Transcript File - ECpE Senior Design

Frozen Precipitation Detector for
SODAR Systems
Dec1006
Design Solution
Abstract
Atmospheric Systems Corporation (ASC) produces the Sonic Detection and
Ranging (SODAR) system used to determine wind speed and wind direction of
the atmosphere up to 200 meters. The instrument is used in the wind industry to
measure wind shear conditions at potential wind project sites. The SODAR
produces an audible beep at a very specific frequency, and then listens for the
reflection of sound waves from aerosols in the atmosphere. Using the Doppler
shift of the returning signals, the SODAR can determines wind speed and
direction. The SODAR uses a phased array of speakers built into an enclosure
which helps shape the sound direction. The enclosure acts as an antenna to
shape the outgoing sound waves and collect the returning signals.
Piezoelectric sensors will be used to detect snow that accumulate on the heating
pad. These sensors will make use of the signals generated from the SODAR to tell
the difference when there is snow on the sensors or not. When snow is present on
the sensor, the voltage being read will be less than the voltage when the reflector
pad is clear. The heater will only be turned on when the piezoelectric sensors has
snow on them along with the readings from the temperature sensors. The solution
circuit that incorporated amplifiers, sample-and-hold circuits and filters will be
powered by the power source from the equipment. OR gates are included to foolproof the piezoelectric sensors while an AND gate is used to determine heater
operation.
System Diagram
Problem
Power
Source
During the SODAR operation, it is important
Temperature
Sensor
Heater
that the reflector pad remains clear of
debris. Snow collection on the reflector pad
can impair the SODAR operation. A heater
AND Gate
Master
Control
is built into the antenna to melt snow.
However, the heater is very power-intensive
and should only be used when snow is
Snow accumulation on the heating pad can
cause distortion to the sound reflections.
present system.
Currently, the unit operates with a sensor
Piezoelectric
Sensors
that determines the presence of
Amplifiers
Filters
Sample &
Hold
OR Gates
Testing
precipitation and freezing conditions. This
sensor can report many “false positives”
where sensor conditions are met, but
heating is not needed. This leads to
increased fuel usage and prolonged
downtime (due to running out of fuel). A new
solution should be devised to turn on the
heater only when necessary.
Testing setup in the lab.
Testing setup with the equipment.
Output from the piezoelectric sensors.
The frequency detected is 4.5KHz as
from the SODAR.
Output after feeding the readings from
the piezoelectric sensors into the circuit.
After noise was filtered, the frequency
detected is 4.5KHz as from the SODAR
Requirements
The solution must:
•be compatible with the current system.
•be powered by the solar panels on the equipment.
•use less power than the current detector.
•be able to function during extreme weather conditions.
•must only be on when there is frozen precipitation on the heating pad.
•must be able to take inputs from the temperature sensor as well to turn on the
heating pad.
Summary
•know when to turn on the heater
The testing shows that with a exposed reflector pad ,the piezoelectric sensors
generate around 100 millivolts and with any sort of debris, the sensors generate
Team Members
Faculty Advisor
Client
a lower voltage. This is used to differentiate between a clear reflector pad and a
Ashor Chirackal (EE)
Professor Timothy Bigelow
Mr. Josh Underwood
covered reflector pad. ASC can used this solution as a more efficient way to
detect any frozen precipitation on the reflector pad.
Imran Butt (EE)
Luke Lehman (EE)
Michelle Tan (EE)
Website
http://seniord.ece.iastate.edu/dec1006