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ArcticMyst Security by Avery

steppers in spiro for precise control?

Joined
May 18, 2008
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I've been thinking it would be fun to have extremely precise control of a spiro. You could even do math with it, and dial up specific patterns! (like, #1 rotating at 80rpm, #2 at 160rpm #3 at 120rpm).

And, having the speed STICK is a concern, too. Even w/ PWM, regular DC motors drift around.

Would steppers do what I want? Or, even the 2nd thing I want (drift free speed). I realize the 1st thing will require software control.

I've never worked w/ steppers, and most of the info on them seems to be for very slow rotation (robotics and such) and when used for lasers, for actually stepping back and forth like a psudo-galvo. Will they work for fast but precise spinning?

Thanks
 





3zuli

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steppers usually lost steps at higher rpm - this makes software control (in order to create specific pattern) almost impossible
you could do this with PWM, standart DC motors and a microcontroller and set few settings like (a, b, c = motors)
1. a=100% b=50% c=40% reverse
2. a=70% reverse b=20% c= 100% reverse
etc...
and then randomly switch between these settings

also forget about creating animations - this is done with galvo scanners
 
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Morgan

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I actually think this is highly possible. The OP is only after precision speed control which is exactly what stepper motors can provide. It doesn't matter if they lose a step or two here and there as the avarage speed it going to be much more precise than a standard DC motor and infinitely more controllable. The hard part is the control of course.

The control is something I too am looking into so I don't think you should abandon the stepper motor idea just yet.

For cheap display units, stepper motors are often used instead of galvos, (this is why I'm interested in the stepper motor control). The animations are poor quality and resolution is appauling but they do create patterns more than just your flowers and stars.

M
:)
 
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Tell me more guys I have been wanting to use steppers for years -have a ton of them -will send free in trade for info on how to use-preferably with music- I have a stepper contoller kit and one that came assembled--never got around to making any moar progress on it.. flowers and stars!!! nice but boring after awhile.... lol
 
Joined
Apr 2, 2009
Messages
10,662
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I've been thinking it would be fun to have extremely precise control of a spiro. You could even do math with it, and dial up specific patterns! (like, #1 rotating at 80rpm, #2 at 160rpm #3 at 120rpm).

And, having the speed STICK is a concern, too. Even w/ PWM, regular DC motors drift around.

Would steppers do what I want? Or, even the 2nd thing I want (drift free speed). I realize the 1st thing will require software control.

I've never worked w/ steppers, and most of the info on them seems to be for very slow rotation (robotics and such) and when used for lasers, for actually stepping back and forth like a psudo-galvo. Will they work for fast but precise spinning?

Thanks
+rep for asking how-- sounds like a good idea to meh.
 
Joined
Oct 24, 2009
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well i had something rigged up for a while.
Was not great but it could do simple patterns.
another user even got it to do 4 letter stick words.
you can use a cnc controller and just use your pc to control them.
but that can be a bit pricy for a cnc controller it will cost you about 50-80$ to buy
or you can make on for about 30$.
and the cnc software is very easy to use. well the g code is
altho to get the patterns you want i dont think you want them to spin just vibrate.
between 1 step
this will let you get all basic patterns and great beam shows but very very limited words.
you can get a pair of glavos and amps and psu for around 100$ used so after all your time and effort you might just want to get the real deal.
or you can make your own 12-18k galvos too.
you could use fan motors and get their exact rpm and use that.
but there is an instructable with that already even the code for it too.
steppers are fun but to tell you the truth i got almost better results out of the motors in cd drives to open and close the tray.
i mounted a mirror on them and glued a spring to the mirror in a U shape and at the center secured it to the motor.
then just played audio files threw it or used a frequency generator and was able to make boxes flowers infinity signs.
it was cool and very cheap cost me less than 2$ to make the setup but it is what got me started before i invested in my galvos.
play with the small stuff but put aside some money for a set of gavlos, you will want them soon enough.
heck i want to sell my 18k galvos and get a pair of 30k galvos. i was thinking 50k but still cost too much.
 
Joined
May 18, 2008
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I don't want to do the galvo thing.. I mean, some day I will purchase them.. they're cheap enough now.

I want a precisely controlled spiro. I've noticed the good patterns have to do w/ harmonic frequencies.. Like, the motors buzz when they spin.. and when its drawing a good shape, the 3 motors buzz making a harmonic chord.
I want to dial in a 'frequency' or, RPM in this case, and have that motor stay at that exact RPM. It's for personal scientific/physics enjoyment, more than a laser show, maybe :). Similar to drawing Lissajous patterns w/ a synth(or signal generator) and scope.

Physics makes us all it's bitches
 
Joined
May 18, 2008
Messages
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Tell me more guys I have been wanting to use steppers for years -have a ton of them -will send free in trade for info on how to use-preferably with music- I have a stepper contoller kit and one that came assembled--never got around to making any moar progress on it.. flowers and stars!!! nice but boring after awhile.... lol

As far as how it's controlled, the stepper controller hooks to the motor.. but the stepper controller needs a controller of its own.. Feeding it pulses.
I'm old and analog, and can build a little circuit to generate the PWM. But, it would probably make more sense for someone to write something for a PIC or arduino or whatever the kids are using these days :).

Wait.... Can I take a few pulse waves from VCO's or LFO's from my modular synth and send that to the stepper controller? I could use the motors almost as oscillators and "play" different shapes.
I guess i need to get a few stepper controllers.

Hak, you might be more interested in using them like galvo's. I think it's pretty easy.. the laser show software already knows how to work w/ them, etc. There's plenty of info on the forums about that.. (it's all I could find when I was trying to figure out if I could just control how fast they spin)
 

dnar

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I have built a dual stepper projector for my 200mW green module.

Steppers are 200 step (1.8 degrees per step), usable range is approx 72 degrees optical. (very "steppy").

The steppers I am using are very nice, there is little overshoot.

I have ordered Alegro stepper drivers that enable half, quarter, eigth and sixteenth step stepping. Once I get back from working in Canberra (2 weeks time) I will connect them in to my Arduino driver and take some shots.

With 1.8 degree stepping that I have now, my projector produces really nice beam effects (approx 30 different effects coded thus far).

So I think your idea is a good one for a spyro.
 
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Feb 26, 2010
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One thing that came to my mind is using cheap hobby servos to control the motorspeed. Ie. glue tiny frontsurface mirrors on those tiny motors inside the servos and use the position potentiometer to change speed of motor.
Anyone tried this?
 

Morgan

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One thing that came to my mind is using cheap hobby servos to control the motorspeed. Ie. glue tiny frontsurface mirrors on those tiny motors inside the servos and use the position potentiometer to change speed of motor.
Anyone tried this?

Servo motors are considered too slow to be useful as far as I've read. (isn't that mfo's avatar?)


Here is a thread from not so long ago with some useful links in it. As the 445nm and other projects took priority this one got, 'back-burnered', but it still progresses in the, 'Thought Lab'. Some good explainations and circuits for stepper motor contollers and I think there's also a link to a cheap stepper motor kit. (I have read elsewhere that the motors may not last too long. Apparently you end up burning the coils out as they are over driven to get the response speed but it's a solution to be built upon).

http://laserpointerforums.com/f42/micro-stepper-motors-bluray-sleds-50795.html

M
:)
 
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Joined
Feb 26, 2010
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Morgan, I didn't mean that you drive them from the geared down servo output shaft. I meant drive them directly on the motor inside the servo. I have been experimenting with these kind of servos a few years ago, taking them apart and testing and whatnot.

When they are in center position without any PWM signal on input you can get the motor to spin CW or CCW depending on wish way you're turning the feedback potentiometer.
You're essentialy opening up a closed loop servo system.
 
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Morgan

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^But isn't it the closed loop that gives you the positional control? Otherwise you're just back to a spinning motor with little control. These things are not my strong point but the OP definitely needs that positional control to create the non-spiro patterns and if I'm right the servo motors without the gears and feedback are just DC motors again.

M
:)
 
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Since it has been a while since I messed around with these servos I don't remember the specifics of the controller.
But I recall that the further the feedback pot was away from center the faster the motor spin and it kept it's RPM pretty stable at diffrent positions.

Only difficult thing with this is that it would be hard repeating exactly those potentiometer values that you have a second time, and ofcourse software control would be out of the question if you would'nt be willing to do some hacking and reverse engineering with those controllers...
 
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Oct 24, 2009
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Freitsu
I just going to give you a heads up before someone gets mad about it.
That picture you have has already been taken,
Laser pumpkin.
I would advise you to change it to your own image, now if you are the original creator of said image and can prove it then by all means but if you just found it and said hey this is cool. its been taken or just photo shop it a bit.

the servo motors without there gears are almost useless.
You would need to keep 2 or 3 gears or else the wight of the mirror would turn the shaft.
I was playing around with these for a while too and found that without the gears the shaft would always over shoot but if you kept 2 or 3 gears you still had some speed and it kinda solves the problem.
Better off with stepper motors or fans.

Laser show for poor man

The guy was nice enough to modify the code for me to allow you to store patterns but this is what you want.
This is one of the best spiros you can ever build.
with stepper motors they are more useful to energize one coil then send your pulsing signal threw the other.
this is a old thread of mine and it shows what stepper motors can do when pushed to the max.

http://laserpointerforums.com/f47/building-scanner-44932.html

Not bad some great images in there, more than enough to make flowers words multiple circles.
What ever path you decide you will find you can do alot just some paths are easier to do more on.
 
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