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Boston
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Hi,
Looking for advice on buying a stepper motor.
Thinking of buying this bipolar one http://www.sparkfun.com/products/9238
Quote
12V rated voltage (you can drive it at a lower voltage, but the torque will drop) at 350mA max current
28 oz*in, 20 N*cm, 2 Kg*cm holding torque per phase
35 ohms per winding

and driving it with this 1A H- bridge. http://www.sparkfun.com/products/315
I will need to move 3- 4 pounds around in a circle on a lazy susan very slowly, like maybe 1 full rotation per day.
Will this work for my purposes?

Thanks.
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I believe it can work fine. You'll want to reduce the action with gears for movement that slow -- this will give you additional torque, which will probably help.

Is this for a solar cell aiming at the sun? :-)
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Boston
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Thanks jwatte.
No, nothing solar.
I had an idea to use this under a plant in a window so it doesn't get all tilted toward the window.
Sort of a revolving plant stand.
Still wrapping my head around how to connect the motor to the lazy susan.
What would be the best way to combine the two?
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Denmark
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Maybe you could use this one,
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=126

It has a 1:64 gear so maybe you don't need more gearing. Just put a wooden dish or similar on the axel and your plant on top.
Maybe I should do the same, my girlfriend complains because I don't turn my plants (they are all leaning against the window  smiley-grin)


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Dallas
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This is going to be a terrible waste of power. A stepper motor burns the same (or more) power when holding still as it does when rotating. If you use the sparkfun motor you will be using a constant 35W of power. Since it sounds like you don't need very much precision, you might consider using a gear motor and just running it in short bursts every so often, or figure out a way to turn the stepper motor off, but the stepper motor will freewheel when it's off.

Running a gear motor 1 second every hour sounds easier, plus you can use a single transistor to drive it.
« Last Edit: February 13, 2012, 09:10:59 am by BetterSense » Logged

Boston
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Thanks for all the advice.
I've already ordered the stepper motor from Sparkfun.
I should be able to turn it off when not needed to save power.
If freewheel becomes a  problem I will try a gear motor.
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Boston
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Ok, I've got the stepper motor working and now am trying to envision the mechanics of this.
I managed to get some plastic gears from an old VHS player and one small one fits snugly onto the shaft. I could connect this to another gear attached to the lazy susan. http://www.ikea.com/us/en/catalog/products/90074483/.  I can't really put it directly in the middle as the bearing and metal plate get in the way.
Another thought I had was to skip the lazy susan and just drill a hole in a board and mount it directly on the shaft.
I'm not sure how much weight the shaft can hold.

So two question.
1. I have the stepper wired as in the 4 wire example.http://arduino.cc/en/Reference/StepperBipolarCircuit  After about 3 or 4 minutes of rotating (10 steps and then resting for 10 seconds) my motor gets pretty hot.  Almost too hot to touch. Should the motor be getting hot or do I have it wired up wrong?

2. Anyone have suggestions for how to connect the motor shaft and make the board/plate rotate?

Thanks.
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Manchester (England England)
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Quote
Should the motor be getting hot or do I have it wired up wrong?
Motors will get hot. This is not the result of miss-wiring but he result of too much current down it.
In turn this is caused by either setting the driving regulator to too high a current or giving the motor too much voltage if you do not use a chopping regulator driver.
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Boston
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Ok, so if I have it wired up like this http://arduino.cc/en/Reference/StepperBipolarCircuit and am using a 12v 600ma wall plug, how do I set the driver regulator lower?  I am using the Stepper examples in Arduino for now.
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Manchester (England England)
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using a 12v 600ma wall plug
Give it a lower voltage, use a voltage regulator, say down to 9V for a start.
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Phoenix, Arizona USA
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I'm not sure how much weight the shaft can hold.

The bearings on the motor shaft are not likely to be thrust bearings which would be able to handle the weight of a plant and board sitting on top. If you did go this route, you would want to support the board by some other means to keep the weight off the shaft (perhaps by rollers at right-angles under the board). Another option would be to support a circular board on the outside edge by rubber rollers at right-angles, with one of the rollers being attached to the shaft of the motor (or leave the lazy-susan bearing as-is, and drive the board similarly). You could also use a belt drive. Lots of options possible to keep the load off the motor.
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Boston
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Thanks guys.   I switched to a 9 volt plug and the motor is a lot cooler.
Got my parts sorted.  Now all I need to do is cut some wood and try assembling it.
I am putting the large gear in the middle under where the plant will go.  I will also use some rollers to help support the weight.

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Boston
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I've got the motor working with an Uno and am trying to get it working with an RBB Pro http://shop.moderndevice.com/products/rbbb-pro but no go.  Using 9v to power the motor and all it does is shake or wobble.  I've tried switching the motor leads but that does nothing.  I've switched out the H-Bridge chip and that does nothing.  I've wired it up twice with the same results.  http://arduino.cc/en/Reference/StepperBipolarCircuit
Is the RBB Pro board missing some critical component or am I just missing something in my wiring?
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Boston
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Any suggestions as to why my stepper works fine with an Uno, but not with a RBBB Pro?
I've rewired it twice and am powering it with a 9v wall plug.  All it does is vibrate or shake.

Thanks
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Denmark
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A guess: are you using a 3,3V RBBB and therefore the control voltage is lower?
« Last Edit: March 03, 2012, 08:30:56 am by Erni » Logged

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