Strange issue with Z Zero touch plates.

**ger21** · 01-28-2018, 11:42 AM

There's no guarantee that you won't have issues with an isolated board either.
From the users of my screenset that have contacted me with this same issue, the capacitor has worked every time.

Another option is to use a 24V breakout board, which is much more immune to noise issues than 5V boards.

**jimskeet** · 01-28-2018, 11:45 AM

Yeah I have read about that too, the higher the voltage, the less sensitive to noise. Ok so for now I will try to see if the capacitor will resolve my issue.
Changing the break out board is a project for later down the road.

**Kenny Duval** · 01-28-2018, 12:24 PM

Originally Posted by jimskeet

Thanks for the answer man.
Will this do the same thing with the capacitor???
Also when you say you looped the touch plate through it how exactly do you mean? Can you draw a wiring diagram so I get this clearly?

Literally the wire goes through the bead then it's wrapped around and pulled through the bead a second time. I used that as the solution for mine when I noticed that if I kept my hand on the probe wire I never got the fault. If I had not noticed that the idea to use a ferrite bead would probably not have entered my mind.

**jimskeet** · 01-28-2018, 12:28 PM

Originally Posted by Kenny Duval

Literally the wire goes through the bead then it's wrapped around and pulled through the bead a second time. I used that as the solution for mine when I noticed that if I kept my hand on the probe wire I never got the fault. If I had not noticed that the idea to use a ferrite bead would probably not have entered my mind.

Hmm
I will try that too. Though in my case I can some times trip the sensor if I touch the face of the touch plate with my hand while the z axis is probing down.

**mactec54** · 01-28-2018, 03:41 PM

Originally Posted by jimskeet

I tried also to use a debounce value in general config. I went up to debounce interval at 4000 and the issue still happened. If it was noise from EMI shouldn't it not trigger the input at such a high debounce value?

When your system is wired correct the Denounce is not needed, 4000 is a big number, I have never used it, on any builds, it is set at the default of zero

So the noise is on the Ground wire

If your touch plate / tool setter has a micro switch inside then you can connect the 2 wires direct to your Breakout Board, this will eliminate the noisy Ground wire, which is causing you this problem

**jimskeet** · 01-28-2018, 04:08 PM

Yeah I have it at 0 too. I tried it up to 4000 to see if it would nake any difference on my issue. But since debounce doesn't affect the probe input as ger21 said it didn'tmake any difference.

My touch plate is just an aluminum plate on a plastic housing connected with a cable to the input pin. The spindle is connected to ground through the vfd so when the endmill touches the aluminum plate the circuit closes and gives the signal.
I didn't understand what you mean to connect the 2 wires straight on the bob

**mactec54** · 01-28-2018, 04:28 PM

A tool setter like this would only connect to your Breakout Board, this is an active tool setter

https://nl.aliexpress.com/item/Facto...e22f9ea5&tpp=1

Or one like this

https://nl.aliexpress.com/item/High-...f77d43cfb32fb8

**mactec54** · 01-28-2018, 04:33 PM

Originally Posted by jimskeet

Yeah I have it at 0 too. I tried it up to 4000 to see if it would nake any difference on my issue. But since debounce doesn't affect the probe input as ger21 said it didn'tmake any difference.

My touch plate is just an aluminum plate on a plastic housing connected with a cable to the input pin. The spindle is connected to ground through the vfd so when the endmill touches the aluminum plate the circuit closes and gives the signal.
I didn't understand what you mean to connect the 2 wires straight on the bob

This is where the problems start to happen, the tool is not in a direct line to Ground, the Ground would be going through the bearings and grease etc. not an ideal Ground to make a reliable contact, with only 5v

**jimskeet** · 01-28-2018, 04:39 PM

The problem is not that the connection is not reliable. The connection registers correctly without any issue if it gets there. I have been working with a single touchplate for a year now. The issue is that probably cause of noise I have false activation of the signal. I will try with the capacitors to see if they resolve the issue. We plan to make some modifications on the machine and I will probably look into getting a much better bob than this one with more features like analog output for spindle speed control and better noise protection. Thanks for the links. I will take a lookk into them too.

**jimskeet** · 01-29-2018, 05:13 AM

I got some capacitors today. 0.1 0.2 and 0.3uf and will try them out. Starting from the lower one. The slight delay in the signal activation wont be an issue cause I can program the second touch on the plate to be with very slow feed and have an accurate reading.

**coherent** · 01-29-2018, 08:56 AM

I understand what you are saying regarding the ground through the spindle, but there is no way it is as reliable as a wire ran directly from the breakout board (even if it is not isolated) to an alligator clip clipped to your bit while zeroing it. Like mactec54 stated, you're currently grounding through bearings, grease, your spindle, VFD etc. It would cost nothing to run a simple wire with a clip to attach to your bit from your breakout board taking everything else out of the loop.

**jimskeet** · 01-29-2018, 09:01 AM

That is what I am saying. Even if I run a wire to the spindle with a clip on the end mill this won't remove the ground that already exists on the spindle and won't remove any noise that is there either. It will just be another parallel connection from my breakout board ground to the spindle. This would change nothing. The issue is not that the signal is not reliable when touching the plate and closing the circuit. The issue is that noise is triggering the signal before the plate touches. I cannot remove the ground from the spindle because then vfd and spindle won't be connected to ground together.

**ger21** · 01-29-2018, 10:06 AM

The issue isn't the ground on your spindle, but the wire on your plate picking up the noise. That's what's triggering the input, not the ground.

**jimskeet** · 01-29-2018, 10:10 AM

Originally Posted by ger21

The issue isn't the ground on your spindle, but the wire on your plate picking up the noise. That's what's triggering the input, not the ground.

Probably yes. Though I managed once to make it trigger even without any wire connected in the input pin. I was moving around the machine and touching it on various places on the frame. This happened only once though. Tried it a lot of times and didn't manage to make it trigger again. I will try to connect the capacitor today or tommorow and test it.

**mactec54** · 01-29-2018, 11:04 AM

Originally Posted by jimskeet

That is what I am saying. Even if I run a wire to the spindle with a clip on the end mill this won't remove the ground that already exists on the spindle and won't remove any noise that is there either. It will just be another parallel connection from my breakout board ground to the spindle. This would change nothing. The issue is not that the signal is not reliable when touching the plate and closing the circuit. The issue is that noise is triggering the signal before the plate touches. I cannot remove the ground from the spindle because then vfd and spindle won't be connected to ground together.

It's like I said in the first post, the motor that is driving the Z Axes is causing the noise, which is being carried by the Ground wire

Try this lower the Z axes with the motor turned off, and use the touch plate, this will show you where you have to fix the wiring for noise control, the X and Y axes could also be part of the noise problem as well if not correctly wired, with shielded cables and have correct termination of the shields

**jimskeet** · 01-29-2018, 01:24 PM

Ok new problem... I connected the capacitor between the pin and ground and now my optical home switches won't work. They are normal closed switches working with 12v and now they are open. Thia happened after I installed the capacitor and removing it didn't make 5em work again... Did I damage my home switches???

**jimskeet** · 01-29-2018, 05:43 PM

After banging my head on the wall for several hours about this.... I found out that my parallel adapter that is on the control box and connects the bob to the parallel port cable, was not solid. I accidentally moved it a little bit when I installed the capacitor and home switches couldn't function properly...
After I found out I pushed it to a spot that the home limits were working and connected back the capacitor. Now the Z plates work perfect. Tried it 5-6 times without any issue. Also now when I touch the plate on the endmill the led stays ON all the time. Before it would randomly pulse.

**mactec54** · 01-29-2018, 06:30 PM

Originally Posted by jimskeet

After banging my head on the wall for several hours about this.... I found out that my parallel adapter that is on the control box and connects the bob to the parallel port cable, was not solid. I accidentally moved it a little bit when I installed the capacitor and home switches couldn't function properly...
After I found out I pushed it to a spot that the home limits were working and connected back the capacitor. Now the Z plates work perfect. Tried it 5-6 times without any issue. Also now when I touch the plate on the endmill the led stays ON all the time. Before it would randomly pulse.

That's great, it gets you running again, but is only a band-aide fix for the real problem

**jimskeet** · 01-29-2018, 06:35 PM

Originally Posted by mactec54

That's great, it gets you running again, but is only a band-aide fix for the real problem

Well yeah. I do not seem to be able to find any other solution. All my cables are shielded as the guys that built the machine told me. I tried to route the cables of the touch plates as far away from motor cables as I could. Over half a meter away. The issue still happened. And something tells me the noise was coming through the frame of the table... Because usually when I touched the cable on the table it would trip the signal. I need some more testing though to be sure but now it seems to work fine. And didn't notice any delay on the signal activation. Not one that was visible to human eye anyway. So all seems good at the moment.

**jimskeet** · 02-03-2018, 01:07 PM

Originally Posted by jimskeet

After banging my head on the wall for several hours about this.... I found out that my parallel adapter that is on the control box and connects the bob to the parallel port cable, was not solid. I accidentally moved it a little bit when I installed the capacitor and home switches couldn't function properly...
After I found out I pushed it to a spot that the home limits were working and connected back the capacitor. Now the Z plates work perfect. Tried it 5-6 times without any issue. Also now when I touch the plate on the endmill the led stays ON all the time. Before it would randomly pulse.

Ok I got a new adapter today. The previous adapter was glued on the control box so I decided to test the new adapter before removing the old one just to be sure... I connected the new adapter and again the proximity switches were not working. Their leds didn't light up and it was like they didn't get any power. I connected the old one again and after moving pushing the cable connection back and forth I could find spots that it was working and spots that it didn't.
So then it struck me that maybe there is not an issue with the adapter and had something to do with where the adapter was touching. The next test proved me right.
When I touched the metal surrounding of the adapter on the sheet metal that the connectors are held the switches get powered on and work. When the adaptor is not touching the sheet metal the switches get powered down...

So something is weird with the connections.

I also tested this. I touched a cable on the metal case of the adaptor and the -12v supply and again the switches powered on. So for today I connected a cable on the small bolt that the parallel cable screws on to and connected the other end on the -12v so the machine worked the whole day fine.

I upload some images of my control box, how the proximity switches are wired and how I connected the cable to work around the issue. If anyone knows why this is happening would be great.