How should the limit switches on the X and Y axis be connected correctly?

Hi.Please I connected you to the Ender5Plus motherboard OCTOPUS V1.1. How should the limit switches on the X and Y axis be connected correctly? Should it be: Signal + GND or Signal + 3.3V?Thank you in advance for your help.

So there are 2 answers to this question..

The best way is to connect your end stop to ground. The reason this is the best way is because it is ground we are playing with. If this wire were to short or chafe it will only latch ground to ground and have little affect on the rest of the printer past maybe that end stop not working. Because any and all metal on the robot should be latched to ground. So grounds are safer to play with wherever possible and power wires are things to take care of because there is the potential danger of shorts everywhere.

However, because we have the ability to adjust the firmware we can do whatever the hell we feel like doing. And so You can latch your endstop to signal and power if you like. There is nothing wrong with it. And it can and will work. You will just need to set it up differently in Marlin.

Marlin lets you choose whether the endstops are latched to a pullup or pulldown resistor. You can select all endstops to be latched or you can select individual endstops to be latched to one or the other. If your endstop is connected to a ground then you will want that endstop latched to a pullup resistor and if you want to drive your endstop with power then you will latch that endstop to a pulldown resistor in Marlin. So the controller sees a different state when the switch is open.

Because logic circuits, as it were, are actually kind of stupid. They only understand power or ground. They do not understand and often do not even see neutral or nothing. So the pullup or pulldown resistor is so when the switch opens the controller sees the opposite state.

Also in Marlin you can invert the logic for an endstop. This does exactly as it sounds. So instead of your Octopus looking for a switch from power to ground to know it has triggered a stop it will expect to go from ground to power. This has a use beyond just whether you are using power or ground. There is also a thing about how your endstop is wired. there are 3 pins on a microswitch. common, NO, and NC. depending on how we are wired at the endstop switch can also determine whether or not we want our endstop logic inverted.

Thank you for your great help.

In proper theory the mechanical endstop switch itself SHLOUD be wired to common and NC. This is important for self diagnostics.


If the switch is wired to NC when you send the home command if the switch is unplugged then the printer will not move that axis or it will move it a bit in the opposite direction of home and then trigger an error.


If the switch is wired to NO the circuit is naturally in an open state and the controller doesn't have the resolution to know if a fault is present so when homed it will crash the carriage into the gantry frame expecting a signal to show up at some point.


For self diagnostics it is far better to have the circuit normally Closed and open when the switch closes. No matter whether you are doing it with power or ground.

Hi.Please, I'm just learning everything, that's my problem, even if I disconnect the limit switches, all the axes will start and hit the end and not turn on. How exactly should I connect and set up the NC?

Your end stop switch should have 2 wires attached to common and NC or Normally Closed contacts at the switch itself.

Those 2 wires should connect to signal and gnd in that end stop connector on the mainboard.

In Marlin under the configuration.h tab you will first select the end stops you are using..

https://imagizer.imageshack.com/v2/xq90/922/B8zwVt.png

Once you have selected the end stops you are using and just below that is where you need to make sure you have a pullup resistor tied to that end stop pin..

https://imagizer.imageshack.com/v2/xq90/923/Basgew.png

Then you just need to figure out what signal you are sending when you hit the endstop. And Marlin is helpful here in explaining whether or not your end stop logic needs to be inverted here..

https://imagizer.imageshack.com/v2/xq90/923/meulE4.png

And hopefully all will be good. But to check you should start homing your printer with the axis at mid travel and operate the endstop switch by hand so if it doesn't work you can shut it down before things start crashing into each other.

I have it set as in those photos except // # define USE_YMAX_PLUG I don't know what it's for. End Stop is not functional. I also tried false and true. Even if I disconnect the End Stop, the axes will start. When the printer is turned on, it reports Failed to enable Bed Leveling.Attachment 16878Attachment 16879

If you have it wired as stated in my last post then you will set the inverting for that end stop to false. Like it says at line 821.

I do not know why you get the failed to enable bed leveling message. I think that suggests problems with the way you have your Z probe and/or ABL settings configured. Or maybe that message is just because of the end stop problem?

I have something misconfigured somewhere, I'm just learning.

Thank you for your great help and yours who provided me.