# Powering a NEMA 17 motor: wattage vs voltage

I'm working on a project involving:

1. Three NEMA 17 stepper motors with 4.2 kg-cm torque
2. Three A4988 drivers

The motors are rated at 3.2 V, 1.2 A/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.

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

Is an 18 V, 2 A supply sufficient or do I require a 12 V, 4 A power supply?

• @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. Commented May 1, 2021 at 5:13
• Assuming your motors picked well, select the PSU for power, mostly. You computed the "quiescent" power, add the mechanical power needed for more than mere milliseconds and allow for efficiency < 1. The voltage needed depends on acceleration and speed required. Watterott's FAQ answers looked helpful beyond what I'd be willing&able to answer. Commented Dec 16, 2022 at 11:51

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

• Shouldn't this spell out why the PSU didn't need to provide 1.2 A for each of two phases? And how to account for 3 NEMA 17 Stepper motors [+ drivers], just in case? Commented Dec 15, 2022 at 5:12
• Sorry, I forgot what I wrote long time ago. I need to read my old posts to refresh my memory: penzu.com/public/a3cacdc5 Commented Dec 15, 2022 at 5:46
• I have a couple of answers on A4988 in this forum, but many of them are locked. Here is another one: electronics.stackexchange.com/questions/560123/… Commented Dec 15, 2022 at 8:28
• This one doesn't spell out why for a single 2-phase stepper with 1.2 A phase current a 2 A supply suffices when using an A4988. Nor did I find that skimming all of the posts/pages hyperlinked. Commented Dec 15, 2022 at 9:03
• It is not clear if you wired the A4988 for full stepping or microstepping. Perhaps you can let us know how you connect the MS1, 2, 3 pins. Commented Dec 15, 2022 at 14:14