The Eggbot coordinate system - Revision history

Windell at 16:15, 20 June 2019

2019-06-20T16:15:06Z

Windell at 16:07, 20 June 2019

2019-06-20T16:07:39Z

216.167.174.66: /* The relative motion of stepper motors */

2013-02-15T17:14:18Z

‎The relative motion of stepper motors

Ericblazek: typo - changed 'comimg' to 'coming'

2012-08-28T14:02:23Z

typo - changed 'comimg' to 'coming'

205.156.36.64: /* Where does my drawing start? */

2011-04-18T16:35:56Z

‎Where does my drawing start?

Windell at 23:45, 24 December 2010

2010-12-24T23:45:08Z

Windell at 23:44, 24 December 2010

2010-12-24T23:44:52Z

Windell at 23:03, 24 December 2010

2010-12-24T23:03:03Z

Dnewman: moved Where will my drawing begin on my egg? to The Eggbot coordinate system: New "Framing and Pen Centering" page is more apropos to the subject "Where will ny drawing begin on my egg?" This page is now more focused on the how/why of the co...

2010-12-23T21:52:24Z

moved Where will my drawing begin on my egg? to The Eggbot coordinate system: New "Framing and Pen Centering" page is more apropos to the subject "Where will ny drawing begin on my egg?" This page is now more focused on the how/why of the co...

Dnewman: /* Where does my drawing start? */

2010-12-23T21:50:19Z

‎Where does my drawing start?

← Older revision		Revision as of 16:15, 20 June 2019
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	Download a copy of the SVG file for that plot and try plotting it on a light bulb or an egg. If you use the "Start with pen centered" option, then where the pen is when you begin the plot is where the line y = 400 from the drawing will be started. This is because the drawing uses a height of 800 pixels and thus the line y = 400 is the page's horizontal midline.		Download a copy of the SVG file for that plot and try plotting it on a light bulb or an egg. If you use the "Start with pen centered" option, then where the pen is when you begin the plot is where the line y = 400 from the drawing will be started. This is because the drawing uses a height of 800 pixels and thus the line y = 400 is the page's horizontal midline.

−	~~http://mtbaldy.us/~dnewman/tspart/coordinate-demo-21.png~~

	== Notes ==		== Notes ==

← Older revision		Revision as of 16:07, 20 June 2019
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	== Introduction ==		== Introduction ==
−
−	'''Note:''' This discussion applies to version 2.1 and later of the Eggbot Control extension. For earlier versions of the Eggbot Control extension, see [[Where will my drawing begin on my egg? (v20)]].
−

	* How does the Eggbot frame my drawing on my egg?		* How does the Eggbot frame my drawing on my egg?

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 A direct consequence of this relative nature of stepper motors is that the Eggbot has no idea what position the egg or pen arm is in when it begins a plot.  Let's repeat that: the Eggbot has no idea where the pen or egg is when it begins a plot.  At best, the Eggbot can track the cumulative number of forward (positive) and backwards (negative) steps each motor has taken since starting a plot [4].  Knowledge of the cumulative number of steps allows the Eggbot to return the pen to any previous position in the current plot, but that's all.  The "Return to home" option is implemented this way: after finishing a plot, each stepper motor is stepped the opposite number of net steps that that motor took while drawing the plot.  The final net travel for each motor then becomes zero steps.
-Another direct consequence of this relativity is that there is little if any utility to having absolute Eggbot coordinates.  What's the use of an absolute position (0,&nbsp;0) in Eggbot plotting space when the Eggbot has no idea what asbolute position either stepper motor is in?  Nonetheless, it sure would be nice to know where your drawing will land on your egg....
+Another direct consequence of this relativity is that there is little if any utility to having absolute Eggbot coordinates.  What's the use of an absolute position (0,&nbsp;0) in Eggbot plotting space when the Eggbot has no idea what absolute position either stepper motor is in?  Nonetheless, it sure would be nice to know where your drawing will land on your egg....
 == Where does my drawing start? ==

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 * A stepper motor rotates the egg clockwise or counter clockwise
-* The egg can be rotated in either direction up to 3200 steps before comimg full circle back to where it started
+* The egg can be rotated in either direction up to 3200 steps before coming full circle back to where it started
 * A stepper motor moves the pen arm back and forth
 * The pen arm can be moved about 1000 steps of total travel

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 == Where does my drawing start? ==
-Enter the "Start with pen centered" option of the Eggbot Control extension's "Options" tab.  What this option says, when checked, is that the pen is '''assumed''' to be at the (x,&nbsp;y) point (W/2,&nbsp;H/2) in your drawing -- the drawing's geometric center.  Here, W is your drawing's width and H is your drawing's height.  For a drawing with dimensions 3200&nbsp;&times;&nbsp;800, this corresponds to the point (1600,&nbsp;800).
+Enter the "Start with pen centered" option of the Eggbot Control extension's "Options" tab.  What this option says, when checked, is that the pen is '''assumed''' to be at the (x,&nbsp;y) point (W/2,&nbsp;H/2) in your drawing -- the drawing's geometric center.  Here, W is your drawing's width and H is your drawing's height.  For a drawing with dimensions 3200&nbsp;&times;&nbsp;800, this corresponds to the point (1600,&nbsp;400).
 If you do not check the "Start with pen centered" option, then the Eggbot assumes that the pen is located at the starting point of the first line segment in your drawing.  For all but the simplest drawings, it's anyone's guess which part of your drawing this will correspond to: Inkscape chooses how to order pieces of your drawing.  As such, operating without the "Start with pen centered" option is something of a gamble.

← Older revision		Revision as of 23:45, 24 December 2010
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	== Introduction ==		== Introduction ==

−	'''Note:''' This discussion applies to version 2.1 and later of the Eggbot Control extension. For earlier versions of the Eggbot Control extension, see [[Where will my drawing begin on my egg? (v20)]]. ~~To check which version of the Eggbot Control extension you have installed, select the '''*''' tab within the Eggbot Control extension.~~	+	'''Note:''' This discussion applies to version 2.1 and later of the Eggbot Control extension. For earlier versions of the Eggbot Control extension, see [[Where will my drawing begin on my egg? (v20)]].

← Older revision		Revision as of 23:44, 24 December 2010
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−	{{~~EggBotDocs~~}}	+	{{EggBotDocs210}}

← Older revision		Revision as of 23:03, 24 December 2010
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		+	{{EggBotDocs}}
		+
		+
	== Introduction ==		== Introduction ==

← Older revision	Revision as of 21:52, 23 December 2010
(No difference)

← Older revision		Revision as of 21:50, 23 December 2010
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−	Where is (0, 0) on your egg? Turns out it really doesn't matter. But if you must know, when you start the plot with "Start with pen centered", the point (0, 0) will be W/2 egg rotation steps to the right ~~and H/2 pen arm steps "up"~~ towards the headstock.	+	Where is (0, 0) on your egg? Turns out it really doesn't matter. But if you must know, when you start the plot with "Start with pen centered", the point (0, 0) will be H/2 pen arm steps "up" towards the headstock and W/2 egg rotation steps to the right or clockwise if looking from the tailstock end towards the headstock.

	And, now that you understand that the Eggbot uses relative coordinates, what about the Inkscape drawing template? Does it need to be 3200 by 800 units? Not really. Nor is it too important what the coordinates of its corners are. About all that really matters about the drawing template is whether or not you use the "Start with pen centered" option. If you use that option, then you want to know where the geometric center is in your drawing. That's because the Eggbot will assume that the pen starts there.		And, now that you understand that the Eggbot uses relative coordinates, what about the Inkscape drawing template? Does it need to be 3200 by 800 units? Not really. Nor is it too important what the coordinates of its corners are. About all that really matters about the drawing template is whether or not you use the "Start with pen centered" option. If you use that option, then you want to know where the geometric center is in your drawing. That's because the Eggbot will assume that the pen starts there.