Quote Originally Posted by m_c View Post
Given an Arduino Uno is being used, I'd guess it's most likely GRBL that's being used.

First step would be to use a multimeter and check if the Arduino pin is seeing a change in voltage. Given the description, I'd guess the internal pull-up resistor for the pin should be enabled i.e. getting a bit under 5V, or 3.3V if it's a low voltage board, with nothing connected, then when the touch probe wire is connected to ground, it should drop to 0V (it's got to be as near zero as possible).


Thanks for the advice. Still wouldn’t work but just tried connecting the neg. to my limit switches that have pill up resistors and all ni now working