I've come across a stepper with the operation logic shown in the snippet below.

image of stepper logic

I've read elsewhere that I can operate the stepper using an EasyDriver or BigEasyDriver by simply ignoring the center taps. I have had some success, but it very frequently skips steps or jerks as though it is skipping steps. I have verified that I am running it at the rated voltage (12 V). I have also tried a few different micro-stepping options on those driver boards. At certain operation speeds, it looks like it sort of works, but too slow or too fast and it doesn't move at all or moves questionably. Based off the logic diagram, I'm suspicious I might not be able to run this stepper using the mentioned drivers.

However, I'd like very much if someone can prove me wrong. Otherwise, my next step is to source a bi-polar stepper with similar dimensions.


So I've been looking at using this bi-polar stepper (it won't let me post the link, so its the DRV8825 from www.pololu.com) to drive this particular motor. It seems like if I leave the center tap's powered at 12 volt as intended then the driver should successfully power half of the coils shown in the diagram. What I'm not sure about is what will happen when one of the driver's outputs (A for example) is at 0 current. Does this mean the H-Bridge for A is fully open (meaning no current can flow)? Or does it mean that the outputs are both high or both low? I hope the former because then I should be able to drive this in half coil without fear of damaging the motor or the driver. I'll do some experimenting...


To answer update 1, you can control the stepper without damaging the stepper motor. Only half the coils are charged, however.

  • \$\begingroup\$ A unipolar motor is intended to be used with the center taps connected directly to a supply and the ends of each winding controlled alternately to produce what is effectively both polarities. So the rated voltage is between the center tap and one end. If you use the entire winding, then the equivalent bipolar driving voltage would be twice the unipolar rating, if you ignore the insulation breakdown. But for 12/24V, I think the insulation is probably fine. Also consider heat from having twice the number of windings active than it was designed for; if it stays cool, you're still okay. \$\endgroup\$ – AaronD Jul 31 '17 at 18:21
  • \$\begingroup\$ I've run it at 24V and it behaves slightly better, but it still chokes (seems to get off-step) sometimes and gets uncomfortably hot! \$\endgroup\$ – Troy Weber Jul 31 '17 at 23:57
  • \$\begingroup\$ @AaronD I've also read that you can run it in half-coil mode (which I guess means using the center taps instead of ignoring them). I may give this a try next. \$\endgroup\$ – Troy Weber Aug 1 '17 at 0:10
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    \$\begingroup\$ "I have verified that I am running it at the rated voltage (12 V)." That will result in poor performance, even in half coil mode. To get good performance from a stepper, you need a supply voltage many times the ohmic coil rating, and a current mode chopping driver. Likely you bought a relatively useless high resistance, high inductance motor - look instead for something with a coil voltage of less than 4v. And please see the many existing stepper motor questions over in the sidebar to the right. \$\endgroup\$ – Chris Stratton Oct 9 '17 at 19:28
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    \$\begingroup\$ No, your question is not at all unique - the issue here is the same issue in a larger fraction of the existing questions. \$\endgroup\$ – Chris Stratton Oct 9 '17 at 20:11

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