What's wrong with the Adafruit motor shield?

I've just completed a mock up of a camera slider. Basically a 1.5M length of track, a nema17 stepper motor at one end, an idler pulley at the other, a carriage to carry the camera all connected with a small timing belt. At each end of the track are limit switches.

The whole thing is controlled by an Arduino UNO R3 with an Adafruit motor shield on top.

Everything works perfectly, it's nice and smooth, I'm more than happy with it's operation. I'm powering the motor shield with a separate 12v dc supply, I can't feel any temperature rise with the chip on the motor shield.

My question is, what's wrong with using the Adafruit motor shield? There's no pots to twiddle to adjust current, to me that's a good thing.

Surely Adafruit wouldn't design a motor shield if it was no good for stepper motors?

Ken

Stepper motor needs pulses of current to make them change by a step. The current needed is defined by the resistance of the coil windings. To change the current, you'd have to change the voltage being applied.
Does the documentation say the shield is for stepper motors?

There's no pots to twiddle to adjust current, to me that's a good thing.

The bad thing is that there is no way to set the current through the motor other than adjust the voltage fed into the shield. That means you can not over drive the motor to get current into the coils quickly and so the top speed you can achieve from your motor is much lower that it would be with a current limiting motor driver.

You may find something useful in stepper motor basics

...R

Depends on the stepper motor. High impedance (30 ohms or more) bipolar motors can be driven
from a dual H-bridge motor controller. Such motors are slow (300 rpm if lucky), but will work
fine from something like 12V at 0.4A or something like that.

Low impedance bipolar steppers can be anything from 5 ohms down to 0.3 ohms or so - these
are designed for constant current drive from a chopper driver, they are not suitable from any
plain H-bridge board. They are, however, fast (2000rpm or more from a high voltage supply)

All the commonly available 3D printer steppers are low-impedance bipolars.

CrossRoads,

With your background, I’m surprised you ask if the Adafruit motor shield is for stepper motors.

There’s much information on the web re the above motor shield, such as Using Stepper Motors | Adafruit Motor Shield V2 | Adafruit Learning System

Ken

With your background, I'm surprised you ask if the Adafruit motor shield is for stepper motors.

He asks because it is not very suitable. A sort of rhetorical question.

There's much information on the web re the above motor shield, such as Using Stepper Motors | Adafruit Motor Shield V2 | Adafruit Learning System

Two points:-

  1. There is a lot of crap information on the net about electronics, look at any instructable project to see how bad it can get.

  2. They are trying to sell their own product so they would say it was good wouldn't they?

We are not saying you can not use it to drive stepping motors, just that it is a poor second to using a proper current regulating chopping driver.

If you want state of the art, energy efficient stepping motor drivers, these are currently the best available for the smaller motors typically used by hobbyists. Furthermore, Pololu has by far the best product support.