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

• Current Assignee: John W. Bullock, Lawrence T. Miranda
• Original Assignee: John W. Bullock, Lawrence T. Miranda
• Inventors: Bullock, John W., Miranda, Lawrence T.
• Primary Examiner(s): Dixon, Harold A.
• Application Number:
  US06/221,085
• Time in Patent Office: 841 Days
• Field of Search: 331/65, 315/362, 315/76, 315/150, 361/181, 340/552
• US Class Current: 315/362
• CPC Class Codes: H03K 17/951 Measures for supplying operating voltage to the detector circuit
• CPC Class Codes: H03K 17/9547 with variable amplitude

Abstract

A proximity switch or detector is disclosed herein having an oscillator circuit for establishing a radio frequency field about an antenna so that the presence of an object or agent in close proximity to the antenna causes the oscillator to become loaded and to cease oscillations. A voltage comparator senses a change of voltage from the oscillator and triggers a bistable circuit. A power-up or setting circuit primes the bistable circuit to be responsive to the trigger signal from the voltage comparator which, in turn, actuates an output driver circuit incorporating a light emitting diode network operably coupled to a load plug interconnecting with a suitable electrical appliance intended to be actuated by the presence of the object or agent.

Claims

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.