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| Ev Archive for July 1999 |
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| 1318 messages, last added Wed Aug 08 18:45:48 2001 |
[Date Index][Thread Index]
Re: OT: Phantom loads
At 12:58 PM 7/30/99 -0500, Chris Meier <ChrisM@pptvision.com> wrote:
>
>Mark, an experiment I've always meant to conduct, is to
>measure the inefficiency of different 'size' wall warts. If
>the appliances that use wall warts used a common supply,
>and then was sized for maximum wattage draw, would the
>AC input wattage be substantially reduced?
Yes, however many devices depend on the isolation the independent
transformer supply gives them. For example, I tried connecting my telephone
answering machine to my 12V solar charged ham radio station battery so it
would work during power outages. It has a 12VDC wall-wart. Picking up the
phone, I found a loud hum since the negative supply is not isolated from the
phone line inside the unit. Grounding one side of the phone line gives hum
(and the telco doesn't want you to damage their equipment). External modems
use the AC input to generate +/- 12V for RS-232 to the computer, etc.
>As long as I've turned this even more off topic, does anyone
>know what X10 rf receiver unit is the most power efficient?
Also a few watt phantom load.
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