How to connect and set limit switches

Limit switches are used for reference (homing procedure) and as a safety feature.

In order that software recognizes limit switch activation and makes appropriate action, we need to configure limit switch inputs in settings: File/Settings/Motors/Limit Switches.

Examples below will demonstrate use of different limit switch wiring methods for X axis. All shown principles can be used for all other axes.

CNC machine uses only one limit switch for X axis (for positive direction), switch is connected to limit input 1:

CNC machine uses two limit switches for X axis ( for positive and negative direction), both switches are connected to limit input 1:

CNC machine uses two limit switches for X axis ( for positive and negative direction), each switch is connected to separate limit input, 1 and 2:

Test if PlanetCNC TNG software recognizes limit switch activation. On main screen click “IO” tab and observe controllers Limit input state:

If you use normally closed type of limit switches then you can invert controller limit input in settings: File/Settings/Motors → Limit Switches
Click radio button next to limit pin that you wish to invert.

At this point, limit switches are connected with controller and PlanetCNC TNG software recognizes limit switch activation.

Limit switches can now be used as reference for purposes of Homing procedure.

In order that limit switches are used also for safety purposes, please follow next chapters.

In order that Estop is activated and machine stops during machine operation or jogging (in case of active limit switch), you need to enable its Estop radio button.

If limit switch is activated during program program run, machine will stop and Estop will be activated. If limit switch is activated during machine jogging, machine will stop without Estop.

To enable hard limit switch stop settings, you need to make sure that they are enabled under: Machine/Motors,Limits,Probe/Hard Limits Enable

You can also use gcode command M11. M11 P1 activates hard limits and M11 P0 disables hard limits.

To observe Hard Limits enable/disable state, you can do that by:

• observing Machine/Motors,Limits,Probe/Hard Limits Enable menu item. Checked for enabled, unchecked for disabled
  
• LM light under IO tab which will toggle according to above state. Green when hard limits are enabled, and red when they are disabled
• M11 mode under Active M-codes state panel. When enabled, M11 is visible, when disabled M11 is not visible.