1. User Constructed Sonar Equipment Presented to PSUBS Convention 2004

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

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

4. Basic Sonar Concepts Generate a signal at some frequency f 0 Drive an transducer at f 0 for a short duration of time generating a “ping” Allow the sound waves generated to propagate outward at the speed of the medium V m Receive the return echo signal measuring the time of flight from transmission to reception T f Calculate the distance to target, D = ( T f · V m ) / 2

6. Speeds of Sound v m 0 Degrees Celsius [1] Air 332 m/s 1,090 f/s Fresh water1,404 m/s 4,610 f/s Sea water1,440 m/s 4,730 f/s Copper3,560 m/s 11,680 f/s Iron5,130 m/s 16,830 f/s

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

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

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

10. Spherical Sound Radiation Sound intensity: I = Power / Area (W/m 2 ) Where area of a sphere = 4  r 2 Same power through any radius (r) we can imagine, with the source in the center Let P T = Total power through any radius (r) Therefore: I 1 = P T / 4  r 1 2 and I 2 = P T / 4  r 2 2 Combining we have: I 1 / r 1 2 = I 2 / r 2 2 We have: I 2 = (r 1 2 / r 2 2 ) I 1 or I 2 = (r 1 / r 2 ) 2 I 1 Conclusion: Intensity of sound drops off with the square of the distance (r) from the source

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

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

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

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

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

16. 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

17. 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 f 0. Most small sonar transducers are of a piezoelectric form. Most piezoelectric materials for sonar application are ceramics.

18. Beam Angle

19. Piezoelectric Principles [3] Voltage Creates  W  W Generates Voltage  W = Change in Thickness

20. Piezoelectric Ceramics M anufactured in a Variety of Shapes [4]

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

22. Piezoelectric Modes [5]

26. Typical Piezoelectric Ceramics [6] Channel Industries, Inc.

27. Fish 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 AdvantagesDisadvantages

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

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

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

31. Ping Generator System

32. Ping Generator Module

33. 192-KHz Frequency Generator Section

35. Alternative Design

37. 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

38. Ping Driver Circuit

39. Ping Driver Module

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

42. Ping Reception

43. Ping Receiver Module

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

46. 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!

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

48. Construction and Testing Pressure Housing Electronic assembly Modules Transducer array Testing

49. Pressure Housing

50. Electronics Assembly Microcontroller Board

51. Modules Stepper Motor Driver Board

52. Modules Ping Generator

53. Modules 192-KHz Receiver

54. Transducer Array Gray Cylinder Contains Stepping Motor Drive System

55. Testing Louisiana State University – Shreveport Pool

56. Testing Yes it is a desktop!

57. 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.