This example will explain how to use a piezo as a knock sensor. Knock on it directly, or tape it to a surface and knock on the surface.

Materials

Instructions

1. Attach the shield onto the top of the Arduino board.
2. Connect a 1M ohm resistor across the breadboard gap.
3. Connect one leg of the resistor to A0 and the other to GND using jumper wires.
4. Connect the piezo across the breadboard gap.
5. Connect one leg of the piezo to A0 and the other to GND in parallel with the resistor using jumper wires.
6. Connect the board to the computer and upload example PiezoKnockSensor.

Code

Find the code in Example>EducationShield>Help>PiezoKnockSensor

Commands

• PiezoKnockSensor(analogPin) – creates a PiezoKnockSensor object.
  • Parameters

    • (int) analogPin – the analog pin to which the piezo is connected.

• config(threshold, debounceTime) – configures the PiezoKnockSensor.
  • Parameters
    • (int) threshold – defines how hard you need to knock, and therefore the sensitivity of the sensor. Use test() to check the values returned when knocked.

    • (int) debounceTime – prevents the sensor from returning several hits from one knock, but also limits how rapid you can knock, in milliseconds.

• knocked(timeout) – checks if the sensor is knocked.
  • Parameters

    • (int) timeout – milliseconds within which the sensor should be knocked. Returns 1 if knocked within time, otherwise 0. If not used, the program pauses until knocked.

• test() – prints the sensor value to serial monitor.

Troubleshooting

• Make sure everything is connected correctly.
• Make sure you have connected the piezo to the same pin as you have stated in your code.
• If you are using piezo for both Melody and knock sensor, make sure you distinguish between the two.