Arduino tutorial

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Arduino Tutorial

This tutorial shows you how to use a Piezo element to detect vibration, in this case, a

knock on a door, table, or other solid surface.

A piezo is an electronic device that generates a voltage when it's physically deformed by

a vibration, sound wave, or mechanical strain. Similarly, when you put a voltage across a

piezo, it vibrates and creates a tone. Piezos can be used both to play tones and to detect

tones.

The sketch reads the piezos output using the analogRead() command, encoding the

voltage range from 0 to 5 volts to a numerical range from 0 to 1023 in a process referred

to as analog-to-digital conversion, or ADC.

If the sensors output is stronger than a certain threshold, your Arduino will send the string

"Knock!" to the computer over the serial port.

Open the serial monitor to see this text.

Hardware Required

•

Arduino Board

•

(1) Piezo electric disc

•

(1) Megohm resistor

•

solid surface

Circuit

Piezos are polarized, meaning that voltage passes through them (or out of them) in a

specific direction. Connect the black wire (the lower voltage) to ground and the red wire

(the higher voltage) to analog pin 0. Additionally, connect a 1-megohm resistor in

parallel to the Piezo element to limit the voltage and current produced by the piezo and to

protect the analog input.

It is possible to acquire piezo elements without a plastic housing. These will look like a

metallic disc, and are easier to use as input sensors. PIezo sensors work best when firmly

pressed against, taped, or glued their sensing surface.

click the image to enlarge

Summary of content (5 pages)

PAGE 1
Arduino Tutorial This tutorial shows you how to use a Piezo element to detect vibration, in this case, a knock on a door, table, or other solid surface. A piezo is an electronic device that generates a voltage when it's physically deformed by a vibration, sound wave, or mechanical strain. Similarly, when you put a voltage across a piezo, it vibrates and creates a tone. Piezos can be used both to play tones and to detect tones.
PAGE 2
image developed using Fritzing.
PAGE 3
A Piezo to attached to analog pin 0 with a 1-Megohm resistor Code In the code below, the incoming piezo data is compared to a threshold value set by the user. Try raising or lowering this value to increase your sensor's overall sensitivity. /* Knock Sensor This sketch reads a piezo element to detect a knocking sound. It reads an analog pin and compares the result to a set threshold. If the result is greater than the threshold, it writes "knock" to the serial port, and toggles the LED on pin 13.
PAGE 4
* - connection of the piezo attached to ground * 1-megohm resistor attached from analog in 0 to ground http://www.arduino.cc/en/Tutorial/Knock created 25 Mar 2007 by David Cuartielles modified 4 Sep 2010 by Tom Igoe This example code is in the public domain.
PAGE 5
See Also: • • • • • • • • • • pinMode() analogRead() if() serial.begin() serial.print() AnalogInput - Use a potentiometer to control the blinking of an LED. AnalogInOutSerial - read an analog input, map its values, and then use that information to dim or brighten an LED. Memsic2125 - read a two axis accelerometer. ADXL3xx - read a ADXL3xx accelerometer. Ping - detect objects with an ultrasonic range finder.