Befor I get in to deep, is this the place to discuss a “probe” issue??
grbl loaded Arduino UNO and Open Builds controller software.
Thanks.
Well, probably not the show-and-tell tag — that’s meant for showing off what you’ve done.
Don’t have to worry too much about the wrong category; we can always move your posts if there is a better category. Just please don’t cross-post! 
I’d say that General CNC would be my best guess if I understand what you are saying, but maybe not. It’s not super important to guess right.
There are all kinds of “probes” so you will want to be more specific. Sorry but we have to probe you on what you are talking about. 
The firmware isn’t specific to probes but I will tell you that I’ve got a switch probe on my Marlin based 3D printer(Ender 3) and I’ve used a probe on my small CNC which had GRBL on it and the probing was handled in a script in CNCjs user interface.
Once you specify your use-case maybe Michael can move your question to the appropriate section.
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Thanks, I’ll jump right in. Hopefully someone else has seen this problem.
Machine is set up to probe, lead on A5 connected to the router bit, grounded plate
under it. Activating the probe button in the software, Z axis immediately moves up 5mm
probe window changes from “confirm probe position” to “triggered” indicating it is grounded.
Quick check with the VOM showed a high (Mohm) ground on the router bit,
obviously enough to trigger it.
After lots and lots of trial and error we realized that energizing the stepper drivers and motors
was the source of the ground. We disconnected each stepper separately and energized the
single connected one. Energizing any of the 4 would place the ground on the support so it isn’t
one bad one.
We made up a test jig with a probe thru a piece of plastic to isolate it from the router
support, connected A5 and the probe function worked properly.
Any suggestions greatly appreciated.
I can post a list of all the things we tried tomorrow, if that would help.
Thanks again.
Sounds like we’re talking about a CNC as in desktop milling /router machine.
My probe pad is insulated from everything via a plastic cup under it and it’s wired to the controller. The other wire in the pair has an alligator clip on it which I figure is grounded and is what I clip onto my endmill bit. The script, IIRC just set the Z=0 reference with the known/measured offset of the top of the probe pad to the bottom of its base. That’s set in the script. When initiated after I move the endmill over the probe pad, slowly goes down and touches the probe and then moves up and sets the top service of the work piece.
I do not know what the Open Builds Control software does but the goal is pretty much the same.
And I would expect the endmill to be grounded since isolating that from ground would be silly since it’s part of the motion system which should all be grounded for safety anyways. It’s the touch pad which is what I would expect to be connected to the controller input and that touchpad needs to be mounted on an insulated base.
Mine looks like this:
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The Uno uses pin A5 which is held high to connect to the router bit. A grounded plate
is set below the bit which retracts when contact is made the thickness of the plate
(established in the software) plus the 5mm “safe” height. My problem is the bit already
has a ground so when the probe is ac
tivated it sees it as already triggered and retracts.
THAT is exactly why I stated the ground clip goes onto the endmill bit and the signal(A5) is what connects to the plate on your build surface or work surface. How on earth are you going to isolate your endmill motor, mount, motion system etc from ground when all things in electrical standards say to ground them?
Who told you to connect your A5 signal to the endmill bit?
You are absolutely correct. The old machine worked, the only reason I can think of
is we assumed the red lead was 5v and the black ground but they were reversed.
You have made my day.
Thanks.
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