G38.2 randomly stops

andypugh wrote: A standard touch-probe is short-circuit when not tripped, and tends to be fairly noise-immune because of that.

So maybe I should but a touch probe. I will have to do some research and see what is available for me. I am using a Hitachi router and have both 1/4" and 1/2 collets for it. But it seems to me, that going with a regular probe, I would have to use tool length offsets and figure a way to get the tools in the router at the same depth. I think, at least on the surface, that I need to use the tool as the switch.

andypugh wrote: There is a software debounce component that can help in your situation. I think that probe inputs are monitored in the servo-thread so a software debounce running in the base thread won't introduce a delay.
www.linuxcnc.org/docs/html/man/man9/debounce.9.html

ArcEye mentioned the debounce too. I will certainly look into it.

I am trying to develop the tutorial so that someone new to the CNC hobby can get an idea on how the stuff is added and configured in the environment. I thought, erroneously, that I could show them how to identify an input pin, detect it's level, and bring either a 5V or 0V line out to make the switch. Attach these lines to a clip (for the tool) and a plate.

I didn't take into any account for noise, and you never know how people will wire stuff. So I need a way to help bulletproof it.

Then in MDI, demonstrate the touchoff process for the G-Code before moving on to PyVCP and Classic Ladder. I see that I need to rethink my hardware tutorial portion.

Thanks for the help Andy, and to you ArcEye.

JoeHildreth wrote: I thought, erroneously, that I could show them how to identify an input pin, detect it's level, and bring either a 5V or 0V line out to make the switch. Attach these lines to a clip (for the tool) and a plate.

You aren't wrong, and it will actually work, it is just that there are wrinkles in practice. Perhaps your tutorial could lead in to noise immunity, shielding and grounding? A clear explanation of configuring the debounce component would be useful.

What pull-up resistor did you use? You might want to use a surprisingly small one. 50 ohms is still only 100mA from the 5V PSU. The more current needed the lower the chance of false tripping.

Although, I am not sure what you mean by screening.

A wire which passes inside an outer screen which can be grounded. One end only (control box end usually as that will have a grounded back plane) or you can set up a loop worse than the original problem.

ArcEye wrote:
My favorite, use a 12v plus low wattage plugin PSU to power the probe line and have this activate a SSR which switches a 5v / 3.3v feed to the BOB.
I have used this a few times, especially with limits, the switches are completely noise immune and the SSRs make and break so rapidly there is no lag.

regards

Is this to keep your signal wires as short as possible?

Obliquely yes, it is to do with TTL logic mostly.

A 3.3v signal, which is what most parports are now, only has to drop to 2v or rise from 0v to 0.8v and it is in a nebulous range which could be HIGH or LOW.
It does not take much in the way of induced voltages to throw false signals especially in long cable runs.

Having a 24v signal and converting to TTL would bring up the levels to 11v and 4v respectively, which is pretty noise immune

An alternative to save the 24v>TTL conversion, is having the 12 - 24v signal actuate a relay and the 3.3v signal is passed through the contacts only when they are closed and triggers the actual signal (inverted if needs be)
Because this takes place inside the control cabinet typically, the short run need to bring in the signal to the BOB is pretty well shielded

Is there a supplier of specific brand or type SSR that you recommend?

The ones I used were Omron, but only because I had them in my bits box of stuff stripped from other machines.

regards

andypugh wrote: What pull-up resistor did you use? You might want to use a surprisingly small one. 50 ohms is still only 100mA from the 5V PSU. The more current needed the lower the chance of false tripping.

The breakout board has 4.7K pull up resistors on it. Would it be safe to run an external pull up resistor resistor with the BOB, assuming I took into account the 4.7K in parallel with it?

I seems I have more work to do before I release that part of the tutorial. It is better that I run into these problems now and resolve them then pass the information on than to jump the gun and create headaches for people. I agree, the tutorial should cover things like noise immunity, grounding and proper shielding. And once I have figured out the debounce component, I will share that too.

Thanks Andy,

Joe

ArcEye,

You have given me a lot of great information. Now, I realize there may be a LOT of flaws with my wiring setup, I will attach a couple of pictures of my electronics drawer and perhaps you can give me some pointers in cleaning it up.

I built a small computer rack in the stand of my machine to house the electronics, computer etc. The drawer that I made was broke from some sheet metal and rails added to it. In the pictures you will see (2) 36V supplies for the stepper controllers, a 5V supply on its edge to supply the BOB. (4) stepper controllers and the BOB. The BOB is held off the bottom of the drawer with plastic standoffs. Everything else is directly attached. Motor wires run to 4 pin MIC jacks (The top row) The bottom row is 2 pin MIC The ground wire runs to the supplies, but not to the drawer itself. You see I have signal wires and motor wires bundled together. Here are a few things that I think need to happen.

1) The motor wires are bundles alongside the signal wires of the BOB. These probably should be routed in two groups?
2) In network wiring, it is common practice to twist the pairs to help prevent cross talk. Should I do that for the signal wires as well? Should I do it for the motor wires?
3) I probably should attach the The AC and Power supply grounds to the metal drawer itself. That would create a grounded plane to work with. I may have to scrape some paint off in some areas.

Now some questions.

1) The screen ... Not sure if I am following you. Are you saying the screen goes over the electronics in the drawer and the screen gets grounded?
2) Do you or others have recommendations to make my wire job better?

Joe

JoeHildreth wrote: 2) Do you or others have recommendations to make my wire job better?

It's nice and neat, at least.

I like to use ferrules into cage-clamps when using stranded wire:
www.rapidonline.com/cables-connectors/rv...-pack-of-100-33-1280