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25D Motor Encoder Repair?

I have a brand new 25D motor with encoder (Item 4846). Actually purchased 10 months ago but just opened the box today. One of the encoder lines (yellow line) doesn’t seem to be working. Looks like there is continuity from the connector to the motor. Is there any sort of repair procedure for this or can you send out another one?



Hello, Erik.

We test to make sure both the motor and encoder are functional on every unit we ship, so it is uncommon for us to hear about problems like this where one of the channels does not work at all. Can you tell me more about how you are using your encoder, like how you are powering it and reading the signals, and send me some pictures of your setup. Are you having any trouble with the other encoder channel, or the encoders on any of your other motors?

- Patrick

@PatrickM, I actually have about 20 of these motors, maybe more of various gear ratios and have not had any trouble with them before. I am powering them with the 1365 motor controller that is being fed by 12V from a Rigol D832 power supply. The encoder is powered by the Rigol DP832 supply at 5V and I am just watching the encoder signals on the scope of a Rigol 1054Z scope. After finding the problem with this motor I decided to check the other motors that I have not used so far. All of these worked properly.

I then took the cap off the back of the motor to try to see if there was anything loose and couldn’t see anything to check. I think it’s just an odd motor that got through your QC and I’m willing to attempt a repair if you can give me some pointers.

The motor and encoder look fine but I am 100% certain it is something with this one particular motor.

I can still send some photos if you like.


@PatrickM here are photos of the setup.

First the 1365 controller is connected to the PC using USB. It is provided with 12V of power from the Rigol832DP.

This next photo shows the setup in the Pololu Simple Motor Control Center G2 where I’m simply setting a speed command of 16.7%

The encoder is wired per the Pololu recommendations:

This photo shows the actual connections.

First I ran an old 20.4:1 motor that I have (shown connected in the firs photo). The results from the scope are good:

Next I connected the 75:1 ratio motor and obtained the following results. Note that the yellow encoder line is connected to the yellow output on the scope.

If you zoom into the scope display you see noise in the signal that you don’t see on the 20.4:1 motor.

Removing the back cover of the motor reveals the encoder. There is good conductivity from the motor side of the yellow wire to the input to the scope so the problem isn’t an open circuit in the wire.

It is clear from this that:

  1. The connections are good.
  2. The 75:! motor has a bad line on the yellow (A channel)

I coach three robotics teams and have $1,000’s of Pololu components in my basement so we have parts available for any project, some purchased years ago, and certainly did not solder them together and test them at time of purchase. Overall quality has been very good with this being the encoder issue that I have encountered.

Please advise if you are looking for any additional information on the setup. Like I said also if there is a way to repair the encoder I can try.


Hello, Erik.

Thank you for your thorough posts showing your investigation! Unfortunately, it does appear more certain that your encoder is damaged. It is not going to be practical to repair your encoder, but if you send an email to support@pololu.com with your order information and a reference to this thread we should be able to help you out with a new unit.

- Patrick

@PatrickM Thanks - I’ve contacted support and am waiting on a response.