⚙️ 4-Bit Binary Adder using Logic Gates

🧠 Overview

Hi everyone! 👋
Recently, I’ve built a 4-bit binary adder using full adders implemented with basic logic gates.

This project demonstrates how binary addition works at the hardware level using XOR, AND, and OR gates — the core building blocks of digital electronics.

The adder takes two 4-bit binary inputs through DIP switches and displays the sum and carry outputs using LEDs.
It’s a simple yet powerful way to visualize how computers perform arithmetic operations at the logic gate level.

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🔩 Components Used

Component	Quantity	Description
7486 IC	2	Quad XOR Gate (used for Sum bits)
7432 IC	2	Quad OR Gate (used for Carry generation)
7408 IC	1	Quad AND Gate (used for Carry propagation)
DIP Switch (4-bit)	2	For binary inputs (A and B)
LEDs	5	For displaying Sum (4 bits) and Carry
Resistors	5	220Ω or 330Ω (current limiting for LEDs)
Breadboard	1	Circuit prototyping
Jumper Wires	As needed	For connections
5V Power Supply	1	Logic-level power source

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🔍 Circuit Description

Each full adder is formed using basic gates as follows:

Sum = A ⊕ B ⊕ Cin
Carry = (A ⋅ B) + (Cin ⋅ (A ⊕ B))

By cascading four full adders, we obtain a 4-bit binary adder.
The DIP switches act as inputs (A3–A0 and B3–B0), and LEDs display the output sum bits (S3–S0) along with the final carry bit (Cout).

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🧾 Truth Table (Example for 1-bit Full Adder)

A	B	Cin	Sum	Cout
0	0	0	0	0
0	0	1	1	0
0	1	0	1	0
0	1	1	0	1
1	0	0	1	0
1	0	1	0	1
1	1	0	0	1
1	1	1	1	1

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💡 Working Principle

1. Set input bits A3–A0 and B3–B0 using the DIP switches.
2. Observe the LED outputs — they represent the binary sum and carry.
3. Changing switch combinations dynamically updates the results, demonstrating live binary addition.

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📸 Project Image

Here’s the actual circuit implementation on a breadboard:

![4-Bit Binary Adder Circuit]

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🧰 Key Learning Outcomes

• Understanding binary addition and carry propagation
• Practical use of logic gate ICs (74xx series)
• Cascading multiple full adders to create multi-bit arithmetic circuits
• Breadboard circuit wiring and debugging

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🚀 Future Improvements

• Add a 7-segment display for showing decimal equivalents of inputs and outputs
• Implement subtraction mode using 2’s complement
• Design a PCB version for permanent setup
• Interface with a microcontroller (Arduino/ESP32) for automated input control and output display

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👨‍💻 Author

Mohammad Sharique Arshad
B.Tech in Electronics and Communication Engineering (ECE)
Lovely Professional University

📫 GitHub Profile
💬 “Building circuits that bring logic to life.”

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🧩 Tags

#DigitalElectronics #LogicGates #4BitAdder #ElectronicsProject #ECE #HardwareLearning