I have made use of a frequency to voltage converter (LM2917, 8pin version) to convert the frequency from my car's RPM tach signal wire to voltage to then read it with my Arduino and make a digital RPM readout.
Here is the circuit I have done:
The resistor, capacitor and the diode connected to the tach signal wire is to get rid of the DC offset.
There are 2 problems at the moment:- 1) The chip doesn't convert the signal properly, the higher the RPM from the car the less accurate the output voltage, hence a very off RPM compared with the RPM dial in the car. For example when car's RPM dial reads 3000 RPM the digital output reads 2400 RPM.
2) The chip itself gets very hot even if there is no signal into it and even when nothing is connected to the output voltage pin.
Has anyone got any experience with this chip at all?
Any help is appreciated.