The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Phil Allison"
Subject: Re: Wall wart with two blade polarized plug,,,Why?
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sat, 5 Oct 2002 18:33:57 +1000
NNTP-Posting-Date: Sat, 05 Oct 2002 18:22:04 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Kevin McMurtrie" wrote in message
> >> There's likely a resistor between the DC negative and the AC neutral.
> > ** Very unlikely in a wall wart. If there it would be several
> > . . .. . . . . . . . . . . . Phil
> But there are there. You cut off my explanation. TVs throw off
> electricity and they must have the resistor to prevent arcing.
** Can you explain this a bit more. I know about the use of
special high value, high voltage rated resistors in double insulated TVs
from antenna sockets to neutral. I understood that was to discharge static
build up on the antenna due to wind.
Even non-polarized wall warts have a 10M Ohm resistor for general
> against static discharge which could damage the insulation.
** Not legal under European or Australian double insulation rules.
No cap or resistor can bridge double insulation and all wall warts are
required to meet this rule by law. The one exception AFAIK is for antenna
sockets on TVs.
> Jeff said he found a 500K Ohm resistor. This makes sense since TVs can
> throw off too much current for 10M Ohm and it explains the need for a
> polarized plug.
** No it doesn't explain a real need - but it could be a rule in the
USA. The resistor could be wired to active and work the same - it would
still be quite safe at only 240 uA.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup