help to figure out PWM Signal being sent to motor driver board

Other Hardware Motors, Mechanics, Power and CNC
1

I have been trying out how to figure out if the Arduino Uno 3 can determine PWM signals from the upper control board being sent to the motor driver board of a treadmill. I will eventually get rid of the upper control board.

I know the Fast/Slow pins are 5V, I tried using an Audio Oscilloscope with 10000 ohm resistor and a diode to determine the hertz but I think it was picking up interference from the motor. It was reading 60 hz on one channel and 120 hz on the other across about 8ms time span. I noticed that when I pulled it out of from the jumper it had a very similar waveform. Is it possible that the resistance was too high to make the needed observations and it was reading the interference/impedance?

Does anyone have a suggestion for trying to interpret the signal to try to get the arduino to replicate it?

Board1.jpg
Board1.jpg4128×3096 1.93 MB

2

Too many pixels to fit in my screen - please edit the photo to about 800x600.

Firstly do you know for certain that the treadmill is using a DC motor? If not
then it may not be as easy as I describe.

pulseIn () function is probably the way to measure this, successive calls looking
for high pulses and low pulses, record in some variables and then print to Serial.

The PWM frequency for a motor though is mainly a function of the size of the motor,
try 8kHz or 16kHz if a small motor, maybe 4kHz if large. Each motor driver circuit
has a practical upper limit to PWM it can handle too.

[ Seeing mains frequency suggests you didn't have grounds commoned up - you always
need to measure w.r.t. circuit ground. ]