I've already searched this well covered topic, but couldn't find an answer :? .
I want to pulse measure the tacho for cars & motorbikes, however are unsure about a suitable generic interface.
What different types of signals can I expect?
12V, 5V, low side of coil, high side of coil, max voltage, negative voltage?
I'm thinking a resistor divider, 10k/10k, with a 1nF filter & zener clamp, followed by 100k of series isolation into the micro.
Alternatively, perhaps a input series 400V diode (cathode on output), 2.2k series isolation, 1k pullup to VCC, 1nF filter, reverse voltage diode clamp to ground, and 100k series isolation into micro. This may provide the most protection and accommodate any positive voltage switching input to ground.
Apart from that, I was thinking of a transistor buffer for further isolation.
Any advice most appreciated. I don't know a lot about the different tacho pickups to expect. (speed pulse interface will be the next topic :wink: )
P.S. This looks a neat forum...