1. Fig. 4 Block diagram of system
ECE Computer Engineering Design Project
Ultrasonic Rangefinder
Matt Johnston & Brett Griffin
2013
Introduction
Ultrasonics have been used for decades in a wide variety of industries. Ultrasound is a sound pressure wave that oscillates at a frequency higher than that of audible noise. For our application, ultrasonic transducers were used in conjunction with the Altera DE2 development board to create a accurate rangefinding system. The transducers can be set up side-by-side to detect the distance of other objects or, for increased range demonstrations, set up across from one another pointing at each other.
Theory
Ultrasonic transducers typically contain a small piezo-electric crystal inside. When this crystal is subjected to an oscillating wave at its
Results
With the transducers set up parallel to one another and sensing the range of a different object we were able to obtain a range limit of ~3 feet with errors of around ±1 inch. When pointing at each other a maximum range of ~7.5 feet with errors of ±1 inch was obtained.
With increased signal verification in software using a cross correlation algorithm, we believe the range and accuracy of the system can be improved on.
Fig. 4 Block diagram of system
Fig. 2 DE2 interfacing hardware circuitry
Testing
Numerous different hardware and software components were required to interface our system with the DE2 board. Multiple VHDL components were created for different purposes. These components were tested individually to ensure proper operation.
An analog to digital converter was also required and was interfaced with the DE2 board with a custom driver component created in VHDL. Black box testing was also done on the ADC before integration testing was done.
An Op-amp was also needed to amplify the output peak to peak voltage of the receiving transducer. Adequate gain was needed to increase the distance limit of the rangefinder.
Once all hardware components were operating properly, integration testing was done to ensure proper operation of the system as a whole. Most integration testing/debugging was then done in the NIOS II IDE to tweak the accuracy of the system.
resonant frequency, it generates an ultrasonic sound wave at that same frequency. A different transducer then receives this wave, causing its crystal to oscillate at the same frequency. This analog oscillation can be converted to a digital signal and interpreted using software via the DE2 board. By measuring the time difference between the transmit and receive signal, distance can be measured.
Extensions
As mentioned, the hardware was designed with the intention of being adaptable depending on different applications. We believe this system could be used as a leak detection system for a gas pipeline. By using transducers to measure transmission times of the sound wave through a moving fluid, we can accurately detect changes in the fluid velocity. Changes in fluid velocity could be attributed to undesirable changes in flow rate caused by a leak.
This system could be realized by increasing the accuracy of the signal detection. No changes need to be made to the physical hardware of our design. Proper care would need to be taken to ensure that the system is properly coupled to a pipeline to decrease signal attenuation.
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Fig. 1 Transducers set up at 1 ft. distance
Goals
The goal of this project was to create a system that could reliably produce ranges up to ~10 feet when the transducers were pointed at each other. Our goal was to also design a system that could be adapted for a wide variety of applications. The hardware was designed such that only changes in software are required for different applications.
Fig. 3 Transmitter with receiver response
Department of Electrical & Computer Engineering