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BClemens

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"Limit Switch Triggered"
« on: January 12, 2009, 07:50:55 AM »
Original post copied here....

Debounce set to 1000  - done that! Did no good. Probably something that I'm totally missing but I cannot see this problem on the machine end.

This machine conversion has failed. I cannot get past the "limit switch activation" in Mach3 and after spending a week on that problem alone, there is nothing left. The "combo board" wiring has been checked time after time and the limit switches have been totally rewired a couple of times with shielded wire. The servo motors run fine, no noise and will fast feed, just not very long. I have been able to home the axis and begin to run the 'roadrunner' then - 'plunk '- reset. The spindle has not even been started - cannot get past the limit switch problem and set-up.

I have read here and there about this problem and have tried everything that has been suggested. The hours spent are beginning to seem like a total waste.

What fails? The Combo Board? The cable from LPT1? (actually tried another of those). Cannot see what else could possibly be done with the limit switches and wiring - they are just switches! I don't detect any noise on the limit switch leads with an oscilloscope although they are advertised as 'floating ground' - I do see that they in fact are. The switches are series wired on each axis with a common ground and are active high with a 470 ohm resistor from the 12V at each input to the signal input.

I have other components to get working like a pendant and a VFD spindle drive but cannot even begin to start on them!

BTW - hello everyone!   ..... and looks like goodbye at the same time. Can't get it to work after all the serious precision conversion with ball screws, servo motor mounting and set-up....

Thanks,
Bill Clemens

Offline Tweakie.CNC

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Re: "Limit Switch Triggered"
« Reply #1 on: January 12, 2009, 08:53:38 AM »
Change your limit switches AND e-stop to active low. Reconfigure Mach input signals accordingly. (You may need to use pull up resistors to +5V (not +12V) on each of the limit switch and e-stop inputs).

Tweakie.
« Last Edit: January 14, 2009, 03:39:58 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ger21

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Re: "Limit Switch Triggered"
« Reply #2 on: January 12, 2009, 09:07:36 AM »
Set the debounce to 25,000 (or even higher) and see if it works. If it does, then it's noise on the switch lines. This seems to be the most common problem I see posted, and it's not easy to tell you how to fix it.
Gerry

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http://www.thecncwoodworker.com/2010.html

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BClemens

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Re: "Limit Switch Triggered"
« Reply #3 on: January 12, 2009, 09:46:49 AM »
25,000 X 40uS....long time....

Interesting to change the limit switches and e-stop to active low..... so there will be 12V present until a switch is opened?

Thanks
Re: "Limit Switch Triggered"
« Reply #4 on: January 12, 2009, 09:52:16 AM »
Bill,

Do you see your swiches activated on the diagnostics screen when you trigger them?

BClemens

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Re: "Limit Switch Triggered"
« Reply #5 on: January 12, 2009, 10:47:37 AM »
Yes, I see the yellow 'leds' light when the switches are activated.

Offline ger21

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Re: "Limit Switch Triggered"
« Reply #6 on: January 12, 2009, 11:10:26 AM »
25,000 X 40uS....long time....


I'm not saying to run the machine like that, but see if it gets rid of the false triggers. If it does, then it's most likely your getting noise.

Also, you mention 12V, but aren't they really wired to 5V? If they are 12V, what are they connected to?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

BClemens

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Re: "Limit Switch Triggered"
« Reply #7 on: January 12, 2009, 11:27:36 AM »
This interface board is the Bob Campbell Combo Board that has 12V available at the limit switch input terminals for use with Hall or other powered proximity sensors. Three terminals: 12V, Sig, and Ground.

I just went through a driver update for both LPT1 and 2, and seem to be having less problems with the limit resets but LPT2 seems to be acting sort-of dead. I attempted to shift Mach3 over to LPT2 and absolutely nothing would happen... StarTech PCIP_LP parallel card.

Offline Tweakie.CNC

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Re: "Limit Switch Triggered"
« Reply #8 on: January 12, 2009, 11:41:13 AM »
The basic circuit I have in mind would look something like this.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: "Limit Switch Triggered"
« Reply #9 on: January 12, 2009, 11:54:49 AM »
I am also using the Bob Campbell board.  Most of the parallel port cards that I have used have internal pull up resistors so what I have done is take the limit switch directly into the signal input on the Bob Campbell board.  When the switch is closed it pulls the input to ground providing the  "active low".  One end of the limit switch tied to "ground" terminal on the break out board and the other to the "signal" terminal on the break out board.

I have used the proximity sensors and just plain ole switches.  Both work fine.

Hang in there!