E&E PROJECTS

Library is the place of peace and silence where students get opportunity to study and view different reference materials. Peace and silence is the most important feature of library. But many times students dont give much attention to it and consider it to be the normal place. So students make noise in library and ruin its attribute. So taking this issue into consideration, we decided to fabricate a simple electronic device that can solve this problem.This project is for the design and construction of the NOISE DETECTOR IN LIBRARY. This device is able to detect the noise, compare the intensity of louder sound and hence producing the warning signal to the librarian. This system is very economical and helpful in maintaining peace in library.

In this project we have designed a technology to detect the noise and produce the output according to the intensity of noise made. When the sound exceeds the threshold, it is considered as noise which in turn triggers the timer and an output is seen in the LED. Sources of our literature survey are mainly the books, websites and consultation with the faculty members and interaction with colleagues. All those sources were very much useful for us to get knowledge about different components and upgrading our project.

2.1 Hardware Description

In our project various technical processes and devices have been used. We were able to have brief knowledge about them. The various electronics component that are to be used are:

 2.1.1 Operational Amplifier:

An operational amplifier is a versatile device that can be used to amplify dc as well as ac inputs signals and designed for addition, subtraction, multiplication and division. With the addition of suitable external feedback components the op-amp can be used as ac and dc signal amplification, oscillators, comparators and others. In our project we have used op-amp as an amplifier and a comparator.

In our project we have used the op-amp both as inverting and non-inverting amplifiers.

2.1.1.1 Inverting Amplifier

In the inverting amplifier only one input is applied and that is to the inverting input terminal. The non-inverting input terminal is grounded. Since v^­₁ = 0V, and v₂ =  v_in from the equation

                              v^­₀ = -A v_in      

The negative sign indicates the output voltage is out of phase with respect to input by 180⁰ or is of opposite polarity. Thus in the inverting amplifier the input signal is amplified by gain A and is also inverted at the output.

 

2.1.1.2 Non inverting amplifier

The non-inverting Amplifier is the open-loop in which the input is applied to the non-inverting input terminal, and the inverting terminal is connected to the ground.

 

In all two open-loop configurations any input signal (differential or single) that is only slightly greater than zero drives the output to saturation level. This results from the very large gain (A) of the op-amp. Thus, when operated open-loop, the output of the op-amp is either negative or positive saturation or switches between positive and negative saturation levels. For this reason, open-loop op-amp configurations are not used in

linear applications.

2.1.1.3 Operational amplifier as comparator

 A fixed reference voltage V_ref of 1.09 V is applied to the (+) input, and the other time-varying voltage V_in is applied to the (-) input. Because of this arrangement, the circuit is called the inverting comparator. When Vin is greater than V_ref, Vo goes to -V_sat(=-Vcc). Thus Vo changes from one saturation level to another when Vin= Vr_ef. In short, the comparator is a type of analog-to-digital converter. At any time the Vo waveform shows whether Vin is greater or less than V_ref. The comparator is sometimes also called a voltage-level detector because, for a desired value of V_ref, the voltage level of the input Vin can be detected. The amplitude of V_in must be large enough to pass through Vref if the switching action is to take place.

  2.1.2  555 timer

One of the most versatile linear integrated circuits is the 555 timer. A sample of these applications includes monostable and astable multivibrators, dc-dc converters, digital logic probes, waveform generators, analog frequency meters and tachometers, temperature measurement and control, infrared transmitters, burglar and toxic gas alarms, voltage regulators, etc. The SE555 is designed for the operating temperature from -55­^o to +125^o. It operates on +5 to +18 V supply voltage of monostable mode.

2.1.2.1 The 555 in a monostable mode

A monostable configuration is a pulse generating circuit in which the duration of the pulse is determined by the RC network connected externally to the 555 timer. In a stable or standby state the output of the circuit is approximately zero or a logic-low level. When an external trigger pulse is applied, the output is forced to go high(=Vcc). The time the output remains high is determined by the external RC network connected to the timer. At the end of the timing interval, the output automatically reverts back to its logic-low stable state. The output is low if voltage at trigger pin is greater 2/3 Vcc. However when a negative-going pulse of amplitude larger than 1/3 Vcc applied to this pin, the timer output is high. The output stays low until the trigger pulse is again applied. Then the cycle repeats. The monostable circuit has only one stable state (output low), hence the name monostable. Normally, the output of the monostable state is low. The pin numbers and connections is shown below:

The trigger pulse, produced by pressing the button, must be of shorter duration than the intended output pulse.

The period, T, of the output pulse can be calculated from the design equation:

T = 1.1 * RC secs where R is in ohm and C is in Farad.

2.1.8 Resistor:

Resistor is one of the basic parameter of the electric circuit. In a general way, resistor can be described as that property of a circuit element which offers opposition to the flow of current and in doing so converts electrical energy into heat energy. Resistor is a passive

Circuit element i.e. it does not have ability to produce gain. It also has the bilateral circuit element i.e. it can conduct current in both direction. The resistor that are found in electric circuits doing many different tasks are of several types as regards to physical construction, power dissipating capability, and tolerance of the resistance value.

2.1.9 Capacitor:

A capacitor is a passive electronic component that stores energy in the form of an electrostatic field. In its simplest form a capacitor consist of two conducting plates separated by an insulating material called the dielectric. Capacitance is directly proportional to the surface area of the plates and is inversely proportional to the plates separation. Capacitance also depends on the dielectric constant of the dielectric material separating the plates.

The standard unit of capacitance:

Farad: F

Microfarad: µF (1 µF=10^-6F)

Nanofarad: nF(1nF=10^-9F)

Picofarad:pF(1pF=10^-12)

2.2.7 Light Emitting Diode (LED):

LED is the light emitting diode made of off gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP) or gallium phosphide (GaP) which emits light.   GaAs LEDs emit Infrared (IR), radiation which is nonvisible, GaAsP produces either red or yellow visible light and Gap emits red or green visible lights. The normalize output of the visible red LED picks at 660 nm, the yellow at 590 nm green at 540 nm and the IR LED picks at 940 nm. In this project color LEDs are used as indicator and IR LED as transmitter.

2.2.8        Microphone

Microphone is an acoustic to electric transducers or sensor that converts sound into an electric signal. In our context we have used a readymade microphone which will receive the noise made in the library and used to send the electric signal to the preceding circuit. Every microphone has its fixed resistance value to which it gives the maximum performance.