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What are some alternative types of motors/actuators that can be used instead of servos? I need some way of inducing a slight bit of motion/movement but with very little force and power consumption. Even the tiniest sub-micro servos use quite a bit of current and may have quite a bit more torque than is necessary. I thought about using muscle wire, but I need something that doesn't take up much space, and they don't appear to have shorter lengths of wire available. Not only that, but I would prefer to have a rotary rather than a linear actuator. What would be some options for such an actuator running at say 3v and requiring somewhere in the range of 20-40 mA of current?

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  • \$\begingroup\$ Can you put some numbers to the torque, speed and distance values you need? \$\endgroup\$ – Dave Tweed Feb 24 '15 at 23:44
  • \$\begingroup\$ Does the device have to retain its' position after power is removed from the actuator? For example, could you use a voice coil or galvanometer type actuator? For example, galvo actuators are used in laser visual effects machines to move the mirrors that steer the laser beam. \$\endgroup\$ – Dwayne Reid Feb 24 '15 at 23:55
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    \$\begingroup\$ What about hacking a battery operated clock mechanism? Low power, low voltage, cheap, available and rotary. \$\endgroup\$ – JIm Dearden Feb 25 '15 at 1:12
  • \$\begingroup\$ I was thinking a piezo, for rotary motion something like the squiggle drive/? New focus has a piezo rotary drive.. none of those are cheap. \$\endgroup\$ – George Herold Feb 25 '15 at 2:22
  • \$\begingroup\$ Pager motors. And search ebay for "small motor" etc. There are a vast number there. \$\endgroup\$ – Russell McMahon Feb 25 '15 at 3:45
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Here is the drive mechanism from my beloved Butterfly Livingroom Flyer... enter image description here

It is a pager motor connected to a reduction gear. By picking the size of the gears (or possibly adding additional gear stages), you can have pretty much any viable torque/power combination you want, down to single digits of mA.

If you need even a smaller actuator, Plantranco also sells the MicroAct Magnetic Actuator - 0.4g...

enter image description here

You could also make something similar to this yourself with some very high gauge enameled wire and a small super-magnet. This would give you lots of control of the power/torque/range-of-motion trade offs.

(Note that I have no connection to Plantranco other than I have bought more of their flyers than I'd care to admit!)

I also love Jim's suggestion of hacking a clock motor if that could work for your application. These things use impossibly small amounts of current.

Here is a product that is basically a clock motor, but good for hacking because it comes with lots of possible gear combinations, and also provides continuous rotation (the yellow metal disk acts a a flywheel), whereas clock drives usually have unneeded timing circuits and often move in a a once-per-second jerk ...

enter image description here

They cost about $30 on Amazon, much cheaper if you need more than about a dozen.

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