Are the scooter motors similar to the hoverboard motors?
Looking for something a bit smaller than the hoverboard ones.
eg something like https://www.ebay.co.uk/itm/Electric-scooter-motor-wheel-135x40/113960725652?hash=item1a8896ac94:g:vIEAAOSwcBpdo6xh
Thanks
Sam
You’re probably going to have to test it yourself if it doesn’t have any real information. Let us know what you find out!
There seem to be 3 main sizes as far as the stator/magnet goes. The magnets are 10 pole pairs at 25mm height for the smaller 4.5 inch wheels and 15 pole pairs at 25mm or 30mm heights for 6.5 inch wheels.
The ebay link provided looks to be a 5.5 inch wheel. It probably uses 10 pairs of 25mm magnets inside. For reference here is a link that lists all 3 sizes and their specs:
https://item.taobao.com/item.htm?id=525520922665
I have been prototyping for my project and used both hoverboard and scooter motors. The scooter motors with dual shafts that I have tried all seem to have 10 pole pairs.
I do have some 4" and 6" motors that I am not using and may be able to sell if you are interested. Some are 24V and some 36V.
Thanks all, is it easy to get the 10 pole pairs working with Odrive?
I’ve got my eye on these now https://www.uumotor.com/4-inch-robot-brushless-servo-hub-motor.html a bit more expensive, but the encoder is built in…
I have used 4" motors that look identical but only have Hall sensors (5 wires, not 9) but does not have the encoder.
I would like to understand what extra value is provided by the encoder.
They are very easy to set up with ODrive - just follow the hoverboard instructions.
If you do not need the encoder, I can offer my 4" motors at $70 each plus shipping from California.
Anil Sawe
Anil,
The extra value is resolution. The field-oriented control scheme that the ODrive uses is not really very useful with Hall sensors, as you need more information than simply which is the next coil to energise. Hall sensors are like having a really low-resolution encoder, but for good torque efficiency at low speeds (including holding position at zero speed), you need the highest resolution encoder you can get your hands on.
I was looking at these servo hub motors as well. The only downside I could see is that most of them have 1024ppr opto encoder and the unshielded encoder wires exit through the same hollow shaft with phase wires. I would have preferred higher resolution (maybe magnetic) encoder with shielded encoder wires. When working with low speed high torque applications extra resolution helps.
I did find one servo hub motor that claims to have magnetic encoder which in theory can have higher resolution. I have messaged the store owner to see what resolution it has.
@zee_mono have you got a link to that please?
This might be of interest to someone 4096 encoder built in to 6.5 inch wheel. Looking for smaller myself
Hi Towen,
Thanks for the clarification. I do have a follow-on questtion.
I would like to be able to hold the position at zero speed - with my encoderless hub motors. Is it possible to switch to position control mode from velocity control mode and vice-versa? I am wondering if I can set the velocity to zero and then switch to position control mode to hold the motors to Zero position - as if a brake is applied.
Thanks,
Anil
@sam_uk here are 2 hub motors with claims of magnetic encoder:
Your source looks more polished though. I remember seeing them selling these “robot/servo hub motor” on taobao 2 years ago, that was long before this product category became trendy enough for 3-4 suppliers to attack it at the same time. I am sure you could ask them to put 4096ppr encoder on 4.5 inch wheel as well as using custom shielded wire.
If your requirement on torque is lower, there is also large gimbal motor with pre-integrated encoders to consider. Just search for “gimbal motor as5048a” on aliexpress and you will see plenty. I ordered this recently and still waiting for it to arrive:
No, you need an encoder for that.
You cannot efficiently hold position without an encoder. Hall sensors are not sufficient for this.
AS5047P modules are pretty cheap…
@sam_uk
My inquiries on the 2 aliexpress servo hub motors with magnetic encoder came back, one of them said the encoder is actually 1024 line opto encoder, the other one said their encoder has resolution of 1096 (!). Bottom they are just resellers and can’t be trusted.
On the other hand the source you quoted has this on their page:
“Built-in high precision encoder 12-21 bits optional, also can be customized, electric brake, high load carrying etc”. That looks real nice.
@sam_uk
Here is another specialized supplier: they do servo hub motor and nothing else. They seem to supply only Chinese domestic market and don’t have Alibaba, aliexpress or Made-in-China presence:
https://shop1458061140552.1688.com/
Their 4inch motor is slightly cheaper than ZL’s:
https://detail.1688.com/offer/528462066400.html
https://detail.1688.com/offer/568201687752.html
Disclaimer: I have only used taobao shopping services (bhiner, freeshoppingchina) against taobao/1688 sellers and sometimes the shipping charge can be significant. FOB prices will likely be 2x of what you see on 1688/taobao for things like motors or lead bricks.