Beginners • Re: Help wanted with NEMA17 stepper motors

I've connected up the opto-isolator as you have shown. The only difference is that I have taken my +5v from the power supply rather than from the Pi, but it's the same supply that powers the Pi, so that should make no difference. The first clip shows the voltage at the output, just over 5v which is fine. The second shows the current, 13.09mA, which also seems to be fine, and within the range specified in the driver data manual. The two LEDs in both clips are just indicators to show the input and output signals.

While both the voltage and current seem to be ok, I am not getting any movement of the stepper motor, although there is a ticking sound which indicates that it is at least attempting to do something. Compare that with one of my previous tests with the Pi connected directly to the stepper driver, when the stepper motor operated correctly.

How have you verified this? Does the motor turn when PUL is driven by something other than the Pi?

This is the test I'm referring to - connecting the Pi directly to the stepper drivers without trying to do any logic level shifting.

https://www.dropbox.com/scl/fi/o6gj4zbm ... qvl6&raw=1

https://www.dropbox.com/scl/fi/9yljfp7b ... 1gj0&raw=1

I have to admit I have problems trying to get my brain to work with NPN logic - it seems like the work of the devil to me with everything back to front and not intuitive at all. But from your diagram of the Sparkfun connections it is clear that the logic signal is the -ve connection, and the PUL+ connections remains at a constant +5v.

Statistics: Posted by Newlands — Tue Apr 01, 2025 10:53 am

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