Use this DIY Alarm in your home - small business premises - shed - garage - lock-up etc. It has provision for both normally-closed and normally-open input devices such as - Magnetic-Reed Contacts, Foil Tape, Movement Detectors, PIRs, pressure mats etc.

Four-Zone Module


SCR Alarm
Front Page
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Instant Zones - Circuit Description

Extra Zones For The
SCR Burglar Alarm

Parts List

Parts List


RS Components

UK & Ireland

Construction Guide

Click here if you're new to constructing stripboard projects.

The terminals are a good set of reference points. To fit them, you may need to enlarge the holes slightly. Then turn the board over and use a felt-tip pen to mark the 10 places where the tracks are to be cut. Before you cut the tracks - double check the position of each cut.

When you're satisfied that the pattern is right - cut the tracks. Make sure that the copper is cut all the way through. Sometimes a small strand of copper remains at the side of the cut and this will cause malfunction. Use a magnifying glass - and backlight the board. It only takes the smallest strand of copper to cause a problem. If you don't have the proper track-cutting tool, then a 6 to 8mm drill-bit will do. Just use the drill-bit as a hand tool - there's no need for a drilling machine.

Pattern for Cutting
The Tracks on the
Underside of the Board

Next fit the 9 resistors, the 5 capacitors and the Four Wire Links. For the links - I used bare copper wire on the component side of the board. Telephone cable is suitable; the single stranded variety used indoors to wire telephone sockets. Stretching the core slightly will straighten it; and also allow the insulation to slip off.

The resistors and diodes are all shown lying flat on the board. However, those connected between close or adjacent tracks are mounted standing upright. See The Photograph Of The Prototype.

Add The Nine Resistors - 
The Five Capacitors - And
The Four Wire Links

The next stage is to fit the diodes, transistor, and LEDs. Pay particular attention to the orientation of the diodes and LEDs.

You'll probably want to mount the LEDs on the front of your alarm panel. Connect them to the circuit board using pairs of flexible wire - the cores from a piece of alarm cable are ideal.

The wires may be connected to either the front or the rear of the circuit board. Leave them long to start with - and twist them into pairs to keep them tidy. You can cut them to size later - when you come to assemble your alarm panel.

Add The Eight Diodes - The Transistor - 
And The Four LEDs

Turn the board over and examine the underside carefully - to make sure that there are no unwanted solder bridges or other connections between the tracks. If you backlight the board during the examination - it makes potential problem areas easier to spot. When you're satisfied that everything is in order - add the 3 solder bridges.

You're Now Ready To Test Your Circuit

External Connections

Connecting External Devices 
To The Four-Zone Module

Four-Zone Expansion Module - Veroboard Layout
Four-Zone Module - Photograph The Rest of Ron's Circuits Write To Ron More Free-to-Use Circuits Circuit Exchange International