Hello,
I am trying to use the A4988 stepper driver for the first time and I have run into a very strange problem: the motor steps fine but regardless of the input on the DIR pin the motor turns only in one direction (anticlockwise). I searched both the forums and the internet and I did not find anything other than “check your wiring” which I have done without success.
Setup:
- Vmot 12V, 1.5A max
- Vdd roughly 4.6V from Arduino Nano 5V
- Stepper SY35ST26-0284A
- Wiring according to the minimal wiring diagram on product page (SLEEP/RESET connected, Vmot capacitor present)
- Vref set to 0.11V to achieve maximum motor current of 0.26A
What I tried / checked:
- I have measured the voltage between ground and DIR pin and it does change between 0 and roughly 4.6V as expected but the motor direction does not change with it. I measured directly on the pin on the driver board to rule out contact problems.
- I have replaced the STEP input from Arduino with a push button (connected to Vdd) which works fine, motor steps on button push and is stationary otherwise.
- I have replaced the DIR input with the same push button as above but that does nothing, motor turns only in one direction regardless of button position.
Observations & questions:
- There is a tiny coil whine from the stepper even when it is stationary. Is that usual?
- The small heat sink I added to the A4988 chip gets really hot (almost too hot to touch) within seconds of connecting Vmot, even though measured current through the stepper is only 0.26A. Is that normal?
- I did not post a picture of the wiring as I cannot think of any wiring error which would cause this behavior (since I checked the voltage on the DIR pin). If you can think of any such wiring error let me know and I’ll post a picture.
- Can you think of any failure mode which would result in the driver working fine (stepping) but ignoring the direction selection? How likely is it in your opinion I damaged the driver in such a selective way vs. this being a manufacturing defect?
Thanks in advance for your reply, I’ll be glad for any suggestions.
Best regards,
Regis