FERROR on Z with float switch

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29 May 2011 19:13 #10154 by BigJohnT
All three actually, if I write a file by hand I put it in, my sheetcam post does it automagically and now I'm adding ngcgui to it so it will be in the subroutines.

John

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29 May 2011 19:52 #10157 by jcizek
Thanks John... it looks like I'm back to the drawing board again... I'm very ready to scrap this entire project.

Been messing around with this exact same configuration (hardware and software) for several weeks now. Haven't had any problems (except the weird THC problems where it just "forgets" to move Z down to the metal to fire the torch once in a while)

Today, I use aptitude to install emc-devel package, run comp --install thcud.comp It builds successfully.
Now I can't use the machine at all, I get a "Joint 0 limit switch error" while doing ANYTHING. I can't home it, can't move the other axis's without
getting it... nothing..

So I start doing some research. Check the X axis limit switch... continuity is good all the way back to the BOB. I figure, maybe it's some new noise source that is causing a glitch... so i up my debounce delay to 1/2 second... still have the problem.

I start a HAL scope and watch the debounced output. There is NOTHING on it until the switch actually trips... then I see the switch trip on the HAL scope. Yet, EMC just keeps throwing random "joint 0 on limit" errors.

just to keep my sanity, I rebooted into the the other partition (windows XP) and tossed on a trial copy of Mach3 and configured the 3 axis's and limits. No issue. They all work fine and the machine homes just fine. So it's definitely an EMC problem, I just don't know where it could be (and how it could have ANYTHING to do with compiling the thc module).

One thing I didn't do was to go remove the .ko file.. I guess I could try that and see if it makes any difference at all. Kind of doubt it, but i'll give it a go.
-James

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29 May 2011 20:32 #10160 by BigJohnT
I can appreciate your frustrations for sure as I've been there too many times.

When you added the thcud comp was that to a fresh config? The other one is so complex I have no idea what it is doing...

When you installed the comp I assume you did:

sudo comp --install thcud.comp

or did the flaky joint.0 error just start after installing thcud comp?

John

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29 May 2011 20:45 #10163 by jcizek
Yes, i installed it with a sudo comp --install thcud.comp
It built a .ko file successfully. This is when everything went to heck.... the new config, nor the old config would home anymore. I started getting the joint 0 problems.

But, i don't think it has anything to do with your comp file. I went back out, deleted it, and everything was working fine again. However, after about 10 minutes, it came back. It appears to be related to how long everything is powered up. Only thing I can guess is that I have some type of grounding problem. The noise problem would make sense, but with a 1/2 second debounce built it, it isn't noise causing the problem.

I am using shielded cable out to the switches, but i am having the problem even with the plasma (and everything else in the shop) turned off. Basically just the PC and the motor controllers fired up.

I don't have an isolated BOB, just using a simple one (two actually) that break the signals out. Wondering if switching to an isolated board might help.
I don't know why this just cropped up today, been running the table for 2 months without issue.. but something is causing EMC to think that switch is fired (or rather un-fired since I use NC loops on the limit switches).

i guess i could build a hardware debounce/isolation circuit for my limit inputs.

-James

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29 May 2011 21:00 #10164 by BigJohnT
Isolated I/O is best... could be a loose wire somewhere in the limit switch chain. I assume you have only grounded the shields on one end and left the other end floating... just thinking out loud atm.

So for 1/2 second of debounce you have to set the debounce.n.delay counter to something like 15k-17k?

I'm usually on the IRC if you need to chat a bit and bounce ideas back and forth I'm JT-.....

John

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29 May 2011 21:40 #10169 by jcizek
oh ok John, thanks for the note on IRC, i'll have to jump on there.

Ya, all the grounds are tied together at the controller, the shields are left unconnected at the limit switch end.

So, I found a whole tube of opto's on the electronics bench I forgot I had. I'm going to etch up a little board that will isolate ALL my input signals and mount it RIGHT AT the BOB. That should eliminate any noise issues, or at least minimize them. The high impedence of the LPT is a pain sometimes :-)

Yes, I had the debounce delay set to 15,000 something... I calculated it all out earlier, can't remember exactly now but it was very very high like that.
Might have have even longer than that.. i was watching it on the hal meter... it was SO long that the z axis switch tripped and went right on by while homing because the switch wasn't closed long enough :-)
For my wood router, I use debounce delay = 10 and have never had a false trip once. (Strange too as I use the exact same controller box between the 2 machines, just carry it from one to the other) One difference is that the wood router uses actual microswitches and the plasma is using alarm type reed (magnetic) switches.

I'll report back after I have the opto's installed... hopefully then I can get back on track with the THC stuff !! Thanks for the continued support. -James

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29 May 2011 22:00 #10171 by BigJohnT
jcizek wrote:

(Strange too as I use the exact same controller box between the 2 machines, just carry it from one to the other) One difference is that the wood router uses actual microswitches and the plasma is using alarm type reed (magnetic) switches


Anytime I hear "same but different" and I get that all the time when modifying machinery the little hairs stand up and I take notice of what is different. I'd look close at those switches...

John

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