What defines controller/motor compatibility?

I’ve dealt with my fair share of issues with incompatibility between a motor and a controller. Can anyone explain what causes this?

Naively I understand a controller and motor need to speak to each other in regards to hall sensors and phase wires, so why so much incompatibility? What is causing the differences between controllers?

I have some old controllers that I’d love to bring back to life but are collecting dust b/c they don’t work with some of my motors.

Any insight or technical reading recommendations would be appreciated.

Some controllers are hardwired to do 60 degree phase, but the motor is 120 degree phase. ( programmable controllers usually have the ability to switch )
Some controllers use proprietary hall/phase wiring combos and you have to play musical chairs to get them to work.
Some controllers cannot drive high enough of an eRPM to move high pole / high reduction geared motors or RC motors.

Those are usually the causes of incompatibility.

Thanks for the reply.

> Some controllers are hardwired to do 60 degree phase, but the motor is 120 degree phase.

Great point hadn’t thought about that. Do you know if there is anyway to look at the PCB to determine what it’s set ar? Is it relatable easy to switch it? I have basic/decent soldering skills


> Some controllers use proprietary hall/phase wiring combos and you have to play musical chairs to get them to work.

I definitely get that! No fun but I’m experienced dealing with figuring out the combos, but thanks for mentioning, I know early on this was a foreign concept to men

> Some controllers cannot drive high enough of an eRPM to move high pole / high reduction geared motors or RC motors.

Interesting, I’m not familiar with this, time to do some googling.

NeedForSpeed said:

Great point hadn’t thought about that. Do you know if there is anyway to look at the PCB to determine what it’s set ar? Is it relatable easy to switch it?

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Only one of the controllers I've opened up (of dozens) had anything obviously for this, and it was a pair of pads marked as 60/120, with a jumper between them. None of the others had anything like that, but since all the motors I've had worked with all the controllers I tried them with (eventually), either they were automatic, or none of my motors happened to be whatever the controllers werent' compatible with. AFAIK, they'd all be 120.


Another hall issue is that some motors have hall sensors that give a signal that isn't clean enough for the controller to read, and some controllers are better at reading those so they work anyway, but others don't.

Then there's sensorless controllers, and some of those are better than others at correctly reading the phase position of various motors, especially at low speeds and high loads.

> Some controllers cannot drive high enough of an eRPM to move high pole / high reduction geared motors or RC motors.

Interesting, I’m not familiar with this, time to do some googling.

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You can just look up "erpm" here on ES and find a number of discussions about it. Mostly it's geared hubmotors of various kinds (Ezee comes to mind), or other high-RPM high-pole-count motors.


FWIW, another source of incompatibility can be low-inductance motors, which can either blow up controllers that don't have good current limiting, or can cause ones with good limiting to keep shutting down under load at startup. Mostly these are going to be big RC motors.