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boats_ranger
Joined: 26 Apr 2009
Posts: 5
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 26 Apr 2009 17:36 earth gnd |
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Hi, Is there a perfered method connecting earth gnd to a low voltage power supply and circuit boards?
Normally, I would connect the earth gnd and power supply together at the AC input of the low voltage power supply. I would then connect that gnd to the case.
I would then fan out low voltage power and gnd to the other circuit boards.
It seems the return path for current who source is the 5 volts would be the 5volt ground. The 5v power is derived from ac, who's return path is back to the ac mains using the neutral as the path.
I have recently seen earth ground faned out to each pcb in a parellel fashion.
Is there a benifit to this layout? would this create two gnd loops?
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Kral
Joined: 28 Mar 2005
Posts: 1182
Helped: 187
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26 Apr 2009 20:12 power supply dirty earth |
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boats_ranger,
Your concern about ground loops is justified. "Daisy Chaining" the Earth ground to several PCB boards is not a good idea. The "star" grounding scheme is almost always the best one to use. In this scheme, all power supply grounds are connected together at one point only.
Regards,
Kral
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bws
Joined: 29 Apr 2007
Posts: 20
Location: Denmark
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26 Apr 2009 20:52 Gnding between earth gnd and power suppy gnd |
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| i always connect the DC supply GND to the Earth GND wiht a 1-5Mohms resistor, or a capacitor whit a high Xc to 50hz/60Hz and low on HF, and use the DC supply GND to the Chassis/case...
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26 Apr 2009 20:52 Ads |
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boats_ranger
Joined: 26 Apr 2009
Posts: 5
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27 Apr 2009 0:18 Re: Gnding between earth gnd and power suppy gnd |
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I have not used a 1meg ohm resistor from power supply gnd to earth gnd.
My thought are: if the return current paths have low impedance then the voltage drop would be mineral, with the benefit of lower noise. From experience, earth ground seem to add noise to my system, so I can understand using a isolation strategy between the two gnds.
I can rationalize (right or wrong) a connection through a inductor or a low resistant& (100 -150 ohms.) What are the benefits of connecting the two gnds through a high impedance?
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ferdie444
Joined: 23 Sep 2007
Posts: 4
Helped: 1
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28 Apr 2009 16:01 Re: Gnding between earth gnd and power suppy gnd |
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| yap,i agree w/ kral to use star grounding system to keep it intact and less prone from loose connection unlike the daisy chain grounding,because once you have a loose ground connection noise will be generated from your system.and @ the same time i agree w/ bws to use resistor or capacitor for the dc voltage before connecting to the chassis ground from which the ac is connected because,dirty ground is high voltage and clean earth is (low voltage grounding dc) and it's not a good practice to mix the two grounding system together,otherwise noise will be generated again.thanks and more power.....
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boats_ranger
Joined: 26 Apr 2009
Posts: 5
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12 May 2009 14:28 Re: Gnding between earth gnd and power suppy gnd |
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because,dirty ground is high voltage and clean earth is (low voltage grounding .
Can you explain what is ment by "dirty ground is high voltage"
thanks
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