XYZ Probe Plus with VFDs and other ground-loop inducing components

I also note from your other posts you have a VFD, check that the VFD isnt shorting the clip to GND via the spindle, our recommended Dewalt router setup is isolated, the VFD might not be (particular if you get the error Alarm 4 Probe fail. The probe is not in the expected initial state before starting probe cycle, where G38.2 and G38.3 is not triggered and G38.4 and G38.5 is triggered.)

 

Screenshot the alarm messages. As i said above, we need to see which error exacly to give better advice, as Grbl has different reasons

 

Yes, big difference between earth (mains earth, spindle body is earthed to dissipate EMI and safety against shorts) and GND (DC common negative)!

Never connect those together.

Also, you removed the Gnd from spindle. It should be earthed... Dont forget to put that back (correctly, not gnd... Earth) or you'll have EMI issues

 

Wiring GND (DC Negative) to Mains Earth IS DANGEROUS!

Earth could potentially be at mains live level if some appliance shorts a live wire to a chassis, anywhere in the house mind you. That's what Mains Earth is for, to safely conduct that leakage down to the Earth through a copper rod in the Ground

NB Earth connects to the copper spike in "the ground" [not gnd but the ground, as in soil outside sounds the same, but very different]
GND connects to DC negative of a DC power supply and is isolated from mains

That's why the DC side one is called GND. But the mains one is EARTH. not the same thing!

So, no, the probe is correct, you have an unsafe wiring setup that CAN kill you and fry your electronics

If in doubt, get in a Sparky

 

That EEPROM error looks more like your spindle is busy killing your controller (or already caused damage) - disconnect it and make sure its High Voltage side is correctly wired

You can reset the EEPROM with gnea/grbl (if its just corrupted settings, if its been physically damaged by high voltages it won't help)

Again: Understand the difference between GND and EARTH. If your spindle is connected to the DC GND (causes the Probing issues) something is wired terribly wrong on the Spindle!

Keep in mind there are many other Spindle users who successfully use the same probe setup. Except their spindles are wired correctly to not join AC EARTH to DC GND (somewhere in your set up by mistake)

 

Something (I am not at your machine, so cannot tell you what) is thus GNDing the spindle body - The Magnet is the Signal pin, when the Signal pin, touches a DC GND, it completes the circuit and lights up the LEDs + tells Grbl the probe made contact. The Plate is also GND (thus when magnet touches plate via Endmill, it completes the circuit)

So, check your machine over, how is there an electrical path from the spindle body (shaft, collet etc) back to DC GND? Via the frame, via Earth wiring done incorrectly etc

NB You mention there is No earth! That's terribly dangerous, you DO WANT an Earth to safely dissipate any mains potential instead of killing you. Please get an Electrician in, VFDs are not for DIY Guys to play with Guessing games - it can be really lethal! Get a Sparky in, to come wire it properly with Earthing to trip the Earth Leakage Breaker, conduct the short back to Earth (via an Earth wire, not via your body) etc if something goes wrong! Ignoring electrical codes does not make sense

 

So, check with a Multimeter, if you have continuity between the spindle and DC gnd, find why, and fix

100% sure the cheap chinese spindle / vfd is not shorting DC GND from the terminals to Earth or even a coil inside the VFD or Spindle (; ?

 

If a plain Z probe works: is the clip attached to SIG or GND? If the clip is GND, the spindle Ground and clip ground are already the same (and you can technically even skip the clip then) and it touches the plate that is SIG

You can wire the XYZ plate the same (except VERY NB do not connect V+ then as you will short out V+ and kill the controller) using just the SIG and GND terminals

docs:xyzprobe:wiringgeneric [OpenBuilds Documentation]

 

Any of these shorting to the frame (thus providing a GND to the spindle body via and endstop?) - forgotten rubber spacer for example?


At the end of the day it is just a matter of probing around with a multimeter in continuity to find where your collet is finding a path to DC GND from, then removing that link. The spindle shaft should not be connected to DC gnd under normal circumstances. (logically right). The fact that it is, is a warning that something is set up wrong, and somehow your spindle body is directly connected to DC GND.

One of the people from earlier in this thread later got back to me via PM that they had wired DC- to AC GND at the PSU terminals (super dangerous) based on some youtube video about EMI. That is super scary. Explains how they had a path back to DC GND via a spindle body earth though. Fixed it by removing that wire they added.

 

Yip that is one way (keep the spindle GNDed and make the plate the SIG pin)

I mentioned it here

But keep in mind that is working around the spindle connected to GND, which can still someday cause serious issues with mains voltages getting into your DC rails

Please, try to eliminate the GND/EARTH interaction first

 

Problem confirmed, now the hunt for why:

1) Disconnect the limits one-by one, and keep on measuring - see if goes away
2) Look for other possible ways that the path could be completed back to DC GND

Thank you for taking the time to try and fix the root issue

 

Aha! Good catch! Will make a note to amend that in the next version! Excellent detective work!

The hole is not plated on the inside edges, its just that outside face (normally against the rubber spacer), so if you can flip the switch and mount it with the rubber spacer on the "bottom" side it should be isolated.

This will also only affect cases with the following combinations all met:
- Switch mounted "upside down" (screw touching the PCB pad)
- On the Z axis only (as rest of machine is isolated by plastic v-wheels
- Only on Z-Axis designs where the router is not isolated from where-ever the Z-Axis limit switch is attached to (normally isolated by plastic V-Wheels, and plastic Leadnuts if the switch is not mounted to the same carriage)

So wouldn't be the case for everyone, but easy fix (mount the switches the other

way round if you are affected - with the rubber washer on the bottom )​

 

Yeah, spindle case should be AC EARTHED for safety and EMI reasons

(to avoid confusion, GND = DC, Earth = AC)

Machine Frame is no longer DC GND right? But when you attach the spindle, the frame, via the spindle body, is now AC EARTH as well (which is fine and what you normally want)

So then, why does the probe SIGNAL get connected to DC GND via the EARTH?
Possible reasons:
- VFD badly designed and the DC inputs aren't isolated from mains earth
- Wiring mistake somewhere on the VFD inputs connecting DC GND to an Earth?

 

Well if the VFDs are the path, then the fix from earlier in the thread will be your only way forward. Swop SIG and GND so the plate is signal, magnet is GND. Then NB NB do not connect V+ (works fine, just no pretty green LEDs)