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THE ELECTRONICS CLUB HOMEPAGE

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Introduction

I started the Electronics Club at E.A.B.J.M. some time back in the early 1980’s. It was an after school voluntary activity intended to introduce students to the world of electronics through the construction of projects like a sound operated switch, a simple radio receiver etc. In the beginning it was the students themselves who suggested what they would like to make and we sat down together and worked something out. After a year or two of this I decided that it was worth collecting together all the circuits in a book. It is this book which is presented here.

If one or two of the circuit look a little "eccentric" it might be due to the fact that my main aims were

a) to evolve designs which used an absolute minimum of components and

b) to limit myself to using components, the operation of which could be relatively easily explained to beginners.

On the other hand, the appearance of eccentricity might be due to the simple fact that they are eccentric…

The circuits have all been tested though there might remain slight errors in some of the diagrams (especially the "vero" diagrams). You have been warned!

The circuits are all my own designs except

i) the two transistor reflex radio

ii) the stroboscope

iii) the 10Watt audio amplifier.

The radio was designed by G. W. Short and published in "The Radio Constructor" magazine in 1968 but it remains one of the best, most reliable, simplest designs for an a.m. radio receiver I have ever found.

The stroboscope was taken from an excellent French electronics magazine (sadly, no longer published) called "Elex".

The 10W amplifier is taken from "Transistor Audio and Radio Circuits" published by Mullard.

In all three of these projects, the printed circuit board design is my own and some of the component values may have been modified slightly.

Having collected together all the projects, I decided to write an introduction to some of the basic components and ideas necessary to understand how the circuits worked. One obvious limitation of this introduction is that it was written with one or two specific pieces of apparatus in mind; notably, a kit containing pre-wired and, nand, or gates etc. However, it is hoped that the basic ideas about resistance, capacitance etc might be helpful…

A final note about making printed circuit boards:

if you do not possess the equipment for making pcb’s the "professional way" ie photographically, here is a suggestion. Take the copper covered board and cover it with some of that thin brown plastic tape which is often used in packaging. Print he pcb layout onto a piece of adhesive paper (the sort that is used to print addresses for sticking on envelopes). Stick the paper on top of the brown tape and use a sharp cutter to cut away the paper (and tape) in order to expose the copper you want to dissolve away. It works well for simple pcb layouts of the type shown here. I used it for the two channel infra-red switch receiver but, I admit that it cannot really be used for anything more complicated that that.

David Hoult 2012

INDEX

PART 1
Some Basic Ideas and Components

PART 2

 

PART 3

 
 

Circuit Number

Two Transistor Radio

1

LED Flasher

2

Relay Driver

3

Sound Operated Switch

4

Infra-Red Switch

5

Low Power Amplifier

6

Simple Alarms

7

Long Duration Timer

8

"Person Counter"

9

I.R. Headphone System

10

Stepper Motor Driver

11

Optically Isolated Triac Driver

12

Combination locks

13

Reaction Timer

14

Sound to Light

15

10 Watt Power Amplifier

16

Triac Light Dimmer

17

Stroboscope

18

Appendix 1 Fault Finding

Appendix 2 Resistor/Capacitor Colour Code

Appendix 3 Pin Connections

Link to obtain .pdf files of these pages

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© David Hoult 2013