Anyone out there ever put an oscilloscope on the kill switch signal on the SEM ignition - ie the orange wire out of the CDI?
I have a Trailtech computer I am fitting. They normally use a length of wire wrapped around the spark plug lead to capacitively couple a signal to drive the tachometer. This in itself sounds a bit dodgy and you are kinda setting yourself up for the plug lead to fail!
I was hoping to use the kill signal to drive the tacho input instead so the extra wires don't have to run down from the headstock. I measured the "signal" on my scope & it blew it off scale!!! I then made a 100:1 voltage divider and confirmed the kill switch wire carries 200+ volts peak-to-peak at idle & up to 450V p-p when you rev it!!! Therefore, if a the kill switch ever falls apart on you, DON'T put your finger into the contacts - they will likely give you a nasty bite! Also make sure you treat this wire with care when working on it with the engine running.
The other thing is, connecting a 1.2k resistor across the orange to ground will not stop the bike while a 1k resistor will. You don't need much of a short to ground at all on the kill circuit to stop the bike.
The waveform looks like it is actually coming from the CDI charging coils, not the trigger coil so should not be any use to drive the tacho. Does anyone know for sure what the internal CDI circuit looks like or have you had experience with aftermarket tachos?
I have a Trailtech computer I am fitting. They normally use a length of wire wrapped around the spark plug lead to capacitively couple a signal to drive the tachometer. This in itself sounds a bit dodgy and you are kinda setting yourself up for the plug lead to fail!
I was hoping to use the kill signal to drive the tacho input instead so the extra wires don't have to run down from the headstock. I measured the "signal" on my scope & it blew it off scale!!! I then made a 100:1 voltage divider and confirmed the kill switch wire carries 200+ volts peak-to-peak at idle & up to 450V p-p when you rev it!!! Therefore, if a the kill switch ever falls apart on you, DON'T put your finger into the contacts - they will likely give you a nasty bite! Also make sure you treat this wire with care when working on it with the engine running.
The other thing is, connecting a 1.2k resistor across the orange to ground will not stop the bike while a 1k resistor will. You don't need much of a short to ground at all on the kill circuit to stop the bike.
The waveform looks like it is actually coming from the CDI charging coils, not the trigger coil so should not be any use to drive the tacho. Does anyone know for sure what the internal CDI circuit looks like or have you had experience with aftermarket tachos?
