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Author Topic: The solutions to my false limit switch triggering issues  (Read 7090 times)

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Offline bfgstew

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Re: The solutions to my false limit switch triggering issues
« Reply #10 on: December 10, 2015, 03:11:51 PM »
Electrics/electronics is a definite dark art, being mechanical all my life and now only getting into electrics I have found this out.
Working with electricians who have been at it for all their lives they too find hard with ground loops, feedback, earth impedances, shielding and so on, especially with modern day control equipment. It has become a very scientific art to make every component work together without interference of some form or fashion. Following the manufacturers guidelines is a must, but for some people decide they know better and go their own way. Good test equipment again is a must but unfortunately this is financially beyond some. So it boils down to advise from guys who have been there and done it, for that I take my hat off to you and thank you for the time, patience and effort you put in to helping us lesser mortals through the dark art of electrics and electronics. Definitely without Tweakies help I would not have Scrappy up and running.

Stewart
Re: The solutions to my false limit switch triggering issues
« Reply #11 on: December 10, 2015, 08:50:38 PM »
I Must admit, I did try writing a guide (for beginners) to wiring a CNC machine about a year ago. http://openbuilds.com/threads/electronics-101.693/

The further I got into it the more I realized just how much of a grey area it really is. Sadly, few of the newcomers to that forum took much notice and all the same wiring mistakes are still being made and re-discovered all over again.  ;D

Tweakie.

This would have been nice to have read before I started!  I did read Chaoticone's post though.  Everything everyone posted helped, even the misleading stuff lead to learning more about how things worked or didn't work as it were, hehe.  I'm happy to have those issue solved, moving forward with the tuning and cutting!

It sure felt like Gremlins were in my system with the troubles that were happening!  lol
Re: The solutions to my false limit switch triggering issues
« Reply #12 on: December 10, 2015, 09:07:42 PM »
The thing that gets me is, you can do all the correct things by the book and still have problems.
I don't run any shielded cable on my machine. I run all my motor wires and switch wires through the same cable tray. Initialy I had false triggers happening, but simply installing some 0.1uf caps on my switch input terminals, all has been good for years now.
I must admit that I delibrately didn't run my spindle to VFD cabling in the same run though. I have those cables and my camera cable coming down from above the router spindle.
My rebounce setting is set to 200.

Offline Tweakie.CNC

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Re: The solutions to my false limit switch triggering issues
« Reply #13 on: December 11, 2015, 03:20:50 AM »
All this, I think, goes to highlight the benefits of our forum dwelling. We all learn from each other (sometimes from the mistakes and sometimes from the explanations) and the vast pool of knowledge we have all helped to create here has made our forum what it is today.

Keep up the good work guys.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: The solutions to my false limit switch triggering issues
« Reply #14 on: December 11, 2015, 03:27:21 AM »
Here was another really good link I had found in my searching...    http://www.cnccookbook.com/CCCNCNoise.html

Offline Chaoticone

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Re: The solutions to my false limit switch triggering issues
« Reply #15 on: December 11, 2015, 10:10:02 AM »
Tweakie, I got started reading yours last night. I did not finish but what I have seen so far is better than great!

Quote
Here was another really good link I had found in my searching...    http://www.cnccookbook.com/CCCNCNoise.html

Yes it is. Having been down this road do you think I should put a link to Tweakie's and the CNC cookbook in my attempt at prevention as the first 2 links?
;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: The solutions to my false limit switch triggering issues
« Reply #16 on: April 18, 2019, 02:55:24 PM »
All this, I think, goes to highlight the benefits of our forum dwelling. We all learn from each other (sometimes from the mistakes and sometimes from the explanations) and the vast pool of knowledge we have all helped to create here has made our forum what it is today.



Keep up the good work guys.

Tweakie.


Tweakie Have read many post from you and always appreciate the input. I thought maybe you could either point me or teach me a couple things.

I am running MACH3 and right now just using Parallel port the CNC4PC C11G rev.9 board. Having issue on spindle control. I have it all working but when the BOB is not in Green status one of the Relays (relay 2) chatters and is on. This is an issue cause I am using that relay to control spindle light.
Artuo says its an ground loop, which I agree. I can disconnect my analog 12 volts from the BOB or from the aviation connector which feeds my speed control. I have a HF mill the speed board is the FC350BJ. Any Ideas?

Also, I stumbled across this post and I am having limit switch and estop false triggers. Would it be better to ground the lines from these switches to chassis or use the .1uF cap plan?

Thanks in advance

Offline reuelt

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Re: The solutions to my false limit switch triggering issues
« Reply #17 on: April 18, 2019, 03:43:09 PM »
"I am having limit switch and estop false triggers"

This thread shows a fundamental mistake.
Limit/home switches should be wired NORMALLY CLOSED and NOT Normally OPEN as done by the author of this thread. So his "solution" is a just a waste of time and effort.
You cannot have any false trigger if voltage is NORMALLY already high and current is already flowing in the limit switches.
Noise cannot turn what is already normally voltage high, "falsely on'.
« Last Edit: April 18, 2019, 03:48:06 PM by reuelt »
"the gift of God is eternal life through Jesus Christ our Lord"

Offline Tweakie.CNC

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Re: The solutions to my false limit switch triggering issues
« Reply #18 on: April 19, 2019, 01:37:06 AM »
Hi Truckeic,

Because there are so many variables, unfortunately, there is no one solution that suits every situation.

Initially check that you have set a Debounce Interval (config. – General Config.) of at least 100 (up to 500 max.).
For your inputs (limit,home,estop,etc) they should be wired using good quality twin core shielded cable with the shield connected to a single point Earth connection at the controller end only (not chassis). Also check that you do not have any Earth loops within your machine wiring layout. If problems persist then fit 0.1uF caps. connected between each used input and GND.

Hope this helps.
« Last Edit: April 19, 2019, 06:33:20 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline reuelt

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Re: The solutions to my false limit switch triggering issues
« Reply #19 on: April 20, 2019, 04:54:48 AM »
[quote
any Ideas?
[/quote]

1. If you limit/home switches are wired Normally Open (NO) - change it to NC (Normally Closed).
This will eliminate/minimize ALL "false limit switch triggering issues". Debounce more than 50 is ABNORMAL.
It is also better for safety because M/C won't even start if any limit switch wire is broken.
In the NO wiring, a broken wire could go unnoticed until M/C crashed HARD when limit switch didn't work because a wire had been broken for a long time.
2. Earthing should be done at the negative terminal of the DC (24V?) power and the ground of the limit switch wiring.
3. The ANALOG 0-10V controlling spindle speed is the usual trouble spot. This is because the Analog ground is isolated from the digital or DC & m/c ground.
So install ferrite core (aka chokes) on both wires of the 0-10V out of the BOB that controls the spindle speed. Put wire through as many turns as possible. This will make spindle speed more accurate and stable.
4. AC Power source should have AC "EMI filters". This is even more crucial if you upgrade to VFD Spindle and inverter.
5. I would NEVER use a USB Motion Controller. I would go from parallel port to an Ethernet motion Controller. USB Motion Controller are too sensitive to EMI noise. 
"the gift of God is eternal life through Jesus Christ our Lord"