For a project in my research job I am required to use a stepper motor to turn a screw (this is done using a timing belt configuration). Given the maximum required torque to turn the screw, my supervisor ordered this stepper motor 57STH56-2804B - 1.8 Degree - 2.8A Stepper - 15:1 Gearbox - 3333_0 at Phidgets and it finally came in and I am very eager to at least turn it a few steps.
I am quite new to this area involving arduinos and stepper motors, however it was convenient that my supervisor has an arduino uno and the motor shield rev3. I am well aware that the max current for this motor is 2.8A which is higher than the 2A motor shield. THAT BEING SAID, this is the maximum current required to turn the motor at top speed which is not what I need anyways. The screw needs to turn a maximum of 2 revolutions over the span of, say 15 seconds, or even longer. Therefore the application needs the motor to go very slow.
I was hoping I could get some insight on whether or not I need an H-Bridge for the application or even a pololu a4988 driver to give some "relief" for the current. Any other recommendations for the set up for this project is appreciated. Also, the motor was 70 dollars therefore I would prefer if any of the recommendations wasnt as pricey.
The "motor shield rev3" is not intended for low impedance motors, and won't work at all with that motor.
You MUST use a current limiting stepping motor driver, but most hobby type motor drivers won't provide more than about 1.5 A on a continuous basis.
The motor torque is proportional to the motor current, so if 1.5 A provides enough torque, then the MP6500 driver will work. If not, you need an industrial type driver as suggested in reply #1.
Thank you very much for both of those suggestions! I will look into them. Just a question for my own curiosity @jremington but why is the REV3 not intended for low impedance motors?
Yeah I am just looking to make an order for one in the next couple of days and I see in his tutorial he posted he used a different one and I was just curious of some other recommendations. I believe I am sold on the TB6600 tho! All the help was appreciated.
Right, around 50lb-in of torque is needed for the application where the max of the motor is 130 oz-in. I am not sure how to convert this information into the current needed granted the max current of the motor is 2.8A.
Motor torque is proportional to winding current. So to get 50 in-lb torque from that motor, you need 50*2.8A/130 = 1.1 A.
Most of the inexpensive, modern, current limiting stepper motor drivers can handle that current. My recommendation of the MP6500 in reply #2 stands.
Edit: the motor is actually capable of producing 192 kgf-cm torque@2.8 A, which is 166 in-lbs in antique units. So the current required is even less: 50*2.8/166 = 0.84 A. You could even ruin the gearbox if you operate the motor at full current.
kylekozielski:
Thank you very much for both of those suggestions! I will look into them. Just a question for my own curiosity @jremington but why is the REV3 not intended for low impedance motors?
Its a voltage source, not a current source. Nearly all steppers are current driven, not voltage driven.
A voltage driven stepper can never move quickly, 100 rpm or so is all you can expect, but current
driven low impedance steppers can get to 1000's of rpm, making they usable for leadscrew driving,
because the current source can overcome lots of backEMF.
Incidentally the dynamic torque from a stepper (torque when moving) is a lot less than the pull-out
torque (which is a static measurement), and falls with speed - the datasheet for your motor should have
curves of dynamic torque v. speed for various supply voltages.