Thursday, November 21, 2019

Current and voltage we need to supply to the stepper motors

So you’ve decided how many stepper motors you need and the torque rating. It’s then just a matter of matching to a suitable controller. All controllers will have stepper drivers that either individual modules or integrated into the controller board. The digital stepper drivers are designed to supply current and voltage, which in most cases is adjustable. It’s important to match the current with the stepper motor. Stepper motors can work at very low voltages but they are usually driven at much higher voltages up to 8 times by a chopper driver. If you would like more information check this link This gives higher torque and speed.

Current and voltage we need to supply to the stepper motors


If you use a stepper that needs 2.8 amps and your drivers only supplies 1.5 amps it may still work but slowly and may not be enough to overcome the load.

Generally, NEMA17’s are run on 12 volts and NEMA23 24 volts. If you supply less then the motors will turn slowly. Its to do with something called back EMF. So when you are deciding on the controller check the current rating of the steppers and make sure the controller or driver modules can be adjusted to match as close as possible but don’t supply more or the motor may fail.

My foam cutter uses 57BYGH56-401A NEMA 23 which are rated at 2.8 amps and 3.36 Volts per phase. I run this with a 24-volt power supply and the current is at 2.25 amps set via DIP switches on the board. This has run for several years without any issues

Power Supply
The CNC power supply needs to be able to deliver the voltage and current for your chosen motors and controller. Going bigger on the current won’t hurt but the voltage needs to match the controller’s voltage. So for my foam cutter, I use 4 x 23HS22-2804S NEMA 23 rated at 2.8 amps and the controller need 2 amp. So 4 x 2.8 amps plus 2 amps for the controller gives 13.2 amps. If we multiply that by 24 volts to give Watts that comes to 316.8 Watts. Powers supplies can be rated by Amps or Watt so I use a 15 Amp 350 Watt supply.

CNC controllers for the DIY machine

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