User Constructed Sonar Equipment

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User Constructed Sonar Equipment

• Presented to
• PSUBS Convention 2004

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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Basic 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

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Speeds of Sound vm0 Degrees Celsius 1

• Air 332 m/s 1,090 f/s
• Fresh water 1,404 m/s 4,610 f/s
• Sea water 1,440 m/s 4,730 f/s
• Copper 3,560 m/s 11,680 f/s
• Iron 5,130 m/s 16,830 f/s

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Attenuation of Sound Through Water 2

• Absorption
• Roughly Related to frequency squared
• Scattering
• Signal scatters use to foreign materials in
  the water

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Spherical Sound Radiation

• Sound intensity I Power / Area (W/m2)
• Where area of a sphere 4pr2
• 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 / 4pr12 and I2 PT / 4pr22
• Combining we have I1 / r12 I2 / r22
• We have I2 (r12 / r22) I1 or I2 (r1 / r2) 2
  I1
• Conclusion Intensity of sound drops off with
  the square of the distance (r) from the source

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Sonar Considerations

• Attenuation of signal by water
• Spherical radiators
• Sonar patterns
• Choice of frequency
• Sensitivity of receiver
• Types of transducers

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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Transducers

• 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

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Sonar 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.

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Beam Angle
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Piezoelectric Principles 3
Voltage Creates DW
DW Generates Voltage
DW Change in Thickness
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Piezoelectric CeramicsManufactured in a Variety
of Shapes 4
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Ring and Disk Transducer Elements
Rings Helps Eliminate Lateral Resonance Modes
Thin Discs Showing Conductive Coating
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Piezoelectric Modes 5
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Piezoelectric Modes 5
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Piezoelectric Modes 5
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Piezoelectric Modes 5
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Typical Piezoelectric Ceramics 6
Channel Industries, Inc.
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Fish Finder Transducers
Advantages
Disadvantages

• 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

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Fish Finder Transducers(Eagle 7)
Transom Mount
Cylinder Thru Hull
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Available Specialty Transducers 7
Thru Hull Bronze
Thru Hull Plastic
Trolling Motor Mount
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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Ping Generator System
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Ping Generator Module
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192-KHz Frequency Generator Section
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Alternative Design
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Ping 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

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Ping Driver Circuit
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Ping Driver Module
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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Ping Reception
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Ping Receiver Module
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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Post-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!

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Sonar Principles

• Basic Concepts
• Transducers
• Ping generation
• Ping reception
• Post-ping processing
• Construction and testing

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Construction and Testing

• Pressure Housing
• Electronic assembly
• Modules
• Transducer array
• Testing

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Pressure Housing
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Electronics Assembly
Microcontroller Board
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Modules
Stepper Motor Driver Board
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Modules
Ping Generator
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Modules
192-KHz Receiver
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Transducer Array
Gray Cylinder Contains Stepping Motor Drive System
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Testing
Louisiana State University Shreveport Pool
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Testing
Yes it is a desktop!
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Bibliography

• 1 Sidney Borowitz and Arthur Beiser,
  Essentials of Physics, Addison Wesley
  Publishing, 1971.
• 2 http//www.fas.org/man/dod-101/navy/docs/fun/p
  art08.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.