What are limit switches?

Noob question inbound. What are limit switches? What do they do? Are they the same as honing switches? If not, what are honing switches?

Limit switches are used to tell the machine what the limit of its movements are. One switch is placed on each of the 3 axis of the machine. Each switch is closed when the axis it is attached to reaches its limit. For the X axis that is all the way to the left. For the Y axis that is all the way to the front. And for the Z axis that is all the way at the top. When the machine moves and hits one of these limit switches that axis will stop moving, and the controller now knows where the limit for that axis is. This is used for automatically setting a home position.

Hope that helps!

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Super cool thanks man

Jamie, I’m not sure if you might misunderstand the terminology or just had a doubble :stuck_out_tongue_winking_eye: typo on your original post.

The correct term is HOMING. Your post had it as hoNing, I can understand how that woud cause confusion.

By default the x-carve’s home position is all the way forward, to the left with the spindle at the top of it’s travel.

I could easily be mistaken as I understand it, and from my brief experience the limit/homing switches are actually nonfunctional when jogging the axis’s and when in operation under g-code via easel, chilipeppr, or UGS and all 3 axis’s can be run to the end of thier limits (crashing ) in this state and it will throw off the step count screwing up your work piece.

BTW every expert was once a noob!


In a standard machine with what Inventables calls a limit switch kit in fact you are wiring up HOMING or Reference switches. These switches as configured in a standard machine DO NOT limit anything. There sole purpose in life is to tell the software where MACHINE zeros are. Once they have done that when you start your machine and tell the software to home or reference they go dormant until the next time you tell the software to home the machine again because you have crashed the machine and lost your reference to machine ZERO.

Those 3 switches will not prevent you from jogging to a hard stop or a Gcode program that has an error that runs the machine into a hard stop. If 1 of those 3 switches is in the way when this happens there is a good chance that switch will be destroyed.

If you want true limit switches configured on your machine you have some work to do. First you have to control the electronic noise that the brushed DC motor that is used for the spindle on the standard machine. Then you need to add 2 more switches 1 on the opposite end of the X and Y axis. Wire the switches using shielded wire. Switches on the X and Y axis are wired in series NC (normally closed) and the Z switch is NC

The 3 original switches should be wired to 3 pins on your controller and a common ground. Because you have added a new switch on X and Y that are in series with the original switches the wiring travels from the pin to the first switch NC pin and then continues from the switch common pin to the next switch NC pin and then from that switches common pin back to the controller common ground. You do this for both X and Y. So if either switch is triggered it opens the circuit and the software say and event has happened.

Now the fun part you have to figure out how to configure your control software so the software knows that you have it configured as follows
Z homing active, Z+ limit active
X homing active, Z+ limit active, Z- limit active
Y homing active, Y+ limit active, Y- limit active
You also tell the software if you want to home in the positive or negative direction.

Do you need to go to all this trouble, no. But be prepared to fix things when they get broken from crashing the machine.

Also be prepared to ruin more material than is necessary if you had homing and limit switches configured correctly.

Hope this helps


Hi guys. Thanks for that. This post is quite old now and I have had my x carve for a bit so have learnt in the mean time. However i’m sure those explanations will be very helpful to people in the same position that I was. I have my limit switches installed but never use them, I just manually home the machine

I love the way the forum puts up the suggested topics and then I go and think it’s something new.
I must remember to look at the post date… duh!

probably something in my settings, oh well, maybe someone else will benefit from the post. :relieved:

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