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Author Topic: The ugly cousin...
jcliff
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Post The ugly cousin...
on: October 7, 2011, 23:01
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I've been building something similar for a while - I bought 3 easydrivers from sparkfun several years ago, intending to build a mini cnc, never got them to work right, got an arduino for my birthday and finally got them working, that was april! Since then I've found at least 3 ways to burn out an easydriver, and come to the realisation that after a 12 hour day at work is not the best time to play with electronics.
I had 2 steppers with spools lifting and raising weights on strings and had just been trying to work out how to do the software when I found this site a couple of weeks back. have installed your embedded/server combo, and now have a working machine!
I had to make a couple of changes to the embedded code to make it work with the easydrivers, taking out the Motor1 and Motor2 code and just using the AccelStepper calls:

AccelStepper accelA(1,5,4);
AccelStepper accelB(1,9,8);

I also had an intial issue with having the coils reversed vs what was expected, so when the controller told it to go down it went up, right left etc. swapping coils a & b on the easydriver fixed that. I now have a working system, although its still needs mounting on a decent sized board.
Mechanically rather than putting the motors out on the corners I've put both in the center to simplify cabling, then I'm running the strings out via hooks on the corners of the board and down to the penholder. it literally is string a the minute, need to get hold of something better at some point, but for now have settled for tesco value string on some cobbled together spools. (my kittens loving the rest of the ball of string! shes also pretty keen on the machine when its running!)

https://picasaweb.google.com/lh/photo/6U5Vs3cPjP_sH3WTbtMzLg?feat=directlink

sandy
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sandy
Post Re: The ugly cousin...
on: October 7, 2011, 23:39
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Looks brilliant John, so pleased you could use the software and get it all working - that accelstepper library is ace isn't it. My first version just used thread and sewing bobbins to reel it in too, and worked fine, all the initial drawings I did use that mechanism. I eventually ditched it for accuracy - as the thread (or string) winds out and then back in again, it builds up on the spool in a different way each time, and so the diameter ends up being slightly different, and this meant I couldn't get the pen to go to the same place twice, which is important if I want to do multi-layer stuff and keep things in registration.

HOWEVER, it did add a beautiful bit of randomness to the drawing, and showed as kind of "cracks" between the rows, which I really miss with the big machine, it's a lot more predictable.

Strong thread was pretty good, a lot of bots seem to use fishing line, but I find that stuff an exercise is frustration to use, it's always springing everywhere as soon as you let go of the end - your kittens would have a field day.

Great to hear from you,
Sandy Noble

jcliff
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Posts: 8
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Post Re: The ugly cousin...
on: October 15, 2011, 17:29
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Got the bot mounted on a proper board now (2 quid offcut from B&Q, result!)
Set it going doing a drawing to show my mum it while she was paying a visit today, seems to work ok, although one of the motors is skipping steps, think I need to play with the current regulator on its easy driver.

https://picasaweb.google.com/lh/photo/nACDed9enZIgJYu-taC_uGQf8X_k_vYw-yk271_kNbE?feat=directlink

just need to write some code to convert svg to bot commands now...

sandy
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sandy
Post Re: The ugly cousin...
on: October 15, 2011, 18:18
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John, looks neat, I got mine from the offcuts bin too 🙂

Would be really interested in seeing what you get up to re vector graphics output - one of those things I meant to get cracked really early on, but got seduced by the pretty bitmap pictures instead, and I wasn't keen to rush into making it just another x-y plotter either.

Have you seen http://tinkerlog.com/2011/09/02/der-kritzler/ ? Most impressive drawbot I've seen, and very good software, readable and capable.

jcliff
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Posts: 8
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Post Re: The ugly cousin...
on: October 16, 2011, 18:12
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Yeah, seen the kritzler bot, that was the code I was looking at using before I stumbled on yours, could get it on the arduino ok, never got it to actually do anything though, may have to have another play, as he already has the vector stuff, may end up creating a frankenstien of the two 😀

Still getting a drawing that gets narrower as it gos down the page, need to work out whats doing that.

vasya
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Post Re: The ugly cousin...
on: January 12, 2012, 14:34
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hello

jcliff
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Post Re: The ugly cousin...
on: January 10, 2014, 00:32
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So after 2 years of it sitting looking sad in a corner (and then hiding it in the shed for a bit out of pure shame) I've finally found some time to play with my bot again. Had left it with a dud sketch on it, and the laptop that I was using before is no longer functional, so started afresh with the latest version. Couldnt get the a1 software to upload to my uno (think it needs a bootloader update, but couldnt work out how to do that) so I bought a sainsmart mega 2560 off amazon and have swapped that out so I can use the mega server. Is working now, but for some reason the vertical axis is flipped. The x axis is correct, but the vertical is inverted. Kinda expected both to be wrong if it was a wiring issue, anyone got any ideas, as I'm a bit stumped?
server is as per the 1.7-1.6 zip on the github, am running the precompiled controller from the same.

sandy
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sandy
Post Re: The ugly cousin...
on: January 10, 2014, 09:58
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Good to see you back 🙂 That's a funny one isn't it. I've always got to scratch my head to figure out the relationships of the wheels and the motion.

Turning both sprockets anti-clockwise will move the gondola LEFT, and that's true even if the motors are flipped. However, flipping _will_ reverse the y axis. It doesn't seem right, but that's why I laugh when I've got to convince myself of the simplicity of it every time.

It is possible that you have the motors flipped (left to right) _and_ the wiring flipped (so that they are moving in the opposite direction). Of course you can change all the values in the source code if you're running from source.

It is possible to switch your motors around, and you will fix your inverted Y axis, but you might have inverted the entire thing instead (ie the right-hand motor is now on the left-hand side), and you really want to have both. The simplest way to do it is to tell it to make a move that only turns one sprocket at a time, and make sure the correct one is moving, and in the right direction.

good luck!
sn

jcliff
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Post Re: The ugly cousin...
on: January 10, 2014, 16:06
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Thankyou! Had not paid enough attention when I modified the config to work with the easydrivers rather than the adafruit board, and had motors A&B swapped from before (I'd even put the correct defs in the post above so I wouldnt lose them - doh!) also seemed to have re-spooled the string at some point, and hadnt respooled them the right way round. is all going in the right directions now. Amazing how much easier this is when you can play with it during the little ones afternoon nap rather than late at night when hes asleep and everything else is done.

jcliff
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Posts: 8
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Post Re: The ugly cousin...
on: January 12, 2014, 01:37
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Replaced my cobbled together spools (catfood box + electrical tape, what all good prototypes are made from) and used some spools that were sitting on the dresser in our bedroom. They were from wrapping ribbon, so at the same time I ditched the string in favor of ribbon, and most of the inconsistency seems to have disappeared. (I'm just going to describe whats left as 'character' 🙂 )

Image

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