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Path: utzoo!watmath!watnot!watvlsi!ksbszabo
From: ksbszabo@watvlsi.UUCP (Kevin Szabo)
Newsgroups: net.analog
Subject: Re: Car Detectors
Message-ID: <2982@watvlsi.UUCP>
Date: Sun, 27-Apr-86 12:54:18 EDT
Article-I.D.: watvlsi.2982
Posted: Sun Apr 27 12:54:18 1986
Date-Received: Mon, 28-Apr-86 04:47:42 EDT
References: <2974@watvlsi.UUCP> <4839@topaz.RUTGERS.EDU>
Reply-To: ksbszabo@watvlsi.UUCP (Kevin Szabo)
Organization: VLSI Group, Univeristy of Waterloo
Lines: 14
Summary: Buried wire is an inductor.  Inducatance changes when car present


To the best of my knowledge the buried wire is actually a single or multi
turn inductor.  When the car is present the core changes from air/pavement
to air+pavement+ferrous material.

The detector would look like this:

	Buried wire coil ====== LC oscillator ===== Frequency detector.

You can use a NE567 phase locked loop for a frequency detector.

	Kevin Szabo'
-- 
Kevin Szabo'  ihnp4!watmath!watvlsi!ksbszabo  (VLSI Group,U of Waterloo,Ont,Can)