R OOM OOM NOISE DETECTOR Project – 2 Third Year of Engineering By Mujumdar Amit Anant Nair Ajesh Rajan Nambiar Rohit Chandran
300832 300833 300834
Under the guidance of
Mr. Ashish Harsola
DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING
Fr. C. Rodrigues Institute of Technology Sector-9A, Vashi, Navi Mumbai – 400 703 UNIVERSITY OF MUMBAI 2010
CERTIFICATE OF APPROVAL Project entitled: Room Noise Detector Submitted by:
Mujumdar Amit Anant Nair Ajesh Rajan Nambiar Rohit Chandran
300832 300833 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. Introduction 1.1 1.2
2.
Literature Survey 2.1 2.2 2.3
2.4 3.
Aim of the Project Organization of the Project Report
Basics of detectors Types of detectors Parameters (a) Sensitivity (b) Resolution Applications
Implementation of Room Noise Detector 3.1 3.2
3.3 3.4 3.5
Circuit Diagram Pin out of IC LM358 Pin out of BC327 Specifications of Microphone Working
4. Software Simulation and PCB Designing 4.1
4.2 5.
Software Simulation using PROTEUS PCB Designing using ARES
Procedure 5.1 5.2 5.3 5.4 5.5 5.6
Circuit Diagram Transfer to PCB Etching of PCB Continuity Testing Drilling Soldering
6. Observations 6.1 6.2
Observation Table - Theoretical Observation Table - Simulation
7. Conclusion 7.1
References
Conclusion
LIST OF FIGURES Sr. No. 3.1 3.2 3.3 3.4 4.1 4.2 6.1 6.2 6.3 6.4
Caption Circuit Diagram Internal Configuration of LM358 Pin out of BC327 Electret Microphone Proteus – ISIS Schematic File PCB layout Proteus Simulated waveforms to describe working Output waveforms for 85 dB Output waveforms for 70 dB Output waveforms for 50 dB
Page No. 8 8 8 9 10 11 14 15 16 16
LIST OF TABLES Sr. No 6.1 6.2
Caption Table showing dB level for different sound sources Table showing software simulation for different dB settings
Page No. 13 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.
2. 3. 4.
5. 6.
Chapter 2: Discusses the basics plus types of noise detectors. Chapter 3: Reveals about the practical implementation of the project. Chapter 4: Discloses the software simulation of the project. Chapter 5: Step-by-step procedure to prepare a working PCB. Chapter 6: Enlists the observations and tabulates the practical results. Chapter 7: Summarizes as well as concludes the project based on above observations.
LITERATURE SURVEY
Chapter 2
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
2.4
Resolution The 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.
Applications of Noise Detectors 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. 1.
Chapter 3
3.1
IMPLEMENTATION OF R OOM NOISE DETECTOR
Circuit Diagram
Fig 3.1
3.2
Circuit Diagram
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 packag e.
Fig 3.3
Pin out for BC327
3.4
Specifications of Microphone
Sensitivity Frequency Range Signal to Noise Ratio
: : :
-45 ± 3 dB 100 Hz to 10 kHz ≥ 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 OPAMPs. 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 procedu re 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
OBSERVATIONS
Chapter 6
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
Fig 6.3
Switch connected to OHM
5.6k
Output Waveforms for 70 dB
Switch
is
connected to
560
OHM
Fig 6.4
CONCLUSION
Chapter 7
7.1
Output waveforms for 50 dB
Conclusion
R EFERENCES
