Minimum RPM: 15 deg/hr?

Noobie here. I’m considering an oDrove but need to be sure it can operate at extremely low RPM (eg. 15 degrees / hr). I need to drive a 3 phase 12 pole large BLDC (Fisher & Paykel Smartdrive) .
Any ideas if this is even possible given BLDC’s are usually high RPM?

With a high enough resolution encoder, maybe it will work. What is your application? If it is a telescope drive or something similar where you are trying to keep a star stationary on your camera, having encoder increments similar or smaller than the angular size of a star is useful (say 3 arcseconds or smaller). It is definitely possible as some off the shelf telescope mounts have direct drive BLDC motors with encoders controlled in a similar way to oDrive. Sensorless control wont work at this low of an RPM so some wort of position feedback will be needed.
Hope that helps


Thanks, good to know it’s possible. I’m using 18 bit absolute encoders interfaced with a RPi so can control the motors with that too for a closed loop. Time to place my order…

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The ODrive will need some form of encoder feedback and will control the motor in closed-loop. Have a look on the wiki to see what encoders are currently supported.

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Curious if anyone else is working on applications like these? Pairing a commodity direct drive motor like the aforementioned + decent encoder to achieve good (slow) motion control with reasonable holding ability? I’m interested in building a satellite tracker, so the resolution requirements aren’t quite as demanding as astrophotography, but smooth motion and good speed control at 1-2 degrees per second is still very desirable.

If I salvage one of the Smartdrive motors would any rewinding be necessary?

Thanks in advance!

I know some people are having success with star tracking applications, and the key really is in the resolution of the encoder. Try to get an encoder that will do at least 10 counts/s at your desired speed, ideally aim for 100+ counts/s. So ideally you would get an encoder with a resolution of 36,000 CPR, or about 15bit. I know you can hit this for fairly cheap with a magnetic encoder and large magnetic code ring.