user constructed sonar equipment presented to psubs convention 2004

User Constructed Sonar User Constructed Sonar EquipmentEquipment

Presented to

PSUBS Convention 2004

Sonar PrinciplesSonar Principles

Basic ConceptsTransducersPing generationPing receptionPost-ping processingConstruction and testing

Basic Sonar ConceptsBasic Sonar Concepts

Generate a signal at some frequency f0

Drive an transducer at f0 for a short duration of time generating a “ping”

Allow the sound waves generated to propagate outward at the speed of the medium Vm

Receive the return echo signal measuring the time of flight from transmission to reception Tf

Calculate the distance to target, D = ( Tf · Vm ) / 2

Speeds of Sound Speeds of Sound vvmm

00 Degrees Celsius Degrees Celsius [1][1]

Air 332 m/s 1,090 f/sFresh water 1,404 m/s 4,610 f/sSea water 1,440 m/s 4,730 f/sCopper 3,560 m/s 11,680 f/s

Iron 5,130 m/s 16,830 f/s

Sonar ConsiderationsSonar Considerations

Attenuation of signal by waterSpherical radiatorsSonar patternsChoice of frequencySensitivity of receiverTypes of transducers

Attenuation of Sound Through Attenuation of Sound Through Water Water [2][2]

Absorption Roughly Related to frequency squared

Scattering Signal scatters use to foreign materials in the

water


Attenuation of signal by water

Spherical radiatorsSonar patternsChoice of frequencySensitivity of receiverTypes of transducers

Spherical Sound RadiationSpherical Sound RadiationSound intensity: I = Power / Area (W/m2) Where area of a sphere = 4r2

Same power through any radius (r) we can imagine, with the source in the center

Let PT = Total power through any radius (r)

Therefore: I1 = PT / 4r12 and I2 = PT / 4r2

2

Combining we have: I1 / r12 = I2 / r2

2

We have: I2 = (r12 / r2

2) I1 or I2 = (r1 / r2) 2 I1

Conclusion: Intensity of sound drops off with the square of the distance (r) from the source


Attenuation of signal by waterSpherical radiators

Sonar patternsChoice of frequencySensitivity of receiverTypes of transducers


Attenuation of signal by waterSpherical radiatorsSonar patterns

Choice of frequencySensitivity of receiverTypes of transducers


Attenuation of signal by waterSpherical radiatorsSonar patternsChoice of frequency

Sensitivity of receiverTypes of transducers


Attenuation of signal by waterSpherical radiatorsSonar patternsChoice of frequencySensitivity of receiver

Types of transducers


Basic Concepts

TransducersPing generationPing receptionPost-ping processingConstruction and testing

TransducersTransducers

Sonar transducer facts Beam Angle Piezoelectric principles Piezoelectric ceramics Ring and disk transducers elements Piezoelectric modes Typical piezoelectric ceramics Fish finder transducers Available specialty transducers

Sonar Transducer FactsSonar Transducer Facts

Transducers convert electrical signals to sound. Transducers convert sound into electrical signals. Most transducers send and receive best at one

characteristic frequency f0. Most small sonar transducers are of a piezoelectric

form. Most piezoelectric materials for sonar application are

ceramics.

Beam AngleBeam Angle

Piezoelectric Principles Piezoelectric Principles [3][3]

Voltage Creates W

W Generates Voltage

W = Change in Thickness

Piezoelectric CeramicsPiezoelectric CeramicsMManufactured in a Variety of Shapes anufactured in a Variety of Shapes [4][4]

Ring Ring andand Disk Transducer Elements Disk Transducer Elements

Rings

Helps Eliminate Lateral Resonance Modes

Thin Discs

Showing Conductive Coating

Piezoelectric Modes Piezoelectric Modes [5][5]

Typical Piezoelectric Ceramics Typical Piezoelectric Ceramics [6][6]

Channel Industries, Inc.

Fish Finder TransducersFish Finder Transducers

Relatively Inexpensive Encapsulated Wiring Attached Wide or Narrow Cone Locally Available

Little Choice of Resonate Frequencies

Unknown Piezoelectric Material Used

Unknown Electrical Properties of Material

Advantages Disadvantages

Fish Finder TransducersFish Finder Transducers((Eagle Eagle [7][7]))

Transom Mount

Cylinder Thru Hull

Available Specialty Transducers Available Specialty Transducers [7][7]

Thru Hull Bronze

Thru Hull Plastic

Trolling Motor Mount


Basic ConceptsTransducers

Ping generationPing receptionPost-ping processingConstruction and testing

Ping Generator SystemPing Generator System

Ping Generator ModulePing Generator Module

192-KHz Frequency 192-KHz Frequency Generator SectionGenerator Section

Alternative DesignAlternative Design

Ping Driver CircuitPing Driver Circuit

Amplifies 192-KHz Signal from Generator and Drives Transducer

Generates Drive Only when Ping Enable is Active

Multiplexes Sonar Transducers if System Requires

Ping Driver CircuitPing Driver Circuit

Ping Driver ModulePing Driver Module


Basic ConceptsTransducersPing generation

Ping receptionPost-ping processingConstruction and testing

Ping ReceptionPing Reception

Ping Receiver ModulePing Receiver Module


Basic ConceptsTransducersPing generationPing receptionPost-ping processingConstruction and testing

Post-ping Processing OptionsPost-ping Processing Options

Sample return analog for feed to computer or microcontroller.

Use analog means of measuring time between ping and the breaking of a return threshold level.

Be creative with your own methods of monitoring returned amplitude vs time!

Sonar PrinciplesSonar PrinciplesBasic ConceptsTransducersPing generationPing receptionPost-ping processing

Construction and testing

Construction and TestingConstruction and Testing

Pressure HousingElectronic assembly ModulesTransducer arrayTesting

Pressure HousingPressure Housing

Electronics AssemblyElectronics Assembly

Microcontroller Board

ModulesModules

Stepper Motor Driver Board

ModulesModules

Ping Generator

ModulesModules

192-KHz Receiver

Transducer ArrayTransducer Array

Gray Cylinder Contains Stepping Motor Drive System

TestingTesting

Louisiana State University – Shreveport Pool

TestingTesting

Yes it is a desktop!

BibliographyBibliography

[1] Sidney Borowitz and Arthur Beiser, “Essentials of Physics”, Addison Wesley Publishing, 1971.

[2] http://www.fas.org/man/dod-101/navy/docs/fun/part08.htm

[3] http://www.Azom.com

[4] Keramos Advanced Piezoelectrics

http://www.piezotechnologies.com/keramos.htm

[5] “Piezoelectric Ceramics”, EDO Corporation.

[6] “Piezoelectric Ceramics”, Channel Industries, Inc.

[7] Lowrance Electronics, Inc.

user constructed sonar equipment presented to psubs convention 2004

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