1. Ultrasonic Rangefinder
Matt Johnston & Brett Griffin

2. Motivation
Various ultrasonic technologies used in a wide number of industries in Alberta
Numerous industry specific applications through modification of design
Interest in H/W aspect of computer engineering

3. Background
Transducers convert energy in one form, to energy in another
In our case AC signals at 40 kHz cause a piezoelectric crystal to oscillate at 40 kHz
The crystal produces a 40 kHz ultrasonic sound wave that is recovered at another transducer
400EP250 Transducer

4. Theory
Send square wave pulses from DE2 to transducers at 40 kHz and start a timer
Receive sine wave at 40 kHz → verify signal
→ stop timer
Measure distance based on speed of sound in air
Pulse train sent to Tx transducer
with response of Rx transducer

5. Hardware Requirements
Transducer interfaced to DE2 via custom hardware
Numerous custom .vhdl components needed
ADC, Operation amplifier, bandpass filter, voltage regulators

6. Hardware Requirements

7. Software Requirements
User interface
Initiate transducer transmit & and reading of ADC
Controlling timer start/stop
Distance calculations
Distance accuracy optimization algorithm

8. Difficulties ADC Integration Signal processing/noise eradication
Minimizing error

9. Demonstration Accomplishments Distance measurements up to 6.5-7 ft.
Distance error ~1-4 inches;
Solid foundation for further work involving ultrasound
Demonstration

10. Future applications Leak detection in a pipeline
Changes in transmit time along a moving fluid would indicate a change in fluid velocity
A un-wanted change in velocity could indicate that there is a leak in the pipeline

11. Questions?