Path: utzoo!attcan!uunet!cs.utexas.edu!uwm.edu!linac!midway!ncar!umigw!mthvax!wb8foz
From: wb8foz@mthvax.cs.miami.edu (David Lesher)
Newsgroups: sci.electronics
Subject: Re: AC-DC at wall current voltage
Message-ID: <1990Oct6.220317.18337@mthvax.cs.miami.edu>
Date: 6 Oct 90 22:03:17 GMT
References: <1990Oct6.193138.6583@athena.mit.edu>
Reply-To: wb8foz@mthvax.cs.miami.edu (David Lesher)
Distribution: na
Organization: NRK Clinic for habitual NetNews Abusers
Lines: 29


{plan to rectify ac-->dc with cap. filter}

>  This is a BAD idea. If you size the capacitor large enough to get
>rid of the ripple you will be running the blanket at the AC peak
>voltage not 110. This will mean it will be running at about twice
>its rated power. The controller will probably still work, but the 
>resistance wire in the blankets will get hot too quickly. You are
>asking for a fire! Please don't do this for safety reasons!!!

Sorry, I disagree. 

You only charge the cap up to peak if the load is not there.
With a load, the cap cannot stay at peak.  What you are implying
is that you somehow get double the energy from the wall while
drawing the same current.

On the other hand, many thermostats are rated AC only, and lack
the spacing to break a capacitive DC load. 

Maybe what he really wants to do is make a blanket with many
feet of embedded plastic tubing, and run warm water thru it.
Use a small pump and external heater for the water.

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