I have a Pololu Tic 36v4 USB that I would like to run a brushed stepper motor with. The problem that I am encountering is that over a short distance say about 10 to 12ft away the motor works great. As soon as I try to extend the length of the wires to about 40 to 50ft the motor just vibrates and when I scope the signal all I get is noise. I assume that these controllers are probably made to run motors nearby but I would like to use these controllers because of their compactness and versatility.
Any advice on what can be done to mitigate this problem?
Thanks in advance.
Hello.
I think the description of your motor does not makes sense. Brushed DC motors have a single phase, and stepper motors do not have brushes. Can you post more information about the parts in your setup, like what specific motor, power supply, and wires/cables you are using?
It sounds like the long wires are between your motor controller output pins and your motor; is that correct? Some pictures showing your connections would also be helpful.
- Patrick
Hello,
Sorry about the limited information. Here is what I have as for setup of the drive system. Basically, the stepper motor is connected to the end of a cable system approximately 40-50ft long. The motor is a Bipolar stepper motor. At the other end of the cable system is the Pololu Driver board. I made a PCB with two of these drivers on board so that I could drive two motors from one PCB. The Pololu board on this PCB accepts a TTL clock at 40HZ and the Output enable and Direction input signals are also TTL. The cable system wire gauge is 22AWG. The supply power comes from a bench power supply with +24VDC output at 3A max current. I am hoping that the driver will be able to drive a shaft which will then move a unit up and down this shaft. As stated in the first message, the driver works great if the cable length is shorter but as soon as I connect it to a longer cable the motor just vibrates. It may be that the cable wire gauge may be too small. I don’t know why the signal is just noise when I scope the the phase inputs at this length while the signal is a nice clean square wave in the shorter cable length. Your input would be greatly appreciated.
I forgot to mention that If this problem could be solved I would like to connect the motor up to the system as pictured in the last photo using the long red cable system. Also, The power resistors were used as a test where a 47 ohm resistor was connected in series to one end of the “phase A” coil and another resistor was connected to the other end of the same “phase A” coil in series. The same was done for “Phase B” then connected to the Pololu Driver Outputs. This completely eliminated the noise and I got a nice clean drive signal but the only thing is that The current to drive the motor was drastically reduced as would expected.
Hello,
Please disregard all of the above questions. I found the problem on why the motors were vibrating/chattering. The connection long cable harness were of 24AWG and I tried out some 16AWG wire and the motors are running fine now. The motors were not being supplied with enough current because of the wire gauge. Thank you for your time. Problem Solved!
I was suspecting the issues were being caused by some combination of resistance and inductance introduced by the long cables. I am glad to hear that you were able to correct the issue by switching to a bigger wire gauge!
For anyone else who might come across this thread with a similar scenario, a good starting point for figuring out how to deal with this might be to try characterizing the cable connection resistance and inductance so you can compare it to the motor. That would give you an idea for how much the cable should be affecting things. Aside from thicker wires, it is possible that using a higher voltage might also help, but ultimately the best solution for this is to avoid the long connections to begin with.
- Patrick
