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Author Topic: Removed EMI, but still need debounce?  (Read 3527 times)

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Offline Mogal

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Removed EMI, but still need debounce?
« on: January 01, 2014, 08:47:10 PM »
Hello everyone!
Its been awhile since I've cruzed the forums here, but its great to see Mach3 still holding strong, and Mach4 coming soon!

I've been overhauling and upgrading my machine, and have now come into a problem.
I've rewired the machine with shielded cable, and pretty much completely eliminated all noise!
I used to run my debounce at 2000, but now I can reliably run the machine with it at 50!
*EXCEPT*
For when I home my axis in the Y direction!
Both Z and X axis will home correctly with a debounce setting of 50,
but the Y axis requires a minimum debounce of 1250, before it causes the limit switch to trip the machine.

I've been scratching my head or a few hours with this one, but can't nail it down.
any thoughts on why just the Y axis would require the higher debounce setting?

Thanks!
Chris

P.S. I'm not sure if this is a carry over from before the upgrades or not, as the debounce was set at 2000 before.
I'm pretty sure the machine is wired exactly as before, just with new wires.

Offline Fastest1

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Re: Removed EMI, but still need debounce?
« Reply #1 on: January 01, 2014, 08:50:44 PM »
Is the limit wiring parallel to the stepper wiring for any distance? What kind of limit switches?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Mogal

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Re: Removed EMI, but still need debounce?
« Reply #2 on: January 01, 2014, 09:02:30 PM »
Hi, thanks,

Yes, the wires are parallel for a small distance, maybe 2 feet.
The switches are mechanical.
Each axis has a 2 limit switches, forms a closed loop, and set active low.

Offline Fastest1

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Re: Removed EMI, but still need debounce?
« Reply #3 on: January 01, 2014, 09:48:37 PM »
I would try to separate the 2 wires if at all possible as a test. What kind of controller? If you are using mechanical switches only. I believe this is a 5 volt circuit and is very susceptible to noise. Do you have a star ground? Are all of your shields connected there?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

Offline Mogal

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Re: Removed EMI, but still need debounce?
« Reply #4 on: January 01, 2014, 11:36:41 PM »
Yes, I have a star ground now.
My controller is an (older - 7-8yrs) C10 BOB
Yes, it is a 5v system

I also have some ferrite beads on the way...
Re: Removed EMI, but still need debounce?
« Reply #5 on: January 01, 2014, 11:53:20 PM »
Ferrite beads will do absolutely NOTHING of value - they are only for reducing radiated and conducted emissions at MUCH higher frequencies - far beyond what logic circuits will respond to.

Regards,
Ray L.
Regards,
Ray L.

Offline Mogal

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Re: Removed EMI, but still need debounce?
« Reply #6 on: January 01, 2014, 11:56:44 PM »
Good to know, thanks!

Offline Hood

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Re: Removed EMI, but still need debounce?
« Reply #7 on: January 02, 2014, 03:46:44 AM »
If the axis runs to the switch before you have problems then it is likely a weak switch that is bouncing on its contacts. If the action of the switch is not a nice clean snap open/close action then you will get it triggereing then as Mach reverses it will close then open then close etc, Mach will see that as a limit (assuming it is also set as a limit in Mach)

Hood
Re: Removed EMI, but still need debounce?
« Reply #8 on: January 02, 2014, 06:49:03 AM »
Chris,
In my opinion, the easiest way to "remove" noise from limit and home switch inputs is to bypass it to ground with capacitors.  Installation of a .1 ceramic capacitor on all inputs at the BOB to ground has been proven effective in many instances.

Regards,
John Champlain

Offline Mogal

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Re: Removed EMI, but still need debounce?
« Reply #9 on: January 02, 2014, 03:05:46 PM »
100 points out to Hood!
Looks like it was a bum switch. changed it out and all is well!

I do have some caps (but I think they are 0.2uf)
(should I change them out to 0.1uf?)

I have my debounce set at 200 now (just to make sure)

THANK YOU for all that helped!

Chris