Hello,
I have a homebuilt airplane that uses a Rotax 912 engine and I want to make an engine monitor for it.
Most of the engine parameters I need will come from resistive sensors, so I will set up voltage dividers to read these.
The one input that I am unsure of is reading the pulses from the RPM sensor on the engine. I think I have a handle on the coding aspect, but getting the input to the digital pin is what I am unsure of. I have searched and found some information but nothing that just spells it out for me.
Taking what I have read online I have come up with the circuit below using a LM393 comparator. I am just a tinkerer and have no formal electronics background.
Can someone who actually knows what they are doing tell me if my approach is sound?
If not can you guide me?
Thank You,
John Brannen
Here is the output from the sensor on the engine. (I'll make images visible shortly) As you can see, with a 100 ohm load the voltage across the load varies with RPM with the peaks of the pulses at about 2.5 V at min RPM and 7.5 V at max RPM.
On the left, I started with the sensor circuit having a diode to clip the negative voltage and the 100 ohm load. I then put the LM393 circuit to the right with a bout 1 V reference to the comparitor through a voltage divider. The as I understand it , the LM393 will output Vcc, which in this case is 5 V which goes to the digital input through a load resistor.
