DC touch control switch circuit

• US 4,758,735 A
• Filed: 04/15/1987
• Issued: 07/19/1988
• Est. Priority Date: 09/29/1986
• Status: Expired due to Term

• Current Assignee: Nartron Corporation
• Original Assignee: Nartron Corporation
• Inventors: Ingraham, Ronald D.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Logan, Sharon D.
• Application Number:
  US07/038,832
• Time in Patent Office: 461 Days
• Field of Search: 307/116, 307/125, 307/252 B, 307/308, 315/34, 315/74, 315/208, 315/246, 315/362, 318/345, 318/446, 323/19, 323/24, 328/5
• US Class Current: 307/116
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

A switching circuit includes a source of direct current for operating an oscillator which in turn applies a signal to a detector circuit including a touch plate. The detector includes a voltage dividing capacitive system or, in one embodiment, a phase detector circuit. In either embodiments, the output signal from the phase detector circuit or the voltage divider provides a control signal which can be used for actuating a solid-state switch such as a transistor or the like for providing control functions.

Claims

1. A direct current powered touch controlled switching circuit comprising:

a source of direct current power;

an oscillator coupled to said source for providing periodic output signals therefrom;

a series voltage divider circuit coupled to said oscillator for receiving said periodic output signals therefrom, said voltage dividing circuit including at least one capacitor and an input touch terminal for coupling a person'"'"'s body capacitance in series with said at least one capacitor such that the voltage at the junction of said at least one capacitor and said touch terminal will vary upon a person touching said touch terminal; and

a control circuit coupled to the junction of said at least one capacitor and said touch terminal and responsive to a change in voltage thereat for providing a control output signal in response to the touching of said touch terminal.

2. A circuit as defined in claim 1 wherein said control circuit includes a pulse stretcher circuit coupled to the junction of said one capacitor and said touch terminal for providing output pulses having a duration longer than said periodic output signals of said oscillator.

3. A circuit as defined in claim 2 wherein said control circuit includes a Schmitt trigger circuit.

4. A direct current powered touch controlled switching circuit comprising:

a source of direct current power;

an oscillator coupled to said source and providing periodic output signals;

a comparator circuit including first and second input terminals each coupled to said oscillator; and

an input touch terminal for coupling a person'"'"'s body capacitance when touched to one of said input terminals of said comparator such that the periodic signal thereat will be varied when said touch terminal is touched wherein said comparator responds to the signal variation to provide an output control signal indicating the touching of said touch terminal.

5. A circuit as defined in claim 4 wherein said comparator comprises an exclusive OR gate.

6. A circuit as defined in claim 5 and further including a pulse stretcher circuit having an input coupled to the output of said OR gate and responsive to said output control signal for providing a predetermined logic output signal when said touch terminal is touched.

7. A circuit as defined in claim 6 and further including a switch circuit having a control input terminal coupled to the output of said pulse stretcher circuit and switch terminals coupling a load to a source of power.

8. A direct current powered touch controlled switching circuit comprising:

a source of direct current power;

an oscillator coupled to said source for providing periodic output signals therefrom; and

a detector circuit coupled to said oscillator for receiving said periodic output signals therefrom, said detector circuit including an input touch terminal said detector circuit responsive to signals from said oscillator circuit and the simultaneous presence of a person'"'"'s body capacitance coupled to said touch terminal when touched by a person to provide a control output signal in response to the touching of said touch terminal.

9. A circuit as defined in claim 8 wherein said detector circuit comprises a series voltage divider circuit including at least one capacitor coupled to said touch terminal for coupling a person'"'"'s body capacitance in series with said at least one capacitor, and a control circuit coupled to the junction of said at least one capacitor and said touch terminal and responsive to the change in voltage at said junction when said touch terminal is touched for providing a control output signal in response to the touching of said touch terminal.

10. A circuit as defined in claim 9 wherein said control circuit includes a pulse stretcher circuit coupled to the junction of said one capacitor and said touch terminal for providing output pulses having a duration longer than said periodic output signals of said oscillator.

11. A circuit as defined in claim 10 wherein said control circuit further includes a Schmitt trigger circuit coupled to said pulse stretcher circuit and responsive to output pulses therefrom to provide a predetermined logic output signal when said touch terminal is touched.

12. A circuit as defined in claim 9 wherein said detector circuit comprises a comparator circuit including first and second input terminals each coupled to said oscillator and one of said input terminals of said comparator coupled to said touch terminal such that the body capacitance when coupled to the touch terminal will effect a change in voltage at said one input terminal resulting in the generation of said control output signal by said comparator circuit.

13. A circuit as defined in claim 12 wherein said comparator comprises an exclusive OR gate.

14. A circuit as defined in claim 13 and further including a pulse stretcher circuit having an input coupled to the output of said OR gate for providing a predetermined logic output signal in response to the receipt of a control output signal from said OR gate.

15. A circuit as defined in claim 14 and further including a switch circuit having a control input terminal coupled to the output of said pulse stretcher circuit and switch terminals coupling a load to a source of power.