Calculating Speed in a car

Giuseppe

So my goal here is measure a car's speed. Would I have to use a Vehicle Speed Sense wire or the tachometer wire? Also, I really do not what kind of method either one of those wires use to actually send this particular data to a speedometer. Does it just send pulses or does it send data through CAN BUS? Anyone ever obtain speed data from a car before?

Chet

You can read the speed from the OBDII port. Depending on what type of car you have, you can use an ElmXXX chip to ease the burden. (www.elmelectronics.com)

Good luck