I am trying to get a Engine RPM signal from the primary coil on my 98' Ninja 500r.
The first scope pattern is of the primary coil building up current and then collapsing it (the peak voltage) to create current in the secondary coil to then fire the spark plug. This one is with out the BS2 connected between the resistors.
My plan is to monitor the voltage drop across the 10k resistor. I would use the pulsin command to measure the time in state 0. With the first scope pattern and a on/off threshold on the BS2 of 1.5v, This would measure the time between coil firing peaks and then be converted to engine rpm. As engine speed increases, the pattern frequency increases and the pulsin duration would decrease proportionally.
The second scope pattern is with the BS2 pin 0 connected between the resistors.
When the BS2 is connected, my voltages are pulled down by the input pin. Rendering my calibrations useless.
I simulated the same resistor circuit with a constant voltage, a 9v battery in place of the primary coil, and got these voltage readings:
9.6v across the battery
3.1v dropped across 10k w/o BS2 connected
1.48v dropped across 10k w/ BS2 connected
I also tried removing the 10k resistor with the BS2 connected and it had no affect on the voltage readings.
Why is the BS2 pulling my voltages down?
Isn't it supposed to be able to read voltages with a high internal impedance that won't affect the circuit operation? Like a DVOM.
How can I get a engine rpm signal in another way?
Thanks for your time and help.