Free Details Of How To Build An Anti-Hijack Alarm - Using Cheap Off-the-Shelf Components.
IMPORTANT. The following construction details are for the First Hijack Alarm. If you want to build the Enhanced Hijack Alarm - an alternative Construction Guide is provided.
Veroboard Layout
Parts List
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, 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.
Actual Size Of Pattern
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.
Now fit the 4 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.
Fit the seven capacitors. Pay particular attention to the orientation of the electrolytic capacitors. Note that while C3 & C6 both have their plus terminal facing upwards - the plus terminal of C4 faces downwards.
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.
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