$3 Stepper Motor

What am I looking for in the specs a stepper motor? Will any one work? I am not really willing to pay the $90 USD each for the one in the BOM. Will this $3 USD work just as well? [www.goldmine-elec-products.com].

Thanks,
Matt

cool. that is a nice find. from the looks of it, it could work. it says its unipolar, and we are using bipolar motors. it *may* be possible to treat them as bipolar motors, but YMMV.

if you're in the US, you might want to check out automation direct... they have some $20 steppers that look pretty good.

ZachHoeken Wrote:
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it *may* be possible to treat them as bipolar motors, but YMMV.

You can use bipolar motors with unipolar drives but not the other way round.

Also, I think this motor is too small. Seems to be a floppy drive motor, only 1.65 in square. I doubt that it has enough torque and the shaft is smaller and it has 100 steps rather than 200.

Nice price but apart from that not really suitable unfortunately.

nophead Wrote:
> Also, I think this motor is too small. Seems to be
> a floppy drive motor, only 1.65 in square.

It looks to me like an old head-positioner stepper from the days of 20MB 5.25" and 3.5" MFM disk drives.

> Nice price but apart from that not really suitable
> unfortunately.

That's a shame.

-ethan

Mendelson's had Lin Engineering 5618S-54 steppers for $5 dollar, but 20% off so $4.00 plus 0.28 tax! If you are in Columbus, you are only an hour away. www.meci.com,
but it is best to look around, and bring your multimeter, you'll need it!

I own some Lin Engineering steppers. They are NEMA standard and very solidly made. From Brett's experience, however, they do not take well to being dropped onto hard surfaces.

What about scavenging? Steppers are everywhere, but I presume a typical stepper from an inkjet, or scanner won't do. Is there anything to look for in a motor or a device?

> Steppers are everywhere, but I presume a typical stepper from an inkjet,
> or scanner won't do. Is there anything to look for in a motor or a device?

Torque, number of steps/revolution, and coil resistance all matter. You can work around the last one with "honking great resistors" which some people have done successfully (Hi Eric!). 400 steps/rev is ideal, 200 steps/rev loses you some precision but is probably still OK for experimenting. I don't know what the torque requirements are. Adrian has posted some info on this here in the forums somewhere, I think?

I think we need a Wiki page called "StepperMotorSpecifications" -- this sort of question is being asked by quite a few people these days.

Jonathan

Just a thought...

If the studding is M6, it means every whole turn will advance the position by 1mm
This means that we go from a resolution of 2.5 um to 5 um.

Since we are looking at extruded plastic at about 0.2-0.3 mm (200-300 um) at best I wonder if the resolution has any impact on the precision at all?

/Erik

Studding is only used on the z-axis. The other two use timing belts so are much lower resoltion but faster moving.

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[www.hydraraptor.blogspot.com]

also, the studding used in the project is 8mm. additionally, the gears on the X/Y axes are *very* small. still lower precision, but not as big as you'd think.

Does the belt drive offer an advantage over screw drive? Seems like the screws would be more precise, and belts might have a slipping problem. I guess that belts are faster when speed is needed.

Well slipping isn't a big problem because these are toothed timing belts. However, it is still true that a screw drive would offer more precision and perhaps stability. However, if I recall correctly belts were chosen because (1) they allow greater speeds than a screw drive and (2) almost all commercial 2D printers and scanners use them, so it was assumed the designers of those systems knew what they were doing. I suspect cost might have had something to do with it as well.

Actually it's the other way around, nophead and Zach. Unipolar motors have more wires, which can be tied together and then it can used as if it were a bipolar motor. Not the other way around. Very confusing, I know, but still important if you're trying to decide whether you can buy a motor or not. Because we use bipolar on the RepRap, we don't have to worry too much, because either unipolar or bipolar motors will work if you wire them properly.

Some reference material:

[www.solarbotics.net]
[www.cs.uiowa.edu]

Samuel, yes I got myself confused, sorry Zach.

Unipolar motors do indeed have more wires because they have centre taps. You can use them on bipolar drives by ignoring the either the centre tap, or one of the end connections depending on whether you are going for torque or speed.

Living up to my nom de plume there.

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[www.hydraraptor.blogspot.com]