User Constructed Sonar Equipment Presented to PSUBS Convention 2004

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

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

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

Speeds of Sound vm 0 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

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

Attenuation of Sound Through Water [2] Absorption Roughly Related to frequency squared Scattering Signal scatters use to foreign materials in the water

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

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

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

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

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

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

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

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

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.

Beam Angle

Piezoelectric Principles [3] Voltage Creates DW DW Generates Voltage DW = Change in Thickness

Piezoelectric Ceramics Manufactured in a Variety of Shapes [4]

Ring and Disk Transducer Elements Rings Helps Eliminate Lateral Resonance Modes Thin Discs Showing Conductive Coating

Piezoelectric Modes [5]

Piezoelectric Modes [5]

Piezoelectric Modes [5]

Piezoelectric Modes [5]

Typical Piezoelectric Ceramics [6] Channel Industries, Inc.

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

Fish Finder Transducers (Eagle [7]) Transom Mount Cylinder Thru Hull

Available Specialty Transducers [7] Thru Hull Bronze Thru Hull Plastic Trolling Motor Mount

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

Ping Generator System

Ping Generator Module

192-KHz Frequency Generator Section

Alternative Design

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

Ping Driver Circuit

Ping Driver Module

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

Ping Reception

Ping Receiver Module

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

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!

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

Construction and Testing Pressure Housing Electronic assembly Modules Transducer array Testing

Pressure Housing

Microcontroller Board Electronics Assembly Microcontroller Board

Stepper Motor Driver Board Modules Stepper Motor Driver Board

Modules Ping Generator

Modules 192-KHz Receiver

Gray Cylinder Contains Stepping Motor Drive System Transducer Array Gray Cylinder Contains Stepping Motor Drive System

Louisiana State University – Shreveport Pool Testing Louisiana State University – Shreveport Pool

Testing Yes it is a desktop!

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/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.