XXL limit (not homing) switches

In my original Shapeoko 2 I had a third-party set of limit & homing switches which I loved. Now I’ve upgraded to the XXL. The XXL includes prewired homing switches in the drag chain, but no limit switches.

I’d like to add the limit switches. I could remove the stock homing switches from the drag chain, and restore my original third party homing & limit switches, but I’d have to solder in longer wires to accommodate the XXL’s greater dimensions.

Have other people had this issue? Is there any other approach to this problem? Thanks!

Instead of limit switches can’t you implement soft limits in software. I don’t know how but we have some advanced users that know how.

Since the switches are normally open you should be able to piggyback off the existing connectors (though possibly best done w/ a daughterboard?) to plug in the extra switches.

Since you would put them on the front left corner and left edge of the gantry (not sure if a limit switch for Z bottom is practicable or makes sense) might be that your existing wires would be long enough.

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Guy, thanks for the response. I could be wrong, but my understanding is that Carbide Motion implements hard limits but not soft limits. I usually use UGS as my code sender so I’ve enabled soft limits already.

I’m not quite sure of the relation between hard limits, soft limits, and limit switches. Maybe there is an authoritative discussion out there on the topic but i haven’t seen it yet.

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No, it does not implement either. GRBL (firmware on the board) handles this, and can be set either way. By default, both are off. You can configure this however you want, using any GRBL guide you like on limit and homing switches with a little work. All that said, hard limits has it’s challenges - many have found it sensitive to static, though with some careful routing and testing, that should be able to be overcome.

It’s rather an odd situation.

As @mikep notes, Grbl handles hard and soft limits by way of configuration, but Carbide Motion also implements soft limits — during jogging only, when it is in control.

Thanks, Will. The stock XXL homing switch connectors cover the controller board pins I need for the limit switches, so, as you say, I either need a daughterboard or some sort of connector where I can piggyback the limit switch wires. Unfortunately it’s been 40 years since I worked on circuit boards so I have no idea where to find such connectors. Or even what they are called (grove connectors maybe?).

Unfortunately with the controller on the left Y rail, given the limit switch fixtures the existing wires aren’t long enough.

@sjj47 Not to minimize your question, but do you need limit switches? You probably don’t crash much if you’ve been at it for a while.

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It’s a good question. I guess I don’t have to have the limit switches if I have the homing switches installed and soft limits enabled in grbl.

I guess I’m thinking of it as a safety issue. As I understand it, if the hard limits are enabled in grbl and the limit switch is triggered, then the “Alarm” condition is executed and everything shuts down, so no crash will take place.

I don’t think I’ve ever had a X or Y crash. Z axis, of course, several times.

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Ah – Dupont pin connectors. Amazon sells them.

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Not the same as the pins on the Carbide 3D board.

I think it’d be pretty easy to use some 3pin lever nuts or just 6p terminal strips

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Uh, just to make a crash point, @sjj47, 99% of “crashes” occur out in mid-field! :smiley:

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Read the sections on Homing $22, Soft Limits $20, and Hard Limits $21. It does a pretty good job of explaining the relation of homing, soft and hard limits.
As long as you have homing enabled, and have your soft limits set properly ($130, $131, $132), I don’t see why you would really need hard limits.


Thanks for all the feedback, guys!

I guess I will go ahead with the stock homing switches and enable the soft limits in grbl and see how it goes.

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I have a DuPont connector kit and crimp tool in-transit :man_facepalming:

What kind of connectors are they? I was planning on DuPonting a spindle connection.

@sjj47 How are the soft limits working for you?

Which pins?..

I just saw this and applied it to the whole board. I was planning on crimping a DuPont connector to plug into the lower ISP for PWM and ground.

You’re good then! :wink:

:man_dancing: I wanted to be super legit with my electronics hygiene when connecting the spindle so I bought a DuPont connector kit then realized I needed the special crimpers. Come tomorrow, I’ll be a man with a hammer.

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So far so good on the soft limits. Looks like I can live without the limit switches, given the homing switches and soft limits set.