How to Measure Distance Using Raspberry Pi Zero 2 W, Waterproof Ultrasonic Sensor and 16×2 LCD

Introduction

Measuring distance is one of the most common applications in electronics and automation projects. Whether you are building a water level monitoring system, an obstacle detection system, or an industrial automation project, ultrasonic sensors provide an accurate and cost-effective solution.

In this tutorial, we will learn how to measure distance using a Raspberry Pi Zero 2 W, a Waterproof Ultrasonic Sensor, and a 16×2 LCD with I2C interface. The measured distance will be displayed both on the terminal and on the LCD screen in real time.

Project Overview

The Waterproof Ultrasonic Sensor emits ultrasonic sound waves and measures the time taken for the echo to return after hitting an object. The Raspberry Pi calculates the distance based on this time interval and displays the result on the LCD.

Features

• Real-time distance measurement
• Waterproof sensor suitable for outdoor applications
• LCD display for local monitoring
• Raspberry Pi-based processing and control
• Easy integration into water level monitoring projects

Components Required

Understanding the Ultrasonic Sensor

The ultrasonic sensor works by:

1. Sending an ultrasonic pulse through the TRIG pin.
2. Waiting for the reflected echo.
3. Measuring the duration of the echo pulse.
4. Calculating the distance using the speed of sound.

Distance Formula

Distance = (Time × Speed of Sound) ÷ 2

Where:

• Speed of Sound = 343 m/s
• Time = Echo pulse duration

The division by 2 is necessary because the sound travels to the object and back.

Circuit Connections

Ultrasonic Sensor Connections

Important Note

The ECHO pin outputs a 5V signal, while Raspberry Pi GPIO pins are only 3.3V tolerant. Therefore, a voltage divider must be used between the ECHO pin and GPIO24.

LCD I2C Connections

Enabling I2C on Raspberry Pi

Before connecting the LCD, enable I2C:

sudo raspi-config

Navigate to:

Interface Options → I2C → Enable

Reboot the Raspberry Pi:

sudo reboot

Verify the LCD address:

sudo i2cdetect -y 1

Most LCD modules will appear at:

0x27

or

0x3F

Installing Required Libraries

Update your Raspberry Pi:

sudo apt update

Install required packages:

sudo apt install python3-smbus i2c-tools

Install Python libraries:

pip3 install RPLCD smbus2 --break-system-packages

Python Program

The Python program triggers the ultrasonic sensor, calculates the distance, averages multiple readings for improved accuracy, and displays the result on the LCD.

The LCD shows:

Water Level
Dist:125.4cm

The same value is also displayed in the terminal for debugging and monitoring purposes.

Complete Code

import RPi.GPIO as GPIO
import time
from RPLCD.i2c import CharLCD

# LCD Address
lcd = CharLCD(
    i2c_expander='PCF8574',
    address=0x27,
    port=1,
    cols=16,
    rows=2
)

TRIG_PIN = 23
ECHO_PIN = 24

GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG_PIN, GPIO.OUT)
GPIO.setup(ECHO_PIN, GPIO.IN)

GPIO.output(TRIG_PIN, False)

lcd.clear()
lcd.write_string("System Starting")

time.sleep(2)

def read_distance():

    GPIO.output(TRIG_PIN, False)
    time.sleep(0.000005)

    GPIO.output(TRIG_PIN, True)
    time.sleep(0.00002)
    GPIO.output(TRIG_PIN, False)

    timeout = time.perf_counter() + 0.03

    while GPIO.input(ECHO_PIN) == 0:
        pulse_start = time.perf_counter()

        if time.perf_counter() > timeout:
            return -1

    timeout = time.perf_counter() + 0.03

    while GPIO.input(ECHO_PIN) == 1:
        pulse_end = time.perf_counter()

        if time.perf_counter() > timeout:
            return -1

    pulse_duration = pulse_end - pulse_start

    distance = (pulse_duration * 34300) / 2

    return distance


try:

    while True:

        readings = []

        for i in range(5):

            d = read_distance()

            if 0 < d < 600:
                readings.append(d)

            time.sleep(0.05)

        lcd.clear()

        if len(readings) > 0:

            avg_distance = sum(readings) / len(readings)

            print(f"Distance = {avg_distance:.2f} cm")

            lcd.cursor_pos = (0, 0)
            lcd.write_string("Water Level")

            lcd.cursor_pos = (1, 0)
            lcd.write_string(f"Dist:{avg_distance:5.1f}cm")

        else:

            print("No Valid Reading")

            lcd.cursor_pos = (0, 0)
            lcd.write_string("Sensor Error")

            lcd.cursor_pos = (1, 0)
            lcd.write_string("No Echo")

        time.sleep(0.5)

except KeyboardInterrupt:

    lcd.clear()
    lcd.write_string("Program Stopped")

finally:

    GPIO.cleanup()
    lcd.close(clear=True)

Sample Output

LCD Display:

Water Level
Dist: 85.7cm

Terminal Output:

Distance = 85.70 cm
Distance = 85.65 cm
Distance = 85.73 cm

Applications

This project can be used in a variety of practical applications:

Water Tank Monitoring

Monitor water levels in overhead or underground tanks.

River and Canal Monitoring

Measure water levels in outdoor environments using the waterproof sensor.

Obstacle Detection

Detect objects and obstacles in robotic systems.

Smart Agriculture

Monitor water storage tanks and irrigation systems.

Industrial Automation

Measure distances in storage and material handling systems.

Advantages of Using a Waterproof Ultrasonic Sensor

• Suitable for outdoor environments
• Resistant to moisture and humidity
• Long measurement range
• Reliable operation in harsh conditions
• Ideal for water level monitoring systems

Troubleshooting

LCD Not Detected

Check:

sudo i2cdetect -y 1

Verify SDA and SCL connections.

No Distance Reading

Check:

• Sensor wiring
• Power supply voltage
• Voltage divider on ECHO pin

Unstable Readings

• Ensure a stable 5V supply.
• Average multiple readings.
• Keep the sensor surface clean.
• Avoid highly angled targets.

Conclusion

Using a Raspberry Pi Zero 2 W with a Waterproof Ultrasonic Sensor and a 16×2 LCD provides an excellent solution for accurate distance measurement and water level monitoring applications. The project is easy to build, cost-effective, and suitable for both educational and industrial applications.