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From: email@example.com (ted)
Subject: Sensing mains current
Date: 30 Nov 2002 07:20:56 -0800
NNTP-Posting-Date: 30 Nov 2002 15:20:56 GMT
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.
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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