MilesPerTank,
Thats an idea. I was thinking maybe a little capacitor before the zener, to give the zener time to turn on. And when I do mine I am probably going to wimp out
and use opto-isolators, and schmidt trigger comparators behind those. I am going to have to condition my signals anyway due to the hall effect switch I will need to put in the speedo. I have no vss sensors.
dcb,
I would think if the pulse is short enough, it may occur and die away before it can be read by the cpu. Again, I have no idea if this is an issue, but I worry about slow and undetected damage to the cpu chip input over long periods of time. Even the digital scope used to show the 65? volt spike may not have detected the peak, if the peak was short enough. We also don't know how long/how-much-capacitance the scope leads were. That scope screen looks like a pc running windows, which suggests it is not exactly the highest MHz on the block.
I am happy to be proven wrong, though.
Also, I want to say you are a genius for coming up with this thing, and I salute you.
