Ultrasonic Speed Measurement

The project gives the significance of the following field of engineering.

P - signifies the phenomenon of planning which deals with symbolic nation and proper arrangement of sense and suggestion receptivity accordingly to the needs R-it is associate with the word resources which guides to promote planning .

OJ - this letter signifies the overhead expenses in unestimated expenses that may occur in the manufacture design or layout of the project.

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E - signifies the word engineering.

C - signifies the convey about phenomenon of construction low cost.

T - the word T stands for technique. unless there is a technique; it is impossible to complete the project . The conclusion thus arrived is that project is a systematic consideration discussed and proposal in a particular subject . we can say that project includes complete requirement of mechanism , tools , application and needs. It considers the circuit diagram and various operational performances in sequence and data about the instrument and in the last we can say about the project profit loss.

The concept of using ultrasonic waves instead of any other communicating tools as infrared and RF is its high preciseness and very less interference by the surrounding. There can various methods that can be opted to design this instrument such as Doppler Effect etc. but we have used the concept of distance measurement at a regular interval. The pulse is being transmitted at a regular interval and the corresponding distance is measured of the two pulses. The difference in the distances is observed and is then divided by the time duration between the two pulses. As result the corresponding speed is obtained.

The range of this device is directly dependent on the performance of the transmitter and the receiver. Higher the transmitting and receiving frequency better will be its range.

The major advantages of our project are One of the major advantages our project is its multi utility. It can be used as 1 Speed measurement 2 Distance measurement 3 Car parking controller The other advantage of this project is its cost. Its cost is less than 1000 INR. The precise result is one more advantage of our project. Limitation of our project. The major disadvantage of our project is its range. Due to the use of low frequency transmitter and receiver.

For this we are using the Ultrasonic Sensors. We first generate a 40 KHz signal by taking the time period of 25 microseconds. Then we actually generate the pulse burst with a delay of 5 milliseconds. For this we programmed the microcontroller. We send the pulse by pressing the switch that is connected to the pin no. 1 of the microcontroller. At this moment the distance of the object from the device is measured and is stored in the microcontroller. Then after the delay of 5 milliseconds the second pulse hits the moving object. Again the distance of the object is measured and is stored in the microcontroller.

Then we can easily find out the difference in the distance by simply subtracting these two distances. Now we have the distance and also the time. Therefore by the formula speed = distance / time we can find out the speed of the moving object. In the transmitter part we have LM311which is a voltage comparator and is used here as the precision squarer whose pin no. 2 is connected to the pin no. 2 of the microcontroller.

Then at pin no. 7 and pin no. 8 the ultrasonic transmitter is placed. In the receiver part we have LM833 for amplification and 74HC14N as the Hex inverting Schmitt trigger. The pin no. 1 of 74HC14N is connected to the pin no. of LM833. The ultrasonic receiver is connected between pin no. 6 of LM833 and ground. These ultrasonic transmitter and receiver are placed close to each other so that there will be minimum noise.

Why ultrasonic signal?

'ULTRA'-sonic is a sound wave with a frequency above the normal range of human hearing. Most humans can hear up to 16,000 Hertz. Young people can hear almost to 20,000 Hertz. Bats and mice and other small critters can hear much higher and use those sounds to 'see' the world around them. An ultrasonic imaging device sends a signal into a medium and then listens for the reflected waves.

The more receiving transducers you use to pick up the sound the better you can tell what you are 'looking' at. Reflected waves will reach one receiver before the next based on where the reflecting object is located. Electronics are fast enough to determine the direction and distance to the reflected objects. Also the higher the frequency you broadcast the better resolution you will see. A computer is interfaced with an array of receiving tranceducers and it calculates the direction and distance that the many echos must represent and then it plots the picture of the results.

The Image can be displayed or printed. In ultrasonic non destructive testing, high-frequency sound vibrations are transmitted into material by an ultrasonic transducer. The test instrument then analyzes the ultrasonic signals which are received using either a pulse-echo or through-transmission method. In the pulse-echo mode, the transmitting transducer also serves as the ultrasonic receiver and analyzes the reflected signal with respect to amplitude and time. In the through-transmission mode, the ultrasonic signal is received by a separate transducer which analyzes the amplitude loss of signal.

These ultrasonic NDT methods will indicate material defects such as longitudinal and transverse cracks, inclusions and others as well as ID/OD dimensions and dimensional changes such as thickness and ovality.

Components Component required

1. Ultrasonic Transmitter and Receiver
2. Resistor
3. Capacitor
4. Crystal
5. Preset
6. Switch
7. LCD
8. Power Supply
9. JCs

The purpose of this application note is to aid the user in the selection and application of the Ultrasonic ceramic transducers. The general transducer design features a piezo ceramic disc bender that is resonant at a nominal frequency of 20 – 60 KHz and radiates or receives ultrasonic energy. They are distinguished from the piezo ceramic audio transducer in that they produce sound waves above 20 KHz that are inaudible to humans and the ultrasonic energy is radiated or received in a relatively narrow beam.

The “open” type ultrasonic transducer design exposes the piezo bender bonded with a metal conical cone behind a protective screen. The “enclosed” type transducer design has the piezo bender mounted directly on the underside of the top of the case which is then machined to resonant at the desired frequency. The “PT and EP” type transducer has more internal damper for minimizing “ringing”, which usually operates as a transceiver – oscillating in a short period and then switching to receiving mode. Comparative characteristics :

When compared to the enclosed transducer, the open type receiver will develop more electrical output at a given sound pressure level (high sensitivity) and exhibit less reduction in output as the operating frequency deviates from normal resonant frequency (greater bandwidth). The open type transmitter will produce more output for a specific drive level (more efficient). The enclosed type transducer is designed for very dusty or outdoor applications. The face of the transducer must be kept clean and free of damage to prevent losses.

The transmitter is designed to have low impedance at the resonant frequency to obtain high mechanical efficiency. The receiver is constructed to maximize the impedance at the specified anti-resonant frequency to provide high electrical efficiency. Sound propagation : In order to properly select a transducer for a given application, it is important to be aware of the principles of sound propagation. Since sound is a wave phenomenon, its propagation and directivity are related to its wavelength.

Due to the reciprocity of transmission and reception, the graph portrays both power radiated along a given direction (in case of wave production), and the sensitivity along a given direction (in case of wave reception). As an example of a typical situation, a transducer of 400ET250 has an effective diameter of 23 mm (1mm wall thickness) will produce a main beam (-6dB) with full width of 30° at a frequency of 40 KHz. For open type transducers, the beam is decided by the angular and diameter of conical cone attached on the bender inside of housing and the opening diameter so it can not be simply calculated by the diameter of the housing.

The intensity of sound waves decrease with the distance from the sound source, as might be expected for any wave phenomenon. This decrease is principal a combination of two effects. The first is the inverse square law or spherical divergence in which the intensity drop 6dB per distance doubled. This rate is common to all wave phenomena regardless of frequency. The second effect causing the intensity to decrease is the absorption of the wave by the air (see figure 2). Absorption effects vary with humidity and dust content of the air and most importantly, they vary with frequency of the wave.

Absorption at 20 KHz is about 0. 02dB/30 cm. It is clear that lower frequencies are better suited for long range propagation. Of course, the selection of a lower frequency will result in less directivity (for a given diameter of source of receiver). How far the transducer could reach? One of the most frequently asked questions is “How far the transducer could reach? ”. This question can be answered by a simple calculation that is based on the published specifications in the Ultrasonic Ceramic Transducer Data Sheets.

The basic procedure is to first determine the minimum sound pressure level developed at the front end of the receiver for a specific transmitter driving voltage and distance between the transmitter and receiver (transceiver has double distance between reflect target). This SPL must then be converted “Pa” (Pascal) or “? bar” (microbar) units. The sensitivity of the receiver must then be converted from a dB reference to an absolute mV/Pa or ? bar level resent to obtain the final output.

Assume a 400ST160 transmitter is driven at a level of 20Vrms and a 400SR160 receiver is located 5 meters from the ransmitter and loaded with a 3. K Ohm resistor (loaded resistor value varies receiver sensitivity, please see “Acoustic Performance” of transducer data sheet). The analysis is necessary to the fundamental understanding of the principals of sound wave propagation and detection but it is tedious. The figure 10 below is a graphical representation of previous analysis which may be used once in the SPL at the receiver is determined. Enter the graph from the SPL axis and proceed upward to an intersection with –dB sensitivity level of the receiver using the 1V/? bar referenced data. Follow a horizontal line to the “Y” axis to obtain the receiver output in V.

At Receiver Ultrasonic echo ranging : Ultrasonic ranging systems are used to determine the distance to an object by measuring the time required for an ultrasonic wave to travel to the object and return to the source. This technique is frequently referred to as “echo ranging”. The distance to the object may be related to the time it will take for an ultrasonic pulse to propagate the distance to the object and return to the source by dividing the total distance by the speed of sound which is 344 meters/second or 13. 54 inches/millisecond. IC’s [pic] BASIC OF LM833

The LM111 series are voltage comparators that have input currents approximately a hundred times lower than devices like the mA710. They are designed to operate over a wider range of supply voltages; from standard ±15 V op amp supplies down to a single 3 V supply. Their output is compatible with RTL, DTL, and TTL as well as MOS circuits. Further, they can drive lamps or relays, switching voltages up to 50 V at currents as high as 50mA. Both the inputs and the outputs of the LM111 series can be isolated from system ground, and the output can drive loads referred to ground, the positive supply, or the negative supply.

Offset balancing and strobe capability are provided and outputs can be wire-ORed. Although slower than the mA710 (200 ns response time versus 40 ns), the devices are also much less prone to spurious oscillations.

The 7805 series of three-terminal positive regulator are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output current. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain adjustable voltages and currents.

The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry- standard 80C51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning.

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