Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Tony Bullard on November 27, 2013, 08:13:03 AM
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Signal ground / Earth ground
In reference to ground loops as a source of “noise”:
Quote from Tweakie.
“Also check for GND loops - in particular the LPT cable shield should not be connected to GND at both the computer end and the machine frame if they are both, in turn, connected to earth etc.”
“Quote
Interesting Tweakie, what about the signal grounds like pins 18-25 on a DB25 connector? can that be grounded at both ends? I hope.
Tony
Hi Tony,
Yes, the 18-25 is common signal GND between the PC and the controller but remember that this is signal GND, it is not Earth.
Tweakie.”
I believe the LPT signal grounds are connected to the computer chaise which is also the -5V and -12V power supply GND which in turn is connected to earth ground through the AC power card. Is this correct?
Is it OK to have the signal grounds be connected to earth ground at both the computer and a controller which is grounded at the machine?
Thanks for any help.
Tony
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This thread may help you; http://www.machsupport.com/forum/index.php/topic,9587.0.html
Tweakie.
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Thanks Tweakie,
That is a help. I don't appear to have any noise issues with my plasma machine but do see where I don't have perfect "star" connections and someday should make them better.
Tony