Ultrasonic Rangefinder Matt Johnston & Brett Griffin

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

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

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

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

Hardware Requirements

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

Difficulties ADC Integration Signal processing/noise eradication Minimizing error

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

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

Questions?