This is a car alarm simulator which using the LED as a simulation output. This simple circuit can tell you whether your car is running or not by detecting the voltage difference when the car is on and off. This occurs because when your car is running the Alternator puts a out a voltage a little bit higher than when the car is off.
The circuit will be activated automatically when the engine is turned off.
How to run the circuit:
1. Connect the circuit to the car electrical system.
2. Adjust RV1 until the LED flashes when the engine is not running
3. Start the engine, the LED should turn off. If the LED still on, the andjust the RV1 slighty
This circuit actually is a kits, you can get the kits at http://www.electronickits.com/kit/complete/surv/vemk126.htm. But it is very possible to you to build your own car alarm simulator circuit.
Download the circuit manual HERE.