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Newbee limit switch false trigger problem
« on: October 08, 2013, 10:21:56 PM »
I am having false triggers with the limit switches.

I have 6 switches, 2 on each axis wired in series. They are wired normally closed. So they are grounded when they are inactive.
Each of the switch functions normally when tested manually on the diagnostic page.
As soon as i enable the limit switches, the Mach3 flashes error "Limit switch triggered" and wont jog.
The diagnostic page has none of the limits lit.
The inputs are normally grounded, the motors are not running, the debounce is set to 1000x40us, i dont think there can be any noise.

What am i doing wrong ? i have attached the xml.
Please help i am stuck.

Offline Fastest1

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Newbee limit switch false trigger problem
« Reply #1 on: October 08, 2013, 11:02:24 PM »
Why don't you suspect noise? What happens if  you raise the debounce to 2000 or 3000 as a test.
Shielded wire on your switches? Is the shield connected only at the controller to the star ground? Do you have the V- of your power supply landed there also?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Chaoticone

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Re: Newbee limit switch false trigger problem
« Reply #2 on: October 08, 2013, 11:03:49 PM »
I just loaded your xml and it sure looks like noise to me. What kind of hardware are your running? XP, 7, 32 bit, 64 bit, what breakout board? Have you tried setting your debounce to 2000? Why do you think there can't be any noise? Is your cable a straight thru or is it a standard printer cable? Are you running any anti virus?

This link may help.
http://www.machsupport.com/forum/index.php/topic,25616.0.html#new

Brett
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My guard dog is not what you need to worry about!
Re: Newbee limit switch false trigger problem
« Reply #3 on: October 08, 2013, 11:21:00 PM »
I am running Windows7 64 bit. No anti virus.
WARP3 USB smooth stepper.
The motor driver is opto isolated to the smooth stepper.

The wires are not shielded. But they are shorted to ground when they are inactive. So I didn't suspect any noise
I have a 300 MHz scope hooked on the input lines to watch for noise, I didn't see any.

I am going to use a shielded wire and try again.
If that works, I am going to kick myself for being a such smart ass.

Iqbal

Offline Chaoticone

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Re: Newbee limit switch false trigger problem
« Reply #4 on: October 08, 2013, 11:22:46 PM »
Hold on, did you try setting any noise filtering in the SS plugin? Set it low and see if ti helps.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Newbee limit switch false trigger problem
« Reply #5 on: October 08, 2013, 11:40:31 PM »
Didn't know about SS settings, will try that first.
Re: Newbee limit switch false trigger problem
« Reply #6 on: October 09, 2013, 12:04:12 AM »
!!! SUCCESS !!!

SS settings for 500 us on each input works.
Strangely the debounce in Mach3 didn't do any good. I am going to remove those. Since they are driven by the SS i am sure the input to Mach3 is noise free. its the noise seen by the SS thats causing the problem.

The power to the entire drive is off, but it would still trigger the limits, so i cannot not understand where the noise is coming from.
I am going to bypass the input limit lines with a 1 uf capacitor, the pull up is 4k, so it should be fast enough. Would like your comment on the bypass cap.
 

Offline Chaoticone

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Re: Newbee limit switch false trigger problem
« Reply #7 on: October 09, 2013, 12:57:13 AM »
 :) Debounce in Mach has no effect when running the SS.

I think you will be fine with the 1uf cap but not 100% sure. Sounds like you've done your math so I'll trust your judgement. Been up for a while and not thinking............. at all, much less remembering that formula. T=RC? I honestly just cant remember right now. I guess really wont matter so much as long as its consistent and snubs it. Just don't borrow one from your 40 HP phase converter.......... might break a hard stop.  :o Seriously though, wait for confirmation for anything I said........... I'm beat.

You may want to check on the Warp9 site/forum. Seems there were some models that breaking a resistor off would help some. Might try running a ground from SS to PC case too. I'm convinced suppressing noise involves a little crows foot, frogs breath, hens teeth black magic at times but I think you know that already.  ;)


Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline Hood

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Re: Newbee limit switch false trigger problem
« Reply #8 on: October 09, 2013, 03:40:28 AM »
500 for the filtering in the SS will be far too high and will delays your signals greately. I suggest you use a small amount (it is 1.43 increments) If you need more than 10 then you have serious problems that need to be sorted.
Hood
Re: Newbee limit switch false trigger problem
« Reply #9 on: October 09, 2013, 06:23:56 AM »
If you use a cap, typically .1 uf is sufficient. 
John Champlain