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Stepper motor power help

visigothe

Hi all,

 

I'm very new to this, but I work in eletronics repair and I believe I understand the essentials.

 

What I need help with is stepper motor power. I would like to lift and lower approximately 2 lbs 5-7 feet up and down for a halloween project. At a fairly slow speed, but constantly, no resting time.

So what size stepper motor would I need? I would like to just wind fishing line on the shaft to keep it simple.

 

Thanks for any help

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  • 0

    Hi Michael,

     

    A stepper motor isn't needed for this, if you want it to perform constantly. You could just use some mechanical switch to know when to turn the motor off. But, the jerky action of a stepper motor will be an advantage at Halloween : )

    The tiniest motor can be used in theory, if you want a slow speed, with just very high reduction ratio with your gearbox.

    If you know the diameter of the pulley/fishing line reel, you can calculate the torque, and then divide it by your gear ratio, to find out what torque motor you need. The same applies for a stepper (and you might need less or no gearing)

    depending on the size of your final choice motor.

    This link and the wikipedia entry will be useful for your calculations. You might need to convert units, since motor torque may be specified in Nm or mNm.

  • 0 in reply to shabaz

    Thanks for the answers, but let me further clarify the problem.

     

    Constant refers to not letting the motor rest, but it would be letting the object (pumpkin) lower approximately 6 feet, then reverse direction to raise up 6 feet, then reverse again.. etc.

    Also due to the need for invisible support, I plan to use a very thin fishing line. Not sure, but I would suspect there would be slippage on most pulleys.

     

    So.. what size stepper can lift about 2 lbs by winding line on its shaft?

  • 0 in reply to visigothe

    Michael,  as suggested could you use two pumpkins, so they counterbalance each other.  The fishing line is fine to carry the load but being nylon it is essentially a bearing with low low friction characteristic.  I think the jerky motion of a stepper motor would exacerbate the problem.  I think you need to look at a pulley on the motor shaft with a high friction to the nylon fishing line and multiple turns of the line around the pulley.  Essentially you need to grip the line.  Possibly a pinch roller to increase the grip, a rubber tyre (UK spelling) would also help.  The larger the pulley diameter and the slower the motor will give more chance of sucess.  Another suggestion is to coat the pulley with a fine abrasive paper.

     

    Hope this helps.

  • 0 in reply to bobcroft

    Actually I was going for 3 pumpkins. But I think 2 in perfect opposite balance would not look quite right. I want 3 random up and down, not in sync. And with the counterbalancing you suggest, what would cause the motor to switch directions?

     

    Also from the vids I've seen, I was under the impression using a driver would smooth out most of the jerky motion.

  • 0 in reply to visigothe

    what would cause the motor to switch directions?

    same as the stepper, the program instructs the direction change.

    I was under the impression using a driver would smooth out most of the jerky motion.

    Your impression is incorrect.

     

    If you don't want to use pumpkins, you could simply use a weight.

     

    Mark

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