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

Multi-Zone Transistor Alarm - Support Material


Transistor Alarm
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Circuit Description

Click Here For A Photograph Of The Prototype.

Circuit Diagram For A 
Multi-Zone 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 17 places where the tracks are to be cut. Before you cut the tracks - use the "actual size" drawing to Check That The Pattern is Correctly Marked .

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

Actual Size Of Pattern

Pattern for Cutting
The Tracks on the
Underside of the Board

Next fit the 13 resistors and the Ten 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 are all shown lying flat on the board. However, those connected between close or adjacent tracks are mounted standing upright.

Add The Thirteen Resistors - 
And The Ten Wire Links

The next stage is to fit the diodes, transistors and LED. Note that the PNP transistors (BC557) are those with the emitter coloured red. Pay particular attention to the orientation of the diodes.

Add The Ten Diodes - 
The Six Transistors - 
And The LED

Fit the remaining Components - the eight capacitors and the relay. Note that C2 has its positive terminal pointing downwards.

Add The Remaining Components
And The Four Solder Bridges

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 4 solder bridges.

You're Now Ready To Test Your Circuit

External Connections

Connecting External Devices 
To The Transistor Alarm

Four-Zone Expansion Module - Veroboard Layout
Transistor Alarm
Veroboard Layout
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