Need lelp selecting encoder/potentiometer to perform multi turn motor homing

Support
#1

Hello,

I am looking to ODrive data since several days and cannot find any tips to make “homing” sequence using an absolut SPI multiturn encoder (like an AMT21) or a multi-turn potentiometer (like 10 turns burns).

My intent is to have 2 motors going to 0 position at startup even if motors have turned more than 360° from the 0 position during power off.

Is it a way we can manage this “homing” from multiturn offset position using ODrive?
I am currently open to any advises in order to set my configuration.
If SPI multiturn encoder are tricky to setup I can move to 10 turns potentiometer or other solution that can fit my needs.

Thanks a lot in advance for your great help!
Cheers,
Fabrice

#2

Amt21 and other cheapcmultiturn encoders don’t store the turn count when the power is off. The counter only tracks the number of turns when it’s on. It’s essentially single turn+turn counter instead of a true multiturn. True multiturns are usually much more expensive.

#3

It is what i thought.
I am now wondering if it will be possible to couple a classic incremental encoder to a geared potentiometer linked to motor shaft to make the homing.

Here an example using a motor that as made 20,7 turns from home position during power off.
If I use a setup coupling an incremental encoder and a geared potentiometer linked to the motor shaft, I was thinking to read the potentiometer value at power-up (using Odrive GPIO) and determine that the motor is 20,7 turns far from home position. From this point, I was thinking to request a self calibration.
When calibration done, the potentiometer should indicate that the motor is at 20 or 21 turns from the home position. So then, I will request the motor move 20 or 21 turns go to home position?

Is this method relevant to perform with Odrive?

#4

If you just want to home it anyway, use a single turn absolute encoder and a normal velocity-based homing. Multi turn encoders are for when you can’t use homing