E A d d - o n P r o j e c t s f o r +- C o m m o d 6 4 , +- a a c V I C - 2 0 , M i c r o : o r n l e c t r o n + OWEN BISHOP t • • Easy Add-on Projects for Commodore 64, VIC-20, BBC Micro and Acorn Electron OTHER TITLES BY THE SAME AUTHOR BP73 Remote Control Pr-ojecte BPS2 Electronic Projects Using Solar Cella BPI04 Electronic Science Projects BP124 Euy Add-on Projects (or Spectrum, ZX81 & Ace • OTHER BOOKS OF INTEREST BP130 Micro Interfacing Circuits - Book 1 SPl3t Micro Interfacing Cil'Cuite - Book 2 8Pl3S Secreta of the Commodore 64 BP139 An Introduction to Programming the BBC Model B Micro BP142 An Introduction to Programming the Acorn Electron BP147 An Introduction to 6502 Machine Code Easy Add-on Projects for Commodore 64, VIC-20, BBC Micro and Acorn Electron by Owen Bishop • BERNARD BABANI (publishing) LTD THE GRAMPIANS SHEPHERDS BUSH ROAD LONDON W6 7NF ENGLAND PLEASE NOTE Although every care has been laken with the production of this book to ensure that any projecta. designs, modifications and/or program! etc. contained herein, operate in a corrrect and Safe manner and alsel th'at any component.ll specified are nonnally available in Great Britain, the PubliaheNi do not accept respofUlibility in any way for the failure, including fault in design. of any project, design, modifi cation or program to work correctly or to cause damage to any other equipment that it may be connected to or used in conjunction with, or in respect of any other damage or injury that may be 80 caused, nor do the Publishen accept responsibility in any way for the failure to obtain specified component.&. Notice is also given that if equipment that is still under warranty is modified in any way or used or connected with home-built equi~~ menl then that warranty may be void. All the projects in this book have been designed and tested by the Author using models of the various microcomputers that were avail· able i.n Great Britain at the time of writing. The Author and Pub lishers accept no responsibility for failure of a project to operate or any damage that may be caused, should the manufacturers of the 80 microcomputers radically change the of their machines s~ification in the ruture or ror a particular overseas market. © 1985 BERNARD BABANI (publishing) LTD First Published - March 1985 British Library Cataloguing in Publication Data Bishop Owen Easy add--on projects for Commodore 64, VIC·2Q, BBC Micro and Acorn Electron. l. Computer interfaces 2. Microprocessors J. Title 001.64'04 TK7887.5 ISBN 0 85934 109 7 Printed and Bound in Great Britain by Cox & Wyman Ltd, Reading Contents Page INTRODUCTION I ••••••••••••••••••••••••••.•.•.•..•.•.•.• ••••••••••••••••••••••••••••• ........................... . Interfacing to Microcomputers ." , I Logic Levels in Computers 2 ••••••••••••••••••••••••••••••••••••••••••••••• User Port 2 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Decoder ............................................................................. . 6 Programming Sum.maries ............................................... . 15 Project I: PULSE DETECTOR 19 •••••••••••••••••••••••••••••••••••••• How It Works 19 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Building It ........................................................................ . 21 Using It ............................................................................. . 21 Detecting "'High Pulse" ................................................. . 23 8 Project2: PICTURE OIGITISER 24 •••••••••••••••••••••••••••••••••• How It Works 24 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Building It ........................................................................ . 29 ....................................................................... Final Check 33 .................................................................... Test Program 33 .. .. Programming ............................. .............................. . 35 " , , .............................................. Project 3: FIVE·KEY PAD 41 .................................................................... 43 HowIt Works Building It ........................................................................ . 45 Testing .............................................................................. 46 • ............................... Project 4: MODEL CONTROLLER 50 .................................................................... How It Works 50 Buildi.ng It ........................................................................ . 55 Programming ................................................................... . 57 ProjectS: BLEEPER ........................................................ 62 How It Works .................................................................... 62 ..................................... .................................. . Building It 64 , Programming ................................................................... . 67 Page ........................................... Project6, LAMP FLASHER 68 ·. .................................................................. How It Works 68 ................................................................... Building It ..... . 71 Programming ................................................................... . 71 ..................................................... Project 7, LIGHT PEN 73 ·. .................................................................. How It Works 73 . .. .. .. . . Building It . . .. . . . ..•...................................................... 74 Progrlllllllli.ng ................................................................... . 81 Project8, MAGNETIC CATCH ..................................... 85 ·. ................................................................. . How It Works 85 Building It ........................................................................ . 88 ............ ............................................. . .......... 92 ~~IlJl1ll1ling , Project 9, LAP SENSOR 94 ................................................. ·. ................................................................. . How It Works 94 Building It ................ ......................................................... 97 ................................................................... . 98 ~~llrlll1li.ng ........................................... Project 10, PHOTO· FLASH 101 ·. ................................................................. . How It Works 102 )f>l"()irI"llIllrlling ................................................................... . lOS ..................................... Project II, GAMES CONTROL 109 ·. .................................................................. How It Works 109 Building It .......... ............................................................... 112 ................................................................... . 114 )f>ro~arllrlling ....................................... Project 12, RAIN DETECTOR 116 How It Works .................................................. .................. 116 Building It ........................................................................ . 117 ................................................................... . 118 ~irI"IlIllJ1ling Project 13, WEATHERCOCK 120 ........................................ How It Works ................................................. 120 • •••••••••••••••••• Buildi ng the Vane ............................................................ . 123 Building the Circuit .................. ....... ................................ . 124 ................................................................... . 125 Jl1r()~llrJlIlling Page Project 14, ANEMOMETER ........................................... 127 How It Works ...... .............................................................. 128 Building It ......................................................................... 130 Program.m.ing ...................... .............................................. 132 Project 15, THERMOMETER ............. ........................... 135 How It Works .................................................................... 135 Building It ....... ... ............................................................... 138 Calibration and Programming ....................................: . .. 139 Project 16, BAROMETER .............................................. 143 HowIt Works ..................................................................... 143 Building It ......................................................................... 147 Programming ..................... ... ............................................ 150 Project 17, SUNSHINE RECORDER ........................... 155 How It Works .................................................................... 155 Building lt ......................................................................... 158 Appendix k THE DECODER ........................................ 165 How It Works .................................................................... 165 Power .................................................................. 169 ~uJ'J'lies Building the Decoder ............................ ............................ 171 .A5sembling the P.C.B. ...................................................... 171 IC Sockets ................. ......................................................... 177 Fitting the Case ................................................................ 177 Decoder/ComJ'uter 1nterconnectors ................................ 178 Testing .............................................................................. 183 Appendix B, DECODER WITH AN INTERFACE FOR THE ACORN ELECTRON ........ .............. 165 How It Works .................................................................... 185 Testing the Elect) on Version of the Decoder ................... 186 Programming .................................................................... 187 Appendix C, SUPPLIERS OF P.C.B .• AND KITS ..... 188 AppendixTh PIN ANDLEAD·OUTDETAIIS ........... 190 Introduction Interlacin g to Micr ocomputer s This book describes how to build circuits which el~lronic you can attach to your VIC·20, Commodore 64, Acorn Electron or BBC Microcomputer. All the devices have been tested, most of them with most of the machines. Owners of the BBC Microcomputer Model A should note that. they will need the User Port upgrade for their machine to allow it to operate with the devices in this book. For Project 11 they will need the Analogue Port upgrade too. All the devices have been tested with all of these computers. All the projects are simple and inexpensive ones, requir ing only a few transistors or integrated circuits. The inte grated circuits 8.re oflhe less expensive kind. The wiring re quired for each circuit has been kept to a minimum, an unus ual feature for a book oflhis kind, for microprocessor projects tend to need rather more wires than projects of other kinds. The result of this simplified approach used here is that all the projects can be built easily and cheaply, even by a rela· tive beginner. Once built, they are simple to operate. Writ ing programs to control them need not be complicated. Each project includes a simple program or two to get you started. Of course, those readers who are more expert at programm· ing can have lot of fun in writing elaborate programs based 8 on these projects. but the beginner can start with the short program and perhaps add extra fea tures later. The circuit designs apply equally well to the VIC·20. the Commodore 64. the Acorn Electron and the BBC Microcom puter. If you have a VIC·20 now, for example. and later change to one of the other computers, the projects can be operated from your new computer without having to alter them. If you have previously built similar projects for the ZX81 . Spectrum, or Jupiter Ace, as described in book num· ber BP124 . Easy Add-on Projects for Spectrum, ZX81 and 1