Piezo key sensing circuit and method for testing the piezo key sensing circuit

• US 9,804,214 B2
• Filed: 04/30/2015
• Issued: 10/31/2017
• Est. Priority Date: 10/31/2012
• Status: Expired due to Fees

• Current Assignee: Diehl AKO Stiftung & Company KG
• Original Assignee: Diehl AKO Stiftung & Company KG
• Inventors: Dmytriw, Tony
• Primary Examiner(s): Lindsay, Jr., Walter L
• Assistant Examiner(s): Gonzalez, Milton
• Application Number:
  US14/700,359
• Publication Number:
  US 20150260770A1
• Time in Patent Office: 915 Days
• Field of Search: 324658, 324519, 324677, 324678, 324727
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: H03K 17/964 Piezoelectric touch switches

Abstract

A method tests a piezo key sensing circuit having a piezo element and verifies that it is properly functioning. A capacitance of the piezo element is discharged. Then the capacitance of the piezo element is charged during a predetermined time period. An output signal of the piezo element is measured during the predetermined time period resulting in a measured output signal. An operating condition of the piezo key sensing circuit is determined based on the measured output signal.

Claims

1. A method for testing a functionality of a piezo key sensing circuit, which comprises the steps of:

discharging a capacitance via a first terminal of a piezo element;

charging the capacitance via the first terminal of the piezo element during a predetermined time period, the charging of the capacitance of the piezo element being initiated by applying a high impedance state to the first terminal of the piezo element;

measuring an output signal of the piezo element during the predetermined time period resulting in a measured output signal; and

determining an operating condition of the piezo key sensing circuit based on the measured output signal.

2. The method according to claim 1, which further comprises discharging the capacitance of the piezo element by applying a low voltage source to the first terminal of the piezo element.

3. The method according to claim 1, which further comprises connecting the first terminal of the piezo element to a digital I/O pin of a microprocessor and toggling a state of the digital I/O pin between a low voltage state and a high impedance state.

4. The method according to claim 3, which further comprises amplifying the output signal via an amplifier circuit before the output signal is measured, resulting in an amplified output signal.

5. The method according to claim 4, which further comprises forwarding the amplified output signal to a multiplexer having an output connected to an analog-to-digital converter pin of the microprocessor.

6. The method according to claim 1, which further comprises determining from the measured output signal that the piezo key sensing circuit is exhibiting a state selected from the group consisting of a short circuit state, an open state and a properly functioning state.

7. The method according to claim 1, which further comprises providing a microcontroller for sensing the measured output signal for determining the operational condition of the piezo key sensing circuit.

8. A method for testing a piezo key sensing circuit, which comprises the steps of:

charging a capacitance of a piezo element via a first terminal;

discharging the capacitance of the piezo element at the first terminal during a predetermined time period, the discharging of the capacitance of the piezo element being initiated by applying a high impedance state to the first terminal of the piezo element;

measuring an output signal of the piezo element during the predetermined time period resulting in a measured output signal; and

determining an operating condition of the piezo key sensing circuit based on the measured output signal.

9. The method according to claim 8, which further comprises charging the capacitance of the piezo element by applying a high voltage source to the first terminal of the piezo element.

10. The method according to claim 8, which further comprises connecting the piezo element to a digital I/O pin of a microprocessor and toggling a state of the digital I/O pin between a high voltage state and a high impedance state.

11. The method according to claim 10, which further comprises amplifying the output signal via an amplifier circuit before the output signal is measured, resulting in an amplified output signal.

12. The method according to claim 11, which further comprises forwarding the amplified output signal to a multiplexer having an output connected to an analog-to-digital converter pin of the microprocessor.

13. The method according to claim 8, which further comprises determining from the measured output signal that the piezo key sensing circuit is exhibiting a state selected from the group consisting of a short circuit state, an open state, and a properly functioning state.

14. The method according to claim 8, which further comprises providing a microcontroller for sensing the measured output signal and determining the operational condition of the piezo key sensing circuit.

15. A piezo key sensing circuit, comprising:

a microcontroller having a digital I/O pin and an analog-to-digital converter (ADC) pin;

an amplifier circuit having an output coupled to said ADC pin;

a piezo element connected directly to said digital I/O pin and to said amplifier circuit;

said microcontroller programmed to;

discharge a capacitance of said piezo element via said digital I/O pin;

charge the capacitance of said piezo element during a predetermined time period via said digital I/O pin, a charging of the capacitance of said piezo element being initiated by applying a high impedance state to said digital I/O pin;

measure an output signal of said piezo element during the predetermined time period resulting in a measured output signal via said ADC pin; and

determine an operating condition of the piezo key sensing circuit based on the measured output signal.

16. The piezo key sensing circuit according to claim 15, wherein said microcontroller is programmed to toggle a state of said digital I/O pin between a low voltage state and a high impedance state.

17. The piezo key sensing circuit according to claim 15, wherein said microcontroller is programmed to determine from the measured output signal that the piezo key sensing circuit is exhibiting a state selected from the group consisting of a short circuit state, an open state, and a properly functioning state.

18. A piezo key sensing circuit, comprising:

a microcontroller having a digital I/O pin and an analog-to-digital converting (ADC) pin;

an amplifier circuit having an output coupled to said ADC pin;

a piezo element connected directly to said digital I/O pin and to said amplifier circuit;

said microcontroller programmed to;

charge a capacitance of said piezo element;

discharge the capacitance of said piezo element during a predetermined time period, a discharging of the capacitance of said piezo element being initiated by applying a high impedance state to said digital I/O pin;

measure an output signal of said piezo element during the predetermined time period resulting in a measured output signal; and

determine an operating condition of the piezo key sensing circuit based on the measured output signal.

19. The piezo key sensing circuit according to claim 18, wherein said microcontroller is programmed to toggle a state of said digital I/O pin between a high voltage state and a high impedance state.

20. The piezo key sensing circuit according to claim 18, wherein said microcontroller is programmed to determine from the measured output signal that the piezo key sensing circuit is exhibiting a state selected from the group consisting of a short circuit state, an open state, and a properly functioning state.