5.12 Measuring Distance

The ultrasonic module is used for distance measurement or object detection. In this project, we will program the module to obtain obstacle distances. By sending ultrasonic pulses and measuring the time it takes for them to bounce back, we can calculate distances. This enables us to implement distance-based actions or obstacle avoidance behaviors.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
ESP32 Starter Kit	320+	ESP32 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
ESP32 WROOM 32E	BUY
ESP32 Camera Extension	-
Jumper Wires	BUY
Ultrasonic Module	BUY

Available Pins

• Available Pins

  Here is a list of available pins on the ESP32 board for this project.

  For Input	IO13, IO14, IO27, IO26, IO25, IO33, IO32, I35, I34, I39, I36, IO4, IO18, IO19, IO21, IO22, IO23
  For Output	IO13, IO12, IO14, IO27, IO26, IO25, IO33, IO32, IO15, IO2, IO0, IO4, IO5, IO18, IO19, IO21, IO22, IO23

Schematic

The ESP32 sends a set of square wave signals to the Trig pin of the ultrasonic sensor every 10 seconds. This prompts the ultrasonic sensor to emit a 40kHz ultrasound signal outward. If there is an obstacle in front, the ultrasound waves will be reflected back.

By recording the time it takes from sending to receiving the signal, dividing it by 2, and multiplying it by the speed of light, you can determine the distance to the obstacle.

Wiring

Code

Note

• Open the 5.12_ultrasonic.py file located in the esp32-starter-kit-main\micropython\codes path, or copy and paste the code into Thonny. Then, click “Run Current Script” or press F5 to execute it.

• Make sure to select the “MicroPython (ESP32).COMxx” interpreter in the bottom right corner.

import machine
import time

# Define the trigger and echo pins for the distance sensor
TRIG = machine.Pin(26, machine.Pin.OUT)
ECHO = machine.Pin(25, machine.Pin.IN)

# Calculate the distance using the ultrasonic sensor
def distance():
    # Ensure trigger is off initially
    TRIG.off()
    time.sleep_us(2)  # Wait for 2 microseconds

    # Send a 10-microsecond pulse to the trigger pin
    TRIG.on()
    time.sleep_us(10)
    TRIG.off()

    # Wait for the echo pin to go high
    while not ECHO.value():
        pass

    # Record the time when the echo pin goes high
    time1 = time.ticks_us()

    # Wait for the echo pin to go low
    while ECHO.value():
        pass

    # Record the time when the echo pin goes low
    time2 = time.ticks_us()

    # Calculate the time difference between the two recorded times
    during = time.ticks_diff(time2, time1)

    # Calculate and return the distance (in cm) using the speed of sound (340 m/s)
    return during * 340 / 2 / 10000

# Continuously measure and print the distance
while True:
    dis = distance()
    print('Distance: %.2f' % dis)
    time.sleep_ms(300)  # Wait for 300 milliseconds before repeating

Once the program is running, the Shell will print out the distance of the ultrasonic sensor from the obstacle ahead.