Touch probe trouble in universal g code sender

I have picked up a few X carves without the x-carve controller and build my own based on the TP 6600 motor driver and an Arduino.

I really like universal G code sender for sending the g code.

Recently I’ve been trying to get a triquetra touch probe to work with UGS.
For the most part, it wasn’t working, when I would start a zero’ing cycle the bit would start to move toward the plate, and either alarm and stop completely, or act like it had touched off while still in the air and continue the cycle without ever touching the plate.

I had about given up and decided to move on and attack some electrical interference issues that were causing computer monitor issues.

I have the motor drivers connected directly to the power supply ground, but I didn’t have the Arduino grounded to earth ground.

Once I tied the Arduino ground directly to the earth ground on the power supply, not only did the interference on my computer monitor go away, the touch probe worked perfectly.

Hopefully this will help someone else who is trying to chase down why probing isn’t working.