range sensor

[ocool_15]

I am looking to build a sensor for a garage. I want it to sense if the car is below the door or not. Range of about 10ft no car and ~5Ft car there. I would like single sensor above door. I was thinking either Infra red or proximity sensor and have Leds at the front of garage for status. I think a pulsed emitter (555 timer based) would give me larger range but I'm unsure of how to implement the actual change sensing....

I could place sheet aluminium square on the floor if that would make it easier? I realize its not "audio" but I think it would be easy enough to answer.

[homer09]

what about an inductor?

http://electronics.howstuffworks.com/inductor3.htm

[ocool_15]

well I did think of a pressure sensor but I guess a inductor would work with no moving parts I might have to try some experiments with that. If it works for car at a light it seems to be just what I'm looking for.

[Mr Evil]

Similar to inductive sensors, you can also have capacitive proximity sensors. As an added bonus they could also detect a hypothetical non-metallic car

[ocool_15]

I did some testing with the inductor idea using a 555timer for frequency generation up to ~2.5 khz with a transistor on the output with a inductor in series with the base and also parralleling base to ground and can't get it to sense metal objects yet. I will try in a bit with higher frequnecies. I also found thisparts express sensor which would be a much easier alternative but not as diy fun

[ocool_15]

RE: Mr Evil
Ill keep that in mind in case he buys a F1 car