Add optional FAR limit switches

Machine: k40

Board: Laserboard

Firmware: Smoothie Cohesion Stock

Problem/ Question: I’m wanting to put an X and Y FAR end limit switches to my k40 in addition to my homing (endstops). Two questions, where would I connect them on the Laserboard and what changes would I need on the config.txt?
This is so if I am manually jogging and don’t home first it won’t crash into sides.

Hi Brad,

You can connect limit switches to the Endstops row at the bottom of the board. For a standard K40, you will use the ports for X MIN and Y MAX.


Please let us know if you already have switches and what the specs are. If you are using our mechanical switches you will connect to NC (red) to Sig and C (black) to Gnd with the included 2 pin connector. We also offer connectors, should you need them for a different model.

In the configuration file, you’ll want to look at the Endstops and limit switches sections.

The default settings expect (and Smoothie recommends) NC to be connected to Sig and C to Gnd. If the endstop is reading as pressed when it is not actuated or vice versa when testing endstops, then add an exclamation point at the end of the pin value in the configuration to invert it.

## Endstops
endstops_enable                              true             # the endstop module is enabled by default and can be disabled here
#corexy_homing                               false            # set to true if homing on a hbot or corexy
alpha_min_endstop                            1.24^            # add a ! to invert if endstop is NO connected to ground
alpha_max_endstop                            1.25^            # NOTE set to nc if this is not installed
alpha_homing_direction                       home_to_min      # or set to home_to_max and set alpha_max
alpha_min                                    0                # this gets loaded after homing when home_to_min is set
alpha_max                                    200              # this gets loaded after homing when home_to_max is set
beta_min_endstop                             1.26^            #
beta_max_endstop                             1.27^            #
beta_homing_direction                        home_to_max      #
beta_min                                     0                #
beta_max                                     200              #

If you want to stop the machine when the switches are triggered, uncomment the limit switches parameters by removing the ‘#’ at the beginning of the lines and set them all to true. Sending M999 in the console in LightBurn or a board reset will be required to continue.

#optional enable limit switches, actions will stop if any enabled limit switch is triggered
alpha_limit_enable                          true            # set to true to enable X min and max limit switches
beta_limit_enable                           true            # set to true to enable Y min and max limit switches
gamma_limit_enable                          true            # set to true to enable Z min and max limit switches

Ok so the switches I have will be mechanical. And they need to be normally closed. Correct? Also will this effect the homing?

Yes, this is the recommended setup.

The alpha homing direction is defaulted to home to min at 0 (far left of the work area).
The beta homing direction is defaulted to home to max at 200 (far back of the work area).
The only way it would be impacted is if you change your configuration file or settings.

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