This Mitsubishi has a HALL trigger, but apparently it has a series capacitor that causes the very characteristic sharktooth signal.
The trigger is Coil type (one pulse per event ), but alternating positive and negative to distinguish 1-4 and 2-3 cylinders (are you sure?).
Every spark belongs to a step on the figure below. DC: ~2.5V, amplitude: ~2.5V. I recorded the trigger signal:
The signal is processed with LM1815 and series condenser so it is theoretically universal considering trigger type (hall and VR). In 50% of cases, LCD displays right value, otherwise rough half of proper RPM.
I thought about using graetz-bridge but then I loose the information whether 1-4 or 2-3 cylinder needs spark. The camsync could help find the correct cylinder. Note that greatz would not work for other reasons (the grounsd are connected, not independent!).
Any ideas, how to condition the signal?
- try swapping the 10k pullup inside v3.x : use an 1M or even higher (eg. 1.5M) pulldown. The series cap will drop voltage very slowly with that value.
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