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Author Topic: Noise, external e-stop triggering, grounding  (Read 2212 times)

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Noise, external e-stop triggering, grounding
« on: November 24, 2009, 12:13:25 AM »
Hi All,

I've been working on my Takisawa lathe for a few weeks now and am making great progress thanks to Hood, Peter and others.  I was having a noise problem and finally fixed it and wanted to share what fixed it for me in case someone else has the same problem.

What was happening is whenever the spindle was on I would get intermittent false triggering of my external e-stop, and I had some major problems with the computer dropping the USB keyboard connection.  It turns out if the keyboard disconnects while jogging, it keeps jogging (E-stops are good :-)).  Replacing the keyboard made that problem go away, but I was still getting false e-stops all the time even with de-bounce set to 2000.  The computer was plugged into a separate 110V outlet from the rest of the lathe so I knew that the two grounds were probably at substantially different levels, and the noise on one would not be common with the other.  So I decided to run the PC and monitor off of 240V, which almost all monitors and power supplies have an option for.  I lopped off the 110V US plugs and just wired it right into an existing circuit with a breaker inside the control panel, and grounded them to the main tie-point.  No more problems, so far :-)  Everything on the whole machine now runs off of the 240V 3-phase coming in and has a SINGLE nice solid ground back to the service.

I'm sure there are a zillion ways to fix noise, and it is more black magic than science (if you ask me...) but this worked way better than I thought it would so thought I would share.

Re: Noise, external e-stop triggering, grounding
« Reply #1 on: November 25, 2009, 04:23:39 PM »
If you were to look inside the controller enclosure of something like a 80's Mazak/Mitsubishi for e.g., you would first see that the multi-output switching power supply had all the power outputs referenced to a common ground point, also all the low voltage logic boards, the I/O boards and machine control circuitry had a earth ground conductor all going to a central ground point.
There is an excellent PDF on the Siemens site covering this exact issue labelled, Grounding and Bonding of control enclosures, no black magic involved :) .