Point taken but still curious how this module can create 4 different pulse trains if the output is the Vcc. That is why I had it wired backward in the first place. I do not understand how multiple signals can be managed with the signal connected to the outs.

Ok last question, I do not how it can operate multiple signals when they all are connected to the common Vcc. My stepper has separate signal for CW and CCW directions. So the Vcc will go to V+ for both directions and the V- for each will go to the 1 of the 4 channels. I guess I am confused on how the VCC which is constant??? gets manipulated when the input signal is going into V- for two signals at once.

Thanks for this.... I am not sure how it worked either but this was driving a stepper for while but it might explain why it suddenly stopped working =). Is there an advantage of using the open collector? I think what through me off is having my square wave on the lower potential side of the LED.

Thanks for this answer. Just to clarify my understanding ... The square wave signal controls the LED by raising and lower the potential after current has moved through the LED? I ask because I will move this to a stepper controller and the VCC will always show high so I am not sure how the pulses are generated in the corrected circuit.

@Nedd I updated the question with more details including links. This setup worked a few months ago so it is a head scratcher as to what happened. The digitizer appears to work as I can communicate with it but the readings always fail. So I want to see if the load cells need to be replaced.

@AJN I think I see your point... The challenge is to convert my force output back to voltage so I can compare and correct with a PID controller. My emperical force relation has hangle as the independent variable, I am not sure why a Fourier series is not needed the raw data is very much a sinusoid. Are you saying just use a look up table or something? Any chance I could implement feed forward logic in this setup? I am also worried about lag

@AJN thanks for the comment. I concede that is will need to turn around to achieve the middle wave form. I am confused about your suggestion. How do I implement the PID on the motor when the input is voltage and an output of angular velocity? Also when I say empirical formula it really is a Fourier series representation. Would that still work? If you put an answer in I can up vote it. Thank you for your assistance.

Sorry for the long delay I added some force vs time plots. I have also added more detail to my post. I am looking for a way to bridge rotation speed and angle position.

@AJN Sorry for the long delay. I have updated my post. I have created some empirical relations but I still am not sure how to connect voltage input to a force output.

I sort of get you. My problem is I am driving the crank with a DC motor so hard for me to hit a giving position. I was planning on controlling the duty cycle on the voltage and just modulate the speed in which i move from F_min to F_max. I guess my main concern is overshoot. If I over shoot too close to the max it goes down and the PID would have to flip positioning. I guess I could try just doing the controller part with just P ?