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Author Topic: 0.1uF ceramic capacitors not resolving phantom limit/e-stop/home signals.  (Read 3193 times)

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It seems that some electrical noise has been triggering e-stop, home and limit signals on my router, so as suggested in the many threads associated with this issue, I put 0.1uF ceramic caps across the terminals at the break out board. Unfortunately this did not solve the issue.

Shielded wiring is also a recommended fix. Is there a way of shielding existing cables,or should I rip the lot out and replace it with shielded wiring

I haven't done anything with the debounce since I found the caps didn't fix the signal issue, I'll investigate that next. Just interested in suggested ways of dealing with this.

Offline RICH

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A little info first.......

The router itself can generate a lot of noise. The noise is in the form of numerous frequencies and as visual of the noise envelope it would look sort of like the mushroom cloud of a
A bomb thus creating an envelope of noise / an electric field. How strong the field of generated noise is varies with distance. Wires close to / cutting that electric field will
pick up tha noise and thus you have a culprit signal triggering items attached to those wires. Additionaly that noise can be fed back through the AC  cord and into the
everthing else. In extreme cases of noise ie; where the noise field is strong  there may be no fix other than to eliminate the noise source. That is not practical in many cases so
one goes into the mode of minimizing the intensity of the noise and protecting other devices / wires/ etc from coupling with the noise.

If one were to put each device in a seperate metal container the noise would be restricted / contained. If the interfering noise was very small as compared to the device signal
interference  may not be a problem.

So that is why folks like to use higher voltage for signal wiring instead of the basic 5 volt , why shielded cable is used, isolation transformers and a separate noise grounding system, etc are are used.

Sorry for the non-tech language since only wanted to get some basic points across,
That said,

Install 100% shielded wiring   and proper grounding, then see how things work.

I think that trying to shield existing wires is a waste of time. You could also minimize the router noise, but, maybe another day.....

RICH
« Last Edit: January 06, 2014, 08:44:41 AM by RICH »
Do you get the problem when you dry-run code (without the spindle running)?  If not, you can be pretty sure it is an AC noise issue as Rich discusses, and an AC line filter may help.
 
I use this one: http://www.soigeneris.com/line_filter_kit-details.aspx

John Champlain

Offline RICH

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Splint,

On any device that has sparking....BTW, the brushes are the source of noise generation.
The filter / transformer creates a wall so to speak so the noise can't propagate back to the AC supply  and may additionaly provide a
easy path  to a noise ground system. Again.....non techy words! ;)

Suggest you consider it as the cost is not high.
Additionaly, coil the router plug neatly around a non conducting tube for approx four inch length ( piece of pvc or the inner toilet paper
tube works ).

But do replace the wires.

RICH
« Last Edit: January 06, 2014, 09:59:23 AM by RICH »

Offline Chaoticone

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Bravo Rich and John! Sound advice if I have ever heard any.

http://www.machsupport.com/forum/index.php/topic,25616.0.html

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!
My machine has very long cables due to the physical design. I spent a fortune on shielded cables (Igus), one ground point, high voltage and low voltage in separate metal enclosures, wires crossing at right angles etc.  Not a glitch anywhere, ever, until I added two little solenoid valves last week for air and coolant, with shielded cables and isolation relays too.  When either valve turned off all the axis would jump like a full step!  A flyback diode across the solenoid coils took care of it though. Surprised the heck out of me though.
It seems I've done a bad job of electrical design. The machine runs a long bundle of cables consisting of power cables for the servo motors, shielded cable for the encoders and unshielded cables for the limit and home switches. All this leads back to a cabinet made from MDF with the internals from a mig welder as the power supply for the servo motors. Next to the power supply is the capacitors for the power supply (cant recall the specs but the are three of them and they are about 2 inches diameter and 5 inches high). That sits next to the PC to drive the whole thing and the servo drives are mounted above the capacitors.

Interestingly, I've not been running the spindle when these issues occur, so I could quite easily have further issues when I get to running with the spindle powered up. The last time I got a false signal, the machine was sitting idle. I assume this would mean the noise is coming, in part, from the power supply. The power supply sits in the original steel case (but without the side panels on it), so I assume as a minimum, a steel panel should be installed to separate the higher voltage equipment from the lower voltage equipment.

Thanks for the advice, I wish I knew all this at the design stage.

Offline RICH

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EMI problems can be difficult to deal with and even with good engineering practices applied you can still have problems.
My experience came from being a ham radio op.  Our club provided assitance to folks who had EMI problems. Over time, me, the power company,
cable company, tel company became friends...........got to know "all" my neighbors also!

Sometimes a little "black magic" was needed and by that i am meaning,resolution just didn't seem logical, but it worked.

The problem with all this is that one just can't see what's happening but the affects are felt.

Remember this is fun,

RICH

Offline Chaoticone

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Splint, I can't tell you what to do but if you could replace the limit and home cables with shielded and reuse them if your design has to change more I would start there.

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!