If I wanted a stepper motor turning one revolution per day (yes, per day) what electronics do I need to tell it to do that? As an example this motor.
- 45Ncm(63.7oz.in) holding torque
- NEMA 17 bipolar 1.65"x1.65"x1.57" 4-wire
- 1.8 deg. step angle(200 steps/rev)
- Rated current 2A & resistance 1.1ohms
- 12-24VDC
200 steps is REALLY low resolution for 1 RPD (1 step every 7.2 minutes).
ReplyDeleteI would look at a stepper motor with a harmonic drive attached, like https://pgfuntransmission.com/product/harmonic-drive-reducer-with-nema-17-42mm-stepper-motor-1-4-a-2-1-nm-ratio-301-rotary-gear-reducer/
This has 6000 steps, meaning 1 step every 14.4 seconds.
Alternatively, just put a harmonic gearbox on the stepper motor you listed (https://pgfuntransmission.com/product/harmonic-gear-drive-reducer-small-strain-wave-gearbox-gearbox-501-rotary-reduction-actuator-fits-nema-17-stepper-motor/).
That combo would give you 10,000 steps (50 * 200), giving one step every 8.64 seconds with a gearbox design life of 3/4 year continuous running and low backlash.
They are still running fairly low actual torque capabilities (under 2 foot-pounds average torque).
That site also has rotary platforms that may be another option ...
DeleteYes, 200 steps is too low. Thanks for the pointer.
The simplest form of control would be something like this: https://www.robotshop.com/products/8-35v-2a-single-bipolar-stepper-motor-driver-a4988-black-edition
ReplyDeleteYou could then use a simple pulse generator (a 555 timer pulse generator like https://hackaday.io/project/180625-555-pulse-generator-module-how-it-works could work).
If you are using a 30:1 reduction on a 200-step motor and set the controller to 1/16 microsteps, you have 96000 microsteps per revolution. This translates to needing a pulse every 0.9 seconds.
If you use a 50:1 reduction on a 200 step motor with 1/16 microsteps, you are looking at 160,000 microsteps per revolution, for 0.54 seconds per pulse.
It would probably be easiest to get this tuned using something like an oscilloscope rather than trying to hook up the stepper motor and watch it.
Once you have the circuit tuned, put a 'hand' on the output and see how close to 1 RPD you are actually turning.
I suspect such a contraption could be assembled for around $250 or so all in (motor, gearbox and driving electronics).