I have an issue with a noisy VR-sensor signal that my MAX9926 IC isn’t managing to interpret correctly, and instead outputs rubbish. The wheel that’s being used has one long tooth and one short.
Here is the circuit. VR1 is the channel used in this case.
Here is a trace made today with my oscilloscope. Yellow is the VR sensor. Green the output of the MAX9926. The red dots are the actual edges on the encoder wheel that’s supposed to be picked up. Blue lines are gaps between the teeth.
As seen in this, more zoomed in scope, the noise is limited to about maximum 200mV.
I have tried to reduce the R4 to 1Kohm, in an attempt to "load down" the VR-sensor and rid some of the noise. Didn't have any affect at all.
I reach out to you to help me with suggestions on the circuit to filter out the noise or configure the MAX9926 in a better way to handle the signal. Thanks in advance.
Update 2020-03-10: I have added a 400 ohm resistor in parallel with C8 in an attempt to pull the voltage so low, that the MAX9926 doesn't react on it. It kind of worked. But as you can see, the square wave is time shifted from the VR very randomly. And the actual teeth are not translated into square wave.
Here I have made an illustration in RED, as what the actual teeth on the wheel look like, in relation to the YELLOW VR-sensor signal: