23-11-2012, 04:38 PM
Microcontroller Based Ultrasonic Distance Meter
ULTRASONIC DISTANCE METER
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INTRODUCTION
The ultrasonic range finder is designed to measure the distance between two objects. In early days distance between the objects is measured by physically or by using tape. But this is not possible for long distance. This limited only for short distance. Because the cost will expensive or difficult find the end position. The long distance objects like Radar and any other place where person cannot go physically this project is very effective. It takes less time to measure distance of the objects. Measured distance displays in LCD. The displayed values is in digital which can everybody understand. This is cost effective compare to other methods.
Ultrasonic distance meter embedded system project explains about developing new application using microcontroller for calculating distance between two objects accurately using ultrasonic sound. This system uses ultrasonic sound pulses to calculate distance between objects. From source point user will send ultrasonic pulses to other end using transmitter and then receiver will catch reflected pulses and time is calculated for transmitting and receiving of pluses based on this time distance is calculated and displayed on LED. Output is displayed in digital format which can be easily understood by any one.
In existing system it is hard to calculate distance between objects, present system uses manual method where tape is used to calculate distance but this procedure is not possible in calculating long distance. In this cases ultrasonic distance meter can be used.
WORKING PRINCIPLE:
During the transmission micro controller encodes the signal and transmits through the Ultrasonic transmitter. The Ultrasonic transmitter converts the electrical signal to pulse. During this time the time set is zero. Ultrasonic transducer emits a burst of 12 pulses at a frequency, which is roughly identical with resonance frequency of the two transducers. After the burst has been emitted the unit is switched to reception. The sensitivity of the receiver is a function of time. When these pulses hits any object they are reflected back and are received by ultrasonic receiver. The number of clock pulses counted between onsets of the emission the burst and the sensing of echo is equal to distance between two objects. The microcontroller calculates distance by using time. The time taken to detect the target is helpful for finding the distance of the objects. The measured distance or height is displayed on LCD. The senility of the receiver is a function of time. When these pulses hits any object they are reflected back and are received by ultrasonic receiver. The number of clock pulses counted between onsets of the emission the burst and the sensing of echo is equal to distance between two objects.
LCD (LIQUID CRYSTAL DISPLAY)
LCD’s can add a lot to your application in terms of providing an useful interface for the user, debugging an application or just giving it a "professional" look. The most common type of LCD controller is the Hitatchi 44780 which provides a relatively simple interface between a processor and an LCD. Using this interface is often not attempted by inexperienced designers and programmers because it is difficult to find good documentation on the interface, initializing the interface can be a problem and the displays themselves are expensive.
Vital role of LCD in ‘ultra sonic distance meter’
LCD has single line display, Two-line display, four line display. Every line has 16 characters. This is used to display the operation of the system in written form.
Buzzer:
The buzzer subsystem produces a 2 KHz audible tone when powered. The buzzer will sound when the signal coming into the driver is high. It must be connected to a transistor, Darlington or transducer driver subsystem.
The buzzer is connected between the supply rail (+V) and the input signal. This acts as load on the driver. When the input signal coming into the buzzer subsystem is low, a potential difference across the buzzer causes current to flow. It is this flow of current that causes the buzzer to sound.