Acoustic wave touch detection circuit and method
AssigneeIllinois Tool Works Inc.
InventorsTerence J. Knowles, Wayne J. Wehrer, Chris Kalmus, Charles F. Bremigan, III
Life of this patent
Estimating the term…
Abstract
A circuit for an acoustic wave switch or sensor having a resonant acoustic wave cavity detects a touch or sensed event using a time domain approach. The circuit includes a controller that drives an acoustic wave transducer to generate a resonant acoustic wave in the acoustic wave cavity during a first portion of a sampling cycle. In a second portion of the sampling cycle, the controller monitors the time that it takes for the acoustic wave signal from the transducer to decay to a predetermined level. Based on the decay time, the controller detects a sensed event, such as a touch on the acoustic wave switch/sensor.
Claims20
A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
- determining a value representing the time that the acoustic wave in the touch responsive area decays to a predetermined level in the absence of a touch to provide a reference;
- generating a subsequent acoustic wave in the touch responsive area;
- determining a subsequent value representing the time that the subsequent acoustic wave decays to the predetermined level;
- comparing the subsequent value to the reference to determine whether the subsequent value represents a touch on the touch responsive area.
A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
- determining a value representing the time that the acoustic wave in the touch responsive area decays to a predetermined level in the absence of a touch to provide a reference;
- generating a subsequent acoustic wave in the touch responsive area of the device;
- determining a subsequent value representing the time that the subsequent acoustic wave decays to the predetermined level;
- comparing the subsequent value to the reference to determine whether the subsequent value represents a touch on the touch responsive area;
- and
- updating the reference based on the comparison of the subsequent value to the reference.
A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
- providing a signal representing the acoustic wave in the touch responsive area, the acoustic wave signal, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a period of time and the acoustic wave signal, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a shorter period of time;
- determining a value representing the period of time that the acoustic wave signal decays to the predetermined value;
- and comparing the determined value to a reference to detect a touch on the touch responsive area.
A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
- providing a signal representing the acoustic wave in the touch responsive area, the acoustic wave signal, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a number of cycles of the signal and the acoustic wave signal, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a smaller number of cycles;
- counting the number of cycles of the signal having an amplitude above the predetermined level to provide a count;
- and comparing the count to a reference to detect a touch on the touch responsive area.
A method of detecting a touch on a touch responsive area comprising:
- generating an acoustic wave in the touch responsive area;
- providing a signal representing the acoustic wave in the touch responsive area in a sampling cycle, the acoustic wave signal for a sampling cycle, in the absence of a touch on the touch responsive area, decaying to a predetermined level over a period of time and the acoustic wave signal for a sampling cycle, in the presence of a touch on the touch responsive area, decaying to the predetermined level over a shorter period of time;
- comparing the acoustic wave signal for a sampling cycle to the predetermined level to generate a pulse when the amplitude of the signal is greater than the predetermined level;
- counting a number of the pulses generated to provide a count for a sampling cycle;
- and
- comparing the count for a sampling cycle to a reference to detect a touch.
Dependencies are inferred from the claim text.