ROOM NOISE DETECTOR

Project – 2Third Year of Engineering

By

Mujumdar Amit Anant 300832Nair Ajesh Rajan 300833Nambiar Rohit Chandran 300834

Under the guidance of

Mr. Ashish Harsola

DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING

Fr. C. Rodrigues Institute of TechnologySector-9A, Vashi,

Navi Mumbai – 400 703

UNIVERSITY OF MUMBAI

2010

CERTIFICATE OF APPROVAL

Project entitled: Room Noise Detector

Submitted by:

Mujumdar Amit Anant 300832Nair Ajesh Rajan 300833Nambiar Rohit Chandran 300834

In the subject Electronic Hardware Workshop of the degree of T.E. in "Electronics and Telecommunication Engineering" is approved.

Subject Teacher

TABLE OF CONTENTS

List of Figures

List of Tables

1. Introduction1.1 Aim of the Project1.2 Organization of the Project Report

2. Literature Survey2.1 Basics of detectors2.2 Types of detectors2.3 Parameters

(a) Sensitivity(b) Resolution

2.4 Applications

3. Implementation of Room Noise Detector3.1 Circuit Diagram3.2 Pin out of IC LM3583.3 Pin out of BC3273.4 Specifications of Microphone3.5 Working

4. Software Simulation and PCB Designing4.1 Software Simulation using PROTEUS4.2 PCB Designing using ARES

5. Procedure 5.1 Circuit Diagram5.2 Transfer to PCB5.3 Etching of PCB5.4 Continuity Testing5.5 Drilling 5.6 Soldering

6. Observations6.1 Observation Table - Theoretical6.2 Observation Table - Simulation

7. Conclusion7.1 Conclusion

References

LIST OF FIGURES

Sr. No. Caption Page No.3.1 Circuit Diagram 83.2 Internal Configuration of LM358 83.3 Pin out of BC327 83.4 Electret Microphone 94.1 Proteus – ISIS Schematic File 104.2 PCB layout 116.1 Proteus Simulated waveforms to describe working 146.2 Output waveforms for 85 dB 156.3 Output waveforms for 70 dB 166.4 Output waveforms for 50 dB 16

LIST OF TABLES

Sr. No Caption Page No.6.1 Table showing dB level for different sound sources 136.2 Table showing software simulation for different dB settings 14

Chapter 1 INTRODUCTION

A sensor is a device capable of registering a specific substance or physical phenomenon. A detector is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. There are various kinds of detectors like – temperature detector (Thermocouple), light detector (LDR), sound detector (microphone), etc.

Scrutinizing Room Noise Detector: This circuit keeps a tab on the noise levels in a room using detectors like microphone, and displays output in the form of blinking LED’s. It can detect three threshold levels – 50, 70, 85 dB. A three array LED just makes the output look magnificent.

1.1 Aim of the Project

Usually, small-scale and large-scale factories do not have systems to inspect noise levels. The high expenditure to acquire such devices from the current competitive market makes them shy off from installing such systems. Also they have some physical constraints such as – cannot bear heat, heavy mechanical pressure, etc.

Keeping a view of these shortcomings, this project aims at providing a rugged and cost effective detector circuit assembled using low-cost components with the intention of substituting the current commercially existing versions. This project aims at giving a highly accurate output thus providing a good calibration of the level of noise in the room.

1.2. Organization of the Project Report:

The information in the subsequent chapters is set in the following fashion:

1. Chapter 2: Discusses the basics plus types of noise detectors.2. Chapter 3: Reveals about the practical implementation of the project.3. Chapter 4: Discloses the software simulation of the project.4. Chapter 5: Step-by-step procedure to prepare a working PCB.5. Chapter 6: Enlists the observations and tabulates the practical results.6. Chapter 7: Summarizes as well as concludes the project based on above observations.

Chapter 2 LITERATURE SURVEY

2.1 Basics of Detectors

A detector is a device which receives and responds to a signal or stimulus. Here, the term "stimulus" means a property or a quantity that needs to be converted into electrical form. Hence, detector can be defined as a device which receives a signal and converts it into electrical form which can be further used for electronic devices. A detector differs from a transducer in the way that a transducer converts one form of energy into other form whereas a detector converts the received signal into electrical form only.

A good detector obeys the following rules: Is sensitive to the measured property. Is insensitive to any other property likely to be encountered in its application. Does not influence the measured property.

A sound detector has its measurement calibrated in decibels (dBs).

2.2 Types of Detectors

Detectors can be classified on the basis of quantity it measures. Some of them are:

1. Temperature detectors like thermocouple, RTD, etc.2. Light detectors like LDRs, phototransistors, etc.3. Sound detectors like microphone, lace sensor, hydrophone, etc.4. Infrared detector like IR sensor, etc.5. Radiation detector like particle detector, etc.6. Position Detector like accelerometer, free fall sensor, etc.7. Pressure Detector like Bourdon gauge, Barometer, etc.8. Flow detector like air flow meter, anemometer, etc.

2.3 Parameters

2.3.1 Sensitivity

The sensitivity is then defined as the ratio between output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the unit [V/K]; this sensor is linear because the ratio is constant at all points of measurement.

2.3.2 ResolutionThe resolution of a sensor is the smallest change it can detect in the quantity that it is measuring. Often in a digital display, the least significant digit will fluctuate, indicating that changes of that magnitude are only just resolved. The resolution is related to the precision with which the measurement is made. For example, a scanning tunneling probe (a fine tip near a surface collects an electron tunneling current) can resolve atoms and molecules.

2.4 Applications of Noise Detectors

1. Checking decibel level in industries, near hospitals, etc.2. Study effect of noise on human body.3. Traffic Noise level studies.4. Scientific analysis of noise.

Chapter 3 IMPLEMENTATION OF ROOM NOISE

DETECTOR

3.1 Circuit Diagram

Fig 3.1 Circuit Diagram

3.2 Pin out of IC LM358

This has two inbuilt operational amplifiers having two inputs and one output each. It provides a high gain for weak signals.

Fig 3.2 Internal configuration of LM358

3.3 Terminals of transistor BC327

This 45V, 500mA PNP transistor has a TO-92 package.

Fig 3.3 Pin out for BC327

3.4 Specifications of Microphone

Sensitivity : -45 ± 3 dBFrequency Range : 100 Hz to 10 kHzSignal to Noise Ratio : ≥ 58 dB

Fig 3.4 Electret microphone

3.5 Working of Room Noise Detector

The complete working of Room Noise Detector has been described under the consideration that sound signal is sinusoidal in nature. Hence a descriptive working for positive half cycle of the signal is in this manner:

1. The R4 – C1 combination is responsible for AC coupling with the high gain OP-AMPs. The R3 – C2 parallel arrangement makes sure that only DC signal flows

through R3 and remains shorted for sound signal.

2. IC1A configuration is employed in non-inverting amplifier mode with variable gain controlled by resistors – R5, R6 and R7.Formula for Gain:

AV = 1 +

where i = 5,6,7. These resistors provide selection for 50 dB, 70 dB and 85 dB threshold respectively.

3. IC1A is coupled with IC1B and the second OPAMP is in difference amplifier mode. For positive half cycles, the R8 resistor takes along a signal synchronized with input signal with its negative cycles clipped. Also input to non-inverting terminal is the original amplified signal.

4. The output of IC1B is only negative pulses in every positive cycles of input. The capacitor is for input coupling and the transistor being PNP – it gets ON when base voltage is negative when compared to the emitter i.e. VBE ≥ -0.7

5. The R11 – C3 combination is an LPF – allowing only low frequency signals to pass through and attenuating high frequency signals.

6. It is clear that noise or sound signals have a positive amplitude w.r.t ground. The PNP transistor produces positive collector current spikes when a negative pulse is provided to base of the transistor.

7. Thus the LEDs show the output – depending upon user selection of dBs.

Chapter 4 SOFTWARE SIMULATION AND PCB DESIGNING

Before practical implementation of Room Noise Detector we carried out a software imitation using ‘Proteus 7.4 sp3 pro’.

4.1 Software Simulation using PROTEUS – ISIS 7 Professional

Initially, the entire circuit was redrawn using Proteus basic tools. Oscilloscope was attached in order to check the output. Then, the circuit was put into simulation mode and for different resistors – R5, R6 and R7 – the waveforms were noted.

Fig 4.1 Proteus – ISIS schematic file

4.2 PCB designing using ARES 7 Professional

After the successful verification of the circuit, its PCB was designed using ‘ARES’ software. Auto-Routing command helped in giving a rough PCB layout which we later modified in order to reduce the number of jumpers, avoid interconnections & faults, & to make the circuit more compact as well as efficient.

Fig 4.2 PCB Layout

Chapter 5 PROCEDURE

The following processes are involved in procedure for making the PCB:-

5.1 Circuit Diagram:

Draw the circuit diagram on a graph sheet considering the width of the lines—1mm for connecting wires, 2.5 mm for Vcc supply, 5mm for Grounding. Then draw the exact circuit on a butter paper with the help of a pencil. Thickness of the lines is needed to be taken care of. The ground and the Vcc terminals are the thickest and the other lines need to be a bit less thick.

5.2 Transfers to the PCB:

Take the butter paper and draw the impression of the circuit on the PCB. The impression would be a mirror image to the actual circuit. Draw the circuit on the PCB with the help of a marker.

5.3 Etching Process:

Take the PCB and dip in a solution of FeCl3. Keep the PCB in the solution till the layer of Cu on the PCB gets dissolved in the solution. To make the Cu dissolve faster keep on stirring the PCB.As soon as the Cu gets dissolved remove the PCB from the solution.

5.4 Continuity:

Check the continuity of the system with the help of multimeter. If at all there is discontinuity then make that part of the circuit continuous with the help of soldering.

5.5 Drilling:

Drill holes on the PCB as per the circuit to mount the components on the PCB. Also scratch the marker ink off the connecting spots so as to ensure continuity.

5.6 Soldering:

Solder the components of the circuit. Break the extra long legs of the components and perform the final working of the project

Chapter 6 OBSERVATIONS

6.1 Observation Table - Theoretical

Table 6.1 Table showing decibel level of different sound sources.

dB Example of sound sources

20 Quiet garden, electric-clock ticking, drizzling rain

30 Blast of wind, whisper @ 1 m.

40 Countryside areas, quiet apartment, wrinkling paper @ 1 m.

50 Residential areas, quiet streets, fridges, conversation @ 1 m.

55 Offices, air-conditioners

60 Alarm-clocks, radio & TV sets at normal volume

64 Washing machines, quiet typewriters

67 Hair-dryers, crowded restaurants

69 Dish-washers, floor-polishers

70 Loud conversation, noisy street, radio & TV sets at high volume

72 Vacuum cleaners

78 Telephone ring, mechanical workshop

80 Passing trucks, noisy hall or plant, shuffling @ 1 m.

90 Passing train, pneumatic hammer, car hooter @ 1 m.

95 Mega "disco", circular saw

100 Motorcycle without silencer

6.2 Observation Table – Software Simulation

The waveforms concerning the above discussion are as shown below:

Fig 6.1 Proteus Simulated waveforms to describe working of Room Noise Detector

The waveforms below detail the output at the three LEDs

Table 6.2 Table showing software simulation

Condition Observation

Switch

connected

to 56k

OHM

Fig 6.2 Output waveforms for 85dB

Switch

connected

to 5.6k

OHM

Fig 6.3 Output Waveforms for 70 dB

Switch is

connected

to 560

OHM

Fig 6.4 Output waveforms for 50 dB

Chapter 7 CONCLUSION

7.1 Conclusion

REFERENCES