Free Details Of How To Build An Anti-Hijack Alarm - Using Basic Readily Available Components.
COMMENTS Homer SUGGESTIONS

Hijack Alarm No.3 - Support Material

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Schematic Diagram
Veroboard Layout
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Circuit Description

Click Here For A Photograph Of The Prototype.

Circuit Diagram For
Hijack Alarm No.3
Click Here To Learn More About The Cmos 4001


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 34 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 - 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 Eleven 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.


Add The Eleven Wire Links


Now fit the 13 resistors. The resistors 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 Thirteen
Resistors


Next fit the 2 transistors, the 10 diodes, the 16v zener and the thyristor. The pnp transistor - BC557 - 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. Just because they look the same - don't assume that they have the same pin configuration.

Pay particular attention to the orientation of the diodes. Again - they're 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.

The positions of the kathode, anode and gate connections are marked on the stripboard layout. I used a TICP106D in the prototype because it's widely available. You'll probably find that any SCR - 30-volts or better - will work fine. But remember that the pin configuration of your SCR may be different from that of the TICP106D.


Add The Semiconductors


Fit the capacitors, the IC socket and the two relays. Pay particular attention to the orientation of the electrolytic capacitors. Note that electrolytic capacitors generally have a stripe down the side next to the negative terminal. See the Photograph Of The Prototype.


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're Now Ready To Test Your Circuit

Veroboard
Layout
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