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Enhanced Hijack Alarm - Construction Guide

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Enhanced Hijack Alarm - Circuit Description

Enhanced Alarm - Veroboard Layout

This layout is almost identical to the original. The main differences are - the stripboard needs an extra three columns of holes on the left-hand side - there are four extra components to fit - and the tracks have to be severed in two more places. The changes are highlighted in red. If you remove the 12-volt input terminals - there's enough room to fit the extra components to the original board.

Modified Veroboard Layout

Parts List

Parts List


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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 36 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
ACTUAL SIZE



Next fit the 15 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 Fifteen Resistors - 
And The Ten Wire Links


Now fit the 5 transistors, the 12 diodes, the 2 relays and the 14-pin socket. The pnp transistor is the one with the emitter arrow coloured red. If you are using transistors other than the BC547 and BC557 - check their pin configuration before soldering them in place. Again, the diodes are all shown lying flat on the board. However, those connected between close or adjacent tracks are mounted standing upright.


Add The Semiconductors
Relays and Ic Socket


Fit the eight capacitors. Pay particular attention to the orientation of the electrolytic capacitors. Note that while C3 & C6 both have their plus terminals facing upwards - the plus terminals of C4 & Cx face downwards.


Add The Remaining Components


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 12 solder bridges.



Add The Twelve Solder Bridges


Finish off by inserting the Cmos 4001 into the socket. Pin 1 of the IC should be in the top left-hand corner. Check that all 14 pins have entered the socket. Sometimes - instead of entering the socket - a pin will curl up under the IC.

You Are Now Ready To Test Your Finished Circuit

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