Well I have been reading and not making much headway. Here is the problem:
90v dc motor driven with a KB electronics KBWS drive, controlled by the Arduino. This is working great.
Incremental optical encoder used to sense position. Was working great till I hooked up the motor. Max pulse frequency is under 500hz.
The KB drive is a PWM drive that runs at 20khz. Must not have good filtering on it as it makes all kinds of radio noise. This noise is interfering with my encoder signal. I get LOTS of random counts as soon as I power the motor drive up.
The cable from the encoder is shielded but it seems I need to add some filtering to get rid of the noise. How?
My initial thought was to add some decoupling capacitors to the encoder power lines and a low pass filter to the signal lines but I am having trouble calculating the proper values for the components.
I have turned on the pull up resisters on the Arduino input lines so I am thinking that perhaps I have a 20k input impedance. The encoder has TTL level outputs and seems I remember that has a drive current around 20 mill amps.
So, what would you do to your signal lines? Simple de-coupling capacitor to ground or a low pass filter series resistor and capacitor? If so, what values?