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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!js2j
From: js2j@mhuxt.UUCP (sonntag)
Newsgroups: net.analog
Subject: Re: AC current monitor
Message-ID: <704@mhuxt.UUCP>
Date: Fri, 22-Mar-85 15:35:11 EST
Article-I.D.: mhuxt.704
Posted: Fri Mar 22 15:35:11 1985
Date-Received: Sat, 23-Mar-85 03:29:09 EST
References: <5139@fortune.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 19

>      I have a tough question here.  I need a circuit to indicate
> the presence of a load on an AC line. Wait, it gets more difficult.
> The load can vary from 100 watts to 1000 watts, and the output 
> signal must be a TTL level.  Also, it cannot drop the 110 volt
> AC line by very much.  One more thing: the ground of whatever 
> circuit is used will be tied to the neutral line of the AC, so complete 
> isolation is not possible.

    How about wrapping a few turns around one of the AC power lines,
and connecting the ends to the coil of a low-voltage AC relay?  You
could pick up your TTL levels off of the contacts of the relay.
    I'm not sure how many turns you'd need, but I doubt if you'd need
more than 10-20 if your relay was reasonably wimpy.

    Well, you *did* ask for *simple* designs, didn't you?
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
    "War is peace."-the ministry of truth