Hi ,

This time i'm planing to build a tachometer to measure engine's RPM and hopefully after that planning to show the delay time between sparks .the next feature which is currently i have in mind is to add a flash light triggered by the first cylinder's spark (which is useful for determining the Cylinder TDC position) to tune the engine's ignition timing. this should make a good diagnostic tool for the mechanics and also myself. (although this is not a new idea)

1- For determining the RPM i'll use the COIL primary pin frequency and divide it by cylinder number. this will connect throught an RC filter to an Optocoupler then fed to the INT0 .

2- As for the spark detection i am planing to use the Spark wires (high voltage) through a Rogowsky coil. so my final device should have 8 Rogowsky coils max. ! i don't have any experience in using Rogowsky coils , but i'm rereading the info in this forum . so my initial plan on this is to use a 'Transistor + OptoCoupler' after the Rogowsky output and then fed all these to an 8 input OR then to INT1 , and output them individually to the Port 1 (something more like the interrupt addressing in x86 architecture ,if i remmember correct). then trigger the timer 1 to detemine the delays , and read the spark number from Port 1 .

3- I didn't know where to buy and what i need for the suitable flash light to be triggerable at frequencies up to 20Hz assuming the 1200 RPM! (turn on/off fast, without much further glowing than the time supply is provided)

How do you think about my initial ideas ?

The whole thing will use a AT89S51 and an LCD , so hopefully it's on topic ;) .

Thanks for your valuable time.
Farshid J.H.