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From: gcouger@olesun.okstate.edu (Gordon Couger)
Subject: Re: Need Inexpensive object direction sensor
Message-ID: <CuC3B3.5tL@osuunx.ucc.okstate.edu>
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Organization: Biosystems and Agricultural Engineering at Oklahoma State Univ.
References: <CuApJp.2Dz@electriciti.com> <32apqp$bno@falcon.ccs.uwo.ca>
Date: Wed, 10 Aug 1994 19:25:51 GMT
Lines: 33

In article <32apqp$bno@falcon.ccs.uwo.ca>,
Paul Picot <ppicot@irus.rri.uwo.ca> wrote:
>mlipsky@powergrid.electriciti.com (Mark Lipsky) writes:
>
>>I am building a project where I need to detect the presence and
>>position of a person standing in front of a sensor.  It does not need
>>to be accurate; I just want to know within say, 5 degrees, where the
>>person is standing in front of my device.  There will be no other
>>objects near the person and the person will be between 2 and 7 feet
>>away.
>
An inexpensive way would be to place 2 induction coils on either
side of the display. Run the output of the coils to a differencial 
amplifier and the output of the differencial amp would corrispond
to the relitive position of the person in front of the display.

It works because a person acts as an antenna for the stray electrical
noise. In the absense of someone in the inductor antenna aray the
stray nosie should be more or less constant on both antennas. When
some one comes into the antenna area they should disturb the balance
of the noise causing more noise in the antenna they are nearest to.
The signal from the antenns will need to be rectified and amplified
some where before getting to the defreenciator.

Good luck
Gordon

                             Gordon Couger                            
                             Biosystems & Agricultural Engineering              
                             Oklahoma State University                         
                             114 Ag Hall, Stillwater, OK  74074                 
 gcouger@olesun.agen.okstate.edu 405-744-9763 day 624-2855 evenings 
    I do not speak for my employer
