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Stepperbee vs Arduino ?

Questions, problems, comments and tips regarding the 3d scanning process.

Stepperbee vs Arduino ?

Postby Christian_Mendez » Fri May 17, 2013 5:23 pm

hello everybody,

I´ve been digging around trying to find threads about planeless laser scanning. I need some info about the stepperbee and how to make it work DAVID. It seems that most of the planeless laser rigs
are using Arduino. I tend to lean more toward the stepperbee as it looks like it´s less work compared to the Arduino?
So what woud you suggest I should pick up? Arduino seems to require some coding skills while Stepperbee seems to be an almost ready to use/out of the box - solution.

Any advice or push to the right direction is very much appreciated.

thanks in advance,
Christian
www.greyscale3di.com "if it ain´t movin´, we can scan it!"
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Re: Stepperbee vs Arduino ?

Postby WalterMo » Sat May 18, 2013 8:09 am

Hi Christian,

I have never worked with the Stepper Bee, so I cannot say something about its programming and controlling via a pc. I found this paper......:
http://www.pc-control.co.uk/images/Step ... manual.pdf

....and saw, regarding the electrical specs of the board, that it can only drive unipolar stepping motors. These kind of motors are not as common than before. E.g. the low cost motors from Phidgets.......
http://www.phidgets.com/products.php?category=23

…...with and without an attached gear are all bipolar ones.

And the maximal output current of the board is only 500mA (under optimal conditions). Newer motors have rather low coil resistances, often less than 2 Ohms. That means higher currents will flow which must be limited by an (adjustable) potentiometer on board (chopping mode). See Pololu.....:
http://www.pololu.com/catalog/product/1201

or the Big EasyDriver...:
http://www.schmalzhaus.com/BigEasyDriver/

The Arduino together with a mentioned above motor driver is well tested here. But why not to try something different?

Walter

PS. There should be 3 reasons to let the number of bipolar motors increase:
1. Better utilization of the motor coils:
Bipolar motor: All windings are current-carrying (= more torque). Unipolar motor: ½ of the windings are current-free. For interested people:
http://www.google.de/imgres?q=unipolar+ ... 66&bih=602
2. In the meantime more and better motor driver ICs are available for the bipolar mode. (It's easier to drive an unipolar motor).
3. I never saw an unipolar motor driver IC which could do micro stepping.
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Re: Stepperbee vs Arduino ?

Postby Christian_Mendez » Sun May 19, 2013 12:57 pm

Hello Walter,

I was trying to understand the difference between a unipolar motor vs a bipolar motor. So it seems that (if i undestood correctly) a unipolar motor
will be less precise than a bipolar motor? So with that info, it´s probably better to try and build an arduino cotroller to drive the laser and use Katie?

I´m not too good in electronics. I used a hacked servo (hacked the pot and tricked the servo to rotate continously) and used a servo tester to control
the speed and finally, I simply reversed the current to change the drive direction by using a switch . It was quite okay for a while but I could´nt do
planeless scans with it.

Anyway, I´m planning to drive a green laser (http://www.apinex.com/ret2/LC532-5-3F.html) as now I´m thinking that a good laser driver and a good
laser should be more suitable for micro scans (currently I´m using scan scales @ 42mm & 23mm) because of a good depth of field a laser brings along with it.
SL scanning is very very good :) but in this scale range it´s just not working (it´s possible, but not always ideal) because of the shallow depth of field of a projector. So unless
there´s a way of replacing the projectors lens with one that has an iris/diaphgram to increase the depth of field, I think planeless laser scanning is the way to
go at these scales.

I´ve been reading this thread over and over again...I´m still trying to make sense out of it all. Setting up a planeless SL scanning rig is child´s play compared
with a planeless laser rig...so to all those who mastered laser scanning - chapeau chapeau !!! you have my admiration ! :)

viewtopic.php?f=6&t=1999

looks like Mike_A already used the stepperbee and he moved on to the arduino controller...I guess he had good reasons.


Thanks again Walter! I´m sure i´ll have more question sooner or later

regards,
Chris
www.greyscale3di.com "if it ain´t movin´, we can scan it!"
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Posts: 188
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Location: Vienna, Austria

Re: Stepperbee vs Arduino ?

Postby WalterMo » Sun May 19, 2013 8:15 pm

Christian,
No, an unipolar stepping motor isn't less precise than a bipolar one. But first: What is the precision of a motor? In my opinion: It's the ability not to lose single steps and to do equal steps (with constant angles).

What I meant above when I mentioned an increasing usage of bipolar motors is that bipolar motors have a higher torque comparing motors with the same size. All windings are current-carrying and not partially inactive waiting for the current. And that they can easily work in micro step mode (sub-division of their full steps).

I would use Sven's Katie and „unavoidably“ my Arduino circuit diagram. If you choose the Pololu board for motor driving then I would hook it up on a carrier board. Like here (March 3th):
viewtopic.php?f=6&t=4154
It's much better to handle.

Your green laser, powered by 3V, would fit to the electronics.

But you are right: Building a planeless laser scanner is much more difficult than to use SL with a projector. Your idea to use an iris inside the projector's lens to increase the depth of field could work. There's more than sufficient light intensity to scan such close by objects. So the iris could be closed to a minimum. One should try to substitute the original lens by a camera lens (with iris).

Walter
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