The attached transistor ignition circuit for a model engine is my diagram of a proprietary kit. I have built and tested it, and surprisingly it works.
I would like to take a tachometer interrupt signal from it for an UNO based engine management system and display.
Initially, I thought I could simply parallel the LED on pins 4 & 5, but now a dangerously slight uderstanding of electronics suggests that probably would not work. I am getting the vague idea that this circuit 'works' on currents rather than voltages.
I would like to get a falling edge signal when the hall sensor switches off, as that corresponds with the spark timing.
I want to avoid having to put another sensor on the engine if possible. If it would help, the hall sensor could perhaps be connected to the ignition circuit in some other way.
Could anyone advise, please?
Ignition_circuit_diagram.pdf (95.6 KB)