Which limit switch should I use ?


I received 2 types of switches. I believe I ordered some switches with a red roller from the shop, while 4 switches without rollers were part of the RAMBo bundle.

The one with the red roller is harder to press.

Which one is better for dual endstops in your experience ?


They will both work great.


I used the one with the roller only because I had 10 of them and only 3 of the other type. I ended up soldering the wire to the roller type because the connectors are a lot shorter and the wire connector pulled off a couple times while I was wiring the mpcnc. Either type work fine.

Is the wiring the same for the red roller switches? Black on COM and white on NC?

@Trevor yes, NC = Normally Closed. The circuit is closed when you don’t press the switch, and open when you press it. This is the opposite if you connect to NO = Normally Open.

Black and white don’t matter. Either wire can be used on each connection. But as Julien indicated, you want an NC connection. Note that Ryan’s firmware is setup to expect NC connections, but if you are using some other firmware/board, you may need to make a firmware change to get an NC connection. NC is safer since if a wire becomes disconnected, homing will just stop rather than ramming into the machine limit.

Ok thanks for the clarification! I understand that the color of the wire doesn’t matter, just that I’m using NC instead of NO, and that the wires match up.

Just to clarify further about the wires matching up, when Ryan talks about signal and negative/ground, is signal=NC and negative/ground=COM ? For example, it says near the top of the “Endstops” section of this page: https://www.v1engineering.com/auto-square-dual-endstops/

“DO NOT USE THE + (positive) Terminal. S & – (signal and Negative) Only”

Which means:
signal (S)= NC
negative (–)= COM


The “DO NOT USE THE + (positive) Terminal. S & – (signal and Negative) Only” sentence is about the pins of your control board.

There are 3 pins for each endstop terminal on the board. We don’t use the “+” pin. Only the “S” and the “-” pins. Pay attention to the diagram because all terminals are not oriented in the same direction. The “-” is always the middle one, but the “S” is sometimes on the right, sometimes on the left.

The switch itself has no polarity because there are no active components inside. Imagine you have only one long wire that goes from the “S” pin to the “-” pin of your board (no polarity right ?). When you press the switch, it is equivalent to cutting the imaginary wire.

You can totally use two black wires, connect one to “-” and the other to “S” of your board, then connect them to “COM” and “NC” of your switch in random order.

Your proposal will work, and the opposite will work too.