Analog Circuit� (2)

Parmida Amngostar

Objective

To create a simple sound-reactive light display where LEDs light up in response to the volume or beat of ambient sound, like music or voice.

Dancing Light LEDs with Music

Required Components

• Transistor
• LEDs
• Microphone
• Capacitors
• Resistor
• Breadboard
• Wires

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LEDs

Transistor

Breadboard

Wires

Microphone

Capacitor

Resistor

The Purpose of Each Component

Transistor

Transistors are semiconductor devices primarily used for amplifying or switching electronic signals and power. 

• Transistor

Transistors are fundamental semiconductor devices used for amplification and switching.

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• Op-amp

Op-amps (operational amplifiers) are integrated circuits, constructed mostly out of transistors and resistors. These integrated circuits multiply an input signal to a larger output.

Transistor and Op-amps

Transistors

• BJT Transistors: A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device that acts as a switch or an amplifier. It's composed of two p-n junctions, typically a PNP or NPN configuration.

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• FET Transistors: A Field-Effect Transistor (FET) is a type of transistor that controls the flow of current using an electric field, rather than a current, like a Bipolar Junction Transistor (BJT). FETs are known for their high input impedance and fast switching speeds.

How Use Bread Board

Breadboards are composed of three (3) parts:

1. Horizontal Rows (yellow and green lines)
2. Vertical Columns
3. Power (red) /Ground (blue) Rails

The middle divider separates both sides. So, if you wire power and ground to one side of the breadboard, you will also need to power/ground the other side.

Circuit Schematic

• Transistor: four 2N3904 (NPN)
• Electret Microphone
• Capacitors: 0.1uF
• Resistor: three100Ω, two 10kΩ, one 1MΩ
• LEDs: three LEDs of different color

Required Systems for Measurement

• DC Power Supply
• Alligator clip Cables

Wiring Up Step by Step

Step 1: Place four transistors on the breadboard according to the picture below.

GND

VCC

Emitter

Base

Collector

Amplifier

Switch

Wiring Up Step by Step

Step 2: Place three LEDs on the breadboard for switches

Collector

VCC

VCC

Collector

Collector

Collector

Wiring Up Step by Step

Step 3: Place three 100Ω resistors for switches

Resistors:

All resistors can be connected in either direction.

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Place them between GND and the Base of a transistor.

Base

Base

Base

GND

Wiring Up Step by Step

Step 4: 10kΩ and 1MΩ resistors placement for the amplifier

Resistors:

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10kΩ: Place between GND and Collector

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1MΩ: Place between GND and Base

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1MΩ

10kΩ

Wiring Up Step by Step

Step 5: 10kΩ and 0.1uF capacitor placement for the amplifier

Resistors:

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10kΩ: Place between VCC and an empty hole

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0.1uF: Place between Base and the chosen empty hole

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10kΩ

0.1uF

Empty

Hole

Wiring Up Step by Step

Step 6: Connect Wires

Connections:

1. Base T1 to Base T2
2. Base T2 to Base T3
3. Base T3 to Collector T4
4. Emitter T4 to GND

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T1

T2

T3

T4

Wiring Up Step by Step

Step 7: Connect Microphone and Powe wires

Microphone:

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Connect the red and black wires according to the picture

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Power Wires:

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Connect two wires to the GND and VCC pins

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Setting Up Power Supply

DC Power Supply

1. Turn on the device
2. Choose channel 2 🡪 Set to 5V 🡪 Push “Enter” pin
3. Connect the “Black” output of channel 2 to GND
4. Connect the “RED” output of channel 2 to VCC
5. Push the “On” button for channels 2 & 3

(1)

(2.1)

(3)

(5)

(2.2)

(4)

VCC

GND

Turn On Circuit

Visualize Signal using Oscilloscope

2 Probes

GND

Signal

Setting Up Oscilloscope

1. Connect two probs to pins 1 and 2
2. Turn on the Oscilloscope
3. Turn on both channels (you should be able to see two signal on the monitor (yellow and green)
4. Turn off the board first and connect the probs to the specific pins to see the signal (next slide)
5. Use Auto Scale and  Run/Stop button to see the signal

(1)

(2)

(3)

(5)

(5)

Channel 1 Connection

Channel 1 is the original signal:

�1. Conncet the black pin to the GND �2. Connect signal prob to interconnection of CAP and RES

GND

Signal

Channel 2 Connection

Channel 2 is the amplified signal:

�1. Conncet the black pin to the GND �2. Connect signal prob to collector of T4

GND

Signal

Visualize the Signals

1. Turn on the board 
2. Start playing a sound
3. Click on Auto Scale button
4. Click on the Run/Stop Button

Amplified Signal

Original Signal