ULTRASONIC AND STRAIN DUAL MODE SENSOR FOR CONTACT SWITCH

• US 20170310321A1
• Filed: 06/30/2017
• Published: 10/26/2017
• Est. Priority Date: 03/05/2014
• Status: Active Grant

• Current Assignee: Measurement Specialties, Inc. (France) (TE Connectivity Limited)
• Original Assignee: Measurement Specialties, Inc. (France) (TE Connectivity Limited)
• Inventors: Toda, Minoru, Park, Kyung- Tae
• Granted Patent: US 10,158,361 B2
• Time in Patent Office: Days
• CPC Class Codes: H03K 17/964 Piezoelectric touch switches
• CPC Class Codes: H03K 2217/94026 Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input
• CPC Class Codes: H03K 2217/94036 Multiple detection, i.e. where different switching signals are generated after operation of the user is detected at different time instants at different locations during the actuation movement by two or more sensors of the same or different kinds
• CPC Class Codes: H03K 2217/96007 by reflection

Abstract

A device for detecting a touch at a surface of a substrate comprises a piezoelectric element positioned at a back surface of the substrate to be touched. A drive circuit is configured to apply a frequency modulated drive signal to the piezoelectric element to detect resonance at the substrate. A first detector arrangement coupled to the piezoelectric element is configured to generate a first output signal indicative of a sensed touch or no touch condition according to detected voltage changes and responsive to the frequency modulated drive signal applied to the piezoelectric element. A second detector arrangement coupled to the piezoelectric element is configured to generate a second output signal indicative of a sensed touch or no touch condition according to a sensed strain on said piezoelectric element. A decision circuit including a processor is configured to identify a touch condition or no touch condition at the surface of the substrate according to the first and second output signals.

Claims

1. A device for detecting a touch at a surface of a substrate, comprising:

a piezoelectric element positioned at a back surface of the substrate to be touched;

a drive circuit configured to apply a frequency modulated drive signal to the piezoelectric element to detect resonance at the substrate;

a first detector arrangement coupled to the piezoelectric element and configured to generate a first output signal indicative of a sensed touch or no touch condition according to detected voltage changes and responsive to the frequency modulated drive signal applied to the piezoelectric element;

a second detector arrangement coupled to the piezoelectric element and configured to generate a second output signal indicative of a sensed touch or no touch condition according to a sensed strain on said piezoelectric element; and

a decision circuit including a processor configured to identify a touch condition or no touch condition at the surface of the substrate according to the first and second output signals.

2. A method comprising:

applying a frequency modulated drive signal to a piezoelectric element positioned at a back surface of a substrate to be touched to detect resonance at the substrate;

detecting voltage changes of the piezoelectric element when said frequency modulated drive signal is applied and generating a first output signal indicative of a sensed touch or no touch condition according to said detected voltage changes;

detecting a voltage signal based on a sensed strain on said piezoelectric element and generating a second output signal indicative of a sensed touch or no touch condition in response thereto; and

determining a touch condition or no touch condition at the surface of the substrate according to the first and second output signals.