SEISMIC SENSOR

INTRODUCTION

Generally seismic sensors are used at the earthquake prone areas; here in this project we are using this seismic sensor concept for security purposes. Security is required everywhere almost.

This circuit simulates the seismic sensor to detect vibrations and sound. It is very sensitive and detects vibrations and caused by movement of human beings and animals. So it can be used to monitor the protected areas to restrict entry of unwanted persons and animals.

Circuit diagram

Components used

• Piezo Element• Integrated Circuit (IC1 TL071 & IC2 NE555 )• Variable resistor (1M)• Capacitor (.01, 0.1, 10, 100 µ F)• Buzzer• Resistor ( 100, 10, 1 K & 330, 470Ω )• Transistor• LED• Switch • Battery (9V)

Piezo element  A  piezoelectric sensor is a device that uses the 

piezoelectric effect to measure pressure, acceleration, strain or force by converting them to an electrical signal.

Applications of piezo element The piezoelectric effect was discovered by Curie in 1880, it

was only in the 1950s that the piezoelectric effect started to be used for industrial sensing applications

They are used for quality assurance, process control and for research and development in many different industries.

It has been successfully used in various applications, such as in medical, aerospace, nuclear instrumentation, and as a pressure sensor in the touch pads of mobile phones.

In the automotive industry, piezoelectric elements are used to monitor combustion when developing internal combustion engines

IC NE 555 The 555 Timer IC is an integrated circuit (chip)

implementing a variety of timer and multivibrator applications. The IC was designed by Hans R. Camenzind in 1970 and brought to market in 1971 by Signetics (later acquired by Philips).

It has been claimed that the 555 gets its name from the three 5 kΩ resistors used in typical early implementations.

Depending on the manufacturer, the standard 555 package includes over 20 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package .

3 modes The 555 has three operating modes:

Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) etc

Astable - free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.

Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.

IC TL071

TLO71 is a low-noise JFET input op-amp with low input bias and offset current. The BIFET technology provides fast slew rates

The JFET-input operational amplifiers in the TL07_ series are designed as low-noise versions of the TL08_ series amplifiers with low input bias and offset currents and fast slew rate.

The low harmonic distortion and low noise make the TL07_ series ideally suited for high-fidelity and audio preamplifier applications. Each amplifier features JFET inputs (for high input impedance) coupled with bipolar output stages integrated on a single monolithic chip.

In the circuit, IC TLO71 (IC1) is wired as a differential amplifier with both its inverting and non-inverting inputs tied to the negative rail through a resistive network comprising R1, R2 and R3

When the piezo element is disturbed , it discharges the stored charge. This alters the voltage level at the inputs of IC1 and the output momentarily swings high as indicated by green LED1.

This high output is used to trigger switching transistor T1, which triggers monostable IC2. The timing period of IC2 is determined by R7 and C5. The high output from IC2 activates T2 and the buzzer starts beeping along with red light indication from LED2

Assemble the circuit on a common PCB and enclose in a suitable cabinet. Connect the piezo element to the PCB using single-core shielded wire. Enclose the piezo element inside a rustproof, small aluminum box.

The piezo element should be firmly glued to the enclosure facing the fine side towards the case. Fix the sensor assembly on the back side of a ceramic tile or granite tile with good adhesive. Fix the tile (or bury it in the earth) near the entrance with the sensor assembly facing downwards.

Whenever a pressure change develops near the sensor, the circuit will be activated.

Applications

It can be used at all the places where we require a lot of security eg in Bank lockers, in jeweler showrooms etc.

It can also be used at the areas where human or any animal enrty is not allowed (eg. Danger zones).

REFRENCES

www.google.com  www.wekipedia.com  Microsoft Encarta encyclopedia

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Thank you…… By..

N.Naveen reddy 08911A0450 P.Praveen reddy 08911A0460 K.L.V.Prasad reddy 08911A0433