Hi Group,
I am working on a project which will detect if a automobile is running. The output of sensor would be a TTL high for running and a TTL low for not running. The circuit will be inside the car, most likely in the glove compartment or storage compartment. It will not be connected to the automobile and run off of batteries.
My thoughts are to use a common 455KHz IF filter and amplitude detect or a 10.7 MHz IF filter and do the same.
Which frequency would be better and/or easier to design around? (455KHz or
10.7MHz). How about VHF or a super-reg with a wide bandwidth?
How much gain would a stage following an IF filter require such that it could be used as a level detect?
Other suggestions? (I want to stay away from any connections into the car).
Paul