3. Experiment 1: Morse Code Generator
● Samuel F.B. Morse transmitted the first telegraphic message through a wire
from Washington to Baltimore in May of 1844
○ First Long distance electronic communication
● The telegraph uses Morse code
○ Dots and dashes represent letters
○ Alfred Vail and Samuel Morse collaborated
in the invention of Morse code
6. Experiment 2: One Wire Telegraph System
● First electronic communication system used by humanity
● Only one wire used and a ground wire on each end
○ Earth acts as the second wire
● In the past, one wire telegraph poles were seen near railroad tracks
○ Railroad used one wire telegraph systems
8. Experiment 2: One Wire Telegraph System
● Error:
○ System did not work with ground wires being open ended or connected by a group member
● Fixed the error by connecting the ground wires
○ Minimal losses in transition
○ Connected by a person creates a longer path for the current, therefore it will experience more
losses
10. Experiment 3: Two-Wire PA System
- The PA (Public Address) system is an amplification system used to reinforce
a sound source and distribute it through a venue or building. It is used to
make announcements in public spaces such as schools, shops, stadia, shops,
train stations and airports
- The PA system in its current form was invented by Edward Jensen and Peter
Pridham of Magnavox after they successfully began experimenting with
sound reproduction in the 1910’s
- In 1915, they built the first ever dynamic loudspeaker that consisted of a
2.5cm voice coil, a 7.6 cm corrugated diaphragm and a giant horn measring 86cm
11.
12. Our PA system was built on a much smaller scale and we used the following
components:
- R1 24kΩ Resistor – applies a positive voltage to the elctrect microphone
- P1 50kΩ Potentiometer – used to control volume
- C1 10µF Capacitor – sends audio signal produced by the microphone to the potentiometer
- C3 4.7µF Capacitor - determines the overall gain of the amplifier. The larger the value of this
capacitor, the higher the amplifier gain
- IC1 LM386 Integrated Circuit – amplifies the audio signal
- M1: Electrect Microphone
- SPK: Speaker
- C4 100µF Capacitor – sends amplified audio signal from the integrated circuit to the speaker
- Miscalleneous - battery snap, breadboard, wires
13. We built our device according to the schematic below. It did not work. We think the
problem was with our amplifier(integrated circuit)
14. Experiment 5: Opto (Optical) Receiver
- An opto receiver is a piece of fiber optical technology that receives
information from a transmitter in the form of light and converts that
information to whatever form that it needs to be used (which in the case of
this experiment the information is converted to sound.)
- The aim of the experiment was to make a circuit that would be able to receive
modulated light beam, process the modulated information then amplify and
reproduce it as sound through a speaker.
16. Components used in the experiment
Phototransistor – converts the light beam into a variable electric current
Electrolytic Capacitors
● C1: 10uF
○ The current is sent through capacitor C1 to the input of the audio amplifier, which corresponds to pin
3 of IC1
● C2: 47uF
○ Acts as a filter providing stability for the circuit
● C3: 10uF
○ Connected between pins 1 and 8 of IC1
○ Determines the overall gain of the amplifier
○ The greater the value of C3, the larger the amplifier’s gain
● C4: 100uF
24K Resistor – provides the necessary positive voltage to the collector of Q1 (Phototransistor)
LM 386 Integrated Circuit (IC1) – amplifies the signal from Q1 and sends it to the speaker through capacitor C4
17. We built our experiment
according to this schematic:
18. Experiment 6: Opto (Optical) Transmitter
- An optical transmitter is a piece of fiber optical technology that takes electrical energy
and converts it with light to be sent to a receiver.
- This experiment takes an electrical input from the battery and uses LED to emit a pulse
modulated light beam. In application, this pulse can contain information that needs to
be received by the Opto Receiver.
- A transceiver is a system created with the combination of an optical transmitter and an
optical receiver.
21. Components used in this experiment
Resistors
● R1: 24 K Resistor – Supplies microphone with positive voltage needed to function in circuit.
● R2: 220 ohm Resistor
● R3: 1 k Resistor
● R4:100 ohm Resistor – Limits current flowing to LED to a safe value that prevents burnout
Potentiometer
● 50K potentiometer
● Used to adjust voltage bias that is present at the base of the transistor which enables the transistor to function
properly
● Also used as a volume adjuster
Electret Microphone (M1)
● Captures sound and turns it into an electrical signal
Capacitors
● 0.1uF Disc Capacitor (C1) – connected to base of transistor to relay steady signal from Microphone
22. Clear LED (L1)
● Emits a beam of light within the visible spectrum
● The high frequency of the pulses (between 100Hz and 10,000Hz), will not be seen as variations in intensity but
instead a steady light beam
NPN Transistor: 2N3904 (Q1)
● Transistor takes audio signal present on its base and depending on the values of R2, R3 and P1 amplifies the signal
that then goes to the LED.
23. Procedure
The circuit was assembled as shown in the image below. The breadboards of the current experiment and experiment 5 were aligned with
LEDs facing each other. The Speaker failed to produce any sound when blowing into the microphone. It was possible that one of the
components may have been damaged due to a short circuit with two component leads touching.
27. Amplitude Modulation
Experiment used Analog Amplitude Modulation.
Carrier signal is varied according to instantaneous value of message signal.
Frequency remains constant.
Uses:
● CB transmitters
● Amateur radios
● Short distance radio links
28. How the Experiment
Works?
1. Blow into Microphone
2. Audio signal to base of transistor
3. Adjust potentiometer
4. Signal Amplified and sent to LED
5. Intensity of light varies(High frequency)
6. Light received by Phototransistor
7. Signal sent to audio amplifier
8. Greater the value of the capacitor the larger the gain
9. Out to Speaker
1
2
2
3
4
5
6
7
8
9
30. What is IR light?
● Infrared radiation light
● Human eyes cannot see
● Between microwaves and visible light
31. How does the receiver work?
● The photodiode (IRM) receives the rectified IR signal to complete a command
● The receiver has to come in contact with signal, directly or indirectly
33. How does it work?
● First IR TV remote was made in 1980 by Viewstar Inc., a Canadian company.
● Digitally-coded impulses sent through infrared radiation through IR LED
35. Why not RF?
● It was more expensive to produce
● It is more complex to apply i.e. touch screen remote
However we are slowly converting to
the Radio Frequency receivers because
our technology is getting more
complex and need more than one
signal sent at a time to complete a task.
37. What is an audible infrared remote control receiver?
● Receives infrared signal
○ From any transmitter
○ TV or VCR remote
● Emits a sound from the speaker
● Used by handicapped people
38. Components
● R1 (100 Ω resistor) - supplies the infrared receiver module (IRM) with positive
voltage.
● D1 (1N4148 Diode) - while connected to the output of the IRM, rectified the
signal produced by the IRM and sends negative voltage to the base of Q1.
● Q1 (PNP Transistor 2N3906) - conducts when negative voltage is applied to
its base, thus causing the speaker to emit a sound.
● R2 (10 Ω resistor)
● IRM - Infrared Receiver Module
● SPK - Speaker
40. What is an infrared proximity detector?
● Motion activated
● Functions with a LED
○ Emits light beam
● Used in motion sensors
○ Used for short distance
○ Touchscreen sensors during calls
○ Parking sensors
41. Components
● L1 (Infrared LED) - emits an infrared light beam that bounces off the object and strikes the infrared
receiver module (IRM).
● R1 (4.7 kΩ resistor)
● R2 (1 kΩ resistor)
● R3 (100 Ω resistor)
● R4 (100 Ω resistor)
● C1 (0.1 µF disc capacitor - 104)
● C2 (0.01 µF disc capacitor - 103)
● IC1 (555 Integrated Circuit)
● IRM - Infrared Receiver Module
● D1 (1N4148 Diode) - tiny silicon diode
● Q1 (PNP Transistor 2N3906)
● L2 (Clear LED) - with mark on the case
● Miscellaneous - battery snap, breadboard, and wires
42. Sources of Error
● Detector would not function properly.
● Reevaluation of the circuit did not produce a different result
45. Sources of Error
● Due to the similarity between Experiments 20 and 21, 21 failed
○ Detector with hand did not function
● Configuration of circuit was checked
○ Possible source of error was IRM
