Homing...is it really this simple

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bharbour
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Homing...is it really this simple

Post by bharbour » Fri Jan 16, 2015 3:14 pm

No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
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cvoinescu
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Re: Homing...is it really this simple

Post by cvoinescu » Fri Jan 16, 2015 3:25 pm

They're internal to the Arduino.

However, while that setup works fine for some people, it doesn't work for many others, because interference causes false triggering of the switches. You're much better off running NC switches to GND, but then you need the pull-up resistors (from each pin to IOREF, 1 Kohm or so).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

bharbour
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Re: Homing...is it really this simple

Post by bharbour » Fri Jan 16, 2015 3:57 pm

RF interference I'm assuming??
cvoinescu wrote:They're internal to the Arduino.

However, while that setup works fine for some people, it doesn't work for many others, because interference causes false triggering of the switches. You're much better off running NC switches to GND, but then you need the pull-up resistors (from each pin to IOREF, 1 Kohm or so).
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

cvoinescu
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Re: Homing...is it really this simple

Post by cvoinescu » Fri Jan 16, 2015 4:08 pm

Electromagnetic, at any rate. Doesn't need to be RF necessarily -- could also be ground-coupling, or capacitive or inductive coupling from the fairly large currents and large voltage swings on the stepper driver wires. I have not had a problem myself, so I had no reason to drag out the scope and look at it, I'm just pointing out that many people have complained about false limit switch triggering. The best proposed solution that emerged from all the collective fiddling with this seems to be an external pull-up (say 1 Kohm to IOREF), followed by a low-pass RC filter (say 10 Kohm in series and 100 nF ceramic to ground). You may have just as much luck adding just a 4.7 uF capacitor to ground, but I don't like that idea for several reasons.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

jarretl
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Re: Homing...is it really this simple

Post by jarretl » Fri Jan 16, 2015 6:00 pm

bharbour wrote:From http://www.shapeoko.com/wiki/index.php/ ... t_Switches
Image

No resistors???
I use this configuration for homing and it works perfectly, but for me they are unusable as limit switches for the reasons cvoinescu indicated. I keep the hard limit switch setting in GRBL 0.9g disabled and set up the soft limits to not allow movement beyond my max X/Y travel distance.
Perhaps some day I will do something about that interference and re-wire things, but for now the homing with soft limits method seems to do the trick :)
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twforeman
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Re: Homing...is it really this simple

Post by twforeman » Fri Jan 16, 2015 7:43 pm

I have this setup and it works great. Took a little fussing to make it stop triggering due to interference.

I used shielded cables for the motors and the limit switches and have a cap across the pins at the board.
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bharbour
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Re: Homing...is it really this simple

Post by bharbour » Fri Jan 16, 2015 7:45 pm

Yea...my intentions were to only use this for homing...tnx!!
jarretl wrote:
bharbour wrote:From http://www.shapeoko.com/wiki/index.php/ ... t_Switches
Image

No resistors???
I use this configuration for homing and it works perfectly, but for me they are unusable as limit switches for the reasons cvoinescu indicated. I keep the hard limit switch setting in GRBL 0.9g disabled and set up the soft limits to not allow movement beyond my max X/Y travel distance.
Perhaps some day I will do something about that interference and re-wire things, but for now the homing with soft limits method seems to do the trick :)
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

bharbour
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Re: Homing...is it really this simple

Post by bharbour » Fri Jan 16, 2015 7:48 pm

That's what I'd do...set up my scope and start looking for the cause. But I plan on only using this for homing right now.

Tnx!!
cvoinescu wrote:Electromagnetic, at any rate. Doesn't need to be RF necessarily -- could also be ground-coupling, or capacitive or inductive coupling from the fairly large currents and large voltage swings on the stepper driver wires. I have not had a problem myself, so I had no reason to drag out the scope and look at it, I'm just pointing out that many people have complained about false limit switch triggering. The best proposed solution that emerged from all the collective fiddling with this seems to be an external pull-up (say 1 Kohm to IOREF), followed by a low-pass RC filter (say 10 Kohm in series and 100 nF ceramic to ground). You may have just as much luck adding just a 4.7 uF capacitor to ground, but I don't like that idea for several reasons.
No longer have a Shapeoko, but use a machine of my own design...
https://www.youtube.com/watch?v=gFY4gC9TqD0
http://deltaguitarworks.tumblr.com

MeanderBolt
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Re: Homing...is it really this simple

Post by MeanderBolt » Fri Jan 16, 2015 8:56 pm

Hey Twoforeman, when you say "across the pins", the x,y,z homing pin to what? Ground?
What value did you use?
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