I have an old bus with some electrical problems that I am trying to solve.
One problem is the dashboard. For many years, the dashboard was leaking rain water because of a broken windshield. The instruments don't work properly and I can't trust the information (air pressure / coolant temp and fuel level).
For the pressure and other sensors it's easy to do with an Arduino, but the Hall effect sensor for the motor RPM is another story.
I've tried to make a "copy" of the schematic for the sensor circuit. I'm not sure if it is correct or not (especially with capacitors and transistor). My sensor has only two wires, one from the dashboard and another one to ground. I can't find any schematics to explain how it works.
How can I use an Arduino to read the value?