How do you use a 3.8V stepper with a Marlin RAMPS 3D printer?3D Printer Motors

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How do you use a 3.8V stepper with a Marlin RAMPS 3D printer?3D Printer Motors 

The voltage stated on the stepper motor is basically unimportant. The current, however, is important. If you need a motor to deliver 1amp total (voltage is unimportant), assuming we are talking NEMA 17 - size it accordingly, or it will fail to deliver enough torque, or get too hot in use - as a rule of thumb aim for a 20–40mm sized motor. Over 1 amp, nearing 2 amps then go for a 40+mm sized motor and when you are into consistently over 2.5amps consider going up to NEMA 23. On ramps its 2amp max and even then with serious cooling implemented.

Steppers work by sending pulses of current to magnetic coils, in a quite-complex way (unless you are running full stepping - microstepping is quite complex but desirable for numerous reasons) so it's not a DC motor where you rate it for x -volts and x-amps.

My experience, and others, running duet controllers was that low inductance (often low voltage) steppers were desirable and allowed much higher speeds. My kossel XL running duet could do 16000 mm/min travel speeds, using NEMA 17 motors.

This is taken from stepper motor and explains it nicely.

“Stepper motors have a rated voltage and current. A typical stepper motor like our nema17 might have a rated voltage of 2.8 Volts and a maximum current of 1.68 Amps. This basically means if you hook it up to 2.8 Volts it will draw 1.68 Amps. If you try to run it at a higher voltage it will draw more current and get excessively hot. Most people don’t hook motors straight to a voltage source. They use a Stepper motor drivers regulate the current. If you hook it up to to 12V, for example, the motor while attempt to draw more current, but the stepper motor driver will not allow that to happen and use high-frequency pulses to limit the average current to the desired maximum value.

Stepper motors are designed to work this way and it is safe to run the motors at up to 20 times the rated voltage. You will actually get better performance by running at a higher voltage than the rated voltage.”

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