Miniature BLDC motor for laser scanning head

What’s the smallest BLDC motors you’ve worked with?

I want to create a 2D laser scanning head, like this one:


Those heads are usually based on very fast and precise galvo motors:

But instead, I would like to use BLDC motors. The reason is that I need wider scan angles that what a galvo motor can provide, and I don’t need the speed and precision.

Features I’m looking for:

  • As small as possible: diam. < 16, length < 40
  • With a position sensor
  • Compatible with SimpleFOC
  • Cheap

Any idea?

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I have build stuff with small stepper motors from older DVD-drives. Diameter 16mm and 12mm long.
They could be found supercheap on Aliexpress at that time.
They don’t come with sensor.

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There is another guy on here who is doing this professionally, his company makes the scanners. I talked with him. All you really need is the open loop drive. A stepper motor would also work fine with a tmc2209 driver, and ideally a large heavy disk to smooth out torque ripple.

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Actually, I was also wondering about this, as I work with some optics too :slight_smile:
I think the “encoded” part is what will kill you. There are plenty of small, cheap BLDC and stepper motors on aliexpress. If you search PTZ motor you will find a great variety.

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Thanks @Anthony_Douglas and @VIPQualityPost .

Yes, the encoder seems to be the main challenge here. I need to investigate the open loop scenario, as I’m only familiar with closed loop. I always though this kind of application is possible only with absolute positioning, but maybe the position can be calibrated with mechanical hard stops?

@Anthony_Douglas , may I ask the name of the company you mentioned?

Maybe something like this :
If you are clever mechanically you could put a flag on the backside upper and lower parts of the mirror and use photointerrruptor to home it.
There are also some small motors with build-in hall sensors, that might be useful too.

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There are some pretty small BLDCs from the micro-copter world, both fast turning ones normally used for the props, and slow turning ones used for gimbals…

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These constar ones are awesome but you have to request pricing… do you know about how much these run? I would love to use something like this in my project.

Thanks @runger, excellent!
I have a newbie question about the first motor you mentioned: what about the “CCW”? Can this be a problem in a CW/CCW application?

I think this is about the threading on the ends, so that if you attach a propeller it does not unscrew itself during flight.

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Nope, no idea what they would cost. Karlito has experience with custom-ordering motors, but the problem is the MOQ will be like 500 pieces, so even if they only cost $10 you’re looking at thousands of $$$

Perhaps we can do something like a Groupon motor purchase, lol, but I fear everyone’s requirements are too different to get sizeable numbers on a single model type.

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I’ve just asked Constar for a quotation (for this motor), I will let you know.

I had a look at sensorless/open loop, but as my use case requires low-speed control, I don’t think it can work.

Not sure they want their pricing made public, but if you could DM me the price I would be very interested!

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Wouldn’t it be a pity if constar would agree to a groupbuy price and you’d then figure out, their motor cogging is too much for laser-position control…
I’d ask for an evaluation sample first…

IMHO the EMAX motor is a good starting point. I’d probably rewind it to a lower kV.
The winding scheme for a 9s12p motor is super simple.


That’s good to know and it makes me curious. Any source for this? (not only about the wiring, but also on how to target a precise impedance or kV)

However, I need a professional solution, as this is about a commercial product.

The winding scheme is U V W U V W U V W, which means all statorteeth are wound in the same direction.
For calculations I always used “drivecalc”, which can also estimate efficiency and torque curve, etc.

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This was why I was thinking about those BLDC on aliexpress which have gearboxes. Minus backlash, it should remove the cogging, I would think.

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I’m not familiar with gearboxes, but don’t they limit the reactivity? See, my application is a portable laser projector that needs both low speed for precision steering, and high reactivity for stabilization…

I’m not sure what you mean reactivity? I googled “mechanical reactivity” but I don’t see anything that makes sense. If you are meaning reaction speed, doesn’t that conflict with “low speed”?

Sorry, I meant responsiveness (dynamic response). I’m not sure it conflicts: I am using gimbal motors, and they allow for both precise low speed control and high responsiveness. I’m not sure other types of motor (stepper, high speed) can do that, even with a gearbox or a heavy disk (as proposed by @Anthony_Douglas)…