EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Harvs on May 01, 2020, 05:54:50 am
-
Anyone come across a source for buying multi-pole radial magnets off the shelf? Even better if it comes with a shaft mount like this:
https://www.alibaba.com/product-detail/Stable-Robust-Ring-Diametral-8-Poles_62228800993.html (https://www.alibaba.com/product-detail/Stable-Robust-Ring-Diametral-8-Poles_62228800993.html)
Alibaba is about the only place I've been able to locate them, which I find strange. Given they're quite common for hall sensors on PMSM/BLDC motors (which is what I'm planing on using it for). Seems like the sort of thing I should just be able to by from Digikey with everything else?
This isn't the first time I've wanted something like this, and Alibaba is just such a pain to buy couple of parts for a few dollars. I haven't even been able to find them on aliexpress.
-
supermagnetman.com
A few years ago I was dealing with them. They seemed professional and willing to do custom stuff. Perhaps give them a call?
-
Thanks, I'll give them a call if I have to go the custom route.
I was just hoping to avoid getting something custom.
-
There are some on aliexpress, you may have seen those already. I would suspect they are relatively custom, as they tend to be epoxied on to the motor shaft.
Most people are not going to be assembling motors from parts off digikey IMO. They'd either buy the motor fully assembled with motion control, or add an encoder to an existing motor (CUI encoder (https://www.digikey.ca/product-detail/en/cui-devices/AMT203-V/102-2050-ND/2278846) or AMS IC (https://www.digikey.ca/en/product-highlight/a/ams/as5048-magnetic-rotary-encoder)). Both of those options are a magnitude more expensive in volume, however if its a one off, they will be cheaper.
If you don't care about absolute positioning, and want low cost, what about sensorless?
https://www.digikey.com/en/articles/controlling-sensorless-bldc-motors-via-back-emf (https://www.digikey.com/en/articles/controlling-sensorless-bldc-motors-via-back-emf)
-
There are some on aliexpress, you may have seen those already. I would suspect they are relatively custom, as they tend to be epoxied on to the motor shaft.
No I hadn't been able to find anything. But searching again now I came across one store, which then leads into many more as always on aliexpress.
Pretty much found what I am after this time:
https://www.aliexpress.com/item/32817651811.html (https://www.aliexpress.com/item/32817651811.html)
It'll be easy to turn up a mount for it.
Most people are not going to be assembling motors from parts off digikey IMO. They'd either buy the motor fully assembled with motion control, or add an encoder to an existing motor (CUI encoder (https://www.digikey.ca/product-detail/en/cui-devices/AMT203-V/102-2050-ND/2278846) or AMS IC (https://www.digikey.ca/en/product-highlight/a/ams/as5048-magnetic-rotary-encoder)). Both of those options are a magnitude more expensive in volume, however if its a one off, they will be cheaper.
If you don't care about absolute positioning, and want low cost, what about sensorless?
https://www.digikey.com/en/articles/controlling-sensorless-bldc-motors-via-back-emf (https://www.digikey.com/en/articles/controlling-sensorless-bldc-motors-via-back-emf)
As much as it may seem odd, but repairing and modifying motors is quite common. The motors themselves can be expense, but often there's also quite a lot of work in adapting a new motor to fit the machine it comes off. True probably not digikey, but there's mcmaster carr etc.
For the purpose of commutation (FOC control), 3 hall effect sensors and a magnet don't get much simpler which is why it's still almost universal. Often paired with a high-res optical encoder for servo control.
Sensorless is great, but much harder if you also need full torque at low rpm. Quite common on fans, centrifugal pumps etc where the starting torque is low.