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Proximity switch

  • US 4,380,721 A
  • Filed: 12/29/1980
  • Issued: 04/19/1983
  • Est. Priority Date: 12/29/1980
  • Status: Expired due to Fees
First Claim
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1. A proximity switch for sensing the presence of an object or agent comprising the combination of:

  • an antenna;

    an oscillator coupled to said antenna and adapted to modify oscillations in response to the presence of an object or agent in close proximity to said antenna;

    a voltage comparator operably coupled to said oscillator for initiating a trigger signal in response to modification of oscillations from said oscillator;

    a voltage setting circuit producing a threshold voltage level;

    a bistable circuit operatively coupled to said voltage setting circuit and responsive to said trigger signal in the presence of said threshold voltage level to provide an output voltage level;

    a load operably connected to said bistable circuit for receiving said output voltage level and being actuated thereby;

    a feedback circuit connected between said antenna and said oscillator;

    an amplifier circuit interconnecting said oscillator circuit with said feedback circuit for rectifying its output;

    an output driver network including a light emitting diode circuit operably coupled between said load and said bistable circuit;

    said voltage setting circuit is a first flip-flop circuit and said bistable circuit is a gate circuit having a second flip-flop circuit;

    an inductive load compensator network coupled to said load;

    said voltage comparator is coupled to said oscillator circuit via said amplifier circuit for sensing a dip in voltage therefrom resulting from the inference with an electromagnetic field surrounding said antenna; and

    said electromagnetic field is established by said oscillator.

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