.. note:: Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts. **Why Join?** - **Expert Support**: Solve post-sale issues and technical challenges with help from our community and team. - **Learn & Share**: Exchange tips and tutorials to enhance your skills. - **Exclusive Previews**: Get early access to new product announcements and sneak peeks. - **Special Discounts**: Enjoy exclusive discounts on our newest products. - **Festive Promotions and Giveaways**: Take part in giveaways and holiday promotions. 👉 Ready to explore and create with us? Click [|link_sf_facebook|] and join today! .. _py_ultrasonic: 6.1 Measuring Distance with an Ultrasonic Sensor ================================================ In this lesson, we'll learn how to use an **ultrasonic sensor module** with the Raspberry Pi Pico 2 to measure the distance to an object. Ultrasonic sensors are commonly used in robotics and automation systems for object detection and distance measurement. **What You'll Need** In this project, we need the following components. It's definitely convenient to buy a whole kit, here's the link: .. list-table:: :widths: 20 20 20 :header-rows: 1 * - Name - ITEMS IN THIS KIT - LINK * - Newton Lab Kit - 450+ - |link_newton_lab_kit| You can also buy them separately from the links below. .. list-table:: :widths: 5 20 5 20 :header-rows: 1 * - SN - COMPONENT - QUANTITY - LINK * - 1 - :ref:`cpn_pico_2` - 1 - |link_pico2_buy| * - 2 - Micro USB Cable - 1 - * - 3 - :ref:`cpn_breadboard` - 1 - |link_breadboard_buy| * - 4 - :ref:`cpn_wire` - Several - |link_wires_buy| * - 5 - :ref:`cpn_ultrasonic` - 1 - |link_ultrasonic_buy| **Understanding the Ultrasonic Sensor** The ultrasonic sensor works by emitting a short ultrasonic pulse from the **Trig** pin and listening for the echo on the **Echo** pin. By measuring the time it takes for the echo to return, we can calculate the distance to an object using the speed of sound. |ultrasonic_prin| * **Trigger Pulse**: A 10-microsecond high pulse on the Trig pin initiates the measurement. * **Ultrasonic Burst**: The sensor emits an 8-cycle ultrasonic burst at 40 kHz. * **Echo Reception**: The Echo pin goes high, and stays high until the echo is received back. * **Time Measurement**: By measuring the time the Echo pin stays high, we can calculate the distance. **Circuit Diagram** |sch_ultrasonic| **Wiring Diagram** |wiring_ultrasonic| **Writing the Code** Let's write a MicroPython program to measure distance using the ultrasonic sensor. .. note:: * Open the ``6.1_measuring_distance.py`` from ``newton-lab-kit/micropython`` or copy the code into Thonny, then click "Run" or press F5. * Ensure the correct interpreter is selected: MicroPython (Raspberry Pi Pico).COMxx. .. code-block:: python import machine import utime # Define the pins connected to the sensor TRIG = machine.Pin(17, machine.Pin.OUT) ECHO = machine.Pin(16, machine.Pin.IN) def measure_distance(): # Ensure the trigger pin is low TRIG.low() utime.sleep_us(2) # Send a 10µs pulse to trigger the measurement TRIG.high() utime.sleep_us(10) TRIG.low() # Wait for the echo pin to go high (start of echo pulse) while ECHO.value() == 0: pass start_time = utime.ticks_us() # Wait for the echo pin to go low (end of echo pulse) while ECHO.value() == 1: pass end_time = utime.ticks_us() # Calculate the duration of the echo pulse duration = utime.ticks_diff(end_time, start_time) # Calculate the distance (speed of sound is 34300 cm/s) distance = (duration * 0.0343) / 2 return distance while True: dist = measure_distance() print("Distance: {:.2f} cm".format(dist)) utime.sleep(0.5) Once the code is running, the Thonny Shell should display the distance readings in centimeters. Move an object closer or farther from the sensor to see the readings change. **Understanding the Code** #. Import necessary modules and set up the trigger and echo pins: .. code-block:: python import machine import utime TRIG = machine.Pin(17, machine.Pin.OUT) ECHO = machine.Pin(16, machine.Pin.IN) #. Measuring Distance: * Sends a trigger pulse to initiate measurement. * Waits for the echo response. * Calculates the duration of the echo pulse. * Computes the distance using the speed of sound. .. code-block:: python def measure_distance(): # Ensure trigger is low TRIG.low() utime.sleep_us(2) # Trigger a 10µs pulse TRIG.high() utime.sleep_us(10) TRIG.low() # Wait for echo to start while ECHO.value() == 0: pass start_time = utime.ticks_us() # Wait for echo to end while ECHO.value() == 1: pass end_time = utime.ticks_us() # Calculate duration duration = utime.ticks_diff(end_time, start_time) # Calculate distance distance = (duration * 0.0343) / 2 return distance #. Main Loop: * Continuously measures and prints the distance. * Pauses for half a second between measurements. .. code-block:: python while True: dist = measure_distance() print("Distance: {:.2f} cm".format(dist)) utime.sleep(0.5) **Understanding Limitations** * Blocking Code: * The while loops used to wait for the echo can block other code from running. * For more advanced applications, consider using interrupts or asynchronous programming to avoid blocking. * Measurement Range: * The HC-SR04 sensor typically has a range of 2 cm to 400 cm. * Objects closer than 2 cm or farther than 400 cm may not be detected accurately. * Environmental Factors: * Temperature and humidity can affect the speed of sound. * For precise measurements, adjust the speed of sound based on ambient conditions. **Conclusion** You've successfully used an ultrasonic sensor to measure distance with the Raspberry Pi Pico 2. This fundamental skill is widely applicable in robotics, automation, and interactive projects.