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Brent.Rubin
(@brent-rubin)
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Joined: 3 weeks ago
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2020-11-13 6:37 am  

Hey guys!  My name is Brent and I'm from St Louis, Missouri.  33 years old and I'm just here to learn mostly and share projects I'm working on.  Currently most of my projects are on hold as my first child was born about 4 months ago and that's been keeping me pretty busy.

My most recent interest has been using arduino with stepper motors (specifically larger ones) and just trying to learn as much as I can because there's so many different applications you can use a stepper for.

I'm currently struggling with a NEMA 17 I bought from StepperOnline.com.  Trying to get it to work with a joystick module but I can't get it to produce enough torque to get it to move any real weight and not sure what I'm doing wrong.  Hoping to figure that out here eventually.

Anyway, thanks for having me here and looking forward to meeting everyone.  And big shout out to Bill for all his great videos and work he has done.  I have learned quite a bit from him already.

Brent Rubin


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robotBuilder
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2020-11-13 8:20 am  

@brent-rubin

I'm currently struggling with a NEMA 17 I bought from StepperOnline.com. Trying to get it to work with a joystick module but I can't get it to produce enough torque to get it to move any real weight and not sure what I'm doing wrong.

Gears?

 


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Brent.Rubin
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2020-11-13 2:18 pm  

@robotbuilder Right now I'm using just a shaft coupling attached to a steel rod.  I'm 3d printing a big pulley to be attached to the steel rod in hopes that it can lift small objects attached by a string to move up and down if that makes sense...   I'm not very educated about this kind of stuff so my apologies if I used wrong terminology about anything.  Everything I've learned has been from youtube more or less


 

Brent Rubin


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robotBuilder
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2020-11-13 11:02 pm  

@brent-rubin

Perhaps you could attach an image of your setup as it would save asking lots of questions trying to figure out exactly what you mean.

image

The simple "pulley" arrangement you seem to describe will reduce the lifting power as the wheel gets larger. With pulley arrangements, levers or gears it comes down to a weight acting through a large distance can move a larger weight through a smaller distance and vice versa.  An electric transformer can be seen as a kind of lever where the force is measured in voltage and the number of electrons being moved is the weight. The power into the transformer equals power out minus any heat lost in the transformer windings.

Power (watts) = Force (volts) x Current (amps)

A small gear on the motor shaft driving a larger gear will increase the torque as the little gear turns many times with each turn of the big gear.

image2

 In the electric transformer analogy the number of windings is the size of the gears.

 

This post was modified 2 weeks ago 3 times by robotBuilder

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Brent.Rubin
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2020-11-13 11:20 pm  

@robotbuilder yes that's exactly what I'm doing lol.  Sorry I don't have the pulley system done yet so can't attach any pics.  Below is a link to a video of my setup I have tho.

Nema 17 with a joystick module and a 100K pot for speed control.  Using an L293D motor shield for arduino with the stepper.  Hoping this helps...  Thank you

Brent Rubin


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Foxy
 Foxy
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2020-11-14 12:49 am  

Borrow a trick from mine hoist technology-- hang a counterweight on another drum on the same shaft.  If the two weights are equal the motor only supplies losses.  If the two weights are different the motor only has to lift or lower the difference. Of course the counterweight rope must be wound the opposite direction so when one weight goes up the other goes down

This post was modified 2 weeks ago by Foxy

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robotBuilder
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2020-11-14 2:22 am  

@foxy

Regardless of the actual weight (difference or not) the question was one of torque. If you are running the stepper motor at max voltage then I would suggest the only way to increase the torque would be gearing. You can lift any weight you like with any motor with the correct gearing. The heavier the weight required for any given motor the slower it will have to move.

 

@brent-rubin

Why a stepper motor? Are you wanting to stop it at fixed points? What is the project supposed to do?

 


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Brent.Rubin
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2020-11-14 6:21 am  

@robotbuilder I appreciate all the input guys. I work in finance for my day job and this is all just fun for me and trying my best to learn but sometimes it's hard.  Thanks for being patient.  I'm gonna try the small gear to big gear idea and see how it goes.  I'm only trying to lift about 3-4 oz objects with it and I think it's gonna work out ok.

Thanks again!

Brent Rubin


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robotBuilder
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2020-11-14 6:39 am  

@brent-rubin

I'm only trying to lift about 3-4 oz objects with it and I think it's gonna work out ok.

Most likely it will 🙂

 

This post was modified 2 weeks ago 2 times by robotBuilder

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frogandtoad
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2020-11-15 1:55 pm  
Posted by: @foxy

Borrow a trick from mine hoist technology-- hang a counterweight on another drum on the same shaft.  If the two weights are equal the motor only supplies losses.  If the two weights are different the motor only has to lift or lower the difference. Of course the counterweight rope must be wound the opposite direction so when one weight goes up the other goes down

Posted by: @robotbuilder

@foxy

Regardless of the actual weight (difference or not) the question was one of torque. If you are running the stepper motor at max voltage then I would suggest the only way to increase the torque would be gearing. You can lift any weight you like with any motor with the correct gearing. The heavier the weight required for any given motor the slower it will have to move.

Indeed, we have two different approaches, but both solutions affect the overall torque at the output shaft, whether it be by direct coupling or gear ratio/transmission does not really matter... what matters is choosing the one that most comfortably fits into the design of the mechanism 🙂

Cheers.


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Foxy
 Foxy
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2020-11-15 2:58 pm  

@frogandtoad

You're right and when you come down to it we don't know the design of the mechanism.  If we had enough information on the motor we could probably dig out a data sheet and find the rated torque then if we knew the weight Brent.Rubin wants to lift we could calculate any required gear or pully ratio. All that "NEMA 17" tells us is that the mounting flange is 1.7" diameter.

By the way, "steppers" are commonly described as dc or dc pulse but if you dig into them they turn out to be 2 phase ac synchronous motors and there is plenty of literature over many years on synchronous motors.  But most of it is well beyond amateur level.   


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frogandtoad
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2020-11-16 2:13 am  

@foxy

Posted by: @foxy

By the way, "steppers" are commonly described as dc or dc pulse but if you dig into them they turn out to be 2 phase ac synchronous motors and there is plenty of literature over many years on synchronous motors.  But most of it is well beyond amateur level. 

Agreed, and thanks for the info above... I haven't heard of steppers described as such before.


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Foxy
 Foxy
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2020-11-16 3:23 pm  

@frogandtoad

I first ran into "steppers" in about 1962 or 63 and I wasn't quite sure what they were and didn't have much to do with them afterward.   Bill's description of them in his lecture would apply directly to a synchronous motor except that a synchronous motor doesn't a "detent" at power off.

The only quibble I have with Bill's description is that I would draw a diagram of it with the pole axis parallel to the pm magnet axis rather than at right angle to it.

Some years ago I met up with some large synch motors (several thousand HP) fed from SCR converters which generated the pulses to build up a variable frequency power supply to get variable speed. Pretty much big steppers though the term wasn't used at that time.   


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