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I am an electronics hobbyist and I have come across an issue with stepper motors.

I have an existing mechanical clock assembly that I want to drive with a stepper motor. Due to size constraints of the enclosure behind the clock assembly, I can only choose stepper motors with a 18° step angle. I have attached a tiny 24-tooth gear on the shaft of the stepper motor and a matching 24-tooth gear to the mechanical clock to test the stepper motor to see if it can actually drive the mechanical clock. My currently chosen stepper motor can definitely move the clock hands.

My problem is that the mechanical clock assembly is geared at 6° per step which equates to one minutes hand movement (the clock only contains a minute and a hour hand). So if I drive the clock with the stepper motor, I get triple the amount of wanted movement. I have tried microstepping with the stepper motor to no avail and would like to avoid losing the torque using the microstepping method.

Is there a mechanical (and hopefully cheap) way to reduce the step angle from the stepper motor's 18° step angle to the mechanical clock's 6° angle?

I would like some guidance on what I could do to achieve this.

ocrdu
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Tony
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  • Sounds like a nice clock. Try changing the gear ratio to get your 6 degree step. – Gil Aug 05 '21 at 02:19
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    a question about gears is not really an electronics design question – jsotola Aug 05 '21 at 02:37
  • 3:1 gearing. Replace the driving gear with an 8 tooth pinion, or the driven with a 72 tooth gear. –  Aug 05 '21 at 12:57
  • 12T:36T would not be the only option to maintain the centre distance: You could vary the modulus if you are swapping the pinion anyway. – greybeard Jan 23 '23 at 08:20

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Instead of a 1 to 1 gear setup change to 1 to 3, that will reduce the 18 degree rotation to 6 degree rotation.

Gil
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