Fake Car Alarm Circuit

This simple fake car alarm or alarm decoy circuit device will simulate the presence of a burglar alarm in automobiles or homes. It has a few components, uses LM3909 and is easy to build. Mount R1 where daylight can fall on it. You may change the capacitor value for different flashing rates.
During darkness, LED1 flashes, making potential intruders think an alarm system is installed.

Fake Car Alarm (Decoy) Circuit Diagram

fake car alarm circuit diagram


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  • Syed Shiyas

    Dear Sir,

    Me like to construct one security system for my car, Santro GLS model. Can u help?

    Thanks in Advance


  • Göransson

    This is a cool circuit, LM3909 has been discontinued, but can still be found. Ordered a few from Ebay yesterday. Can’t wait till I get a chance to build this circuit!

    One question, I assume that the LED’s will be brighter as night falls, not switching on/off at a certain level, is that right? And if so, is there a way to make it turn on/off without fade?

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