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From: "petrus bitbyter"
Subject: Re: Sensing mains current
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Sun, 01 Dec 2002 13:36:31 GMT
NNTP-Posting-Date: Sun, 01 Dec 2002 14:36:31 MET
Organization: chello broadband
Reading your post I got the impression you'r winding the mains cable as a
whole in your air coil and around your ferrite. Current in both wires has
the same level but opposite directions so the magnetic effect is almost
null. So you have to split your mains cable and wind only one of the wires
or - more effective - wind them in opposite direction relative to each
other. Most simple form I ever saw was a pot core which had two coil
compartments. One was filled with a lot of windings to provide the ouput
voltage, the other contained just the split up main cable. The wires went
along opposite sides of the centre, giving effectively two half windings in
"ted" schreef in bericht
> Any ideas for sensing the current taken by a mains appliance (mainly
> ligthing equipment 50-300W each) in the cheapest possible way?
> There may be 50-60 of these connected at the same time, so a very-very
> cheap solution is paramount.
> It must be non intrusive (no connections with the mains circuit, i.e.
> fully isolated).
> It should not add any resistance or components in series with the
> Some form of magnetic coupling is obviously the way to do it, but I
> can't figure out how to do it in practice, or what cheap components to
> Trying to make an "air" transformer, by winding the mains line cable
> with a bit of extra secondary couple of turns connected to a
> voltmmeter only produces a few microvolts of 50Hz signal (and quite a
> lot of HF noise as well). Not very practical.
> Also tried wrapping around a ferrite with similar results, obviously I
> am not using the rignt kind of magnetic material. but I wouldn't know
> how to choose one anyway. or where to find cheap ones..
> The system does not need to be accurate, more like an on/off detector,
> say detect from 1/5Amp in 1/10 Amp steps (or even less accurate).
> Any ideas anybody?
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