ASHOR CHIRACKALMICHELLE TANIMRAN BUTTLUKE LEHMAN

CLIENT:MR. JOSH UNDERWOOD, ASC

ADVISOR:DR. TIM BIGELOW

ISU SODAR Teamsddec 10-06

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

Piezoelectric Sensors

Amplifiers

Filters

Sample & Hold

OR Gates

Temperature Sensor

Power Source

Heater

AND Gate

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

Heater

Temperature Sensor

SODAR speakers

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

StateInput from piezoelectri

c

Peak amplitude after filtering (V)

Output from peak detector

(V)

Comparator output (V)

Clear150 mV 3.5 3 0

Covered100 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?