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# Powering a NEMA 17 motor | Wattage Vs Voltage

I apologize if the question is silly as this is my first project involving stepper motors and I’m confused about power supply specifications.

So I’m working on a project involving:

1. 3 NEMA 17 Stepper motors with 4.2 kg-cm torque
2. 3 A4988 drivers

Now the motor is rated for 3.2 V 1.2 Amps/phase. So, at 3.2 V the motors require 3.6 A of current in total which means a wattage of about 11.5 W.

So can I use any power supply which can deliver sufficient wattage or should the power supply be capable of delivering 3 Amps regardless of its voltage?

Is an 18V 2A supply sufficient or do I require a 12V 4A power supply?arduinopower-supplyvoltagestepper-motorstepper-driverShareCiteEditFollowFlagasked 8 hours agoA. Joshi1122 bronze badges New contributor

• @Joshi, Ah, let me see. (1) Usually the motor current rating is important. So for your 1.2A per phase motor, 1.2A x 2 = 2.4A ~= 4A should be good enough. (2) For A4899, you can use 8 ~ 35V to drive the motor. So, I don’t usually consider power! 🙂 See my answer below for motor details. Have a great project. Cheers. – tlfong01 2 mins ago    Edit

You should use a 3.3V supply with at least 4A and miniature 12V fan for cooling the drivers since they need cooling from 1 to 2A. A surplus PC PSU would be handy.

Otherwise the linear current limiter FETs set by the pot will overheat.

12V Stepper motors might have been better, while the interface logic supports 3.3 or 5V.

If you’re using an Arduino, consider an open source windows app called GRBL Panel with gcode (grbl) flashed to the arduino. Awesome Windows software, used it 3 yrs ago.ShareCiteEditFollowFlagedited 8 hours agoanswered 8 hours agoTony Stewart EE75109k33 gold badges4040 silver badges149149 bronze badges

• 1But can I use a 12V 4A power supply I have lying around or a 18V 2.5A laptop power supply as the A4988 has current limiting and voltage limit from 8-35 V. I mostly want to know that should I try to match the Wattage of the supply or the Amperage regardless of the voltage? – A. Joshi 8 hours ago
• Also most schematics I came across used a 12V power supply for some reason – A. Joshi 8 hours ago
• No you can’t use 12V on a 3.2V motor with a linear current limiter – Tony Stewart EE75 6 hours ago
• Do you understand yet you must match the voltage and exceed the current capacity? – Tony Stewart EE75 6 hours ago
• Drivers like the A4988 use current limiting by PWM. This is achieved by using the inductance of the motor such that the voltage the motor sees ends up within its (e.g 3.2V) rating from a higher voltage supply – it’s essentially acting like a buck converter with the motor. The higher voltage allows for greater torque by allowing the current through the motor to reach its rating faster. So using a 12V supply or even 18V supply for such a motor is perfectly fine as long as the current limit is set correctly. – Tom Carpenter 5 hours ago
• @TomCarpenter Okay, so from what I’ve gathered I can use a 18V or 12V power supply which provides sufficient Wattage? So a 18V 2.5A supply will be fine? – A. Joshi 2 hours ago

Question

Which PSU to use for microstepping NEMA17 steppers at 3.2V, 1.2A per phase?

(1) Using A4899 and DM542 microsteppers, you can set max phase current, say 1.2A, for your NEMA17.

(2) So you can use high volt PSU as high as 36V, 2A, for your NEMA17 at 3.2V 1.2A /phase.

References

Appendices

Appendix A – A4899 driving NMEA stepper schematic