Continuous capacitive slider controller for a smooth surfaced cooktop

• US 20060016800A1
• Filed: 07/20/2004
• Published: 01/26/2006
• Est. Priority Date: 07/20/2004
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Paradiso, Joseph A., Bourque, Lance L.
• Granted Patent: US 8,017,890 B2
• Time in Patent Office: Days
• US Class Current: 219/497
• CPC Class Codes: H05B 2213/05 Heating plates with pan detection means
• CPC Class Codes: H05B 3/746 Protection, e.g. overheat cutoff, hot plate indicator

Abstract

A touch responsive capacitive control for a smooth surfaced ceramic cooktop provides a continuously variable control voltage which indicates the last touched position on an elongated control surface. An A.C. potential is applied between a transmitter plate and a pair of receiver plates all of which are positioned below the surface of the cooktop. The relative area of overlap between the touching finger and the two receiver plates varies along the length of the control surface, and the resulting change in the relative currents flowing to the two receiver plates is sensed to provide a position indication used to control the cooktop.

Claims

1. A capacitive sensor for indicating the position of a movable conductive object comprising, in combination,

a source of alternative current electrical energy,

at least one conductive transmitter plate connected to said source,

first and second elongated coplanar receiver plates position adjacent to one another, said first and second receiver plates each being capacitively coupled to said transmitter plate to receive electrical energy from said source, said first and second receiver plates defining first and second areas of overlap respectively with respect to a movable conductive object positioned adjacent to said plates, said first area of overlap increasing and said second area of overlap decreasing as said movable object moves in a direction parallel to the long dimension of said elongated receiver plates, and

a control circuit connected to said receiver plates for producing a variable position indication signal in response to changes in the amount of electrical energy received by said receiver plates from said source.

2. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 1 wherein said at least one conductive transmitter plate comprises two elongated transmitter plates, said first and second receiver plates being positioned between said two elongated transmitter plates.

3. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 1 wherein said first and second receiver plates are each shaped to define alternating tongues and spaces and wherein the tongues defined by said first receiver plate are positioned in the spaces defined by said second receiver plate to form an interleaved array of tongues.

4. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 3 wherein said at least one conductive transmitter plate comprises two elongated transmitter plates, said first and second receiver plates being positioned between said transmitter plates.

5. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 3 wherein:

the area of the tongues defined by said first receiver plate increases and the area of said spaces defined by said first receiver plate decreases in said direction parallel to the long dimension of said receiver plates, and wherein

the area of the tongues defined by said second receiver plate decreases and the area of said spaced defined by said second receiver plates increases in said direction parallel to the long dimension of said receiver plates.

6. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 5 wherein said at least one conductive transmitter plate comprises two elongated transmitter plates, said first and second receiver plates being positioned between said two transmitter plates.

7. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 3 further including conductive shielding positioned to overlay portions of said first and second receiver plates exclusive of said interleaved array of tongues.

8. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 3 further comprising a linear array of lights positioned adjacent to said receiver plates and means for illuminating a variable number of consecutive ones of said lights to indicate the value of said position indication signal.

9. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 1 further including conductive shielding positioned to overlay portions of said first and second receiver plates exclusive of said first and second areas of overlap.

10. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 1 further comprising a visible display for indicating the value of said variable position signal.

11. A capacitive sensor for indicating the position of a movable conductive object as set forth in claim 10 wherein said visible display comprises an linear array of lights and means for illuminating a variable number of consecutive ones of said lights to indicate the value of said position indication signal.

12. A touch controlled cooktop heating element comprising:

a smooth cooktop surface,

an electrically operated heating element positioned below said cooktop surface,

a position sensor positioned below and adjacent to said cooktop surface for detecting the position of a human finger relative to an elongated control area on said cooktop surface, said position sensor producing a continuously variable signal value as said human finger is moved across said control area, and

a signal processor connected to receive and process said continuously variable signal to produce and store a control value indicating the position of said human finger when said human finger last touched said control area, and

means responsive to said control value for controlling the energization of said heating element.

13. A touch controlled cooktop heating element as set forth in claim 12 further comprising a visible indicia on said cooktop surface positioned to visually indicate the position of said control area.

14. A touch controlled cooktop heating element as set forth in claim 12 wherein said position sensor comprises a conductive transmitter plate connected to a source of an alternating current electrical potential and a pair of side-by-side conductive receiver plates, each of which is positioned in said control area adjacent to and is capacitively coupled to said transmitter plate, said receiver plates being shaped such that, as said human finger is moved across said control area said finger overlaps an increasing area of one of said plates and overlaps a decreasing area of the other of said plates, and a control circuit connected to at least one of said plates for producing said continuously variable control signal value.

15. A touch controlled cooktop heating element as set forth in claim 14 wherein said control circuit includes a microprocessor and an analog-to-digital converter for converting an analog signal value from at least one of said receiver plates into a digital signal value processed by said microprocessor to produce and store said control value.

16. A touch controlled cooktop heating element as set forth in claim 12 further comprising an linear array of lights and means for illuminating a variable number of consecutive ones of said lights to indicate the value of said control value.

17. A touch controlled cooktop heating element as set forth in claim 16 wherein said array of lights is positioned adjacent to said control area.

18. Touch responsive apparatus for controlling a heating element positioned beneath a smooth surfaced ceramic cooktop, said apparatus comprising, in combination,

a source of alternative current electrical energy,

at least one conductive transmitter plate connected to said source and affixed to said ceramic cooktop

first and second elongated coplanar receiver plates affixed to said ceramic cooktop and position adjacent to one another, said first and second receiver plates each being capacitively coupled to said transmitter plate to receive electrical energy from said source, said first and second receiver plates defining first and second areas of overlap respectively with respect to a human finger positioned adjacent to said first and second receiver plates, said first area of overlap increasing and said second area of overlap decreasing as human finger moves in a direction parallel to the long dimension of said elongated receiver plates,

a first control circuit connected to said receiver plates for producing a variable position indication signal in response to changes in the amount of electrical energy received by said receiver plates from said source, and

a second control circuit for producing a control signal indicative of the position of said human finger when it was last positioned adjacent to said first and second receiver plates.

19. Touch responsive apparatus as set forth in claim 18 wherein said ceramic cooktop is translucent and further comprising a linear array of lights positioned beneath said cooktop adjacent to said receiver plates and means for illuminating a variable number of consecutive ones of said lights to indicate the value of said control signal.

20. Touch responsive apparatus as set forth in claim 19 wherein said first and second receiver plates are each shaped to define alternating tongues and spaces and wherein the tongues defined by said first receiver plate are positioned in the spaces defined by said second receiver plate to form an interleaved array of tongues.