I have been playing with the CNC machine and all too often I’ve accidentally hit both X and Y extreme limits of travel. I don’t know if there is any damage being done but felt I should do something about it. The controller software has a panel in the setting menu for both positive and negative limit switches for all three axis so I needed to find the associated hardware connections. The company I bought the machine from claimed not to have hardware schematics for the CNC controller or the USB interface. However, I did receive an image of the CNC Driver Board board indicating where limit switches may connect (top left).
Through trial and error, I found that the model of my controller only provides one input per axis for a limit switch. This means that in the X and Y axes, a limit switch only works when the unit is traveling in a positive direction (i.e. towards the back and right edge). For the Z-axis, the limit switch only works when the spindle moving downwards. In normal operation the limit switch input is open circuit. If and when the machine moves to a limit, the switch shorts the input to GND and this stops the movement immediately.