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From: "The Al Bundy"
Subject: Re: Detecting current drawn through wire...
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Wed, 2 Oct 2002 23:39:17 +0200
NNTP-Posting-Date: Wed, 02 Oct 2002 23:28:14 MEST
Organization: @Home Network
"Mr_Ree" schreef in bericht
: 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
: 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?
Just like you said, detecting the magnetic field by some coil around the
You can use some small round ferrite core where you wind some copper wire
around. Then the wire which you want to detect straight through the hole (or
also turning around the core, to get more voltage from the coil)
Then maybe you can simply rectify the voltage that you get from the small
coil, and detect the DC level with some comparator (opamp). You can set then
the tirgger level on one input of the opamp.
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