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rosmo-robot / Rosmo_ESC

Dual brushless motor ESC in #M5Stack module format
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Additionally support small steppers? #2

Closed samuk closed 2 years ago

samuk commented 2 years ago

I was just wondering how much extra effort would be required to support these dirt cheap steppers on the board alongside the 2205's https://thepihut.com/products/small-reduction-stepper-motor-12vdc-32-step-1-16-gearing?variant=27740538257

They are not that interesting to me personally, but would drop the price for the lowest cost version, enabling competition on price with the ubiquitous DC & gearmotor platorms where many seem to start their robotic journey.

If it introduces a load more complexity then let's not bother with it, but if it's easy do you think it's worth doing?

runger1101001 commented 2 years ago

Hi @samuk,

This stepper should already be supported, it is just a regular stepper motor (low pole count) with integrated gear-down. It is closed at the back, so closed loop might be a bit harder to set up than with models that have the shaft accessible. Since the shaft at the front already has a 1/16.032 gear down, one might have to open it to see if the actual motor shaft is accessible on the back for attaching a magnet/encoder.

You could try to attach the encoder to the existing output shaft, but would have to modify the sensor class to multiply the angle by 16 and effectively lose 4 bits of precision on the sensor.

That kind of complication offsets much of the price-benefits for new users, IMHO.

runger1101001 commented 2 years ago

Ok, I'll reopen this as I just realised it is in the Rosmo project and not the simplefoc. Doh!

In terms of the Rosmo ESC, this would mean differences to the hardware: the stepper needs 5 wires for its 2 phases as opposed to the BLDC which needs 3 wires for 3 phases. The driver chips and driving circuit would be different.

In terms of making a driver board with both stepper and BLDC drivers, each for 2 motors and in m5stack format, I would say this is not possible in terms of the space available. And it is not consistent with trying to provide a cheap solution, since each customer type (BLDC or stepper) would be paying for a driver architecture they're not using.

I think it would be better to make a separate stepper driver board.

samuk commented 2 years ago

Ok makes sense. Thanks. As there are existing open source M5 stepper shields we can just point to them if people want steppers.