I have a bit of s strange situation. I am busy building a telemetrics device for my motorcycle. But also as 'n shift light. The rpm I read perfectly using the attached circuit.
I am trying to read the bike’s existing speed sensor but here is where my problems start.
I have a test led connected to see when the sensor is on and off.
With the LED on I get ±2.8 volts coming to my circuit. With the LED off I get like -28 volts.
When checking this circuit’s output I get 4.88 volts with LED on and 4.90 volts with LED off and with the signal wire disconnected I get 0 volts.
Oh and if I connect a LED with 270rohm resistor to my output (input to Arduino Uno) then it stays half lit but you can see flashing from the sensor signal.
I guess this is why I can’t detect anything on the Arduino as there is not enough difference in the signal
Do I need a pull-down resistor perhaps or do I just need to adjust my resistor values in the circuit?