1. Ultrasonic Rangefinder
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 distance of other objects or, for increased range demonstrations, set up across from one another pointing at eachother.
Theory
Ultrasonic transducers typically contain a small piezo-electric quartz crystal inside. When this crystal is applied an oscillating wave at its resonant
Testing
Numerous different hardware and software components were required to interface our system with the DE2 board. Multiple different 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.
Op-amps were 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 testing was then done in the NIOS II IDE to tweak the accuracy of the system.
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 of a 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 unwanted 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.
Fig. 2 DE2 interfacing hardware circuitry
resonant frequency, it generates a ultrasonic sound wave at that same frequency. A different transducer then receives this wave, causing its quartz 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.
Fig. 1 Rig set up at 1’ distance
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Goals
The goal of this project was to create a system that could produce 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.
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 eachother a maximum range of ~7.5 feet with errors of ±1 inch.
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. 3 Transmitter with receiver response
Department of Electrical & Computer Engineering