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What should I do when using a 10V .5A NEMA14 stepper motor with this board: https://reprap.org/wiki/MiniRambo (beyond setting proper current limits in firmware)? If I understand it correctly, the board uses 12V by default as it normally controlls 12V NEMA17 motors. Will the voltage difference be a problem and if so, how can I fix it? If I just use resistors, won't it limit the current too? The board uses A4982 stepper motor drivers, the datasheet is here: http://www.allegromicro.com/~/media/files/datasheets/a4982-datasheet.ashx

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  • \$\begingroup\$ Arguably, your motor's coil voltage rating is too high for your controller. You typically want a controller supplied with several times the motor's nominal voltage, otherwise you will have poor performance at speed. But perhaps your application only moves slowly or does not need the motor's rated torque, for example a 3d printer Z axis will often have cheap motors with high coil impedance, while the X, Y and extruder might have ~4v motors, all supplied from 12v. \$\endgroup\$ Feb 19, 2019 at 0:49

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The rated voltage doesn't really matter much for steppers, as long as the current is regulated you should be good to go

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  • \$\begingroup\$ In that case, I should be able to even use a 3V motor and as long as the current is in check it should work, right? \$\endgroup\$ Feb 18, 2019 at 21:31
  • \$\begingroup\$ This is oversimple: the voltage matters a great deal, in that the supply voltage should be several times the motor voltage unless it is a fairly low performance requirement or the motor is oversized for the need. \$\endgroup\$ Feb 19, 2019 at 0:51
  • \$\begingroup\$ Looks like Chris is right. Steppers are used and rated differently from other motors. \$\endgroup\$
    – DKNguyen
    Feb 19, 2019 at 2:29
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A 10V 0.5 stepper will draw 5W in each winding or 10W max with an 80'C temp rise at full step which means the DCR of each coil is 10V/0.5A = 20 Ohms

The design uses Current sense Rs 0.1 Ohm with Imax programmable by DAC software 100%=2V/8Rs which exceeds the 500mA.

The drivers are 350mohm max so 12V / (0.35+20+0.1)ohms= 587 mA, so 12V may be too hot in certain step positions if using microstepping. This temp. rise can be improved with a 35mm microfan attached to motor.

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