I'm looking to have multiple motors rotating metal discs at different speeds (each motor would be for a single disc, which weighs maybe 100g and 20cm in diameter), ideally at the pace of a clock (I tried a clock mechanism but it wasn't strong enough to turn the weight of the disc).

The small motors I've found here in NZ seem to be the typical low torque, high speed, but these go much too fast. Initially I thought a potentiometer would do the trick because then I can vary the speeds on each motor/disc pairing, but then though a transistor could possibly achieve the same thing. However, I am brand new to this stuff and am really just fumbling around in the dark.

Short version: How can I best make a small motor that is 11000+rpm rotate as slowly as a clock?


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    \$\begingroup\$ Put a gearbox in front of it. \$\endgroup\$ – Ignacio Vazquez-Abrams May 12 '18 at 3:05
  • \$\begingroup\$ Are they DC motors? What you want for something precise like this is a stepper motor. \$\endgroup\$ – Hearth May 12 '18 at 3:05
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    \$\begingroup\$ how slowly , once per hour, or once per minute? once per 12 hours? \$\endgroup\$ – Jasen May 12 '18 at 9:37
  • \$\begingroup\$ If you have plenty of power, use a stepper. Otherwise, gears. You can find AC mains motors already geared down to clock dial speeds, in timer switches. \$\endgroup\$ – Brian Drummond May 12 '18 at 11:03
  • \$\begingroup\$ Some motors can't turn slowly, they cog and can't overcome their internal friction. \$\endgroup\$ – Voltage Spike May 14 '18 at 17:54

you can't make such motors ran that slowly easily, go looking for some gear motors. These are motors with a built-in gearboxes that slows the output down to a few revolotutions per minute.

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    \$\begingroup\$ The gearbox does not slow the motor down to a few RPM. Downvoting until corrected, I'm afraid. \$\endgroup\$ – TonyM May 12 '18 at 7:54
  • \$\begingroup\$ It slows the output shaft down to a few RPM if want to be pedantic. aliexpress.com/item/DC-12V-3RPM/32831021499.html \$\endgroup\$ – Jasen May 12 '18 at 9:27
  • \$\begingroup\$ youtube.com/watch?v=0z_fAuXgnok \$\endgroup\$ – Janka May 12 '18 at 9:43
  • \$\begingroup\$ that's just a machine to strip the teeth off the 19th gear, but the fist gear will wear out before that happens. \$\endgroup\$ – Jasen May 12 '18 at 9:53
  • \$\begingroup\$ Hardly pedantic. Don't you want your answer to be accurate and clear for OP and others. Takes seconds to write it better. Be fair, pedantic would be pointing out the bad capitalisation and spelling. \$\endgroup\$ – TonyM May 12 '18 at 16:59

I'm guessing you're connecting the potentiometer in series? This works by basically reducing the motor power down by limiting the voltage and current the motor receives, but from 11krpm to 1rpm, I think the motor would probably just stall if you tried this. Same with a transistor, as it'll work in effectively the same way.

A gear or belt drive system might work, or you could consider using PWM to drive the motor.

PWM is a technique where you rapidly switch on and off the power to the motor to slow it down. If you don't need a precise speed you could just rig up the potentiometer to a 555 timer to generate a pulse wave for the motor and fiddle with it till you get the speed you want.

If you want a precise rotation speed (especially if you're going to put a varying load on the motor) you might consider some sort of control system (Might be best to go off the shelf for this).

Still though, it would be good to keep searching for a motor that's designed to go slower. Using the motor you've got, I'm honestly not sure if it'll work as slow as you want it to go.

  • \$\begingroup\$ Use 1/T control \$\endgroup\$ – Gregory Kornblum May 12 '18 at 10:13

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