Ultrasonic Digital Ruler .
Ultrasonic Digital Ruler – Accurate Distance Measurement with HC-SR04 and Arduino/ESP32
Project Overview
In this project, I designed and developed an Ultrasonic Digital Ruler capable of measuring distances with high accuracy using the HC-SR04 ultrasonic sensor and a microcontroller (Arduino/ESP32). The system reads real-time distance measurements and displays them on a digital screen, with features like unit conversion (cm/inches), calibration, and optimized low-power operation.
Why This Project?
Traditional rulers and tape measures are practical but can be limited in certain scenarios—especially when measuring hard-to-reach places. I wanted to create a contactless digital alternative that is compact, easy to use, and demonstrates skills in sensor interfacing, embedded programming, and real-time data processing.
Components Used
- Microcontroller: Arduino Uno / ESP32
- Ultrasonic Sensor: HC-SR04
- Display: 16×2 LCD (I2C) or OLED Display (SSD1306)
- Battery Pack: 3.7V Li-ion Battery with Boost Converter (5V output)
- Push Buttons: For unit switching and calibration
- Voltage Regulator/Power Management: For efficient power usage
- Miscellaneous: Resistors, PCB, connectors, casing
How It Works
The HC-SR04 sensor emits an ultrasonic pulse and listens for the echo. The time delay between sending and receiving the pulse is directly proportional to the distance between the sensor and the object. The microcontroller processes this time to calculate the distance using the formula: Distance=(Time×Speed of Sound)/2\text{Distance} = \left( \text{Time} \times \text{Speed of Sound} \right) / 2Distance=(Time×Speed of Sound)/2
where the speed of sound is approximately 343 m/s at room temperature.
Key features include:
- Real-time Measurement: Updated several times per second.
- Unit Conversion: Easily switch between centimeters and inches.
- Calibration Mode: Adjust measurements for environmental factors like temperature.
- Low Power Optimization: Sleep modes on ESP32/Arduino and efficient display usage.
System Architecture (Block Diagram)
pgsqlCopyEdit+------------+ +-------------+ +----------------+
| HC-SR04 | ----> | Arduino/ | ----> | Display (LCD/ |
| Ultrasonic | | ESP32 | | OLED) |
| Sensor | | (Processing) | | |
+------------+ +-------------+ +----------------+
| |
| Calibration Button | Unit Switch Button
v v
Calibration Logic Unit Conversion Logic
Development Highlights
- Sensor Interfacing: Set up precise timing routines for pulseIn() and digitalWrite() to measure echo time accurately.
- Real-time Data Processing: Implemented interrupt-driven code for non-blocking sensor reads and smooth display updates.
- Calibration Feature: Added an adjustment factor based on environmental calibration for even greater accuracy.
- Power Optimization:
- Reduced sensor polling rate in idle state.
- Used microcontroller sleep modes to conserve battery when idle.
- Implemented display dimming or auto-off when not in use.
- User Interface:
- Single-button calibration setup.
- Toggle switch for units (cm ↔ inches).
Challenges and Solutions
| Challenge | Solution |
|---|---|
| Fluctuating sensor readings | Implemented moving average filtering |
| Power drain issues | Used deep sleep mode and display timeouts |
| Temperature affecting readings | Calibration mode to manually adjust measurements |
| Display flickering | Optimized refresh rates and used buffered screen updates |
Final Output
When powered on, the Ultrasonic Digital Ruler displays the distance in real-time. Users can:
- Switch units between cm and inches at the press of a button.
- Calibrate the sensor manually for enhanced accuracy.
- Enjoy stable and accurate measurements even across varied environments.
Skills Demonstrated
- Embedded Systems Design
- Sensor Interfacing
- Real-time Data Acquisition and Processing
- Signal Filtering and Calibration
- Power Management Techniques
- User Interface (UI) Development
Future Improvements
- Integrate Bluetooth to send measurements to a smartphone app.
- Add a temperature sensor for automatic speed-of-sound adjustment.
- Create a compact custom PCB to further miniaturize the project.
Conclusion:
This project not only delivered a practical tool but also deepened my hands-on experience with microcontrollers, sensor technology, and embedded system optimization. The Ultrasonic Digital Ruler is a small but powerful demonstration of what well-designed embedded systems can achieve.