Not always. Some older engines fire on the compression stroke as well. Before you say phooey, I know because I have one. The pre-made tachometer reads 2X the actual RPM.
The current flowing in a spark lead is oscilliatory - several pulses of alternating polarity can flow over a few uS. The thyristor/555 cleans this up. Nice idea..I've measured one of those clamp-on inductive pickups - a couple of hundred ohms. So quite a few turns.Allan
I'm in the boat with ya, Hexen...I've read over a thousand posts, and gotten two thousand different answers...I'm fairly good with electronics (although never dove into induction), and can build a weather station that'll make a sailor blush...lol....One buddy says NO to going direct from the inductor to a pin, another says it's fine...Ok guys...we really appreciate the help, and in depth discussion...I've learned a lot from it...but can get just a basic answer...Motorcycle Dyno, Arduino control board, inductive pickup.I'm going with the schematic from page 1, Post #5...Your own post, Hexen. =-)