feedbackmotorvibration
I'm trying to make an item with a number of pads that will pulse individually or in sequence with a given signal. I have looked at vibration motors but these are like the ones in video game controllers – they vibrate but the duration is too long. I want to put the motor in a pad that could be worn and give a much more precise 'pulse' or 'beat', potentially at a rate of up to three times per second.
Any ideas where I can find such a motor or other feedback component?
Many thanks.
DC motors don't work well at low RPMs. They stall and have horrible torque. (i.e. they can't turn very hard) So people have created gear motors: motors with integrated gearing. The result looks like a slightly bulkier motor, but one that has low RPMs and high torque. If you were to take apart a running a gear motor, you'd see the motor part actually runs at several thousand RPMs, but it's geared down to something like 60 RPM max.
A common specialized one is the standard hobby servo, which has some additional electronic bits but is fundamentally a gear motor. Check out any place that sells motors for robotics or surplus electronics and you'll see several different gear motors to choose from.
DC gear motors are controlled just like normal DC motors, so an Arduino motor shield works just fine with them.
Here is the drive mechanism from my beloved Butterfly Livingroom Flyer...
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...
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 ...
They cost about $30 on Amazon, much cheaper if you need more than about a dozen.
Best Answer
You need a voice coil actuator (VCA). It is most commonly used as the active component in most loudspeakers - a coil of wire and a permanent magnet produce an excursion proportional to current. In fact, you could probably prototype your application with small, inexpensive speakers.