Capacitive sensor

• US 7,515,140 B2
• Filed: 02/11/2005
• Issued: 04/07/2009
• Est. Priority Date: 02/13/2004
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Philipp, Harald
• Primary Examiner(s): Awad; Amr
• Assistant Examiner(s): PELLIGRINO, JEFFREY S
• Application Number:
  US11/056,781
• Publication Number:
  US 20050179673A1
• Time in Patent Office: 1,516 Days
• Field of Search: 345/173, 261/288, 211/120, 200/511, 200/600, 200/516, 200/532, 178/18.06
• US Class Current: 345/173
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2217/96023 Details of electro-mechanic connections between different elements, e.g.: sensing plate and integrated circuit containing electronics
• CPC Class Codes: H03K 2217/960755 Constructional details of capacitive touch and proximity switches
• CPC Class Codes: H03K 2217/96076 with spring electrode
• CPC Class Codes: H03K 2217/960785 with illumination

Abstract

A capacitive sensor for detecting the presence of an object adjacent a panel is described. The sensor comprises an electrically conducting sensor element coupled to a capacitance measurement circuit. In use, the capacitive sensor is mounted with the sensor element adjacent an underside of the panel. The sensor element includes a flared portion which deforms when pressed against the panel to provide an extended contact area between the sensor element and the panel. When a user touches an upper side of the panel above the extended contact area, the capacitance of the sensor element is modified. This is detected by the measurement circuit and identifies a touch.

Claims

1. A capacitive sensor apparatus comprising:

a measurement circuit for measuring a capacitance of a conductive area;

a non-conductive touch panel having a first side for receiving a user'"'"'s touch and a second side facing a support fixedly arranged at a selected distance from the touch panel so that the touch panel and the support are fixed relative to one another during operation; and

a metal sensor element comprising a spring compressed between the support and the second side of the touch panel, the spring having an uncompressed length greater than the selected distance, the spring having a flared portion that is flattened under compression to form the conductive area on the second side of the touch panel, the spring further comprising a base portion that is stronger than the flared portion and that is connected to the measurement circuit at the support.

2. The apparatus of claim 1, wherein the spring is formed of helical coils.

3. The apparatus of claim 1, wherein the base portion of the spring comprises a tubular portion and wherein the flared portion of the spring comprises a plurality of flexible leaves extending away from an axis of the tubular portion.

4. The apparatus of claim 1, wherein the support is a circuit board.

5. The apparatus of claim 4, wherein the circuit board carries at least a part of the measurement circuit.

6. A method of making a capacitive sensor for sensing the presence of an object adjacent a sensitive area of a non-conducting panel, the method comprising the steps of:

providing the panel;

providing a metal sensor element having a selected free length, the sensor element comprising a stronger base portion at one end thereof and a weaker flared portion at a second end thereof;

connecting, at a support member, the base portion of the sensor element to a capacitive measurement circuit operable to sense the presence of the object;

moving the support member toward the panel until the support member and the panel are separated by a distance less than the free length, so as to compress the flared portion of the sensor element against the panel and thereby define the sensitive area; and

fixing the support member relative to the touch panel at the distance less than the free length.