Cracked the Code on Using Super Touch Plate

Edited 3/28 to correct some things…This may be common knowledge to those of you who have used the Super Touch Plate successfully, but I thought I’d write down what I had to do to make it work for me. My goal was to find a certain corner of the fixed jaw of my machinist vise, positioned on the bed with the fixed jaw towards the +X side of the bed.

(1) I made my own “touch plate” out of a 2" long section of Aluminum bar stock (1/8" X 1/2"), held in place on the top of the vise by a super magnet on top. I used a 2’ section of thin, stranded two-conductor wire for connections. On one end of the wire I put an alligator clip big enough to connect to my bit (6mm in my case) on one lead, and just tinned 1/2" of the other lead with solder. I held that lead to my machinist vise using a super magnet, and clipped the alligator to my bit. For the other end I tinned both wires and attached one wire to the Zmin switch terminal block on the TinyG board, and put the other on the nearby ground. The resulting circuit was such that whenever the bit touched the touch plate (for Z scans) or the side of the bit touched the actual vise surface (X and Y scans) the Zmin pin was shorted to ground. The Zmin pin is internally pulled high by a 2.7K Ohm resistor, so the current flow is only 1.2 mA, well within a safe value for TinyG.
(2) In the TinyG v2 widget (small gear icon) I configured the “Z Axis Switch Mode Max” to “Home” (I have a limit switch there), and set the “Z Axis Switch Mode Min” to “Default”. I saved that configuration, then recycled the power to the TinyG, because I have found that it’s need to really get the new configuration to take effect.
(3) In the Super Touch Widget Settings tab I set the Coordinates to G53, X and Y Plate Widths to zero, Plate Height to 3.15 mm (measured thickness of my plate) and set the bit diameter to zero (seems correct for the Z axis probing). For my machine, at least, this made the touch searches move in the correct direction for all three axes.
(4) In the ST Widget Control tab I hit the Run Z button, and the bit traveled down until it touched my touch plate top, then it reversed 2mm. No visible mark was left on the Al touch plate.The G53 Z read -5.15mm at this point.
(4) I then went to the settings tab and entered my bit diameter (6mm), positioned the bit to the starting position for the X Axis search in ST, and initiated that search. The bit moved in the correct direction then backed up correctly when it touched the vise. The G53 X axis read -5.00mm at that point (3mm bit radius + 2mm back off).
(5) I repeated Step (4) for the Y Axis.
(6) I then jogged until G53 read X=0, Y=0 and Z=-5.00mm, then set the G55 coordinate system to 0, 0, 0. I design with that G55 coordinate system origin in mind. I wrote my own program to generate the GCode, and it selects the G55 as the modal coordinate system for the run.

I’m going to put a panel connector on my control box for the touch plate probe wires. I also may make up a comparator circuit for the “touch wire” I made, but frankly is seems to do well enough as is.

Just an FYI for all of you. Please add to this or correct it, as needed.