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 Current adjustment works backwards and motors jitter
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By: zacgowen (offline) on Thursday, January 13 2011 @ 03:42 PM PST (Read 2144 times)  
zacgowen

Hello Everybody, We got an Egg-Bot for Christmas and it's displaying some odd behavior. When I plot one of the test files we get a lot of jitter. I tweaked the current adjustment like I've read in the instructions and other forum posts but that doesn't help. The pot control is behaving backward from what everyone else seems to be getting. The further anti clockwise I turn the control the easier the spindle moves by hand. The further clockwise I turn the pot the harder it is to turn. Another issue I'm seeing is when I manually tell the pen motor to rotate, it will sometimes pause and when it gets to the end of it's movement it will shake back and forth about 1/16 of an inch until I manually disable the motor. If I I manually move the egg motor it will do the same thing. I have removed the wires from the board and reseated them as well as swamping them to see if the problem continues. It does. Any suggestions? Regards, Zac Gowen


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By: Windell (offline) on Thursday, January 13 2011 @ 07:12 PM PST  
Windell

The pot control is behaving backward from what everyone else seems to be getting. The further anti clockwise I turn the control the easier the spindle moves by hand.


Doesn't sound like it's backwards at all. The graphic on the board-- and the instructions on the wiki site --indicate that current increases as you rotate counterclockwise.


Another issue I'm seeing is when I manually tell the pen motor to rotate, it will sometimes pause and when it gets to the end of it's movement it will shake back and forth about 1/16 of an inch until I manually disable the motor.

Sounds like you may have the motors turned up too high.


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By: Anonymous: Mark in Berkeley () on Sunday, January 16 2011 @ 11:47 PM PST  
Anonymous: Mark in Berkeley

My first plots turned out jittery/inaccurate, and I really thought that I might have miswired one of the stepper motors. The spinning motor axis was OK, but the pen left/right motor's coordinates were running out to the ends too quickly. A little RTFM on the article about making your first plot - the potentiometer adjustment section was exactly what I needed to make things right. Now in addition to making good plots, the motors are both singing nicely while plotting.





       
   
By: zacgowen (offline) on Tuesday, January 18 2011 @ 01:30 PM PST  
zacgowen

Quote by: Windell[/u]

The pot control is behaving backward from what everyone else seems to be getting. The further anti clockwise I turn the control the easier the spindle moves by hand.


Doesn't sound like it's backwards at all. The graphic on the board-- and the instructions on the wiki site --indicate that current increases as you rotate counterclockwise.



I don't think I correctly explained what I'm seeing. Following the graphic on the board and turning the potentiometer counter clockwise makes the motors "weak". When I turn the potentiometer clockwise the motors begin to whine, then begin to shake back and forth, and are hard to move.

Another issue I'm seeing is when I manually tell the pen motor to rotate, it will sometimes pause and when it gets to the end of it's movement it will shake back and forth about 1/16 of an inch until I manually disable the motor.

Sounds like you may have the motors turned up too high.



I have tried plotting a circle a dozen times starting with the current all the way down and gradually increasing the strength and still get erratic lines.

Regards,

Zac


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By: Windell (offline) on Tuesday, January 18 2011 @ 02:31 PM PST  
Windell

I don't think I correctly explained what I'm seeing. Following the graphic on the board and turning the potentiometer counter clockwise makes the motors "weak". When I turn the potentiometer clockwise the motors begin to whine, then begin to shake back and forth, and are hard to move.

This still sounds like 100% correct behavior.

There should be a happy medium somewhere between the two, where the motors start to have some strength, but the motors do not yet whine. Note that the motors may still whine and jitter-- no matter what the setting --while the screwdriver is still touching the current adjustment pot.

I have tried plotting a circle a dozen times starting with the current all the way down and gradually increasing the strength and still get erratic lines.

Again, the setting should be where the motors have moderate firmness, but no whining. Once you have it set there, try to plot a circle again, and tell me exactly how it's behaving. In what way is it erratic?


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