ULTRASONIC TRANSMITTER/RECIEVER USING PIEZOELECTRIC SENSOR

A presentation by Subham GoyalEngineering 40 AEIEHeritage Institute Of TechnologyKolkata 700107

Direct Piezoelectric Effect

Piezoelectric Material will generate electric potential when subjected to some kind of mechanical stress.

Piezoelectric sensor? A piezoelectric sensor is a

device that uses the piezoelectric effect, to measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. The prefix piezo- is Greek for 'press' or 'squeeze'.

Ultrasonic transmitter/reciever

The Ultrasonic Transmitter and Receiver circuit comprises of transmitter and receiver, that operates at the same frequency.

When something moves in the area covered the fine balance of the circuit is troubled and the alarm is activated.

The ultrasonic transmitter is designed with 2-NAND gates wired as inverters and they make a multivibrator the o/p of that drives the transducer. 

Developing theories…

Pierre and Jacques Curie predicted and demonstrated the piezoelectric effect using tinfoil, glue, wire, magnets, and a jeweler’s saw.

They showed that crystals of tourmaline, quartz, topaz, cane sugar, and Rochelle salt generate electrical polarization from mechanical stress.

The converse effect was mathematically derived by Gabriel Lippman in 1881 using fundamental thermodynamic principles and was later experimentally confirmed by the Curies.

Sonic and Ultrasonic Applications Sonar with Ultrasonic time-domain reflectometers Materials testing to detect flaws inside cast metals and stone objects as well as measure elasticity or viscosity in gases and liquids Compact sensitive microphones and guitar pickups. Loudspeakers

Pressure Applications

Transient pressure measurement to study explosives, internal combustion engines (knock sensors), and any other vibrations, accelerations, or impacts.

Piezoelectric microbalances are used as very sensitive chemical and biological sensors.

Transducers are used in electronic drum pads to detect the impact of the drummer's sticks.

Energy Harvesting from impact on the ground

Atomic force and scanning tunneling microscopes.

Electric igniters and cigarette lighters

Consumer Electronics Applications

Quartz crystals resonators as frequency stabilizers for oscillators in all computers.

Phonograph pick-ups Accelerometers: In a

piezoelectric accelerometer a mass is attached to a spring that is attached to a piezoelectric crystal. When subjected to vibration the mass compresses and stretches the piezo electric crystal. (iPhone)

Motor Applications Piezoelectric elements can be used in laser mirror alignment, where their ability to move a large mass (the mirror mount) over microscopic distances is exploited. By electronically vibrating the mirror it gives the light reflected off it a Doppler shift to fine tune the laser's frequency. The piezo motor is viewed as a high-precision replacement for the stepper motor. Traveling-wave motors used for auto-focus in cameras.

Our Experiment

Procedure

1) Attach a mirror to the piezoelectric buzzer. Position that laser so that the beam can reflect off of the mirror and hit the wall across the room.2) Connect the function generator to the Piezoelectric device. Find the resonant frequency of the device by slowly

increasing the frequency at 10Vp-p. The laser will vibrate the most at the resonant frequency.

3) Measure the diameter of the laser without any signal. Then measure the diameter of the laser with the AC signal applied.4) Calculate the displacement of the laser and divide it by two to get the amplitude of the magnified change in volume for the piezoelectric material.5) Measure the distance from the piezo to the wall and to the laser. Also measure the height of the laser and reflected beam in relation to the piezo.6) Calculate the change in volume for the piezoelectric material.