Do you have a motor related question? I enjoy exploring anything motor related. I do not claim to be “A Motor God”, but with over 20 years of motor driving and controlling experience, I may have a tip or two on your next project. Feel free to send me a message through this page and I’ll try to answer as soon as possible.

NOTE: If the question requires a long enough answer, I may transform it into a post. Thanks for your understanding!

4 comments for “Questions

  1. April 14, 2018 at 8:08 am

    I have a dc motor that is turning backwards, the wires are right. how do I fix it

    • avayan
      April 16, 2018 at 4:17 am

      The simplest answer is to apply a negative voltage. Of course, this is a super loaded question/answer as there are many things to consider. First of, when you say it is going backwards, remember the rotation is defined by the manufacturer with respect to a side of the motor. For example, if the motor is single shafted (as most of them are), the manufacturer may have defined Clockwise direction by looking at the shaft side or the rear side. I don’t think there is a standard. Second, the wire coloring often implies a connection polarity with red as positive and black as negative, but if the motor has no diodes (and most of them do not), then there is no reason to only use this convention. In other words, you can connect either wire to either power supply output, in order to obtain the rotation direction you need. Lastly is your power stage. If you have a single Half H Bridge to drive the motor, then there is no way to apply a negative voltage. But if you have a full H Bridge, then you can easily flip the direction by controlling the Direction Signal (on PHASE/DIR H Bridges), or reverse the logic, if your H Bridge is of the INx topology. Hope this helps to steer you in the right direction!

  2. Gustavo
    February 25, 2019 at 10:01 am

    Iam building a CNC based on openbuilds design. I have 4 wantai 57BYGH633 motors with DQ542MA drivers.
    Iam not sure if use half or full coil setup. When you say that at high speed can lost sync in full coil, how much can be that speed?

    Please, tell me if Iam wrong with this:

    – According to the datasheet the motor has 4 phases and 1.6mH/phase. So, in full coil config, has 3.2mH
    – The power supply, according to what I research, may have sqrt(3.2) x 32 = 57v. The driver mas voltage is 50v. I can use a 48v power supply with 3A x 4 motors x 2/3 = 8A.
    – I plan to set microstepping to 1/8 in a belt driving system with GT2 and 20 tooth pulley. So, in a motor turn I will move 40mm and need 1600 pulses to do that.
    My max cutting speed working with wood is 80mm/s. That are 3200pps. In a torque curve I dont see much difference in half coil setup and full coil at that speed. I will use maybe twice of that speed for G0 movements but i dont need torque in that. So, to cut at that speed full coil semms to be adecuate and to cut metals at slow speeds I will have more torque with full coil. I think that for me is the right choice.

    Please, correct me if Iam wrong and any suggestion and recomendation will be appreciate.


  3. Brian
    February 26, 2019 at 2:19 pm

    Hello i am new to the electronics and have plenty of truck related experience when it comes to electrical but nothing in mother boards and those type electronics my question is would you be willing to help me build my own dc motor speed comtroller i have a 90v 10amp 2.5hp dc motor i would like to control the speed to any rpm what i need to know is which componets i will need to use if you are interested i can give you a list of what i allrdy have and possibly set me in the right direction any help would be greatly appreciated thank you, Brian

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