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:
Any idea?
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.
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.
Actually, I was also wondering about this, as I work with some optics too 
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.
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 : https://www.aliexpress.us/item/3256805252534799.html
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.
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…
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.
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.
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!
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.
This was why I was thinking about those BLDC on aliexpress which have gearboxes. Minus backlash, it should remove the cogging, I would think.
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)…
