Grounding for touch probe, G540

[BalloonEngineer]

I have a DIY cnc router. It uses an Ethernet Smoothstepper, a G540 (rev8) fed from a Mean Well 48v power supply driving 4 Nema 23 steppers. The spindle is a water cooled 2.2kw spindle connected to a Huan Yang VFD. Everything is working beautifully - no noise or other issues. The G540 is providing PWM speed control and this is also working well. The 220v VFD input and the 110v input to the 48v power supply and a small 5v power supply for the ESS all have their green wire ground tied together at a single point - star ground, also tied to the cnc chassis. The spindle is grounded using the 4th wire which is connected internally in the spindle.

I would like to add a touch off probe using the G540 input 4. Inputs 1-3 are my X,Y,Z home switches, each wired NO with the common wired back to the -V terminal of the 48v power supply. These also work well.

I have seen two approaches to wiring the touch probe. Some use two wires, one connected to the input pin on the G540 and the touch surface, the other wire connected to the -V terminal of the 48v power supply, and the other end having an alligator clip that needs to be attached to the bit in the spindle. Note my spindle (and the bits) already have continuity to my star ground point (verified), but do not have continuity back to the -V teminal of the 48v power supply.

The other approach is to use only one wire connected to the input pin, and also connect the -V terminal of the power supply to my star ground point, so the input is brought low upon contact to the bit.

I would prefer to not need to connect the alligator clip to the bit, and am concerned that this just creates a long ground loop. Either method is going to result in connecting -V to my star ground. Is one of these ways preferred? Is there any potential issue in tying -V to "earth" ground? With the alligator clip it will only be temporary during the probe, the other method would have a permanent connection, but directly to the star point, with a short wire.

Thanks
Richard

Similar Threads:

• CMM Liquidation: Renishaw TesaStar Probe Head, Touch Probe, Motorized Indexable
• Help!!! Touch probe grounding through spindle???
• Need Help!- Touch Plate Grounding to 110V / 220V
• NO Touch Plate and NC Touch Probe switch inversion using an Arduino UNO
• Grounding the Gecko G540, how?

[motopreserve]

Wondering if you ever figured this out. I am having a hard time getting the g540/Mach3 and simple touch probe to work without having intermittent "digitize" light flashing.

The digitize light does work normally to show the connection when I have it wired as you describe in option #1 (plate on bed, and clip on end mill, connected pin 13 and -v com). But then it also flashes randomly when the two points are not touching.

I'm using shielded wires with the drain going to a common ground on the electronics box end. Tried jacking up the debounce just to see if it works. Made sure that the continuity and wiring was all ok. Tried another open pin. No luck.

The same wiring style/type is being used for my home switches with no issues whatsoever.

Any help would be MUCH appreciated.

Scott

[daniellyall]

The way you describe that you have tried will only work if the spindle is isolated from the machine frame, useing a simple switch will work

[motopreserve]

Thanks so much for the reply! Can you explain what you mean by "a simple switch...". The spindle is definitely not isolated. I was beginning to think that this lack of isolation was my issue - after reading the original post. But I have no idea what to do next

[daniellyall]

I made my own tool height setter and it just has a momentary switch in it. just google this Diy tool setter there are a **** load of diffrent designs you just pick the one you can easily make or get one of fleabay

[motopreserve]

Thanks again for the reply.

My only concern with the momentary switch is that it may not be repeatable? bit if you're having luck with it - I'd be willing to give it a shot.

[BalloonEngineer]

Since I never got any feedback to my original post, I did end up tying -V on the 48V supply to ny star ground point. Works great. Note that all of my electronics are gantry mounted. See my build thread for pictures. http://www.cnczone.com/forums/diy-cn...-new-post.html

[motopreserve]

I'm beginning to realize that I need to check my grounding. I think this is the issue I'm having. I think my star grounding is done correctly - but I definitely do not have the v- tied to that.

Appreciate the help folks.

[DeanR181]

Hi Guys, Reading your comments seems to be exactly the same issue i am having. I have just installed a C62 BoB and Smooth Stepper. Everything is working perfectly (after hours of research and learning) but the one thing that has defeated me so far is the Z Auto touch plate. All cables are shielded but what happens is if I touch the Touch Plate with my hand, the digitizer diagnostic light flickers on and off and also the stepper motor does not move smoothly when driving down. When it touches the plate, the Z axis retracts but not to the correct height.

Now, if I don't touch the plate with my hand it works perfectly. Also, if i touch the Touch plate with my hand and also touch the machine with my other hand, it works perfectly.

It sounds to me to be an earthing issue but i have tried earthing the machine direct to the V- on the power supply and even to the BoB but still doesn't fix it.

I read somewhere else that someone suggested to add a capacitor across the input pin and common, but I am not sure what type or value capacitor to try.

Any suggestions would be appreciated.

Thanks
Dean

[BalloonEngineer]

On my machine the touch probe input pin is normally high, pulled low by the bit grounding the plate attached to the input pin. Is that how yours operates?

My touch probe is a piece of brass attached to a piece of plastic. In the probing screen (I am using Mach4) I need to enter the thickness of my probe and how far I want the retract. I never touch the conductive part of the probe during operation to prevent any false signal.

[DeanR181]

Hi Balloon, Thanks for the reply. Yes I have the inputs the same way as you.

I have the Auto Zero script correct (it works perfect on a different BoB) it is just that if i touch the probe with my finger while it is zeroing, it upsets it. i also see the input light in the diagnosis page flickers on and off if i touch the probe with my fingers.

If I touch the machine frame (earthing myself) at the same time, it doesn't happen.

I have tried grounding the probe direct to the power supply V- and to normal earth but it still doesn't work.

I guess my only option is to make a plastic holder with the metal plate inside to ensure i don't touch it during Auto Zeroing.

It would be really good to find the cause and proper fix.

thanks again
Dean