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Author Topic: Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V too slow
maranatha
Newbie
Posts: 2
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Post Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V too slow
on: March 24, 2015, 15:58
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Hello,
I'm beginer in polargraph so please be patient.
I explain my problem, I have two steppers motor
http://www.emartee.com/product/41757/ and I don't know how to change the program. In fact when I used it, the motor rotation is very slow. How could I accelerate it ?
Thanks in advence
Alexandre
kongorilla
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Posts: 362
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kongorilla
Post Re: Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V to slow
on: March 24, 2015, 21:02
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Hi Alexandre!
Those motors are geared so it takes many more steps for a full revolution than the motors that come with the polargraph kits. When I made a polargraph rig with 28BYJ-48's last year, I found contradictory info about them online, leading me to believe there may be differently geared motors being given the same part number. For example, the info on Adafruit's site (a reputable source) didn't match what I was seeing at all. The source I bought mine from stated a similar step angle to what's shown on the page you linked, but those numbers didn't work out right for me either.

You're going to have to change a few settings in your default.properties.txt and upload the new specs to your machine via the controller.

The settings that worked for me:
machine.step.multiplier=2
machine.motors.stepsPerRev=2037.8864
machine.motors.maxSpeed=1000

The steps per rev being a non-integer is weird, and I don't know what Sandy's code does with that, but according to the math, that's what my motors do. At the time, I found a blog post somewhere that agreed with that number, so I took that as validation.

Most sites recommend running the motors in half-step mode, that's why I set the multiplier to 2.

If I tried running the motors faster than 1000, they didn't work reliably.

Sandy might jump in and explain why I'm all wrong, but those settings worked well for me. A machine with these motors isn't going to be as fast as one with the more typical 200 step motors, but they do work ok within certain limits.
sandy
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Posts: 1317
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sandy
Post Re: Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V too slow
on: March 24, 2015, 22:25
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I remember that Kongorilla mentioned that those motors were beautifully quiet too.

Steps per rev is stored as a float so having a non-integer is fine, what a strange number though eh.

The half-stepping thing is something that should be configured either in firmware (if you're using an adafruit shield), or in hardware if you're using a driver that can do microstepping. The multiplier being 2 makes sense in that case, but not sure it makes any difference otherwise.
maranatha
Newbie
Posts: 2
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Post Re: Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V too slow
on: April 3, 2015, 21:22
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First of all thanks for your advices, i will change the default setting,I hope it will work well 🙂

Secondly, to improve my polargraph I bought two motors with 75 steps in order to be faster, like the previous, does I have to change some settings ?
http://fr.farnell.com/nanotec/sp2575m0206-a/moteur-pas-a-pas-7-5-degree/dp/4743209
sandy
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Posts: 1317
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sandy
Post Re: Polargraph server a1, shield motor V2 - 28BYJ-48 Stepper Motor 12V too slow
on: April 4, 2015, 15:58
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Hello, you won't have to change anything except the steps per rev. 48 steps per rev. It's best to do it by opening default.properties.txt directly and modifying the value there. When you do it in the application itself, it makes all the sizes go a bit screwy, and you've got to reset them.

Be aware, having huge steps like that will mean you can step fast - but I bet you'll struggle to get much torque behind moves that size. You're really better off using a regular 200 or 400 step NEMA 17, 16 or 14 motor, rated to draw the current that your motor driver is able to supply.

sn
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