Adding limit switches.

Discussion about the arduino based g-code interpreter, grbl
potatotron
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Re: Adding limit switches.

Post by potatotron » Thu Jan 10, 2013 4:29 pm

During homing cycle (and assuming, the cycle move toward the home switch everytime), the CNC will home at the center, perfect. But now that I have a home switch in the middle of my area, will this act as limit switch during actual milling ? As far as I understand yes.
So whenever the CNC is aligned with homing switch, the Grbl will goes to ALARM and stop. Right ?
That's correct, that's how it will work.

How about eliminating the middle home switches and using the corners per usual, then after your G28 home cycle you move to a specific location with G0 then reset that to your zero point with with G90?

Alternatively, you could add (human controlled) enable switches to the (CNC controlled) homing switches, then after your home cycle you flip the enable switches to disconnect the home switches.

cvoinescu
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Re: Adding limit switches.

Post by cvoinescu » Thu Jan 10, 2013 5:37 pm

PsyKo wrote:I have my homing switch in the middle of my X/Y area (I know it's not the best, but let's say that's what I have).
That's not a configuration supported by GRBL. As far as I know, GRBL supports homing switches only at the end of travel on a given axis, not in the middle. In your configuration, the limit and homing switches would have to be separate, and connected to separate pins, and GRBL modified to support that.

Edit: I posted the above without reading Potatotron's better answer.
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PsyKo
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Re: Adding limit switches.

Post by PsyKo » Thu Jan 10, 2013 6:33 pm

Ok, thanks to both of you.

I'm asking because my home and limit switch will be 2 separated kind of switch. Homing will be Hall effect sensors for accuracy. Limit switch will be simple lever switches.
I will definitely put my Home switches in a corner of the Shapeoko. I simply wanted to know if my thinking was right.
potatotron wrote:Alternatively, you could add (human controlled) enable switches to the (CNC controlled) homing switches, then after your home cycle you flip the enable switches to disconnect the home switches.
I thought about that as well.I'm not sure what I want right now. I think limit switches on one side and home switches on the other will be good enough. I just have to make sure my homing switches are as far as possible so I do not lose any milling space.
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shachar85
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Re: Adding limit switches.

Post by shachar85 » Thu Jan 10, 2013 9:56 pm

potatotron, thanks for the answer. Helped a lot

raynelang
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Re: Adding limit switches.

Post by raynelang » Fri Jul 12, 2013 4:50 pm

It was mentioned previously that you connect the limit switches to pins 9, 10, 11. When you plug the grblshield into the arduino UNO headers from the shield go into these pins. The only open pins I have is the analog input pins. When you connect the limit switches are you soldering them to the grblshield somehow?
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cvoinescu
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Re: Adding limit switches.

Post by cvoinescu » Fri Jul 12, 2013 8:03 pm

The grblShield has holes right next to its headers, where you can solder wires, or, even better, headers for the limit switches. Or, you can put a shield with the limit switch connections between the Arduino and the grblShield (a prototype shield, or even a ScrewShield).
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ba47
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Re: Adding limit switches.

Post by ba47 » Tue Dec 27, 2016 3:44 pm

cvoinescu wrote:The same physical switch does double-duty. During the homing cycle, one switch on each axis (you can pick which in the GRBL configuration) acts as a homing switch. After that, the machine backs off a little (also configurable) and now the switches act as limit switches.
1) How do you configure GRBL so that during the homing cycle a switch acts as homing switch, then acts as limit switch ?

2) I already have 3 switches that work as homing switches. If I added 3 more (at the other end of each axis) to act ONLY as limit switches, how do I wire them and how do I configure GRBL ?

WillAdams
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Re: Adding limit switches.

Post by WillAdams » Wed Dec 28, 2016 12:11 am

Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

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