Autodesk: Make Anything
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is it possible to determine the direction a motor is spining by attaching a comparator to both leads?

the motor is not being powered with electricity it is being spun by hand. and if it is possible how can I determine the speed.

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lemonie8 years ago
Here's an easy one for direction: solder two LEDs to the motor terminals, with opposite polarities. One will light in each direction only. (if they both light in the same direction only reverse one of 'em and try again)

L
Thats a really good one! I never thought of that... -PKT
evilmadscientistman (author) 8 years ago
these answers are nice but thats not exactly what I'm looking for... it's a dc motor nothing complex no gears or any thing. it's not being powered by electricity, I am spinning it with my hands. and I'm using a comparator non a multimeter or other device. if these details help then your welcome.
. Feed one leg of the motor to one input of the op amp/comparator and the other leg to the other input. Check the voltage and add resistors/dividers as needed. When the polarity it the same as the oa/c, output will slam to max. Reversed, zero.
frollard8 years ago
a permanent magnet dc motor should output pulsed dc current - the commutator inside should make it output the same polarity, not ac.
NachoMahma8 years ago
. There are rotation (phase sequence) checkers for 3-phase motors, but I've never seen one for single-phase. That doesn't mean they don't exist, I've just never seen one. . RPM should be printed on the motor (or on a tag). If you know how many poles, frequency, &c, you can compute the speed (but it's been years since I did that and I don't remember how).
theRIAA8 years ago
a multimeter you mean? i assume just switch the polarities if its a simple DC motor.. if you spin it and the volt reading is positive, then the motor will spin that way if you hook the power up opposite to the multimeter. if it's AC then I have no idea.