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Author Topic: "Limit Switch Triggered"  (Read 31906 times)

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Re: "Limit Switch Triggered"
« Reply #10 on: January 12, 2009, 12:11:57 PM »
Yes, 'hang in there'! If I was really a quitter, it would have quietly occurred about a week ago.... That wiring description is what I have and the switches are in the NC position until the limit is reached. That's what makes this so strange - having trouble with my switches staying at ground potential?

Yes Tweakie, thanks for the rendering! I used NC grounded normally switch wiring so when they open - limit - the signal is high (12V) and to make sure that it goes high I installed 470 ohm resistoes to the signal input to the 12V output terminals.

I have raised the 'debounce' to 3000 to see what happens. This machine can just sit idle and reset on its own!

Offline Tweakie.CNC

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Re: "Limit Switch Triggered"
« Reply #11 on: January 12, 2009, 12:20:38 PM »
To follow my circuit recommendation you will need to use the n.o. switch contacts (or replace the switches if they only have n.c. contacts available) - the switches only close when the limit is reached.

A problem with raising the debounce is that the switch needs to be energized for the debounce interval to be recognized by Mach as a stop and by then the machine may have traveled to the mechanical stop position (crunch).

« Last Edit: January 12, 2009, 12:24:20 PM by Tweakie.CNC »


Re: "Limit Switch Triggered"
« Reply #12 on: January 12, 2009, 01:09:27 PM »
Tweakie, yes that makes very good sense. The set-up recommendation was to use active high for the limit switches because of the fact that if a wire came loose from a switch that there could not be a signal nor would there be an indication until there was a crunch. But, you make sense about the debounce.... I do need to reverse the logic for the pendant that I'm in the process of setting up - CNC4PC basic pendant.


Re: "Limit Switch Triggered"
« Reply #13 on: January 12, 2009, 03:34:02 PM »
Looks like this Combo Board may be the culprit. This thing is making so much of its own noise, I don't see how a signal could possibly not get screwed up getting through it. Speaking of getting screwed.... I noticed that the follow ups from Campbell aren't much - probably knows about these boards. Certainly explains why a basic on or off switch cannot work correctly and sends noise into a computer. Cannot blame Mach3....

So, who makes a good break-out board?

Offline Hood

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Re: "Limit Switch Triggered"
« Reply #14 on: January 12, 2009, 03:41:40 PM »
PMDX122 is what I use and never a problem out of the 5 I have, also never seen a problem reported with them here on the forum, maybe thats just because they are not used by many here? I dont know?
Re: "Limit Switch Triggered"
« Reply #15 on: January 12, 2009, 08:12:39 PM »
PMDX 122 BOARD here.

I got the recommendation from Hood.
No problems.

Ed VanEss
Re: "Limit Switch Triggered"
« Reply #16 on: January 12, 2009, 08:18:16 PM »
Same here. Followed Hood's lead.  PMDX ALL THE WAY !
The 106 is an EXCELLENT spindle interface too.


Re: "Limit Switch Triggered"
« Reply #17 on: January 13, 2009, 01:15:54 AM »
I have been using BOBs board s for years now, no noise issues here.

Just a thought, (;-) TP


Re: "Limit Switch Triggered"
« Reply #18 on: January 13, 2009, 06:44:33 AM »
Yes, I don't like the thought of giving up on the Campbell Combo Board but if it doesn't work...The box fits that board which means going all the way back to coming up with another box for a different breakout board, but if it needs to be..

Maybe I've got a bad one. I wrote to Campbell a couple of times, maybe he will respond with some remedy - try another board...?

I put an oscilloscope on the limit switch inputs to watch for some sort of glitch - never saw one that would have triggered a reset. At the same time the outputs were watched with another channel - they seem to be all over the place with no apparent frequency or amplitude so when some of this noise varies far enough - reset. There has got to be a remedy for this....maybe a leaky capacitor or one of these chips with a bad gate or something.

These combo boards are assembled by flow soldering but I see puddles of flux on some traces. I'm not saying that this was repaired before I got it but why would there be additional soldered joints to a circuit board that had been flow soldered and then totally cleaned? The soldering flux appears to be around the voltage regulators and the main fusible link. Have I been the recipient of the tailings of a once thriving business? Bob Campbell seems OK, but money is money if things are not going well.

Off subject... But anyhow, we'll get to some other tasks while this is sorted out. The LPT2 port in the machine computer seems to be outing where it should be inning.


Offline olf20

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Re: "Limit Switch Triggered"
« Reply #19 on: January 13, 2009, 07:12:16 AM »
I'm sure you have thought about this but I don't see it talked about anywhere.
Are you using shielded cable?? Only one end tied to ground. Common grounding point.
Make sure that the power wires and the signal wires are kept seperate and as far apart as possible.

I moved my machine awhile back and did not pay much attention to the position of
the wiring after the move and had bogas limit and estops till I rearranged the
I use CNC4PC bob. My only problem was my own.
Just a thought.

Mach3, Atlas Knee Mill, 4th Axis, VcarvePro, ESS, Super PID.
Been Heating with corn since 1998