23-02-2013, 03:47 PM
A PROJECT REPORT ON SOUND LEVEL METER WITH AUDIO ANNOUNCEMENT FOR LIBRARY
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INTRODUCTION
As our final year project we are going to present “Sound level meter with voice announcement”. Our project measure sound pressure level and display it on 16*2 LCD. The project is also connected to Audio announcement circuit. So our project continuously measure sound pressure, and compare with critical noise level set using microcontroller programming. If sound noise pressure exceed from set value, voice announcement circuit start play, giving warning massage. This project can be very useful for the college library and everywhere where noise level matter.
A basic sound level meter shows the sound pressure level with different frequency weighting and with different time integration that are used for noise assessment. In almost all countries, the use of A-frequency-weighting is mandated for protection of workers against noise induced deafness.
The standard sound level meter is more correctly called an ‘exponentially averaging sound level meter’ as the AC signal from microphone is converted into DC by a root-mean square circuit and thus I must have a time constant of integration; today, referred to as time weighting. The output of RMS circuit is linear in voltage and passed through a logarithm circuit to give a linear readout in decibels. It follow that decibels is not a unit but simply a dimensionless ratio-in case, the ratio of two pressures. The decibel is a logarithmic unit used to describe a ratio.
Working
Condenser mic is used as an input device. The sound is converted into electrical signal using condenser mic. This signal is than amplified by using LM358.For sufficient amplification we are using two operational amplifiers. The audio output is received through pin 2 and feedback is given through VR1. Here VR1 is used to get an output amplitude level between 0 to 4 volts.
LM 358 is dual operational amplifier consisting of two independent, high gain, internally frequency compensated operational amplifier that are design specially to operate from a single power supply over a wide voltage range. Operation from split supplies also is possible if the difference between the two supplies is 3 V to 32 V and VCC is at least 1.5 V more positive than the input common-mode voltage. The low supply-current drain is independent of the magnitude of the supply voltage.
Applications include transducer amplifiers, dc amplification blocks, and all the conventional operational amplifier circuits that now can be implemented more easily in single-supply-voltage systems. For example, these devices can be operated directly from the standard 5-V supply used in digital systems and easily can provide the required interface electronics without additional +-5-V supplies.
This analog output is fed to the analog input of PIC microcontroller. The PIC microcontroller is used because it has internal analog to digital converter. PIC16F877 belongs to a class of 8-bit microcontrollers of RISC architecture. It has 8kb flash memory for storing a written program. Since memory made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development. IT has data memory that needs to be saved when there is no supply.
PIC16F877
The PIC16F877 is 8-bit microcontroller .The PIC16F877 Microcontroller includes 8kb of internal flash Program Memory, together with a large RAM area and an internal EEPROM. An 8-channel 10-bit A/D convertor is also included within the microcontroller, making it ideal for real-time systems and monitoring applications. All port connectors are brought out to standard headers for easy connect and disconnect. In-Circuit program download is also provided, enabling the board to be easily updated with new code and modified as required, without the need to remove the microcontroller. Since memory made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development. It has data memory that needs to be saved when there is no supply. For instance, one such data is an assigned temperature in temperature regulators. If during a loss of power supply this data was lost, we would have to make the adjustment once again upon return of supply.
All the necessary with a Power and support components are included, together Programming LED for easy status indication. Plus a reset switch for program execution and a RS232 connection for data transfer to and from a standard RS232 port, available on most computers.
RISC
PIC 16F877 has a RISC architecture. This term is often found in computer literature, and it needs to be explained here in more detail. Harvard architecture is a newer concept than von-Neumann's. It rose out of the need to speed up the work of a microcontroller. In Harvard architecture, data bus and address bus are separate. Thus a greater flow of data is possible through the central processing unit, and of course, a greater speed of work. Separating a program from data memory makes it further possible for instructions not to have to be 8-bit words. PIC16F84 uses 14 bits for instructions which allows for all instructions to be one word instructions. It is also typical for Harvard architecture to have fewer instructions than von-Neumann's, and to have instructions usually executed in one cycle. Microcontrollers with Harvard architecture are also called "RISC microcontrollers". RISC stands for Reduced Instruction Set Computer. Microcontrollers with von-Neumann's architecture are called 'CISC microcontrollers'. Title CISC stands for Complex Instruction Set Computer.