Simple Electronic Vehicle Immobilizer

Description

This simple vehicle immobilizer circuit is cheap, easy to make, install and operate . It’s also very discreet.

Thoroughly field tested, it’s robust and weather resistant design can prevent vehicle theft even if the thief has the keys!

In it’s most common application, it prevents the engine from turning over until the vehicles ‘G-Spot‘ is touched at the same time the key is turned to the ‘Start’ position, and the operator is earthed!

Here’s a completed G-Spot beside an AA battery

Animated Schematic and Circuit Description

I know, it’s a little bit ‘fancy’:

I know, it’s a little bit ‘fancy’:

Turning the vehicles key supplys power (red).
The SCR prevents operation of the load until the voltage on the base of the PNP transistor is lowered by the earthed owner contacting the G-Spot (green),
This turns the transistor on and current then flows through the collector circuit and 220 ohm resistor (orange), triggering the gate of the SCR.
Once triggered, the SCR allows power to flow to load (green) and remains on until power is isolated.

Parts and Materials

These are all the electronic components required ~ the diode is not essential:

These are all the mechanical components:


Also require:
Solder, cleaner, tape, lacquer, fiberglass resin and hardener.

S:circuitstoday.com