Wednesday, April 20, 2011

Stepper Issues

This stepper motor is driving me crazy... I've tried all the iterations (I think) and it gets power, the axle won't rotate, it buzzes... but no rotation. I'm going to spend a few more minutes with it tonight... maybe tomorrow... and then move on to the robot project which is next.

I've checked my wiring... double-check it... it's not the wiring. I'm pretty certain something weird is going on with this motor. I have a LOT of stepper motors (4 for my 3D printer and 3 for my CNC machine) but they have unique connectors that I'd have to cut and I'm not going to do that for this project... these are BIG steppers and not cheapies at all.

In the meantime, I've got to solder up a MotorShield that I'll be using for Project 29... will try to get to that tomorrow...


  1. Did you try spinning the motor shaft by hand just to make sure that something wasn't stuck inside?

  2. Yes, it will turn fine when not powered... and when powered, I can still turn it if I twist it hard enough to overcome the resistance. The stepper is energized, but it simply will not rotate.

  3. Odd that it would turn freely, but with resistance when powered, yet it won't turn when you tickle the various leads with power. Look on the bright side though. Since the motor is no good, at least you have an excuse to take it apart and study it's guts!

  4. By the way, my motor shaft will "jump" with power connected to any pair of leads within one of the trios. Once it jumps to the next step, it holds position. There is no buzzing or vibration at all unless I try to force it to turn. When I force it the vibration grows steadily stronger until the break-over point. Then it locks in at the next step. I think the buzzing that you are getting must confirm that the motor is defective.

    For the benefit of others following your blog, I note that the motor driver chip gets very hot over extended periods of slow stepping and this could lead to failure for people trying to embed this circuit in an art project or display.

    One of the experts in my robotics group tells me that these chips really aren't made to drive stepper motors or DC motors directly, but that instead, the outputs should be used to switch a set of high power mosfets. For these experiments, that would be overkill, but I was warned that for a high stress/high reliability application, the driver chip should be coupled to the mosfets via opto-isolators...and truthfully, I have nearly no idea how to implement any of that....yet...

    Anyway, I need to back track to the LCD projects.



  5. found this page and thought it migh help some people out

  6. I too found that my stepper just sat there and vibrated. I found a solution to the problem that works for me. I'm using an Arduino Uno powered with an external 9 volt battery. Vin (looks like a 9 in the book) on the Arduino accesses the (+) power from the external battery supply and can be used to power your stepper motor. The stepper motor came from Adafruit. It's a PF35T-48L4 unipolar stepper. The wiring to the motor is as follows: Winding #1 Green is middle, black is coil side 1a and brown is 1b. Winding #2 is red-middle, orange-coil side 2a and yellow-coil side 2b. The motor used in the authors project seems to be completely different. You need to rearrange the connections in order to make the PF35T-48L4 from Adafruit work properly. The green and red wires are connected together and go to Vin on the Arduino board (THATS THE KEY DIFFERENCE!). Black goes to pin 3 (1Y), Brown goes to pin 6 (2Y), Orange goes to pin 11 (3Y) and yellow goes to pin 14 (4Y). Now it should work! Of course if you are using a different board and a different motor then you are on your own. Good luck!

  7. After tinkering with these motors, the PF35T-48L4, for a bit, I finally rigged up a series of test LEDs to follow the current path of each coil path in this motor. Every possible standard combination was tested, included the connections as posted by EJB back in 2011. Connecting the two supply wires together makes no difference, in fact, they are designed to be connected and that is the source of the name "uinipolar". No standard connections will make this motor turn, and I will test a few non-standard connections for curiosity. But the PF35T-48L is junk.

    I'm beginning to suspect the otherwise reputable Adafruit pulled a fast one with this motor. They put it on sale where they should have put it in the dumpster. Even if I can get it to work after some 12 hours of testing, it is not worth the effort. Shame on you, Adafruit.