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I'm looking into embedding a stepper motor into a wearable device like a wrist watch. I've found these on digikey:

http://www.nmbtc.com/pdf/motors/standard-pg/PG15S-D20-HHB9.pdf

The resolution is great and it's aligned with what I need, but I'm afraid it will draw too much power (100mA @ 15V), and I would appreciate something even smaller. There's no torque requirement. It will just turn a handle.

Do you know a source where to buy even smaller (in power and size) stepper motor?

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  • \$\begingroup\$ Do you have a limited budget for this? \$\endgroup\$ Apr 19, 2012 at 18:15
  • \$\begingroup\$ I'm making one prototype for me (no price limit), but if people like it, it might turn into a consumer product to be sold in the 200-500 dollars price range, so should be less than 50 bucks in quantity. \$\endgroup\$ Apr 19, 2012 at 22:10

6 Answers 6

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You could "relatively easily" make one yourself.
A few coils (2 or 3) and a toothed disk.
Performance would be modest but easily enough for what you want. I can discuss what would be involved in more detail if this sounds interesting.

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  • \$\begingroup\$ It does sound interesting, even more because real estate is so confined \$\endgroup\$ Apr 19, 2012 at 22:13
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You could take a look at The world's smallest stepper motor at elabz. They can be found inside BluRay drives, so might be a little on the expensive side if you want a bunch of them.

Smallest Stepper motor

Also, don't forget that if you want to reduce the power consumption of your stepper motor, you have a couple of options.

  1. Use a lower voltage. You mentioned that you need barely any torque, so you could use the lowest possible voltage that turns the motor. This doubly pays off. If you can halve your voltage, you quarter your power. (if the motor is not moving fast)

  2. Lower the voltage even more when the motor is stationary. If you really need no torque, then you can switch off the motor completely when it's stationary. Send the motor a pulse to make it step round, then switch it off.

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  • \$\begingroup\$ Any ideas on sourcing it? \$\endgroup\$ Apr 19, 2012 at 22:14
  • \$\begingroup\$ @PaduMerloti - Yes, see my edits. You basically have to buy a BluRay drive. If you need thousands, then you may be able to get them from the manufacturer in China. Try alibaba.com \$\endgroup\$ Apr 19, 2012 at 22:17
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While this is an old question, I'll add something to the mix:

These tiny stepper motors are amazing more for their price than for their size:

Stepper Motors

10 of them for $2.69 plus shipping, from eBay.com! These motors are apparently used for focusing within SLR lenses (e.g. Canon STM lenses), according to the seller.

While I haven't been able to find datasheets or details for these motors, at their low price sacrificing one of the motors to determine supply limits isn't too tough a decision.

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    \$\begingroup\$ I would add that working with these motors is difficult due to their size. They don't have wires coming off of them that you can just plug into. The terminals on these motors that you need to connect with are practically nonexistent. I went through 4 motors before I was able to get wires soldered on without burning of the terminals using a soldering station that was set so low it would barely melt the solder. Consider a motor with a plug unless you have a socket for these or have some method of connecting to them that does not involve manually soldering on wires. \$\endgroup\$ Oct 31, 2016 at 4:21
  • \$\begingroup\$ How do you know which is a+, a- and b+, b- ? I know how to find the pair but I can’t figure out how to identify the + and - for each pair. \$\endgroup\$
    – Dominique
    Mar 13, 2021 at 13:04
  • \$\begingroup\$ @ubiquibacon I discovered recently that when I use a temperature so low the solder barely melts, I have to hold the heat on the joint longer, and that means more heat goes into the joint overall than with a higher temp. Once I turned my heat up a bit, I was able to get better results. My work was on a drone motor controller (little larger than a quarter, but reasonable sized wires, so I don't know if I know what I am talking about with this size. If I get these, I will report back if I have any better luck. BTW does anyone have the model number for those motors? The link is dead. \$\endgroup\$ Jan 8, 2022 at 10:23
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Not quite a stepper, but you might consider a squiggle motor: http://innovationsupplychain.com/innovations/report.php?id=974 claims about $10/unit (with driver) OEM. http://www.newscaletech.com/squiggle_overview.html gives an overview. There's a high entry cost for a devkit: http://www.digikey.com/product-search/en/programmers-development-systems/eval-and-demo-boards-and-kits/2622039?k=squiggle, but with the tiny size, maybe more people will like it!

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I'll do ya one better - a colleague of mine saw these and thought they were neat, but he was wanting for an application: PCB Motors. They are small and expensive. Did I mention they're expensive? The data sheet for the stator says that it draws 80mW max. Of course, it's expensive (we're talking hundreds of dollars here).

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  • \$\begingroup\$ Yeah those things are crazy expensive. Still looking for an application where I can use one though. \$\endgroup\$ Apr 19, 2012 at 18:00
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The question is unclear: do you want a manufacturer or a retail source? The problem is logistical, not engineering. Anyway, its interesting.

I have found at least two other manufacturers: TTMotor in mainland china and Vitech in Taiwan that offer small stepper motors some less than 10mm in diameter with geared variants.

Retail: I have seen a tiny Vitech motor on eBay. TTMotors motors are on alibaba. But alibaba seems like a nightmare, to determine a reliable and cheap source of single units.

Note also that the motors used in blu-ray sleds cannot easily be separated from the housing: the motor shaft has a jewel bearing at the end of the worm gear. If you dissassemble it, the motor rotor then lacks support at the gear end.

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