[Robotgroup] EMI suppression on power supply

[Andre Lamothe]

Hmmm, alright, well then this must be a switching supply (13 years ago, so 
you never know) and the R is used as a shunt resistor to damp the input of 
the power supply, so the RC is basically a filter that reduces the high 
frequencies generated by the switching power supply back out in the opposite 
direction. Most switching regulators work at around 20-100KHz, so that noise 
will be dampened by those couple components.

Andre'


----- Original Message ----- 
From: "Def Egge" <robodigest at innervate.com>
To: "The Robot Group Mailing List" <robotgroup at puremagic.com>
Sent: Sunday, March 16, 2008 8:57 PM
Subject: Re: [Robotgroup] EMI suppression on power supply


Thanks for confirming the function of the capacitor, Andre'.

To answer your question, yes, the resistor is in parallel with the
capacitor.


All the best....

Mike



At 20:49  2008-03-16, you wrote:
-=-=-=-=-= begin quoted message =-=-=-=-=-
 >The capacitor is simply to shunt high frequency noise from the
front
 >end of
 >the step down transformer and from the rest of the low voltage
 >regulators as
 >well. But, the resistor is questionable. So you are saying the
 >resistor is
 >in parallel with the capacitor?
 >
 >Andre'
 >
 >
 >----- Original Message -----
 >From: "Def Egge" <robodigest at innervate.com>
 >To: "The Robot Group" <robotgroup at puremagic.com>
 >Sent: Sunday, March 16, 2008 7:42 PM
 >Subject: [Robotgroup] EMI suppression on power supply
 >
 >
 >
 >I am looking over a non-functioning power supply (removed from a
 >mid-1990s desktop system).  I see at the 110VAC power connector a
330
 >nF capacitor (p/n RIFA PHE-830 M) installed between the 100VAC hot
 >and neutral leads, I presume, for EMI suppresion.  Is this correct?
 >
 >The leads of the capacitor are, in turn, connected by a 500 ohm
 >(according to my DMM) 1/4-watt resistor
(green-red-brown-gold).  The
 >gold band indicates 5% tolerance, so this is a 520 ohm resistor
(+/-
 >26 ohm), correct?  What is the purpose of the resistor?  Curious
 >minds desire to know more.
 >
 >
 >--
 >
 >All the best....
 >
 >Mike
 >
 >_______________________________________________
 >Robotgroup mailing list
 >Robotgroup at puremagic.com
 >http://lists.puremagic.com/cgi-bin/mailman/listinfo/robotgroup
 >
 >_______________________________________________
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 >Robotgroup at puremagic.com
 >http://lists.puremagic.com/cgi-bin/mailman/listinfo/robotgroup
-=-=-=-=-= end quoted message =-=-=-=-=-

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