I'm having issues selecting the right Nema 17/ stepper motor for my project. I'm confused about what I need. The project is running 8 AA batteries, so 12v/ 1A. I've tried a couple different Nema 17 motors, and don't feel like I'm getting the proper amount of power or torque out of them. Is there a trick to using the A4988 driver and programming the motor, or is there a motor I can choose that would be optimized at 5v/ 1A? I've also tried 12v step-up units, etc. Any advice appreciated! Thanks.
Confusion will disappear when you determine the ACTUAL torque you require. Then you can pick an appropriate motor. Then you can pick an appropriate controller. Then you can pick an appropriate power supply.
See how the basics determine the whole project?
Paul
Have you carefully set the current limit to 1 Ampere/phase, the maximum current that the A4988 driver can handle?
AA batteries are a problem. Alkaline AA cannot supply 2A peak without a severe voltage drop, as required by that setting. Try using a sensible power supply, capable of at least 2A.
The voltage of the motor power supply has to be greater than 8V, and can go up to about 35V. But higher voltages will only improve the motor response time and maximum step rate, not the torque.
If the specifications say that the 1 amp motor you are using has enough torque for your project and if you are not getting the specified torque then the problem must lie in your stepper driver current setting or the power supply. Batteries are a bad choice for stepper motors because the motors are very inefficient.
These links may help.
Stepper Motor Basics
Simple Stepper Code
...R
dynamicsallen:
I'm having issues selecting the right Nema 17/ stepper motor for my project. I'm confused about what I need. The project is running 8 AA batteries, so 12v/ 1A. I've tried a couple different Nema 17 motors, and don't feel like I'm getting the proper amount of power or torque out of them. Is there a trick to using the A4988 driver and programming the motor, or is there a motor I can choose that would be optimized at 5v/ 1A? I've also tried 12v step-up units, etc. Any advice appreciated! Thanks.
Firstly you won't get much battery life, steppers pull a lot of power constantly. The mechanical output
power is typically much less than the power put in. If you want mechanical power and battery life, steppers are the worst choice of motor by far (factor of ten or more?)
The voltage of the supply is mainly relevant for top speed of the motor. The torque is set by the
current and the motor itself, and the A4988 drives constant current. If you program the motor's nominal
current into the A4988 module, that's the best you can get (at low speeds) for that motor.
Higher voltage supply and lower impedance motor both mean better high speed performance,
assuming the motor is being driven with the correct current level.
The size of the motor is the most important factor in the torque of any motor.
As for torque, the hold-in torque figure is only relevant to holding position - the torque available to
actually spin the motor is much less, and falls rapidly with speed. Most good motor datasheets will give
a variety of torque/speed graphs for a range of driver supply voltages.