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Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University 2006 ASEE K-12 Workshop.

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Presentation on theme: "Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University 2006 ASEE K-12 Workshop."— Presentation transcript:

1 Marconi Challenge: Infrared Data Transmission as the 21 st Century Crystal Radio Dennis Silage ECE Temple University 2006 ASEE K-12 Workshop

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

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

4 Marconi Challenge 2006 ASEE K-12 Workshop 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 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

5 Marconi Challenge 2006 ASEE K-12 Workshop 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 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

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

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

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

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

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

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

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

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

14 Marconi Challenge 2006 ASEE K-12 Workshop Resistors in parallel Resistors in parallel V = I R 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

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

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

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

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

19 Marconi Challenge 2006 ASEE K-12 Workshop IR detector phototransistor IR detector phototransistor Like a transistor it but only has a collector and emitter Like a transistor it but only has a collector and emitter Photon input Photon input

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

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

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

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

24 Marconi Challenge 2006 ASEE K-12 Workshop IR detector phototransistor receiver circuit IR detector phototransistor receiver circuit Sounder produces 70 dB intensity or about 0.00001 W/m 2 Sounder produces 70 dB intensity or about 0.00001 W/m 2

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

26 Marconi Challenge 2006 ASEE K-12 Workshop IR transmitter-receiver Can you apply optical principles to increase the distance? Yes, lens and mirrors can be used quite effectively in lesson modules on optics and ray tracing. IR transmitter-receiver Can you apply optical principles to increase the distance? Yes, lens and mirrors can be used quite effectively in lesson modules on optics and ray tracing.

27 Marconi Challenge 2006 ASEE K-12 Workshop IR transmitter-receiver Can we encode information on the sounder? Yes, we can introduce semaphores such as flags, Morse Code and modern ASCII coding. IR transmitter-receiver Can we encode information on the sounder? Yes, we can introduce semaphores such as flags, Morse Code and modern ASCII coding.

28 Marconi Challenge 2006 ASEE K-12 Workshop IR transmitter-receiver Can more advanced experiments be supported? Yes, IR data transmission can be used to introduce digital signaling. IR transmitter-receiver Can more advanced experiments be supported? Yes, IR data transmission can be used to introduce digital signaling.

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

30 Marconi Challenge 2006 ASEE K-12 Workshop Marconi Challenge Parts 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 AA batteries

31 Marconi Challenge 2006 ASEE K-12 Workshop Marconi Challenge Optional Parts Marconi Challenge Optional Parts Lens, mirrors, brackets, ruler, telegraph key and an inexpensive digital voltmeter.

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

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

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

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

36 Marconi Challenge 2006 ASEE K-12 Workshop Dennis Silage, PhD K3DS Professor Temple University silage@temple.edu


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