How to design a distance meter using ESP32

The Internet of Things (IoT) has transformed how we interact with one another and our environment. As devices become smarter and more connected, do-it-yourself (DIY) projects have become increasingly popular. One such project involves developing a distance meter using the ESP32, a versatile microcontroller with built-in Wi-FI, Bluetooth connectivity, and diverse capabilities.

This project highlights the potential of IoT technology while serving as a gateway for creators to advance their skills in smart device development.

Figure 1. The prototype

Understanding the project

Before diving into the technical implementation, it’s important to understand how a distance meter works. It determines the distance between itself and an object using a sensor to emit and receive signals.

In this project, we’ll use an ultrasonic sensor, which transmits high-frequency sound waves and calculates the time it takes to reflect back after hitting an object. Knowing the speed of sound allows for accurate distance measurement.

The HC-SR04, a widely used and cost-effective ultrasonic sensor, operates by transmitting and receiving ultrasonic waves. Its measurement is based on the time it takes for the sound waves to reach an object and return to the sensor. The process works as follows:

Triggering: The ESP32 microcontroller sends a brief trigger signal to the HC-SR04 sensor.
Wave emission: The sensor emits an ultrasonic wave upon receiving the trigger signal.
Reflection: When the wave encounters an object, it reflects back toward the sensor.
Echo detection: The sensor detects the returning wave and generates an echo signal.
Distance calculation: By calculating the time interval between wave emission and echo detection and factoring in the speed of sound, the distance to the object is determined.

Components

For this project, you’ll require:

ESP32 development board: It’s responsible for processing data and controlling the system.

Figure 2. ESP32 development board

Ultrasonic sensor (HC-SR04): It measures distance by sending and receiving ultrasonic waves.

Figure 3. Ultrasonic sensor

OLED display: It displays the distance measured by the sensor and controller.

Figure 4. OLED display

Jumper wires: These wires are used for connecting various components to the breadboard.
Breadboard: It provides a platform for easy circuit prototyping.
USB cable: This cable is used for programming and powering the ESP32 board.
Computer/laptop: Required for programming the ESP32.

Building the circuit

Figure 5. Circuit diagram

1. Connect the ultrasonic sensor to ESP32:

- VCC to 5V pin on the ESP32
- GND to GND pin on the ESP32
- Trig to GPIO pin (e.g., GPIO 5)
- Echo to GPIO pin (e.g., GPIO 18)

2. Connect the OLED display to ESP32:

- VCC to 5V pin on the ESP32
- GND to GND pin on the ESP32
- SCK to GPIO pin (e.g., GPIO 21)
- SDA to GPIO pin (e.g., GPIO 22)

3. Power on the ESP32

- Connect ESP32 to your computer using the USB cable

Coding the distance meter

After the circuit is completed, it’s time to program ESP32. We’ll use the Arduino IDE for this task.

Here are the steps:

1. Install the ESP32 board package:

- Open the Arduino IDE by navigateing to File > Preferences
- In the Additional Board Manager URLs field, paste https://dl.espressif.com/dl/package_esp32_index.json
- Go to Tools > Board > Boards Manager, search for “ESP32,” and install the package

2. Write the code:

- Below is the sketch to get you started

3. Connect ESP32 to your computer:

- Select the correct board and port from the Tools menu
- Click the upload button

Testing and calibration

Once the code is uploaded successfully, open the Serial Monitor in Arduino IDE. You should see the distance measurements displayed in centimeters. To test its accuracy, simply place objects in front of the ultrasonic sensor.

Figure 6. Test set-up

Conclusion

Integrating the HC-SR04 ultrasonic sensor with an ESP32 microcontroller delivers a reliable and efficient solution for distance measurement across various applications. Its versatility and ease of use make it a valuable tool in robotics, IoT projects, and automation.

By providing accurate, real-time data, this system proves indispensable in advancing smart technologies and enhancing the functionality of modern innovations.