Digital Tachometer using 8051 (AT89C51)

This project implements a digital tachometer using the AT89C51 (8051) microcontroller. The system measures rotational speed by counting input pulses over a fixed time window and displays the RPM on a 16×2 LCD.

The design is fully simulated in Proteus and the firmware is written in Embedded C using Keil µVision.

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📑 Table of Contents

• Features
• Working Principle
• Tools Used
• Project Structure
• How to Run the Simulation
• Notes
• License

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🔧 Features

• AT89C51 (8051) microcontroller
• External interrupt based pulse counting (INT0)
• Timer-based fixed gate time measurement
• 16×2 LCD interface (8-bit mode)
• RPM calculation and display
• Proteus simulation only (no physical hardware)

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🧠 Working Principle

1. Input pulses (simulated using a Proteus CLOCK source) are applied to the INT0 pin.
2. The microcontroller counts pulses over a fixed time window using Timer0.
3. RPM is calculated using: RPM = (Pulse Count × 60) / Gate Time (seconds)
4. The calculated RPM is displayed on the LCD.

Minor variations in RPM are expected due to pulse quantization and simulation time-step limitations of Proteus.

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🛠 Tools Used

• Keil µVision – Firmware development
• Proteus Design Suite – Circuit simulation
• AT89C51 – 8051 microcontroller
• GitHub – Version control

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📁 Project Structure

• firmware/ → Embedded C source and HEX file
  • tachometer.c
  • tachometer.hex
• simulation/ → Proteus project file
  • Digital_Tachometer.pdsprj
• images/ → Circuit diagrams, block diagrams, and results
  • block_diagram.png
  • circuit_diagram.png
  • lcd_output.png

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▶ How to Run the Simulation

1. Open the Proteus project file from the simulation/ folder.
2. Load the compiled HEX file into the AT89C51 microcontroller.
3. Run the simulation.
4. Adjust the CLOCK frequency to observe RPM changes on the LCD.

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📌 Notes

• This project is intended for academic and learning purposes.
• Optical sensor behavior is not physically simulated; pulse input is electrically stimulated.
• Minor RPM variations are normal due to discrete pulse counting.

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📜 License

This project is open-source and available for educational use.