S3135598 Sensor Report
From Physical Programming
James Wynn - Piezoelectric Tranducer
How the device works
A transducer is a device which converts energy from one form to another. Piezoelectric material is most commonly used as a basic component of transducers. When a mechanical force is applied between the faces of the piezo electric crystal a voltage is created. Conversly the crystal deforms when a voltage is applied between it’s faces. When the pad of the sensor is touched, the crystal inside twists and creates a voltage.
This means that the piezoelectric element can act as both a sensing and a transmitting element.
Common types of crystal are potassium sodium tartrate and quartz.
What the device is typically used for
Piezoelectric transducers are generally used to convert electrical signals into sound waves in the form of a buzzer or to convert mechanical vibrations into electrical signals. Piezoelectric tranducers are commonly used in microphones and specifically contact microphones. Contact microphones are a form of microphone used to detect audio vibrations from solid objects. Contact microphones are used in musical instruments such as cello, violin, double bass and guitar. When used with musical instruments they are called piezoelectric pickups. Piezoelectric pickups are used compared to magnetic pickups because they have a much wider frequency range.
Image from (http://en.wikipedia.org/wiki/Pickup_(music_technology))
Piezoelectric transducers are also used as beepers in watches and are sometimes used in cheaper speakers as tweeters.
Underwater applications such as sonar reciverers and transmitters use them as both an input and an output device.
Piezoelectric tranducers are also used in pressure sensors. They can be used to measure mechanical pressure as well as barometric pressure.
How it can be interfaced with the Arduino Micro-controller
(Referenced from http://www.arduino.cc/en/Tutorial/Knock “Arduino Knock”)
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.
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.
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.
Image from (http://www.arduino.cc/en/Tutorial/Knock)
Examples of interactive projects using this sensor technology
Arduino - making a basic drum machine http://luckylarry.co.uk/arduino-projects/arduino-making-a-basic-drum-machine/
References
DIY Contact Microphone & Slinky Lasers, http://spreggo.com/blog/?p=20
Microphone, Wikipedia, http://en.wikipedia.org/wiki/Microphone#Piezoelectric_microphone
Pickup, Wikipedia, http://en.wikipedia.org/wiki/Pick_up_(music_technology)#Piezoelectric_pickups
Loudspeaker, Wikipedia, http://en.wikipedia.org/wiki/Loudspeaker#Piezoelectric_speakers
Contact Microphone, Wikipedia, http://en.wikipedia.org/wiki/Contact_microphone
Pressure Sensor, Wikipedia, http://en.wikipedia.org/wiki/Pressure_sensor
