Originally posted by ren.
Link here --->
http://autospeed.drive.com.au/cms/ar...ml?&A=0059&P=1
This article was originally posted from the above link at Auotspeed!!
If wiring up a couple of relays doesn't worry you and you can handle a soldering iron and a multimeter, this immobiliser is for you.
You only need a:
- 12 volt heavy duty car relay;
- 12 volt Double Pole Double Throw (DPDT) relay;
- 12 volt flashing LED;
- reed switch that closes when a magnet is nearby;
- pushbutton that opens when pushed;
- broken remote from a car alarm;
- and a magnet.
Most of these bits and pieces you can get from an electronics shop.
Like all immobilisers, this one shuts down the car's EFI or ignition system. But what's different about ours is that if the thief steals your keys (with the remote control attached), he still can't drive away with your car. That makes it just about unique!
So how does it work?
The guts of the remote transmitter case are removed and the magnet is placed inside. The circular magnet from a tiny speaker has been used here. When you enter the car, you casually swipe the transmitter case past a special place within the car's cabin. This place might be on the centre console, a part of the dashboard - pretty well anywhere. Hidden behind the area that you swipe is the reed switch - a switch that is sensitive to magnetic fields. The swiping triggers the reed switch that in turn switches off the immobiliser.
Because the reed switch is located behind the plastic of the dash or centre console, there's nothing to see. The swiping movement can be quite natural - part of your hand movement as you put on your seatbelt or settle yourself in the seat. That means that even if a potential thief is watching you closely, he doesn't get any clues.The remote (at right) triggers the reed switch (left) whenever it comes close. Only you know the location of the reed switch!
When you want to arm the immobiliser, you press the button. The pushbutton can be in complete view - the thief gains nothing by ripping it out and either disconnecting the wires or bridging them. When you press the button, the on-dash LED starts to flash, indicating the car is now immobilised. It also reminds you to switch off the system when you re-enter the car.
Linear Mode
