Nidec brushless motor wiring

Team 1164 is evaluating Nidec Dynamo BLDC Motors this year and we’re having an issue.

One of the potential issues identified by this article is the tendency of the motors to run in reverse (with the standard cable harness) if the DIO connector is removed under power.

We are seeing something similar but different, namely:

  • The motor often runs briefly upon robot power-on.
  • The motor often runs if the PWM connector (not the DIO) is disconnected under power.

We followed the instructions on the page above to swap wires in the wiring harness
“(so the connectors are red/black and blue/white)”. This seems to have had little to no effect. In fact, if the PWM cable is disconnected under power, the motor often runs continuously (rather than briefly). The motor is not driving anything at present, but clearly this would be an issue if it were driving something. We have tested this across multiple wiring harnesses in both configurations with similar results.

We’re grateful for any input and ideas as we’d really like to use these motors.

Without actually answering your question because I don’t have any personal experience with them, I’d like to ask why you’re set on using these motors?

They’re very weak (~30W IIRC), don’t save you any money or weight compared to a brushed motor with a gearbox, and they’re far less battle-tested in FRC. I’m not even sure what you could be using them for. If you’re having problems with them, I’d suggest switching to a low-power brushed motor with a planetary gearbox and Spark controller for about the same price and weight. You’ll get more power, and a solution that’s been proven reliable by thousands of teams.

Thanks for your views. There seem to be diverging opinions, as others here swear by these motors.

We’re actually not set on them, but we have some, and we’d like to evaluate them ourselves and understand how to operate them safely. Motors that spin unpredictably are not safe, of course.

I just want to make sure you’re not confusing the Nidec brushless motors (~30W, released last year) with the NEO brushless motors (~350W, released this year). From what I’ve seen, the latter have been rapidly gaining traction in the community because of their high power, increased efficiency, light weight, and small form factor. The former have generally been disregarded* because of their low power and misleading advertising.

*except for their meme potential


You can still Disable the Nidec motor programatically when it is not supposed to be moving.
For example, here is a LabVIEW solution that Disables the motor whenever it’s within a deadband.
(substitute the language of your choice)

Note also that the integrated tachometer does not operate while the motor is disabled.

Thanks Mark. Our issue, however, is that (wired in either configuration) this motor is spinning before the robot is enabled, or the driver station is even connected. It is doing this under two conditions:

  • It spins (briefly) when power is applied to the robot.
  • It spins (continuously) when/if the PWM cable is loose or pulled under power (which could happen, of course, under active play).

This is obviously disconcerting and potentially dangerous.

It is quite possible that we’re doing something wrong, but the two wiring configs we’ve tested (with multiple harnesses) are:

  • Out of the box
  • Wires swapped as per the on-line FRC instructions

No they don’t. There is however, a lot of sarcastic “love” of these motors. If you aren’t “in” on the joke it may be hard to tell the difference. In reality it is hard to find an application in FRC where the Nidec’s are a better choice than another motor.

Unfortunately, I’m traveling and can’t run a test back at the shop until next week.
So I can’t verify the harness connections.

I remember that the PWM connection only provides the Disable/Enable signal.
It isn’t actually used for forward/reverse/stop commands (the DIO does that in the Nidec case).
If disconnected the PWM is supposed to Disable the Nidec, but I can’t verify until I get to our test rig.

I cant remember a single time anyone had anything good to say about that motor.

Just to be extremely clear. This one is gaining traction:

This one really should never be touched:
If you want to use it go ahead. But, I feel there are far to many cons for the potential pros to ever exist.

1 Like

Thanks everyone for the comments. I do indeed understand the difference between these and the Rev Robotics NEOs, their relative power output, and relevance to FRC.

That said, we seem to have a bunch and I’m trying to figure out how to make them basically safe… or get our money back.

Yes… yet in our case disconnecting the PWM seems to make the motor run! Rather the opposite of intended behavior.

I know from testing is that if the PWM is ever disconnected it will just run. I have no idea if that is intentional but you are not alone on that topic.

1 Like

I believe that it’s important that we don’t disregard the Nidec brushless motor quite yet, as it’s the “Best Thing in Robotics Since Wheels!” We need to pay more attention to these motors. I’m excited to see more designs like the 16 Nidec motor drivetrain from last year! Maybe we need another Nidec design challenge?? Hmm.

1 Like

The Nidec brushless motor was significant when it was released in that many correctly believed it was the first of more powerful brushless motors to come.