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Maplin auto electronics projects
The Maplin series This book is part of an exciting series developed by Butterworth-Heinemann and Maplin Electronics Pic. Books in the series are practical guides which offer elec- tronic constructors and students clear introductions to key topics. Each book is written and compiled by a lead- ing electronics author. Other books published in the Maplin series include: Computer Interfacing Logic Design Music Projects Starting Electronics Audio IC Projects Video and TV Projects Test Gear & Measurement Integrated Circuit Projects Home Security Projects The Maplin Approach to Professional Audio Graham Dixey 0 7506 2123 0 Mike Wharton 0 7506 2122 2 R A Penfold 0 7506 2119 2 Keith Brindley 0 7506 2053 6 Maplin 0 7506 2121 4 Maplin 0 7506 2297 0 Danny Stewart 0 7506 2601 1 Maplin 0 7506 2578 3 Maplin 0 7506 2603 8 T.A.Wilkinson 0 7506 2120 6 Auto Electronics Projects UNEWNES Newnes An imprint of Butterworth-Heinemann Ltd Linacre House, Jordan Hill, Oxford 0X2 8DP -^JjA member of the Reed Elsevier group OXFORD LONDON BOSTON MUNICH NEW DELHI SINGAPORE SYDNEY TOKYO TORONTO WELLINGTON © 1995 Maplin Electronics Pic. All rights reserved. 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 holder except in accordance with the provisions of the Copyright, Designs 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 9HE. Applica- tions for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publishers. The publisher, copyright holder and author have taken all reasonable care to prevent injury, loss or damage of any kind being caused by any matter published in this book. Save insofar as prohibited by English law, liability of every kind including negligence is disclaimed as regards any person in respect thereof. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 7506 2296 2 Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress Edited by Co-publications, Loughborough £^ Typeset and produced by Sylvester North, Sunderland all part of The Sylvester Press ^ Printed in Great Britain by Clays Ltd, St Ives pic Preface This book is a collection of articles and projects previously published in Electronics — The Maplin Magazine. Each project is selected for publication because of its special features, because it is unusual, because it is electronically clever, or simply because we think readers will be interested in it. Some of the devices used are fairly specific in function — in other words, the circuit is designed and built for one pur- pose alone. Others, on the other hand, are not specific at all, and can be used in a number of applications. This is just one of the Maplin series of books published by Newnes books covering all aspects of computing and electron- ics. Others in the series are available from all good bookshops. Maplin Electronics Pic supplies a wide range of electronics components and other products to private individuals and trade customers. Telephone: (01702) 552911 or write to Maplin Electronics, PO Box 3, Rayleigh, Essex SS6 8LR, for further details of product catalogue and locations of regional stores. VÜ 1 Car electrical systems The modern motor vehicle is a precision-built highly- tuned machine. High speed performance, low fuel consumption and quiet smooth-running engine all rely on efficient ignition, battery charging and general elec- trical systems throughout the car. The electrical system is very complex. One only has to look behind a dashboard to see the hundreds of wires of all sizes and colours, interconnecting the instruments, high voltage and high current circuits. Also, the electri- cal system is very prone to breakdown, whether this is a blown lamp bulb, a faulty dynamo or badly adjusted con- tact breaker points. 1 Auto electronics projects No two models of cars have identical electrical circuits. The electrical circuits are, however, similar and fall into categories such as conventional ignition or electrical ignition, dynamo or alternator, positive or negative earth. This chapter describes the basic systems: it is left to the individual car owner to interpret the descriptions and diagrams to suit their particular vehicle. One word of warning. Car electric circuits can cause damage to either the car or to the user if tampered with. For instance a short circuit across the battery can gen- erate hundreds of amperes and a lot of heat, even a fire: the ignition circuit generates very high voltages indeed: tampering with the instrument circuits, can cause mis- leading readings and a possible safety hazard to the driver. Before embarking on any changes to the car electrics, make every effort to understand how the cir- cuit works. In this way fault finding should be greatly simplified. The ignition circuit The purpose of the ignition circuit (Figure 1.1) is to sup- ply the high voltage required to operate the spark plugs in the correct sequence and so ignite the air/petrol mix- ture in each cylinder. The explosions generated push the pistons and so turn the engine, causing motion. The cir- cuit comprises the car battery, an ignition coil, the distributor and four (or six) spark plugs. The principle of operation is described later. 2 Car electrical systems Figure 1.1 The ignition circuit Battery charging All electrical systems draw their power from the 12 volt battery (Figure 1.2). If the battery was not continually charged it would become exhausted very quickly, par- ticularly if the lights, wipers and starter motor were in constant use. The turning of the engine charges the bat- tery by connecting it to a dynamo, via the fan belt. A 3 Auto electronics projects pulley network at the front of the engine constantly turns the dynamo which generates enough power to charge up the battery. A control box controls the charging rate and informs the driver via the ignition light if the battery is not charging. Some cars use an alternator in preference to a dynamo. These are more efficient but generate a.c. rather than d.c. and so require rectification of the a.c. output. Battery charging is described later. Figure 1.2 The battery charging circuit 4 Car electrical systems Lighting The lighting circuits are the simplest of all these, com- prising a simple connection of the 12 volt lamp to the battery via the instrument panel switches (Figure 1.3). These circuits are completely independent of the igni- tion and charging circuits, the one connection to each lamp being taken via a single wire and respective switch to the battery; the other connection uses the car chas- sis. The lighting circuits are described in more detail later. Figure 1.3 The lighting circuit 5 Auto electronics projects Figure 1.4 The indicator and accessories circuit 6 Indicators and accessories Contained within this circuit is the starter motor which draws hundreds of amperes from the battery to turn the engine until it fires (Figure 1.4). Heavy duty cable and a heavy duty solenoid carry out this operation, which is prone to trouble for various reasons. Also there is the fuel pump which is a small solenoid operated device to [...]... falls a c c o r d i n g l y T h i s unit, similar to a WC b a l l - c o c k , is s e a l e d for fire r e a s o n s , s e e Figure 1.26 27 Auto electronics projects c* « — Ο Ο ε »_ β> 28 Figure 1.23 Continued Car electrical systems 29 Auto electronics projects Figure 1.24 Mechanical fuel pump Horns c o m e in all s h a p e s and s i z e s Figure 1.27 s h o w s a simple type, working like... 2 Exhaust Induction Compression Power Cylinder no 3 Compression Power Exhaust Induction Cylinder no 4 Induction Compression Power Exhaust 4 - c y l i n d e r and 6 - c y l i n d e r engines 9 Auto electronics projects Figure 1.7 10 The four stages of combustion Car electrical systems • induction — t h e p e t r o l / a i r m i x t u r e is s u c k e d into the cylinder, • c o m p r e s s i o n — t... T h i s a c t s as a four-way s w i t c h t o r o u t e t h e high t e n s i o n to t h e s p a r k plugs, and as a m e a n s of g e n e r a t i n g t h e high t e n s i o n v o l t a g e 11 Auto electronics projects liiilllllillfj^ Figure 1.8 Basic high voltage generating c i r c u i t Figure 1.8 s h o w s t h e b a s i c high v o l t a g e g e n e r a t i n g circuit T h e o p e r a t i o n is as... i g n i t i o n coil Θ I Sparking plugs winding ^ J g n M o n «wteh ^ winding^ "Jl Figure 1.10 Secondary ^ „ g I Γ Ι ΠΙ | ^ o ^ ^ ^ ^ a m ^ ^ ^ ΠΙ ^ Sparking plugs f i r i n g c i r c u i t 13 Auto electronics projects • t h e high t e n s i o n pulse ignites t h e p e t r o l / a i r mix- t u r e in c y l i n d e r 1 c a u s i n g t h e engine to r o t a t e , • t h e d i s t r i b u t o r shaft r... found: • t r a n s i s t o r i s e d ignition or c a p a c i t o r d i s c h a r g e igni- tion — s e e Figure 1.14 and, • c o n t a c t l e s s ( o p t i c a l or m a g n e t i c ) ignition 15 Auto electronics projects Figure 1.11 16 The d i s t r i b u t o r Car electrical systems Figure 1 1 2 Contact breaker assembly Figure 1.13 Timing marks on fan belt pulley T r a n s i s t o r ignition u s e s... u r r e n t signal to t h e d c - d c c o n n e c t o r T h e p o i n t s t h e r e f o r e l a s t far l o n g e r and t h e s y s t e m is virtually m a i n t e n a n c e - f r e e 17 Auto electronics projects C o n t a c t l e s s ignition u s e s a moving magnet or infra-red ray to r e p l a c e t h e c u m b e r s o m e c o n t a c t b r e a k e r s , a trans i s t o r i s e d d.c.-d.c c... e c h e m i s t r y into a c t i o n , c u r r e n t from t h e b a t t e r y turning t h e p l a t e s into lead s u l p h a t e A b a t t e r y c h a r g e r , by Figure 1.15 The battery 19 Auto electronics projects way of t h e d y n a m o or a l t e r n a t o r , r e v e r s e s this p r o c e s s by r e s t o r i n g t h e b a t t e r y p l a t e s to t h e i r original c o m p o sition Modern... n s i s t o r i s e d c o n t r o l c i r c u i t m a i n t a i n s a c o n s t a n t b a t t e r y c h a r g i n g c u r r e n t by adjusting t h e c u r r e n t in t h e r o t o r winding 21 Auto electronics projects Stator windings in which current is generated Diodes convert alternating current to d.c Rotar turns inside stator assembly Figure 1.17 A l t e r n a t o r and control c i r c u i t r... filaments for c o m p a c t n e s s Quartz halogen b u l b s , with a gas surrounding t h e t u n g s t e n filaments, give off g r e a t e r b r i g h t n e s s Figure 1.18 Dual filament bulbs 23 Auto electronics projects As t h e h e a d l a m p s b e t w e e n t h e m c o n s u m e s e v e r a l amp e r e s , t h e h e a d l a m p ( o r f l a s h e r ) s w i t c h has to b e h e a v y duty and high c... h e s t a r t e r m o t o r T h i s wiring is t h e t h i c k e s t t o b e s e e n under t h e b o n n e t and e v e r y s t e p is taken to m i n i m i s e any h e a t g e n e r a t e d 25 Auto electronics projects d e s p i t e t h e c o s t s of t h e t h i c k c o p p e r wire T h e s t a r t e r m o t o r e n g a g e s with t h e engine via t h e flywheel t o s t a r t t h e engine, as s e e . 2053 6 Maplin 0 7506 2121 4 Maplin 0 7506 2297 0 Danny Stewart 0 7506 2601 1 Maplin 0 7506 2578 3 Maplin 0 7506 2603 8 T.A.Wilkinson 0 7506 2120 6 Auto Electronics Projects. lead- ing electronics author. Other books published in the Maplin series include: Computer Interfacing Logic Design Music Projects Starting Electronics Audio IC Projects Video and TV Projects. Projects Video and TV Projects Test Gear & Measurement Integrated Circuit Projects Home Security Projects The Maplin Approach to Professional Audio Graham Dixey 0 7506 2123 0 Mike