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From: firstname.lastname@example.org (Glenn Gundlach)
Subject: Re: Detecting current drawn through wire...
Date: 2 Oct 2002 22:03:21 -0700
NNTP-Posting-Date: 3 Oct 2002 05:03:21 GMT
"Dave M" wrote in message news:<4gMm9.81280$jG2.email@example.com>...
> It would probably be easier to sense the application of mains voltage to the
> security light rather than the current. Just hook up to the output of the
> relay that energises the light, send it through a voltage divider, rectify
> it and then into a transistor (or other technology) switch.
> Dave M firstname.lastname@example.org
> Remove the xx for my correct email address
True, but what if the bulb is burned out? Voltage is still there but
current is not. There are commercial current transformers for just
this task. Heck, a 2.5 volt filament transformer with the secondary in
series with the load will give quite satisfactory output from its
'primary' to drive a solid state relay. I use a gadget like this to
turn on the sound system for the TV by detecting the current drawn by
> "Mr_Ree" wrote in message
> > I have installed a PIR security light (240vac - UK) and want to add an
> > internal sounder. It would be very difficult to add any further wiring to
> > the light, so I need to detect the vast increase in current drawn through
> > the Live feed or Neutral return. I was thinking along the lines of
> > a coil of wire around the cable and detecting the increase in magnetic
> > field.
> > I'm quite versed in electronics, but I'm not getting the time to sit &
> > design , so looking for a jump start. Sounder driving & timing - no
> > just the detection bit.
> > Any ideas?
> > Ta!
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