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Topic: What to do when motor is idle (Read 738 times) previous topic - next topic

sixeyes

I'm currently planning to use an Arduino Mega to run a unipolar stepper motor which controls a turntable on our model railway. The motor will spend a long time doing nothing and then for up to two minutes it will rotate and then be idle again.

My question is should the motor coils be powered when idle?

If not, when I need to move the motor, do I re-energise the coils in their last state or move straight onto the next position?

Iain

Grumpy_Mike

If you disable the motors you will get no holding torque. In your case I think this does not matter. When you re energise them you should keep the same state as before, then you get no movement until you do another step.

sixeyes

Thanks for clarifying the issue.

During my searches on the internet I've seen articles talking about half stepping. Do you think this is a good idea?

Iain

Grumpy_Mike

It depends entirley what you want to do. Half stepping gives you more resolution but with less torque. You can also quarter, eight and sixteenth step as well. However if you are stopping the motor and disabling it you better do it on a full step interval.

sixeyes

Thanks for that. I had only seen an article about half stepping. Didn't know you could do the others. As you recommend full stepping I won't try anything else.

Iain

Grumpy_Mike


sixeyes

Thanks for the link. Fantastic article. Learnt a great deal.

Iain

Terry King

Stepper motors have SOME holding torque even when powered off. For your application it should be fine...

If you can, rotate the motor by hand... you should feel "cogging" as the motor stops in discrete positions. On large stepper motors this is very pronounced. 

When energized but not changing, there is a lot of holding torque. This may be needed if there is considerable force (torque) from the mechanism when the motor is stopped.

I haven't done any kewl model railroad stuff in ... (OMG)  years...  There is the remains of a roundabout that I stop and visit sometimes in the Summer, near the Plattsburg, NY marina.
Regards, Terry King  ..On the Red Sea at KAUST.edu.sa
terry@yourduino.com  LEARN! DO! (Arduino Boards, Sensors, Parts @ http://yourduino.com

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