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Author Topic: motors stuttering and only move down, not back up
sethberry
Newbie
Posts: 8
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Post motors stuttering and only move down, not back up
on: February 18, 2013, 14:41
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hi again,

so I uploaded the compiled hex file using xloader and wired up my motors according to the polargraph instructions .pdf (hopefully the right way, attached are pictures, 1st picture is motor 1 (left), 2nd is motor 2 (right)).

however, my motors are stuttering, when I tell it "move pen to point" they go back and forth without really moving too much, the motion is not smooth. when I "move pen to point" and select a point above its current position, the gondola moves downward instead of up. am wondering what kind of issue this is, seems like something to do with my settings but am not entirely sure. i have these stepper motors from adafruit (http://www.adafruit.com/products/324). thanks for any help.
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sandy
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Posts: 1317
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sandy
Post Re: motors stuttering and only move down, not back up
on: February 18, 2013, 15:16
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You've got your motor coils wired up wrong I think:
"To connect to our shield, put the wires in this order: Red, Yellow, skip ground, Green, Brown (or Gray)" (from the adafruit page you linked to)

Motor coils are red/yellow for coil A and green/grey for coil B. Probably doesn't matter which way the wires are in the individual pairs.

sn

sandy
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Posts: 1317
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sandy
Post Re: motors stuttering and only move down, not back up
on: February 18, 2013, 15:21
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Oh ps, good work on getting the code uploaded.

The wire colours are different for every motor so each new kind you've got to get a datasheet you trust, or test with an ohmmeter to figure out which pairs are connected to which coil (http://digital.ni.com/public.nsf/allkb/0AEE7B9AD4B3E04186256ACE005D833B).

sn

sethberry
Newbie
Posts: 8
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Post Re: motors stuttering and only move down, not back up
on: February 18, 2013, 20:12
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thanks, dont know how I missed seeing that when ordering, it definitely did the trick- rewired then it was running opposite so i switched the wire layout going into the board. am starting to do some drawings now and just need to keep figuring things out. theres definitely a polargraph effect being created but this last one is slanted so will need to check my settings. also am having some issues with the beaded chain slipping so have considered re-doing the sprockets or even using strong thread wrapped around the spool (saw that on the website) so there wouldnt be any issue of slipping. cant see any negative consequences unless it got wrapped up in a way that prevented itself from unwrapping correctly. but anyway, thanks for all the help! cant wait to see what happens now

sandy
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Posts: 1317
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sandy
Post Re: motors stuttering and only move down, not back up
on: February 18, 2013, 21:15
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I think for spools that size you'll be ok with using thread or something, it'll build up on the spools, and the diameter of the spools will change a bit from one end of the wind to the other, but I doubt it'll be that noticable. As long as you keep a little bit of tension on the thread, it'll not get tangled. Look for something with low stretch.

Beaded cord slipping might mean your counterweight needs adjusting?

sn

sethberry
Newbie
Posts: 8
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Post Re: motors stuttering and only move down, not back up
on: February 19, 2013, 04:18
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i think its just the awkward sprocket that i lasered out of acrylic, i designed it based off the 3d print .stl before i even had the beaded cord. i kept messing around with different amounts of counterweights but they kept slipping like the beads weren't set into the grooves well. i just replaced the chain with some white cotton thread, bit thicker than sewing thread and its working out wonderfully- slipped once or twice so might need a bit thinner thread to take up less space on the sprocket. just need to figure out the best settings to make good drawings now.

it seems the machine always draws my image larger on the polargraph than it is displayed on the screen (can see in images). figured out what the frame does already and need to try some different pen sizes. attached are some pictures of first tests! so exciting!
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