`[OLZVSKLY >P[O[OLZVSKLYPUNPYVUIP[[PWPUWVZP[PVUHWWS`[OLLUKVM[OLÅ\_JVYLK ZVSKLY[V[OLQVPU[·[V\JOPUNP[[VIV[O[OLQVPU[HUK[OLZVSKLYPUNPYVU IP[[PW0ML]LY`[OPUNPZHZL_WLJ[LK[OLZVSKLY^PSSTLS[HUKÅV^HYV\UK [OLQVPU[-PN\YLZOV^Z[OPZZ[HNL

FIGURE 5.15 Solder melting and flowing around the pre-heated joint. 121

Starting Electronics Construction

Take Note Some beginners to soldering melt large amounts of solder on the soldering iron bit tip, then dab the soldering iron bit tip onto the joint they want to make – the soldering equivalent of putting glue onto a spatula then wiping the spatula onto something to spread the glue over it. DO NOT UNDER ANY CIRCUMSTANCES DO THIS. While the process might work well for glue, it certainly doesn’t work for solder. Soldering is only effective when the joint is pre-heated, and fresh flux is applied at the same time as solder. If you put solder on the soldering iron bit tip, the flux burns away before applying it to the parts of the joint, and the joint is too cool anyway – causing only bad soldered joints. The moral is: only use the method described earlier to solder joints!

Remove the soldering iron 6UJL[OLZVSKLYOHZÅV^LKHYV\UK[OLQVPU[UV[ILMVYLX\PJRS`YLTV]L [OLZVSKLYPUNPYVU+VUV[TV]L[OLWYPU[LKJPYJ\P[IVHYKHUKKVUV[ TV]L[OLJVTWVULU[VYP[ZSLHKZ\U[PS[OLZVSKLYOHZZVSPKPÄLK0M`V\ TV]LHU`[OPUNILMVYL[OLZVSKLYZVSPKPÄLZ[OLQVPU[TH`ILKHTHNLK

¬

FYI

š

A good soldered joint has a concave, shiny appearance. If the joint is not heated sufficiently, or if you move the joint and damage it, you will probably notice that it is not concave, or that it is a dull, grey colour. Don’t worry — just repair the fault by heating the joint again, until the solder flows properly.

Trim excess component leads 0M[OLJVTWVULU[SLHKZ^LYLSLM[HZ[OL`HYLHUKTVYL[OHUQ\Z[HJV\WSL VMJVTWVULU[Z^LYLPUZLY[LKPU[V[OLWYPU[LKJPYJ\P[IVHYK`V\Y\U[OL PTTPULU[YPZRVMJVTWVULU[SLHKZ[V\JOPUN·LMMLJ[P]LS`MVYTPUNZOVY[ JPYJ\P[Z;VWYL]LU[[OPZ`V\OH]L[V[YPTHSSL_JLZZJVTWVULU[SLHKZVMM PTTLKPH[LS`HIV]L[OLQVPU[-PN\YLZOV^Z[OPZ (M[LYHSSQVPU[ZVU[OLWYPU[LKJPYJ\P[IVHYKOH]LILLUZVSKLYLKHUK L_JLZZSLHKZ[YPTTLKP[»ZHNVVK[PTL[VJOLJRHSS[OLQVPU[Z]PZ\HSS`[V ZLLPM[OL`SVVRºNVVK»VYºIHK»YLWHPYPUNHU`[OH[HYLZ\ZWLJ[(SZVJOLJR V]LYHSS[OLJVWWLYMVPS[YHJR[VZLL[OH[UVZVSKLYIYPKNLZOH]LMVYTLK IL[^LLU[YHJRZVYJVTWVULU[QVPU[Z0M`V\ÄUKHU`ZVSKLYIYPKNLZ\ZL KLZVSKLYPUN[VVSZ·HZVSKLYZ\JRLYVYKLZVSKLYIYHPK·[VYLTV]L L_JLZZZVSKLYHUKYLZVSKLYHU`QVPU[Z[OH[ULLKP[ 122

Soldering

FIGURE 5.16 Trimming excess component leads off, close to the soldered joint, to prevent short circuits.

Connecting leads 0UL]P[HIS`HU`WYPU[LKJPYJ\P[IVHYKOVSKPUNP[ZLSLJ[YVUPJJPYJ\P[PZUV[ PZVSH[LKMYVT[OL^VYSKHYV\UKP[0[T\Z[ILJVUULJ[LK·[VZ^P[JOLZ JVU[YVSZVMMIVHYKJVTWVULU[ZPUW\[HUKV\[W\[ZVJRL[ZHUKZVVU:V P[»ZJVTTVU·PUKLLKUVYTHS·[VULLK[VZVSKLYJVUULJ[PUNSLHKZ[V [OLWYPU[LKJPYJ\P[IVHYKJVWWLYMVPS[YHJR ;VZVSKLYJVUULJ[PUNSLHKZ[VHWYPU[LKJPYJ\P[IVHYK\ZL[OLMVSSV^PUN WYVJLK\YL!

• •

STRIP around 5 mm of insulation from the end of the lead IF the connecting lead is multi-stranded — twist the loose ends of the stripped lead. 0M`V\ZVSKLY[OLSLHK\U[^PZ[LK[V[OLIVHYK[OLYL»ZH WVZZPIPSP[`HSVVZLZ[YHUKTH`IYPKNLHJYVZZ[VHUV[OLY[YHJR



CLEAN and tin the soldering iron bit tip. You should ALWAYS do this ILMVYLHU`ZVSKLYPUNVWLYH[PVU

CONTINUED…

123

Starting Electronics Construction

…CONTINUED • TIN the connecting lead. ;OPZOHZ[^VW\YWVZLZ!ÄYZ[P[YLTV]LZHU` V_PKLZKPY[HUKNYLHZLVU[OL^PYLZTHRPUN\W[OLSLHKZHUK"ZLJVUK [OLZVSKLY`V\HKKPU[OL[PUUPUNZ[HNL^PSSIL\ZLK^OLU[OLQVPU[PZTHKL ·TLHUPUN`V\^VU»[OH]L[VHKKT\JOZVSKLYH[[OH[[PTL;OLZVSKLYPUN PYVUIP[[PWULLKZ[VILX\P[LHIYVHKVUL·HYV\UKTT·MVY[OPZQVI;V [PU[OLSLHK! ¬ OVSK[OLÅH[WHY[VM[OLZVSKLYPUNPYVUIP[[PW\W^HYKZHZZOV^UPU -PN\YLHUKSH`[OLZ[YPWWLKLUKVM[OLJVUULJ[PUN^PYLVU[OL [PW»ZÅH[Z\YMHJL ¬ HWWS`[OLLUKVMHSLUN[OVMZVSKLY[V[OL^PYLUV[[OLZVSKLYPUNPYVU IP[[PW·[OPZTLHUZ`V\JHUZLL^OLU[OL^PYLPZOV[LUV\NOHZ[OL ZVSKLYILNPUZ[VTLS[ ¬ ^OLULUV\NOZVSKLYOHZÅV^LKV]LY[OLSLHKLUKZ[VM\SS`JV]LY[OL ^PYLYLTV]L[OLZVSKLYPUNPYVUHUKZVSKLY ¬ HSSV^[OLSLHK[VJVVSILMVYL[V\JOPUNVYTV]PUNP[

FIGURE 5.17 Tinning a connecting lead — do not heat the lead for too long, as insulation may melt or deteriorate.

CONTINUED…

124

Soldering

…CONTINUED • TIN the printed circuit board. ([[OLWVPU[^OLYL[OL[PUULKSLHKPZ[VIL JVUULJ[LK[V[OLWYPU[LKJPYJ\P[IVHYK»ZJVWWLYMVPS[YHJR[OLJVWWLYT\Z[ IL[PUULK[VYLTV]LV_PKLKPY[HUKNYLHZLHUK[VHWWS`ZVSKLYYLHK`MVY [OLQVPU[[VILTHKLIL[^LLUIVHYKHUKSLHK;V[PU[OLWYPU[LKJPYJ\P[IVHYK [YHJR! ¬ JSLHUHUK[PU[OLZVSKLYPUNPYVUIP[[PW ¬ HWWS`[OLZVSKLYPUNPYVUIP[[PW[V[OLJVWWLY[YHJRVM[OLWYPU[LKJPY J\P[IVHYKH[[OLWVPU[^OLYL[OLSLHKPZ[VILJVUULJ[LK·HZZOV^U PU-PN\YL·HUK^HP[MVYHML^ZLJVUKZ

FIGURE 5.18 Tinning the copper foil track of a printed circuit board — apply the soldering iron bit tip first, and wait for a few seconds before applying solder. ¬ HWWS`[OLLUKVM[OLÅ\_JVYLKZVSKLY[V[OL[YHJRHZTHSSKPZ[HUJL HIV\[¶TTH^H`MYVT[OLZVSKLYPUNPYVUIP[[PW·^HP[MVY[OL ZVSKLY[VTLS[HUKÅV^[V^HYKZ[OLZVSKLYPUNPYVUIP[[PW ¬ YLTV]L[OLZVSKLYPUNPYVUIP[[PWHUK[OLZVSKLY ¬ HSSV^[OLWYPU[LKJPYJ\P[IVHYK[VJVVSILMVYLTV]PUNVY[V\JOPUN[OL solder.

125

Starting Electronics Construction

Take Note While it’s correct to tin the printed circuit board copper foil track at the points where connecting leads are to be jointed, this is NOT the procedure where components are to be fitted to the printed circuit board – if the copper foil track is tinned where a component lead is to be inserted, the hole for the lead may be closed with solder.

6UJL[OLSLHKPZ[PUULKP[JHUILZVSKLYLK[V[OLJVWWLYMVPS[YHJRVM HWYPU[LKJPYJ\P[IVHYK;OLYLHYL[OYLLTHPU^H`Z[OPZJHUILKVUL ZVSKLYPUN[OLSLHK!



1 KPYLJ[S`[V[OLWYPU[LKJPYJ\P[IVHYKJVWWLYMVPS[YHJR



2 to a terminal pin, inserted through a hole in the copper foil track



3 PUZLY[PUN[OLSLHK[OYV\NOHOVSLW\YWVZLS`KLZPNULKPU[V[OL WYPU[LKJPYJ\P[IVHYK»ZJVWWLYMVPS[YHJR

;OLWYVJLK\YLZ`V\ZOV\SKMVSSV^MVYHSS[OYLL^H`ZHYLKL[HPSLKILSV^

1 Soldering a JVUULJ[PUNSLHKKPYLJ[S`[VJVWWLY[YHJR

• TIN the soldering iron bit tip, as described on page 116 • TIN the connecting lead, as described on page 124 • TIN the printed circuit board copper track, at the point where the lead is to be connected, as described on page 125



HOLD the tinned end of the lead on the tinned copper track, as shown in Figure 5.19 CONTINUED…

126

Soldering

…CONTINUED

FIGURE 5.19 Position the tinned connecting lead end over the tinned copper track. • APPLY the soldering iron bit tip to the tinned lead end (not the copper track), pressing down on the lead end to hold it in position, and wait for the solder on both the lead end and the copper track to melt, as shown in Figure 5.20

FIGURE 5.20 Heating the connecting lead end and copper track — the solder already present in the tinning on both the lead end and the track will be sufficient to make the soldered joint. CONTINUED…

127

Starting Electronics Construction

…CONTINUED •

REMOVE the soldering iron, but hold the lead without moving it

• WAIT MVY[OLZVSKLY[VZVSPKPM`ILMVYLTV]PUN[OLWYPU[LKJPYJ\P[ board or letting go the lead.

2 Soldering a connecting lead to a terminal pin



INSERT a terminal pin into the printed circuit board — note that the pin goes through from the copper foil track side of the printed circuit board to the component side of the board ie, the connecting lead will be soldered to the component side NOT the copper track side (see Figure 5.21).

FIGURE 5.21 A terminal pin goes from the copper track side of a printed circuit board, to the component side.



CLEAN and tin the soldering iron bit tip, as described on page 116

• TIN the connecting lead, as described on page 124 CONTINUED…

128

Soldering

…CONTINUED • APPLY the soldering iron bit tip to the terminal pin and wait for a few seconds (See Figure 5.22)

FIGURE 5.22 Soldering a terminal pin to a printed circuit board. • APPLY solder to the terminal pin • WHEN [OLZVSKLYTLS[ZHUKÅV^ZV]LY[OL[LYTPUHSWPUHUK[OL copper track, remove the soldering iron and wait for the soldered joint to cool

• TURN the printed circuit board over, then tin the terminal pin •

HOLD the tinned end of the connecting lead against the tinned terminal pin, as shown in Figure 5.23

FIGURE 5.23 The connecting lead should be vertically aligned with the terminal pin, and touching it. CONTINUED…

129

Starting Electronics Construction

…CONTINUED • APPLY the soldering iron bit tip to the connecting lead and terminal pin

• WAIT for a few seconds for the solder on both the lead and pin to melt, then remove the soldering iron



DO not move either connecting lead or printed circuit board, until [OLZVSKLYOHZZVSPKPÄLK

Hint For both these methods of soldering a connecting lead to a printed circuit board, be extra careful not to allow the connecting lead end to move at all once the joint has been soldered and during the cooling phase, or a defective joint may result.

3 Soldering a lead to a hole



CLEAN and tin the soldering iron bit tip, as described on page 116



INSERT the connecting lead through the hole in the printed circuit IVHYK·KVUV[[PU[OLJVUULJ[PUNSLHKÄYZ[VYP[^PSSUV[NV[OYV\NO the hole!

• APPLY the soldering iron bit tip to the joint, touching both the copper foil track of the printed circuit board and the lead, as shown in Figure 5.24

CONTINUED…

130

Soldering

…CONTINUED

FIGURE 5.24 Soldering a connection lead to a printed circuit board. • APPLY solder to the joint • WHEN [OLZVSKLYTLS[ZHUKÅV^ZV]LY[OLJVUULJ[PVUSLHKHUK the copper track, remove the soldering iron and wait for the soldered joint to cool



DO not move either connecting lead or printed circuit board, until [OLZVSKLYOHZZVSPKPÄLK

Unsoldering ;OLYLHYL[PTLZ^OLUP[»ZULJLZZHY`[V\UZVSKLYJVTWVULU[ZMYVTH WYPU[LKJPYJ\P[IVHYK@V\TH`WLYOHWZOH]LPUZLY[LKHUKZVSKLYLKH JVTWVULU[PUJVYYLJ[S`PU[VWSHJLVYHWHY[PJ\SHYJVTWVULU[TH`IL MH\S[`0UZ\JOJHZLZ\UZVSKLYPUNPZ[OLVUS`VW[PVU ;OLYLHYL[^VIHZPJTL[OVKZVM\UZVSKLYPUNJVTWVULU[ZKL[HPSLK V]LYSLHMHUKIV[OYLS`VUOH]PUNL_[YH[VVSZ!LP[OLYZVSKLYIYHPKVYH KLZVSKLYPUNW\TW

131

Starting Electronics Construction

Using solder braid

• TIN the soldering iron bit tip •

PLACE the end of the solder braid over the joint to be desoldered, as shown in Figure 5.25

• APPLY the soldering iron bit tip onto the solder braid. 7YLZZNLU[S` I\[ÄYTS`HNHPUZ[[OLQVPU[(M[LYHML^ZLJVUKZVYZV[OLZVSKLY^PSSTLS[ HUKZVTL^PSS^PJRPU[V[OLZVSKLYIYHPK

FIGURE 5.25 Desoldering using solder braid — the molten solder wicks into the strands of the solder braid away from the joint.



REMOVE the soldering iron bit tip. 7SHJLHMYLZOWVY[PVUVMZVSKLY IYHPKVU[V[OLZVSKLYQVPU[HUKYLWLH[[OLSHZ[Z[LW\U[PSHSS[OLZVSKLYMVYTPUN [OLQVPU[OHZILLUYLTV]LK



REPEAT the process for all component joints



REMOVE the component.

132

Soldering

Hint

Hint

As you use a portion of solder braid to unsolder a joint, it will become loaded with solder so cease to be usable. Using a pair of sidecutters, trim off the used portion to maintain a fresh solder braid end.

Sometimes not all solder can be removed from a joint (very often a small amount which cannot be removed will still hold the component lead to the copper track). If this occurs, you will find that you have to heat the joint with the soldering iron bit tip one last time, before quickly – before the solder solidifies – releasing the component.

Using a desoldering pump

• TIN the soldering iron bit tip •

PRIME [OLKLZVSKLYPUNW\TWI`WYLZZPUN[OLJOHYNLYKV^UHZ shown in Figure 5.26

FIGURE 5.26 Priming the desolder pump by pressing down the charger. • APPLY the soldering iron bit tip to the soldered joint and wait for the solder to melt

CONTINUED…

133

Starting Electronics Construction

…CONTINUED • APPLY the nozzle of the desoldering pump to the molten solder, as shown in Figure 5.27

FIGURE 5.27 With the soldering iron bit tip heating the solder, apply the desoldering pump nozzle.



PUSH [OLW\TW»ZYLSLHZLI\[[VU;OL]HJ\\T^PSSZ\JR[OLTVS[LU ZVSKLYH^H`MYVT[OLQVPU[HUKPU[V[OLKLZVSKLYPUNW\TWJOHTILY^OLYLP[ ^PSSZVSPKPM`



REPEAT the previous four steps as required, until all the solder has been removed from the joint.

Take Note Every now and again, the desoldering pump chamber will fill with solidified solder to the point that it doesn’t work efficiently. Empty it by repeatedly priming and discharging the pump, so that the solder is forced out of the nozzle.

134

Soldering

Take Note Unsoldering usually requires considerably more application of heat than soldering – the soldering iron bit tip is applied to the joint more times and for longer periods than when soldering. Remember that components may be damaged by excessive heat, so space the desoldering operations out to allow the components to cool down in between.

Care of your soldering iron @V\YZVSKLYPUNPYVUPZH[VVS·H]P[HSVUL^OLUP[JVTLZ[VI\PSKPUN LSLJ[YVUPJJPYJ\P[ZVMJV\YZL·HUKSPRLHU`[VVSULLKZSVVRPUNHM[LY [VRLLWP[PUNVVK^VYRPUNVYKLY[OYV\NOV\[P[ZWV[LU[PHSS`SVUNSPML ;OPUNZHYLTHKLHSP[[SLJVTWSPJH[LKPU[OH[[OLZVSKLYPUNPYVUPZ·0»SS Z[H[L[OLVI]PV\ZOLYL·]LY`OV[ZV`V\HSZVULLK[V[HRLJLY[HPU ZHML[`WYLJH\[PVUZ^OPSL\ZPUNP[)\[MVY[\UH[LS`VU[OLV[OLYOHUKP[»Z HMHPYS`ZPTWSL[VVSZV[OL[OPUNZ`V\ULLK[VKV[VSVVRHM[LYP[HUK[OL WYLJH\[PVUZ`V\ULLK[V[HRL^OPSL`V\»YL\ZPUNP[HYLU»[L_JLZZP]L

3VVRPUNHM[LY`V\YZVSKLYPUNPYVU



USE a stand. >OLUH[YLZ[HZVSKLYPUNPYVUJHUILLHZPS`RUVJRLKVY TV]LK·P[TH`MHSSVMM[OL^VYRZ\YMHJLVYZPTWS`[V\JOHNHPUZ[ZVTL[OPUN LSZLOLYLVUS`[^VKPNP[ZHYLNP]LUPUHULUJSVZ\YL»Z07YH[PUN[OL[OPYKVM [OLZLYLX\PYLTLU[ZPTWHJ[KHTHNLPZUV[YLSL]HU[ZVZOV\SKILPNUVYLK

TABLE 6.1 Ingress Protection (IP) ratings by number, and their equivalent protection levels. Value

Z[KPNP[

UKKPNP[

YKKPNP[

7YV[LJ[PVUHNHPUZ[PUNYLZZVM ZVSPKZ

7YV[LJ[PVUHNHPUZ[PUNYLZZVM SPX\PKZ

7YV[LJ[PVUHNHPUZ[TLJOHUPJHS PTWHJ[KHTHNL

0

5VWYV[LJ[PVU

5VWYV[LJ[PVU

5VWYV[LJ[PVU



7YV[LJ[LKHNHPUZ[ZVSPKVIQLJ[Z V]LYTTLNOHUKZSHYNL[VVSZ

7YV[LJ[LKHNHPUZ[]LY[PJHSS`MHSSPUN KYVWZVM^H[LY

7YV[LJ[LKHNHPUZ[QV\SL PTWHJ[N'JT



7YV[LJ[LKHNHPUZ[ZVSPKVIQLJ[Z V]LYTTLNOHUKZSHYNL[VVSZ

7YV[LJ[LKHNHPUZ[KPYLJ[ZWYH`ZVM ^H[LY\W[V‡MYVT]LY[PJHS

7YV[LJ[LKHNHPUZ[QV\SL PTWHJ[N'JT



7YV[LJ[LKHNHPUZ[ZVSPKVIQLJ[Z V]LYTTLN^PYLZTHSS[VVSZ

7YV[LJ[LKHNHPUZ[KPYLJ[ZWYH`ZVM ^H[LY\W[V‡MYVT]LY[PJHS

7YV[LJ[LKHNHPUZ[QV\SLPTWHJ[ N'JT



7YV[LJ[LKHNHPUZ[ZVSPKVIQLJ[Z V]LYTTLN^PYLZ

7YV[LJ[LKHNHPUZ[^H[LYZWYH`LK MYVTHU`KPYLJ[PVU3PTP[LK PUNYLZZWLYTP[[LK



3PTP[LKWYV[LJ[PVUHNHPUZ[K\Z[ PUNYLZZUVOHYTM\SKLWVZP[

7YV[LJ[LKHNHPUZ[SV^WYLZZ\YL ^H[LYQL[ZMYVTHU`KPYLJ[PVU 3PTP[LKPUNYLZZWLYTP[[LK



;V[HSS`WYV[LJ[LKHNHPUZ[K\Z[ PUNYLZZ

7YV[LJ[LKHNHPUZ[OPNOWYLZZ\YL ^H[LYQL[ZMYVTHU`KPYLJ[PVU 3PTP[LKPUNYLZZWLYTP[[LK



7YV[LJ[LKHNHPUZ[PTTLYZPVU IL[^LLUJTHUK4

8

7YV[LJ[LKHNHPUZ[SVUNWLYPVKZVM PTTLYZPVU\UKLYWYLZZ\YL

9

144

7YV[LJ[LKHNHPUZ[QV\SLPTWHJ[ N'JT

7YV[LJ[LKHNHPUZ[QV\SLPTWHJ[ 2N'JT

7YV[LJ[LKHNHPUZ[QV\SLPTWHJ[ 2N'JT

Housings

Housings and their use ;OLYLHYLZL]LYHS[HZRZ`V\^PSSOH]L[VJHYY`V\[^OPJOHYLJVTTVU ^OH[L]LYOV\ZPUN`V\VW[[V\ZLMVY`V\YLSLJ[YVUPJKL]PJL

The main tasks are:



MOUNTING the printed circuit board



FITTING controls and switches



FITTING connections between the printed circuit board and the outside world



MOUNTING other internal components besides the printed circuit board

• WIRING of all internal parts •

LABELLING the front and rear panels of the housing.

Mounting printed circuit boards 6ULVM[OLWYPTHY`W\YWVZLZVMHOV\ZPUNPZ[VOVSKP[ZPU[LYUHS LSLJ[YVUPJJPYJ\P[»ZWYPU[LKJPYJ\P[IVHYK0[»ZUV[Q\Z[HJHZLVM[OYV^PUN [OLWYPU[LKJPYJ\P[IVHYKPUHUKJSVZPUN[OLSPK[OV\NO(WYPU[LKJPYJ\P[ IVHYKZOV\SKUL]LYILSLM[SVVZLPUZPKLHU`OV\ZPUN0UZ[LHKP[ZOV\SKIL WYVWLYS`HUKZLJ\YLS`Ä_LK\ZPUNVULVYTVYLVMHU\TILYVMTL[OVKZ 6M[LU[OLTL[OVK`V\TPNO[JOVVZL[VTV\U[`V\YWYPU[LKJPYJ\P[IVHYK PUZPKL`V\YOV\ZPUN^PSSKLWLUKVU[OL[`WLVMOV\ZPUN`V\OH]LVW[LK [V\ZLand[OLZPaLHUKZOHWLVM[OLWYPU[LKJPYJ\P[IVHYK0M`V\OH]LH ZTHSSWYPU[LKJPYJ\P[IVHYKHUKHWSHZ[PJOV\ZPUNP[»ZWLYMLJ[S`WVZZPISL [VTV\U[[OLWYPU[LKJPYJ\P[IVHYK[V[OLPUZPKLVM[OLOV\ZPUN\ZPUNVUL VY[^VWPLJLZVMKV\ISLZPKLKHKOLZP]LZWVUNLÄ_PUNWHKZHZZOV^UPU -PN\YL

145

Starting Electronics Construction

FIGURE 6.4 Using double-sided adhesive sponge fixers to mount a printed circuit board inside a plastic housing: (left) applying the sponge fixing pads to the bottom of the printed circuit board; (right) applying the printed circuit board with sponge fixing pads to the inside of the plastic housing. ;OPZTL[OVKZOV\SKUV[IL\ZLK[VTV\U[HWYPU[LKJPYJ\P[IVHYKPUZPKL HTL[HSOV\ZPUN[OV\NO·MVY[OLZPTWSLYLHZVU[OH[ZWVUNLÄ_PUNWHKZ HYL[OPUHUKZVTLVM[OLZVSKLYLKJVUULJ[PVUZVU[OLIV[[VTVM[OL WYPU[LKJPYJ\P[IVHYKTH`[V\JO[OLTL[HSOV\ZPUNIHZLHZZOV^UPU -PN\YLJH\ZPUNZOVY[JPYJ\P[ZHUKWVZZPIS`KHTHNL

FIGURE 6.5 A printed circuit board should not be mounted inside a metal housing using sponge fixing pads, or short circuits may result! 0UZ[LHK^OLU\ZPUNHTL[HSOV\ZPUNVYPUKLLKPMHSHYNLYWYPU[LK JPYJ\P[IVHYKPZ[VILTV\U[LKL]LUPUHWSHZ[PJOV\ZPUNZVTL[OPUNTVYL Z\IZ[HU[PHST\Z[IL\ZLK 146

Housings 6ULVM[OLILZ[TL[OVKZVMTV\U[PUNHWYPU[LKJPYJ\P[IVHYKPUH OV\ZPUNPZ[V\ZLZWHJLYZ;OLZLHYLH]HPSHISLPUZL]LYHSMVYTH[Z:VTL ZWHJLYZ\ZLZTHSSIVS[Z[VOVSK[OLTPUWSHJL[V[OLPUZPKLVMHOV\ZPUN HZZOV^UPU-PN\YL6UJL[OLZWHJLYZHYLIVS[LK[V[OLOV\ZPUN [OLWYPU[LKJPYJ\P[IVHYKPZ[OLUIVS[LK[V[OLZWHJLYZ6I]PV\ZS`[OL OV\ZPUNHUK[OLWYPU[LKJPYJ\P[IVHYKULLK[VILKYPSSLK[VHJJLW[[OL IVS[ZWYPVY[V\ZL

FIGURE 6.6 Bolted spacers, showing the spacers and the bolts.

Take Note If you intend to use spacers to mount a printed circuit board to a housing, you must take into account where the spacers will be positioned on the printed circuit board. Component positions and the copper foil track may have to be adjusted to provide room – not just for the spacers themselves, but to allow access with tools to allow you to tighten the spacer bolts. You need to plan ahead, and decide which printed circuit board mounting method or methods you intend to use, as all the calculations regarding component positions and copper foil track layout need to be done in the very early stages of printed circuit board design – not at the last minute!

6[OLYZWHJLYZHYLWYLMVYTLKZWY\UNSVHKLKWSHZ[PJJSPWZ^OPJOW\ZO PU[VOVSLZPU[OLOV\ZPUNHUK[OLWYPU[LKJPYJ\P[IVHYK 147

Starting Electronics Construction ;OLYLHYLZL]LYHS]HYPH[PVUZVMWYPU[LKJPYJ\P[IVHYKN\PKLZH]HPSHISL 0U\ZL[OLZLHYLMHZ[LULK[V[OLPUZPKLVM[OLOV\ZPUNHUK[OLWYPU[LK WYPU[LKJPYJ\P[IVHYKPZZSPKPU[VWVZP[PVUHSVUN[OLT (WHY[PJ\SHY]HYPH[PVUVMOV\ZPUN·L_[Y\KLKHS\TPUP\T[`WLZ· MLH[\YLZPUI\PS[ZSV[ZPUPU[LYUHSZ\YMHJLZ*VU]LUPLU[S`[OLZLHYLWYPU[LK JPYJ\P[IVHYKZPaLKZVWYV]PKLHUL_[YLTLS`LHZ`TL[OVKVMTV\U[PUN

Take Note In the printed circuit board design stages, make sure no components are positioned close to the edges of the printed circuit board if you plan to use guides of any sort. Further, if you plan to use an extruded aluminium housing, not only must there be no components fitted on the guide edge areas of the printed circuit board, but there must be no copper foil track in those areas.

0M`V\YWYPU[LKJPYJ\P[IVHYKOHZJVU[YVSZHUKJVUULJ[PVUZZ\JOHZ JLY[HPUWYPU[LKJPYJ\P[IVHYKTV\U[LKWV[LU[PVTL[LYZZ^P[JOLZHUK JVUULJ[VYZ[OLU`V\JHU\ZL[OLJVU[YVSZHUKJVUULJ[VYZ[VTV\U[ [OLWYPU[LKJPYJ\P[IVHYKPUZPKL[OLOV\ZPUN^P[OJHYLM\SKLZPNU;OPZPZ WHY[PJ\SHYS`ZVMVYZTHSSWYPU[LKJPYJ\P[IVHYKZ 4V\U[PUN[OLWYPU[LKJPYJ\P[IVHYK[OPZ^H`KLWLUKZVU\ZPUNWYPU[LK JPYJ\P[IVHYKTV\U[LKJVU[YVSZHUKJVUULJ[VYZ-VYL_HTWSL-PN\YL ZOV^ZHWYPU[LKJPYJ\P[IVHYK[OH[OHZHUVUIVHYKWV[LU[PVTL[LYHUK VUIVHYKJVUULJ[VYZ;OLZLLMMLJ[P]LS`OVSK[OLWYPU[LKJPYJ\P[IVHYKPU WSHJLHZ[OL`HYLOLSK[V[OLOV\ZPUNZPKLZ 5V[L[OV\NO[OH[[OLHJ[\HSWYPU[LKJPYJ\P[KLZPNUPZOPNOS`KLWLUKLU[ VU[OLHJ[\HSJVU[YVSZVYJVUULJ[VYZ0UV[OLY^VYKZ[OLOV\ZPUN`V\ PU[LUK[V\ZL[OLL_HJ[ZPaLHUKZOHWLVM[OLWYPU[LKJPYJ\P[IVHYKand [OLHJ[\HSJVU[YVSZVYJVUULJ[VYZHSSULLK[VIL[HRLUM\SS`PU[VHJJV\U[ K\YPUN[OL]LY`LHYSPLZ[WYPU[LKJPYJ\P[IVHYKKLZPNUZ[HNLZ3P[LYHSS` L]LY`[OPUNPZKLWLUKLU[VULHJOV[OLY;OPZTL[OVKHSSV^ZHOPNOS` PU[LNYH[LKH]LY`WYVMLZZPVUHSSVVRPUNHUKVM[LUHT\JOYLK\JLKZPaLVM KL]PJLZVPZVM[LU^VY[O[OLL_[YH[PTL`V\TPNO[ULLK[VPU]LZ[PU[OL LHYS`KLZPNUZ[HNLZ

148

Housings

FIGURE 6.7 Using a printed circuit board mounted potentiometer and connectors to mount a printed circuit board inside its housing. This is the Guitar Headphone Amplifier project, in Chapter 8. (JVTTVUTL[OVKVMTV\U[PUNZTHSSWYPU[LKJPYJ\P[IVHYKZPUZPKL OV\ZPUNZPZ[VTHRL\ZLVMHWHY[PJ\SHY[`WLVMJVUULJ[VYRUV^UHZHU LKNLJVUULJ[VY,KNLJVUULJ[VYZHYLT\S[PWPUULKKL]PJLZJVTWYPZPUNH YV^VMJVU[HJ[ZPU[V^OPJO[OLLKNLVMHWYPU[LKJPYJ\P[IVHYKÄ[Z[PNO[S` (YV^VMJVWWLYMVPS[YHJRZVU[OLLKNLVM[OLWYPU[LKJPYJ\P[IVHYK TH[LZ^P[O[OLLKNLJVUULJ[VYJVU[HJ[ZHZZOV^UPU-PN\YL;OL LKNLJVUULJ[VYPZIVS[LK[V[OLOV\ZPUNVY[VHUV[OLY·\Z\HSS`SHYNLY ·WYPU[LKJPYJ\P[IVHYK;O\ZJVUULJ[PVUZJHUILTHKL[VHUKMYVT[OL WYPU[LKJPYJ\P[IVHYKI\[Q\Z[HZPTWVY[HU[S`[OLWYPU[LKJPYJ\P[IVHYK PZOLSKPUWVZP[PVU(ZTHSSWYPU[LKJPYJ\P[IVHYKTV\U[LK[OPZ^H`TH` ULLKUVV[OLYZ\WWVY[

FIGURE 6.8 Using an edge connector to hold a printed circuit board in position. This particular connector (in white) is a RAM-card holder, common to computer and associated equipment. 149

Starting Electronics Construction

Fitting controls and switches >OPSLVU[OLZ\IQLJ[VMJVU[YVSZHUKZ^P[JOLZ^LZOV\SKPUJS\KL KL[HPSZVUOV^[OL`ZOV\SKILTV\U[LK[VHOV\ZPUN;OLTL[OVKZVM KVPUN[OPZHYLZPTPSHY^OL[OLY[OL`HYLZWLJPHSWYPU[LKJPYJ\P[IVHYK TV\U[LKJVU[YVSZHUKJVUULJ[VYZVYVYKPUHY`TVYL\Z\HSJVU[YVSZHUK JVUULJ[VYZ;OLTL[OVKZHYLHSZVZPTPSHY^OH[L]LY[`WLVMOV\ZPUNPZ \ZLK·TL[HSVYWSHZ[PJVYL]LU^VVK *VU[YVSZHYLYLX\PYLKPUTVZ[LSLJ[YVUPJJPYJ\P[Z;OL`JHUYHUNLMYVT ]VS\TLHUK[VULJVU[YVSZPUHUH\KPVHTWSPÄLY[OYV\NO[PTLZL[[PUNZ MVYHKPNP[HSJSVJRZPTWSLVUVMMZ^P[JOLZVYKPHSZ[V[\ULPUYHKPV Z[H[PVUZ;OLPTWVY[HU[WVPU[PZ[OH[JVU[YVSZHYL\ZLK[VWYV]PKLHU PU[LYMHJLIL[^LLUHULSLJ[YVUPJJPYJ\P[PUWYPU[LKJPYJ\P[IVHYKMVYT PUZPKLHOV\ZPUNHUK[OL\ZLYVM[OLLSLJ[YVUPJJPYJ\P[PUO\THUMVYT ·UVYTHSS`·V\[ZPKL[OLOV\ZPUN Potentiometers 4VZ[WV[LU[PVTL[LYZOH]LH[OYLHKLKZ[LT[OH[HSSV^Z[OLT[VIL TV\U[LK[VHOV\ZPUN\ZPUNHZ\WWSPLKU\[HUK^HZOLY-PN\YL ZOV^Z H[`WPJHSWV[LU[PVTL[LYJVTWSL[L^P[O^HZOLYHUKU\[(OVSL·[OL KPHTL[LYVM[OL[OYLHKLKZ[LT·PZYLX\PYLKPU[OLOV\ZPUN[VPUZLY[[OL Z[LT(SZV]PZPISLPU-PN\YL PZHSVJH[PVUZ[\I[OH[L_[LUKZIL`VUK[OL TV\U[PUNWVPU[VU[OL[OYLHKLKZ[LT;OLW\YWVZLVM[OLSVJH[PVUZ[\I PZ[VÄ_[OLWV[LU[PVTL[LYPUWVZP[PVUHUKWYL]LU[P[ZYV[H[PVU·HZTPNO[ OHWWLUPM[OLU\[ILJVTLZSVVZLV]LY[PTLZH`;OLWYVISLT^P[O[OL SVJH[PVUZ[\IPZ[OH[HZLJVUKZTHSSOVSL[OLKPHTL[LYVM[OLSVJH[PVU Z[\IPZYLX\PYLKPU[OLOV\ZPUNHSVUNZPKL[OLOVSLMVY[OL[OYLHKLKZ[LT ·[OLJVYYLJ[KPZ[HUJLMYVT[OLJLU[YLVM[OL[OYLHKLKZ[LT»ZOVSL

FIGURE 6.9 A potentiometer, showing its threaded stem, washer and nut, and the location stub. 150

Housings 5V^0ZOV\SKWVPU[V\[OLYL[OH[UV[HSSWV[LU[PVTL[LYZOH]L[OPZ SVJH[PVUZ[\IHUKPU^OPJOJHZL[OLZLJVUKOVSLPZUV[YLX\PYLK(UK PUKLLK0OH]LILLUN\PS[`T`ZLSMVMYLTV]PUN[OLSVJH[PVUZ[\IMYVTH WV[LU[PVTL[LYPUJHZLZ^OLYL0MLS[[OLU\[^HZU»[SPRLS`[VILJVTLSVVZL ZVKPKU»[ULLK[OLZLJVUKOVSL 5V[^P[OZ[HUKPUN[OLQVI[VTV\U[HWV[LU[PVTL[LY^P[OZ\JOHZ[\IPZ ZPTWSLLUV\NO

Mounting a potentiometer



MARK the centre of the hole where the potentiometer’s threaded stem is to be, and mark the centre of the location stub’s hole, as shown in Figure 6.10. The distance between centres depends on the particular potentiometer, as does the angle at which you need to position the two holes relative to horizontal along the line of the housings panel.

FIGURE 6.10 Marking the position of the two holes required for the potentiometer of Figure 6.9. • •

MARK both holes using a centre punch DRILL the holes using a pilot drill (no more than 2.5 mm). Position the housing over a block of wood, so that the drill bit doesn’t grab the metal and distort it as the drill bit’s cutting edge exits the hole. CONTINUED…

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Starting Electronics Construction

…CONTINUED •

DRILL both holes using a drill the correct size for the location stub



DRILL the threaded stem’s hole using the correct sized drill



POSITION the potentiometer in place



PLACE the washer, followed by the nut over the threaded stem. ;PNO[LU[OLU\[[VHÄUNLY[PNO[ULZZ

• TIGHTEN the nut, using pliers.

Take Note When you tighten a potentiometer nut (indeed, any nut which is located on a housing’s panel like this), you should take extra care to make sure the pliers don’t slip off the nut and scratch the panel. Figure 6.11 shows how to tighten the nut. Note how the washer underneath the nut protects the panel from the pliers.

FIGURE 6.11 Tighten the potentiometer nut using pliers. Push the pliers against the washer under the nut to help prevent the pliers from slipping off, thereby protecting the housing panel.

152

Housings

Take Note New potentiometers have long control stems, in order that you can cut them to the length you want. The final cut length is fixed however, by the type of control knob you want to use. In order that you can cut the stem to the required length, you therefore need to have the control knob to hand. Follow the instructions below to cut the stem to size.

*\[[PUNHWV[LU[PVTL[LYZ[LT[VÄ[HJVU[YVSRUVI



PUSH the control knob on the stem till it seats fully against the top of the stem



MARK the stem directly in line with the bottom of the control knob (Figure 6.12)

FIGURE 6.12 Push the knob on the potentiometer stem, and mark the stem. •

REMOVE the control knob, and measure the distance from the end of the stem to the mark (Figure 6.13) CONTINUED…

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Starting Electronics Construction

…CONTINUED

FIGURE 6.13 Measure from the stem end to the mark. •

NOW make a second mark on the stem the same distance from the top of the potentiometer’s threaded stem. Actually, some knobs OH]LHUV]LYOHUNZWLJPÄJHSS`PU[LUKLK[VJV]LY[OL[OYLHKLKZ[LTZV[OPZ second mark can be a millimetre or two closer to the stem end if your knob features such an overhang



CUT the stem on this mark. To do this, hold the end of the stem in a vice, with the stem horizontal. Hold the potentiometer body in one hand, while cutting the stem with a junior hacksaw in the other hand, as shown in Figure 6.14

FIGURE 6.14 Cutting the stem of a potentiometer. •

DEBURR [OLJ\[LUKVM[OLZ[LT^P[OHÄULÄSLYour potentiometer PZUV^YLHK`[VILÄ[[LK^P[OP[ZRUVI

154

Housings

Take Note Potentiometers are actually quite fragile. Do not hold the potentiometer body in a vice to cut off excess stem. Make sure you put the stem end in the vice!

Knobs 4HU`THU`[`WLZVMRUVIZHYLH]HPSHISLPUHSSZVY[ZVMZPaLZHUKZ[`SLZ -PN\YLZOV^ZHZLSLJ[PVU4VZ[HYLÄ[[LK[VHWV[LU[PVTL[LYLP[OLY ^P[OHW\ZOÄ[VY\Z\HSS`^P[OHZTHSSNY\IZJYL^[OYV\NO[OLZPKL ^OPJOJSHTWZVU[V[OLWV[LU[PVTL[LYZ[LT

FIGURE 6.15 A selection of common control knobs. Switches :L]LYHS]HYPH[PVUZL_PZ[PUZ^P[JOLZ^P[OZSPKL[VNNSLW\ZOHUKYV[HY` ILPUN[OLTVZ[JVTTVUZLL*OHW[LY>P[OPU[OLZL]HYPH[PVUZ OV^L]LY[OLYLHYLHSZV]HYPH[PVUZPUIVK`ZOHWLZHUKZPaLZ(ZHYLZ\S[ P[»ZUV[WVZZPISL[VPUJS\KLKL[HPSZVMOV^[VTV\U[HSSZ^P[JOLZOLYL 0UZ[LHK0»TNVPUN[VNLULYHSPaLHUKZOV^OV^[OLTHPU]HYPH[PVUZ ZOV\SKILTV\U[LK;OLZLTHPU]HYPH[PVUZHYLKL[LYTPULKI`IVK` ZOHWLUV[PU[LYUHSTLJOHUPJZ4HPUIVK`ZOHWLZHYLJPYJ\SHYHUK YLJ[HUN\SHY^OPJOUHYYV^Z[OLÄLSKKV^UZVTL^OH[ *PYJ\SHYZ^P[JOLZHYLYH[OLYSPRLWV[LU[PVTL[LYZPU[OLPYÄ[[PUNHUKTVZ[ VM[OLKL[HPSZPU[OLWV[LU[PVTL[LYZLJ[PVUHSYLHK`JV]LYLKHYLYLSL]HU[ OLYL:VTLJPYJ\SHYZ^P[JO[`WLZL]LUOH]LHSVJH[PVUZ[\I\Z\HSS`PU 155

Starting Electronics Construction [OLMVYTVMHZOHWLK^HZOLY^OPJOYLX\PYLZHZLJVUKOVSLQ\Z[HZ^P[O WV[LU[PVTL[LYZ[VJVYYLJ[S`TV\U[[OLZ^P[JO-PN\YLZOV^ZH Z^P[JO^OPJOTV\U[Z\ZPUN[OPZTL[OVK;OLTL[OVKVMTV\U[PUNJSVZLS` MVSSV^Z[OH[VMTV\U[PUNWV[LU[PVTL[LYZLHYSPLY)V[OOVSLZZOV\SKIL THYRLKV\[HUKKYPSSLK[OLU[OLZ^P[JOPZÄ[[LK\ZPUN[OLSVJH[PVU[HI ^HZOLYHUKHU\[^OPJOMHZ[LUZV]LY[OLZ^P[JO»Z[OYLHKLKZ[LT(Z ^OLU[PNO[LUPUNHWV[LU[PVTL[LY»ZTV\U[PUNU\[[HRLNYLH[JHYL^OLU [PNO[LUPUNHZ^P[JO»ZTV\U[PUNU\[PUJHZL[OLWSPLYZZSPWVMMHUKZJYH[JO [OLOV\ZPUN»ZWHULS

FIGURE 6.16 A miniature circular toggle switch, complete with location washer having a location tab. :VTLJPYJ\SHYZ^P[JOLZHYLWYV]PKLK^P[O[^VTV\U[PUNU\[Z`V\JHU ZLLVULVU[OLZ^P[JOZOV^UPU-PN\YL;OLZLOH]L[OLW\YWVZLVM HSSV^PUN[OLZ^P[JO[VILHKQ\Z[LKPU[LYTZVMWVZP[PVUZ[PJRPUNMHYV\[ MYVT[OLOV\ZPUN»ZWHULSVYJSVZLY[V[OLWHULS(ILULÄ[VM[OPZZLJVUK U\[PZ[OH[[OLV\[ZPKLU\[ULLKU»[IL[PNO[LULK^P[OWSPLYZ[O\ZH]VPKPUN HU`YPZRVMKHTHNL[V[OLWHULSV\[ZPKLHUKHSS[PNO[LUPUNPZKVUL[V[OL PUZPKLU\[\ZPUNWSPLYZ 9LJ[HUN\SHYZ^P[JOLZHYLYH[OLYOHYKLY[VTV\U[ZPTWS`ILJH\ZL YLJ[HUN\SHYOVSLZHYL]LY`T\JOTVYLKPMÄJ\S[[VLYY¯KYPSS6MJV\YZL PUNLULYHSP[»ZHX\LZ[PVUVMKYPSSPUNHOVSLPU[OLWHULS[OH[PZUVSHYNLY [OHUI\[VUS`ZSPNO[S`ZTHSSLY[OHU[OLZ^P[JOP[ZLSM[OLUJHYLM\SS` ÄSPUNV\[[OLOVSL[PSSP[PZIPNLUV\NOMVY[OLZ^P[JO[VÄ[;OLWYVJLZZPZ HJ[\HSS`LHZ`LUV\NOQ\Z[ZVTL^OH[SHIVYPV\ZHUKMVSSV^ZUV^ 156

Housings

Fitting a rectangular switch



MARK out the rectangular hole to be made



MARK the centre, using a centre punch



DRILL out a hole (using a pilot drill, and subsequent larger drills), Q\Z[ZSPNO[S`ZTHSSLY[OHU[OLYLX\PYLKÄUPZOLKOVSL



FILE [OLOVSL\ZPUNÄULÄSLZ[V[OLL_HJ[ZPaLYLX\PYLK

Hint When you file a hole in your housing’s panel, you’ll need to clamp the housing in a vice. To protect the housing from the vice jaws, you should get two small blocks of wood and clamp the housing between the blocks. Make sure the blocks are positioned close to the edge of the hole you are filing – this prevents the panel from flexing too much and being damaged while you file. This is particularly important with thin aluminium folded-metal chassis-type housings. Also, file from the outside in – this means that any burring you naturally get while filing forms on the inside of the housing, so is not visible from the outside when finished.

:VTLYLJ[HUN\SHYZ^P[JOLZOH]LWHY[PJ\SHYOVSLYLX\PYLTLU[Z-VY L_HTWSLZSPKLZ^P[JOLZV[OLY[OHUULLKPUNHYLJ[HUN\SHYOVSLMVY[OL Z^P[JO[HIP[ZLSM[VWYV[Y\KL[OYV\NOHSZVYLX\PYLOVSLZ[VZ\P[ZJYL^Z ^OPJOOVSK[OLZ^P[JOIVK`PUWSHJL;OLYL»ZUV[OPUNMVYP[I\[[V JHYLM\SS`THYRV\[[OLOVSLZ[VKYPSSHUKÄSLHUKNL[VU^P[OP[

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FYI

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Holes for some common rectangular switch shapes (and some circular ones, for that matter) can be cut out using hole punches, purpose-designed for the task. A hole punch comprises three main parts — a cutting tool, a socket receptacle, and a bolt arrangement. Using them is easy: you drill a hole the size of the bolt diameter, then fit the punch together, with the cutting tool on the front of the housing panel, the socket on the back, and the bolt going through the panel. As the bolt is tightened, the cutting tool punches out the hole in the panel, leaving a very clean hole. Such hole punches are quite expensive, but possibly worth the cost if you intend to make many identical holes.

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Starting Electronics Construction

Hint: There are so many switch variations that it’s usually possible to choose a switch type that is easy to fit. In other words, unless you want to use a rectangular switch for a particular purpose (although personally, I can’t think of any!), my advice is to use circular switches always. Remember that every operation you perform to your housing’s panel is just another opportunity to scratch the panel.

Fitting connections 4HU`LSLJ[YVUPJJPYJ\P[ZYLX\PYLZVTLMVYTVMLSLJ[YPJHSZPNUHSHZHU PUW\[VYHUV\[W\[(UH\KPVHTWSPMLYZH`OHZV\[W\[Z[VSV\KWZLHRLYZ VYHT\S[PTL[LYOHZPUW\[ZMYVTP[ZWYVILZ;OLJVUULJ[VYZ\ZLKMVYZ\JO JVUULJ[PVUZ]HYLS`^PKLS`KLWLUKPUNVU^OH[ZVY[VMZPNUHSZHYLILPUN JVUULJ[LK-PN\YLZOV^ZHZLSLJ[PVU

FIGURE 6.17 A variety of connectors used with electronic circuits and their housings. ;OLTV\U[PUNVMJVUULJ[VYZ[VOV\ZPUNZMVSSV^Z[OLZHTLWYPUJPWSLZHZ [OH[VMTV\U[PUNJVU[YVSZZ\JOHZWV[LU[PVTL[LYZHUKZ^P[JOLZ^P[OVUS` HML^TPUVYHKKP[PVUZVY]HYPH[PVUZ 6M[LUJPYJ\SHYJVUULJ[VYZOH]LHSVJH[PUNRL`VMTV\SKLKWSHZ[PJ^OPJO T\Z[TH[L^P[OHUV[JOJ\[PU[OLWHULSHZ[OLJVUULJ[VYPZÄ[[LK[V[OL 158

Housings OV\ZPUN;OLW\YWVZLVM[OLRL`HUKUV[JOHYYHUNLTLU[PZZPTWS`[V WYL]LU[[OLJVUULJ[VYYV[H[PUN-PN\YLZOV^ZHJVUULJ[VY^P[O[OPZ ZVY[VMYV[H[PVUWYL]LU[PVUKL]PJL0[HSSZV\UKZNVVKI\[P[KVLZTHRL Ä[[PUNZ\JOJVUULJ[VYZHSP[[SLTVYL[YPJR`(M[LYKYPSSPUNHOVSLPU[OL OV\ZPUN»ZWHULS[VÄ[[OLJVUULJ[VY`V\[OLUOH]L[VÄSLV\[HUV[JOPU [OLWHULS[VÄ[[OLRL`(ZL[VMQL^LSSLYZ»ÄSLZPZILZ[[VKV[OH[

FIGURE 6.18 A connector with a location key — a corresponding notch in the housing panel must be filed (using jewellers’ files). *VUULJ[VYZULLK[VILJVUULJ[LKPU[LYUHSS`·\Z\HSS`[V[OLWYPU[LK JPYJ\P[IVHYK^P[OHSLUN[OVMJVUULJ[PUNSLHK:VTLJVUULJ[VYZTH` ILT\S[PWVSLPLOH]L[^VVYTVYLPUKP]PK\HSJVUULJ[PVUZPUZPKL[OL VULJVUULJ[VY^OPSLV[OLYZ^PSSILZPUNSLWVSLPLVUS`VULPUKP]PK\HS JVUULJ[PVU;OL[`WLVMJVUULJ[VYKLÄULZ^OH[ZVY[VMJVUULJ[PUNSLHK `V\ULLK[V\ZL 6M[LUT\S[PWVSLJVUULJ[VYZHYLH\KPVPUUH[\YLTPJYVWOVULLHYWOVULZ HUKZVVUHUK[OL`^PSS\Z\HSS`YLX\PYLHZWLJPHS[`WLVMJVUULJ[PUN SLHKRUV^UHZZJYLLULKJHISL:JYLLULKJHISLPZMVYTLK^P[OHJLU[YHS PUZ\SH[LKSLHKZVTLZJYLLULKJHISLOHZTVYL[OHUVULJLU[YHSPUZ\SH[LK SLHK^YHWWLK^P[O\UPUZ\SH[LK^PYLHUK[OL^OVSLJVUZ[Y\J[PVUPZ PUZ\SH[LK-PN\YL ZOV^ZZVTLZJYLLULKJHISLPU^OPJO`V\JHUZLL [OLJLU[YHSPUZ\SH[LKSLHKHUK[OL\UPUZ\SH[LK^PYL;OL\UPUZ\SH[LK^PYL HYV\UK[OLJLU[YHSSLHKPZPU[LUKLK[VILLHY[OLKZVVMMLYPUNHTLHZ\YL VMWYV[LJ[PVUVYscreening·OLUJL[OLUHTLMVY[OLYLSH[P]LS`ZTHSS ZPNUHSZJHYYPLKI`[OLJHISLHNHPUZ[LSLJ[YVTHNUL[PJPU[LYMLYLUJL 159

Starting Electronics Construction

FIGURE 6.19 Screened cable, showing a central insulated lead, and the wire screening, all encased in insulation. (]HYPHU[VMZJYLLULKJHISLMVY\ZL^P[OOPNOMYLX\LUJ`ZPNUHSZPZ JVH_PHSJHISL3PRLZJYLLULKJHISLJVH_PHSJHISLOHZHJLU[YHSZPNUHS SLHK^P[OHUL_[LYUHSZJYLLUPUN/V^L]LY[OLZJYLLUPUNPZ\Z\HSS`PUH IYHPKLKMVYT