Download File - Senior Design

ISU SODAR Team
sddec 10-06
ASHOR CHIRACKAL
MICHELLE TAN
IMRAN BUTT
LUKE LEHMAN
CLIENT:
MR. JOSH UNDERWOOD, ASC
ADVISOR:
DR. TIM BIGELOW
Background
The SODAR system
 measures wind shear for up to 200 meters in the
atmosphere.
 is designed by the Atmospheric Systems Co.
 is designed to be autonomous.
 powered by a solar panel and has a generator as a
secondary source.
 operates by emitting sound waves from its
speakers and listens for the reflection.
Project Plan
Problem Statement:
Optimizing the number of times the heater is turned on to reduce
power consumption by designing a more efficient and accurate method
to detect the conditions in which the SODAR equipment needs to use
the heater.
The necessary conditions and requirements are outlined below:
 Ability to detect frozen precipitation that distorts the SODAR
readings and needs to be melted.
 Turns heater on only when necessary.
 Turns heater off after frozen precipitation has melted.
Problems Elaborated
 Operation of the SODAR when clear and covered
with frozen precipitation
System Design
Power
Source
Temperature
Sensor
Heater
AND Gate
Piezoelectric
Sensors
Amplifiers
Filters
Sample &
Hold
OR Gates
Master
Control
Current
System

detects the
possibility of frozen
precipitation and
decides whether
melting is required

picks up many “false
positives” where
freezing conditions
are detected, but
heating is not
necessary

wastes fuel during
these “false
positives”
Functional Requirements
 Frozen Precipitation Detector



must withstand the temperature of the heating pad.
must not interfere with the acoustic environment of the
SODAR.
must use less power than the current detector.
Solution
 Use piezoelectric sensors to check the state of the
reflector board.
 Use the voltage from the piezoelectric sensors to
determine if heating is necessary


Below a certain threshold voltage, heater should be on
Above a certain threshold voltage, heater should be off
Piezoelectric Used
 PZ-04 - Raw Piezofilm
 Manufacturer
Concept Sketch
Piezoelectric
sensors plates
Temperature
Sensor
SODAR
speakers
Heater
Concept Sketch
Test Plan
 Obtain several piezoelectric sensor applicable to the project
 Small level testing the piezoelectric sensor characteristics to determine the best





option
Model circuit components
Build circuit components
Test piezoelectric sensors under specific conditions
Integrate components
High level testing using the completed design
Hardware
 Piezoelectric sensor
Detects sound waves emitted from the SODAR
 Minimal power consumption
 Differentiate amplitudes of clear reflector versus snow covered reflector
Amplifier
 Convert small piezoelectric signal to usable level(0-5V)
Filters
 Attenuate signal outside 2-5kHz
Peak Detector
 Samples and holds values produced by piezoelectric sensors for
processing
Comparator
 Used for logic operation





User Interface
The Frozen Precipitation Detector is designed to be
autonomous. User interface should be kept to a minimum.
The variance in voltage will determine if the heater is needed.
Testing
The major parts of the
FPD are as follows:
 Piezoelectric
 Amplifier
 Band-Pass Filters
 Peak Detector
 Comparator
Construction and
testing of these parts
was conducted
simultaneously in order
to produce a rapid
prototype.
Testing
Simulation of a SODAR
signal at a lower level
Signal pulses were
generated using a signal
generator
Results were measured
with oscilloscopes and
a digital multimeter
After these subsystems
were finalized a
prototype system was
constructed.
Amplifier
An amplifier was used
to boost the voltage
from the piezoelectric
sensor.
Rf is a potentiometer
which can be adjusted if
needed.
Gain: 23
Filters
Butterworth filters were
used to filter noise
signal from the output
of the piezoelectric
sensor.
This filter only let the
frequencies between 2
kHz and 5.5 kHz.
Peak Detector
This is used to hold the
maximum voltage
generated by the
piezoelectric sensor.
The output voltage of
this circuit is fed into a
LED. When the LED is
on, heating is not
necessary. If it is off,
heating is necessary.
Comparator
The comparator is used
to implement the final
logic operation of the
FPD
Threshold: 2.25 V
Input/Output relation:
Testing
Combined the
amplifier, filters, and
peak detector together
Input was a waveform
generator
Output was an LED
Implementation
Implementation of the
FPD involves
permanent attachment
of the circuitry and
piezoelectric to SODAR
systems.
These SODAR systems
must be operated in
environments that
produce frozen
precipitation and must
have a heating unit
installed.
Implementation
The FPD was
implemented on a
SODAR system
lacking the heating
hardware.
The output of the
prototype FPD was
routed to an LED
The prototype FPD
was not permanently
installed on the
SODAR
Input
The input is the sound
the speaker emits. The
piezoelectric sensor
generates a voltage
from this sound
Output
The output received by
the oscilloscope
Frequency: 4.402 KHz
Pk-Pk Voltage Range:
30-160mV
Output
After amplifying and
filtering the output is
Pk-Pk Voltage 1: 3.62
V
Pk-Pk Voltage 2: 2.30
V
Pk-Pk Voltage 3: 0.563
V
Final Results
 The voltage generated by the piezoelectric due to the sound




burst is 150mV
The output from the piezoelectric is amplified by a factor of 23
The peak detector gives 85-90% of the peak value at its input
as a DC output
The comparator implements the final logic operation to
determine if the reflector pas is covered with frozen
precipitation
The time taken for the sensor to reflect a change in the state i.e.
from clear to covered is less than 60 seconds
State
Clear
Covered
Input from
piezoelectric
Peak amplitude
after filtering (V)
Output from
peak detector (V)
Comparator
output (V)
150 mV
3.5
3
0
100 mV
2.3
1.9
12
Evaluation
 Mr. Josh Underwood of Atmospheric Systems Corporation in Santa Clarita,
California is our client.
 Correspondence with Mr. Underwood included design criteria, SODAR
specifications and informal evaluation of the FPD.
 Primary evaluation was conducted by the team at Iowa State laboratories in
the Electrical Engineering department and at the Cedar Falls test site.


testing of the individual subsystems using simulated inputs
testing using real-world inputs from the SODAR system.
 Evaluation was based on original design criteria provided by John Deere
Renewables and was modified according to new client interaction and
availability of necessary equipment.
 Primary goals



fabrication of a working prototype,
implementation of a working prototype on a SODAR system
fulfillment of design criteria such as cost, energy consumption, ease of fabrication, etc.
Future Work
•
Adapt prototype to specific SODAR models
•
PCB layout and encasement
•
Protect piezoelectric sensors
•
Permanent attachment of sensors
•
Power & output connectors
Recommendations
•
Interface with existing precipitation detector circuitry
•
•
•
Increase accuracy
Add redundant piezoelectric films and circuits
•
Increase reliability
•
Increase coverage
Conduct a longer evaluation period
•
Installation on SODAR with heating element
•
Use during inclement weather
Questions?