Proximity sensor toggle switch

[Jared J]

Hello all, lately I have been thinking of putting in a "modern" proximity switch in my car. I am wanting it to be like a kill switch. When I enter the car, the switch will activate. When I'm out of the car, the switch will turn off killing the car. My idea is to use it as anti-theft. Does anyone have an idea with may a finger print, prox card, or something like the keyless entry? It's an older car so it should be simple to wire it. But I'm not sure what parts I am gonna need. 

 

Thanks

[greenhorn]

I have heard of the keyless entry systems that come with some modern, more expensive cars. As I understand it, your key transmits a certain signal that can be detected by a receiver in your car. As long as the transmitter is close enough, the received signal will be strong enough for the car to stay unlocked.

While this may sound very convenient, I would strongly advise against it, because this offers multiple opportunities for car thieves to unlock your car. The first problem is that a thief could try to duplicate your transmitter's signal by just recording it and playing it back. This can addressed by designing the transmitter and receiver in a secure way. The other problem is relevant if you let's say park your car in front of a shop and go into that shop for a while. An attacker could just use a repeater to boost your transmitter's signal to make your car think that you are standing next to it, I recall reading about thieves actually doing this to successfully steal a whole number of cars from a parking lot one time (don't remember when or where exactly that happened).

If you plan to DIY such a system regardless, at least make sure that at least the system design is not suceptible to the first type of attack (signal duplication). I would check with your car insurance what would happen if someone stole your car by exploiting this system (I am sure some companies would try to blame it on you instead of paying).