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Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University

Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University. 2006 ASEE K-12 Workshop. Marconi Challenge. A simple and inexpensive yet challenging project. 2006 ASEE K-12 Workshop. Marconi Challenge.

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Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University

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  1. Marconi Challenge:Infrared Data Transmissionas the21st Century Crystal Radio Dennis SilageECE Temple University 2006 ASEE K-12 Workshop

  2. Marconi Challenge • A simple and inexpensive yet challenging project 2006 ASEE K-12 Workshop

  3. Marconi Challenge • 21st century crystal radio 2006 ASEE K-12 Workshop

  4. Marconi Challenge • Guglielmo Marconi pioneered wireless telegraphy at a wavelength of about 1500 meters and succeeded in sending an RF signal with kilowatts of power across the Atlantic Ocean in 1901 2006 ASEE K-12 Workshop

  5. Marconi Challenge • The Marconi Challenge for students is to send an IR signal at a wavelength of about 950 nanometers with milliwatts of power to a detector over the largest distance 2006 ASEE K-12 Workshop

  6. Marconi Challenge • Inexpensive infrared semiconductor emitter and detector 2006 ASEE K-12 Workshop

  7. Marconi Challenge • IR emitter diode • 5 Volts • 0.15 Amperes • 15 milliwatts • 950 nanometers 2006 ASEE K-12 Workshop

  8. Marconi Challenge • IR emitter is a semiconductor diode • No current flow 2006 ASEE K-12 Workshop

  9. Marconi Challenge • IR emitter diode • Current flow 2006 ASEE K-12 Workshop

  10. Marconi Challenge • Ben Franklin’s current flow 2006 ASEE K-12 Workshop

  11. Marconi Challenge • Georg Simon Ohm • Ohm’s Law • V = I R 2006 ASEE K-12 Workshop

  12. Marconi Challenge • IR emitter diode transmitter circuit • R1 = (3.2 – 1.3) V / 0.075 A • R1 = 1.9 V / 0.075 A • R1 ≈ 25 Ω 2006 ASEE K-12 Workshop

  13. Marconi Challenge • Resistors in series • V = I R • V = I (R1 + R2) • Equivalent resistor: R1 + R2 sum 2006 ASEE K-12 Workshop

  14. Marconi Challenge • Resistors in parallel • V = I R • R = V / I • 1 / R = I / V • now I = I1 + I2 • 1 / R = (I1 + I2) / V = I1 / V + I2 / V • 1 / R = 1 / R1 + 1 / R2 2006 ASEE K-12 Workshop

  15. Marconi Challenge • Resistors in parallel • 1 / R = 1 / R1 + 1 / R2 • Equivalent resistor: R = (R1 × R2) / (R1 + R2)product over the sum 2006 ASEE K-12 Workshop

  16. Marconi Challenge • IR emitter diode transmitter circuit • Calculate R1 • 0.075 A diode current 2006 ASEE K-12 Workshop

  17. Marconi Challenge • IR emitter diode transmitter circuit • 3.2 V = (0.075 A) R + 1.3 VR = (3.2 – 1.3) V / 0.075 A • R = 1.9 V / 0.075 A ≈ 25 Ω • R1 is four 100 Ω resistors in parallel 2006 ASEE K-12 Workshop

  18. Marconi Challenge • IR detector phototransistor • 70 Volts • 0.05 Amperes • 850 nanometer 2006 ASEE K-12 Workshop

  19. Marconi Challenge • IR detector phototransistor • Like a transistor it but only has acollector andemitter • Photon input 2006 ASEE K-12 Workshop

  20. Marconi Challenge • IR detector phototransistor receiver circuit 2006 ASEE K-12 Workshop

  21. Marconi Challenge • IR detector phototransistor receiver circuit • Sounder resistance • R = V / I = 3 /.015 = 200 Ω 2006 ASEE K-12 Workshop

  22. Marconi Challenge • IR detector phototransistor receiver circuit • Calculate collector currentI = (3.2 – 0.2) V / 200 I ≈ 0.015 A = 15 mA 2006 ASEE K-12 Workshop

  23. Marconi Challenge • IR detector phototransistor receiver circuit • 15 mA sounder current • 50 mA phototransistor maximum current 2006 ASEE K-12 Workshop

  24. Marconi Challenge • IR detector phototransistor receiver circuit • Sounder produces 70 dB intensity or about 0.00001 W/m2 2006 ASEE K-12 Workshop

  25. Marconi Challenge • IR transmitter-receiverIs the IR photodetector circuit sensitive to other sources? Yes, incandescent lamps and bright sunlight can causethe sounder to operate. 2006 ASEE K-12 Workshop

  26. Marconi Challenge • IR transmitter-receiverCan you apply opticalprinciples to increase thedistance? Yes, lens andmirrors can be used quiteeffectively in lessonmodules on optics and ray tracing. 2006 ASEE K-12 Workshop

  27. Marconi Challenge • IR transmitter-receiverCan we encode information on the sounder? Yes, we can introduce semaphores such asflags, Morse Code andmodern ASCII coding. 2006 ASEE K-12 Workshop

  28. Marconi Challenge • IR transmitter-receiverCan more advanced experiments be supported? Yes, IR data transmissioncan be used tointroduce digitalsignaling. 2006 ASEE K-12 Workshop

  29. Marconi Challenge • Marconi Challenge Parts • www.radioshack.com Total cost ≈ $12 • RS 275-142 Infrared emitter detector • RS 273-053 Mini buzzer 2006 ASEE K-12 Workshop

  30. Marconi Challenge • Marconi Challenge Parts • www.radioshack.com Total cost ≈ $12 • RS 278-149 PC Board (2) • RS 270-401 AA battery holder (4) • RS 271-1331 100 Ω resistors • AA batteries 2006 ASEE K-12 Workshop

  31. Marconi Challenge • Marconi Challenge Optional Parts • Lens, mirrors, brackets,ruler, telegraph keyand an inexpensivedigital voltmeter. 2006 ASEE K-12 Workshop

  32. Marconi Challenge • A Challenge for You! • The simplicity and excitement of the Marconi Challenge could be the 21st century equivalent of the crystal radio. 2006 ASEE K-12 Workshop

  33. Marconi Challenge • A Challenge for You! • The crystal radio provided the impetuous for many high school students to turn-on toengineeringandscience. 2006 ASEE K-12 Workshop

  34. Marconi Challenge • A Challenge for You! • No, it’s not an iPod but at least the students canunderstandhow it works! 2006 ASEE K-12 Workshop

  35. Marconi Challenge • For More Information • astro.temple.edu/~silage • www.arrl.org 2006 ASEE K-12 Workshop

  36. Marconi Challenge Dennis Silage,PhD K3DSProfessorTemple Universitysilage@temple.edu 2006 ASEE K-12 Workshop

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