Motor specifications?

I have built my first SImpleFOCshield and apparently NONE of the motors I have will work, dang. I want to reproduce the reaction wheel example but apparently no one carries the IPower GBM4198H-120T motor any longer. I have found some Ipower motors on Aliexpress but I don’t know what to choose as I can’t find the specifications for the GBM4198H-120T. Can you suggest a motor/encoder alternative for this project.

Thank you!

Hey @Keshka,

What kind of motors have you tried? Maybe there might be one that can work.
I would recommend you stick with a gimbal motor, but any brushless motor with a generally low KV rating (below 400) and a wide diameter would be good. For this project you want a powerful motor, but light enough.

Something like this I think would be a suitable replacement: Iflight Ipower GM5208-200T GM5208 3KG 5208 Hollow Shaft Brushless Gimbal Motor | eBay

Or even something like this: SUNNYSKY V4004 300KV 400kv Multi-copter Motor Outrunner Brushless Motor | eBay

For the encoder I really like the AMT103 that are used in the example but you could use any type of encoder or magnetic sensor, such as the AS5147.

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I found these two on Ali…


are either acceptable?


I have used motors linked below. They are very efficient and reliable.

They have gimble motor with 5mm shaft too.


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Check out EMAX:

I think these will all work… I’ve tried the 2808 and 4008 and I like the prices :slight_smile:

Its also pretty easy to shim up (eg by 3D printing) a magnet-holder that fits in the hollow shaft, so you can make a pretty compact magnetic encoder setup like the far more expensive integrated models of other suppliers.

Regards from Vienna,


As a general guideline, in theory any BLDC motor can work, but in practice there are the following limitations:

  • motor and driver must be able to work together. For most of the drivers I’ve seen so far in conjunction with SimpleFOC, this means a motor that does not require current limiting, e.g. one with fairly high winding resistance. You’re on the safe side if the DC current (no PWM) from phase to phase is within the driver’s capacity for your chosen voltage. Eg. if phase 2 phase resistance is 10Ohm then 10V will be 1A, within the range of all drivers… If phase to phase resistance is 1Ohm then 10V will be 10A, and that’s too much for most small drivers.
  • in practice, you will also need fairly low KV values. There are a variety of reasons why 20000RPM won’r work well at the moment with SimpleFOC. But for the pendulum slow turning, holdable motors are what you want anyway.

In terms of encoders, I highly recommend the AS5048A or AS5048B - they’re not cheap, but they’re the most precise and fast magnetic encoder on the market that I have found at least. The B (I2C) version is simpler to use, while the A (SPI) version can give you very high sample rates. Both versions also have PWM outputs. In my experience the B version is sufficient. You can order test PCBs for either version from AMS for about 13EUR. They work directly with SimpleFOC.

Regards from Vienna,



bought a pair of these…updated to follow!

|EMAX GB4114 Brushless Gimbal Motor Hollow Shaft 42KV 85T - Normal shaft

EMAX GB4114 Brushless Gimbal Motor Hollow Shaft 42KV 85TNormal shaft @ $8.48 + $7 for shipping each

I really like the hollow shaft…makes mounting an encoder much easier

Good choice I would say! I recently bought 4 of these as well (mainly because of the discount;)) and they do the job very well I would say. They are very powerfull, but also quite heavy, not sure if this will be an issue for a pendulum?

Can you please provide the link where you bought it?


Hey, this is the manufacturer, but it looks like they’re sold out, or have discontinued:

It’s also on AliExpress, for example here:

Although it might be a good idea to ask if they really have stock before paying.

Note that any of the other emax gimbal motors should work just fine too. And T-Motor has a line of Gimbal motors that cost a little more but should also all work.

My motors arrived the 15th of Jan.
Took about a month.


If you’re still around, can you explain how the hollow shaft makes it easier? Which encoder are you using?

In fact what you have to attach to your motor is a diametric magnet. With a hollow shaft you can 3d print a shaft to hold the magnet and easily adjust the distance to the magnetic sensor. ezgif-6-f3707d9d8c5f

Which magnetic sensor would you recommend?

AMS AS5048A or AS5047 are well supported…

My recommendation is AS5048A. … It is not the cheapest solution but it works very well. In addition to the SPI interface, it has a PWM interface which is very useful for debugging purposes as you can see if the sensor is working independently of SPI communications.