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Author Topic: 28BYJ-48 Stepper Motor Precision
Ozgur
Newbie
Posts: 3
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Post 28BYJ-48 Stepper Motor Precision
on: July 13, 2016, 23:33
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Hi guys,
soo couple of weeks ago I started to build my polargraph machine with parts lying around like old micro printer belts and 28 BYJ-48 stepper motors. It was working great with svg files I plotted awesome pictures with it then I decided to try that fancy death-to-sharpie code thingy.
It was a total disaster after 24 hours of plotting and at the end I clicked return to home and it went like somewhere else.I think my measurement are false or something wrong with the 28 byjs or 28byjs missing some steps. I tried couple of things like;
converting 28byjs to bipolar mode (which worked great I also get extra torque)
fixing the main gear to shaft with super glue (helped a lot)
these are my settings right now;
37 mm per rev
2039 steps per rev
2 step multiplier
1000 motor max speed (I should lower this I guess)
400 motor acceleration (or this)
also
I am using processing v2.2.1 with polargraph code v2.4.2
arduino code compiled with ide 1.6.7
cheap L239D motor driver shield ( basically adafruit motor shield v1)
yeah thats all for now 🙂
kongorilla
Pro
Posts: 362
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kongorilla
Post Re: 28BYJ-48 Stepper Motor Precision
on: July 14, 2016, 05:38
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I made a rig with 28BYJ-48's a year or two ago, and found much conflicting info about them online. Even a reliable source of info like Adafruit had specs that didn't match what I was observing with the particular motors I bought.

After much experimentation and high school level math, I concluded that the number of steps needed for turning 360 degrees wasn't an integer. Checking my old properties text file shows I settled on 2037.8864 steps per rev. I had 1000 for max motor speed and 800 for acceleration, and a multiplier of 2, so we're very close on that account. I believe I used an old v1 motor shield as well.

I wouldn't bet my house on that non-integer number, but give it a try. I think the machine was drawing reasonably well, but I don't remember doing a plot as demanding as a 24-hour Death-to-Sharpie marathon with it.

It was the output shaft and final gear that you glued?
Ozgur
Newbie
Posts: 3
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Post Re: 28BYJ-48 Stepper Motor Precision
on: July 14, 2016, 07:49
Quote

Thank you for your almost immediate respond 🙂

You guys have got an awesome community here. Yes it was output shaft and final gear. Finally its working great ... actually better than great its perfect. I couldn't have imagined that I would get this kind of precision with those cheap stepper motors. so I was getting this problem. The result of continuously drawing a square for example was this

Layered Square Svg Test

It was overshooting just a little bit with every pass.
I played around with the settings
39 mm per rev (changing this I think solved the issue. More on that down below)
4096 steps per rev
multiplier 1
800 max speed
800 acceleration
as I said changing the mm per rev solved the problem because I am using handmade pulley for the belt and I should have measured the lenght wrong 🙂

Handmade Pulley

And thats the result with the death-to-sharpie sketch

Death-to-sharpie tests

Spitfire mkv

also these are some of my old prints

Old svg tests

Thank you for your help and immediate respond 🙂
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