Maximum Current Concern for REV3 Motor Shield

Using Arduino Motors, Mechanics, Power and CNC
#1

Hello,

I currently have a REV3 Motor Shield and I notice on Arduino Motor Shield Rev3 — Arduino Online Shop it states the max current is 2A per channel and 4A total. I am looking to purchase a stepper motor from 57STH56 NEMA-23 Bipolar Stepper with 15:1 Gearbox - 3333_0 at Phidgets which has current rating of 2.8A. Would this shield suffice for the motor I am looking to purchase or will this cause problems.

Thanks in advance,

Kyle

#2

Hello there!

Since the motor is trying to take more current than the shield can provide, there is indeed going to be a problem. Most likely, the motor controlling chip(s) will break due to overheating trying (unsuccessfully) to provide the current demand of the motor. Your best bet is to find another motor controller than is rated for more than the 2.8A so that the controller chip is not running at its maximum output.

#3

Hey,

Thanks for the insight. This still would cause problems even though the motor would be using 2 channels instead of just the one 2A channel?

#4

kylekozielski:
This still would cause problems even though the motor would be using 2 channels instead of just the one 2A channel?

Interesting idea. I believe this would allow for 4A to be provided (which is more than we need so that's good). However, the voltage at the positive terminal would be doubled, assuming you tell each channel to go to the same voltage. (Motor+ = (C1+) + (C2+))

#5

Ah I see. I will look more into it, thanks!

#6

The ancient, extremely inefficient L298 in that shield is overrated and can't provide anywhere near 2A/channel continuously, Furthermore it drops up to 4V internally, overheats and shuts down. It won't work at all with low impedance steppers.

You are much better off with a modern, current limiting stepper motor driver, such as those produced by Pololu.

#7

Thanks!

#8

A 2.8A stepper is a low impedance stepper (0.9 ohms in fact), so cannot be driven from any DC motor controller,
and definitely requires current drive. Note any voltage specification on stepper motors is usually completely
bogus and should be ignored - the current, resistance and inductance are the key figures.

Steppers of 5 ohms or less are current drive only, 30 ohms and above may be voltage driven (but wont
be capable of high speeds). Anything inbetween is fairly rare and frankly a bit weird!

2.8A is more than most single chip steper drivers can handle though - the TB6560 and similar (which
massive heatsink) is one option, or else a discrete design using separate MOSFETs - both of these are
a lot more expensive than a DRV8825 which can handle 1.5A or so.

If you can change to a motor with a lower current rating you’ll reduce the cost of the driver…

#9

Thanks for that Mark.

#10