NEMA 14 Stepper Motor

Other Hardware Motors, Mechanics, Power and CNC
1

I am building an automatic fish tank cleaner for my final year project and need help with stepper motors!

It is basically going to be a 2-axis positioner mounted vertically against the glass, although it is curved so it will actually go round the glass. I did a little experiment for how much force is required to move the magnetic cleaner that will be inside the tank and it was about 7.6N. From there I found the required torque to be ≈45mN.m

The timing belt for the stepper will be mounted on the glass facing out the way and meshes with a driving gear off the stepper, with coaster wheel supporting the system.

I looked into using a 28BYJ 5V stepper but the torque fell just short as it's stated at 34.3mN.m

I then started looking at the NEMA steppers and thought the 14 might be more suited to my needs. What has me confused is the holding torque values. I looked up what this meant and I understand that it is the amount of torque it can withstand if magnetised but not turning. However does this value also equate to the torque that it can drive?

This is the exact model I was looking at: https://www.accu.co.uk/en/nema-14-stepper-motors/394252-NEMA14-26-0-23-1-8

Also the values on that website for torque are in g/cm... does it really mean g.cm?

Thanks for your help in advance :slight_smile:

2

"NEMA 14" just specifies the dimensions of the mounting plate and has little to do with torque, voltages, current, etc.

Here is a useful discussion of the various torque relationships in stepper motors.

I would avoid a seller that doesn't know the proper units of torque.

3

willduino:
I looked up what this meant and I understand that it is the amount of torque it can withstand if magnetised but not turning. However does this value also equate to the torque that it can drive?

No, its fairly irrelevant really. You find the torque-speed graphs in the datasheet (there should be
several for different supply voltages), and look up the dynamic torque for the speed/voltage you are
interested in. Torque drops rapidly with increasing motor speed, and more rapidly with lower
supply voltages. Constant current drive is assumed in all this.

Holding torque is always much larger than dynamic torque, this is why you can reduce the current by a factor of
2 or more when the motor is stationary to save power.