I'll show you how to set up a touch probe using a arduino CNC shield with GRBL firmware.
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Step 1: Required Items
Here is a list of the things you will need.
1. A CNC machine ( I have a BobsCNC E3, http://www.bobscnc.com/)
2. It needs to use an Arduino CNC Shield, https://blog.protoneer.co.nz/arduino-cnc-shield/
3. A touch probe, https://www.amazon.com/gp/product/B074W58JHW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
4. DuPont connectors, https://www.amazon.com/gp/product/B019DOGV3S/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
5. Crimp tool, https://www.amazon.com/gp/product/B00DHCRVSC/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
6. Computer that can run UGS Platform.
7. Universal G-Code Sender Platform,not classic, http://winder.github.io/ugs_website/guide/platform/
Step 2: Make Connections on Probe
Cut a long enough piece of wire off the probe, for the E3 I cut about 5" off. This will be used to make connecting and disconnecting the probe easier.
On the short short wire crimp 2 male on one end and 2 female pins on the other end.
Wires to not matter on which goes where.
Next put a 1x3 DuPont connector on the female end with the pins going in positions 1 and 3 (middle pin is left empty.) Put a 1x2 DuPont connector on the male end.
On the probe crimp 2 female pins to the wire, and put a 1x2 DuPont connector on the wire.
Step 3: Connect Short Wire to Arduino Board.
Now connect the 1x3 DuPont connector of the short wire to the SCL and GND pins on the Arduino CNC shield. You can see them marked red in the image.
Then just attach the other end of the wire to somewhere easy to get to but out of the way of moving parts.
Step 4: Setup UGS for Using the Probe
Open UGS and click the Windows menu item, then click Plugins, and click Probe Module.
The Probe Module window will open.
Click on the Settings tab.
Units has to be millimeters, I could not get the probe to work with Inches.
If, like me, you are only going to use the probe for Z you don't have to worry about End mill diameter.
Fast Find Rate is mm per min for the rapid to touch plate, I set it at 100, it's not too fast, but I don't want to damage the plate.
The Slow Measure Rate is how fast it retouches the plate to set you z. You want this slow, so it gets an accurate touch.
Retract Amount is how many mm the tool will move off plate after first touch and before second.
Now measure your touch plate thickness in mm, you will need this for UGS.
Now click the Z tab.
Put in your plates thickness in the Touch Plate Thickness box. You may have to adjust this value after testing, I had to increase by .02mm to get it right on.
In the Probe distance/direction box a positive number means your z axis has to move up to touch the plate, a more positive z value, and a negative number means the Z axis has to move down , a more negative Z value. The number is how far away, in mm, you have the tool before probing, This allows the software to stop if it doesn't find the probe.
Step 5: Connect Probe to System
Plug the 1x2 DuPont connector from the probe to the 1x2 DuPont connector on the short wire.
Place the probe on top of the work piece, and connect the alligator clip to the router bit.
Step 6: Finally Run the Probe
Now move the tool over the touch plate, try to get it as close to center as you can. By doing this each time it ensures as close a repeatable reading as possible.
Move the tool in Z until it's about .5" above the plate, as in the picture.
Then click the zero Z axis in UGS, if testing you should click the X and Y zero as well.
Finally click the Initiate Probe in the Probe Module window, in the Z tab. The Z axis will move towards probe and once it touches it will move away and retouch at a lower speed to get the Z setting.
Now remove the touch plate and click the Return to Zero button, in the Common Actions . This will move the tool to the X,Y, and Z zero. The tool should just barely be making contact with the part. If it's not right adjust the Touch Plate Thickness until you get it right, if the tool is too high increase the Thickness, if it's too low decrease it.
Now disconnect your probe and use your machine.