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.. _ar_ultrasonic:

6.1 - Measuring Distance
======================================

The ultrasonic sensor module works on the principle of sonar and radar systems for determining the distance to an object.

* :ref:`cpn_ultrasonic`

**Required Components**

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
        - PURCHASE LINK
    *   - Kepler Kit	
        - 450+
        - |link_kepler_kit|

You can also buy them separately from the links below.


.. list-table::
    :widths: 5 20 5 20
    :header-rows: 1

    *   - SN
        - COMPONENT INTRODUCTION	
        - QUANTITY
        - PURCHASE LINK

    *   - 1
        - :ref:`cpn_pico_w`
        - 1
        - |link_picow_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|

**Schematic**

|sch_ultrasonic|

**Wiring**

|wiring_ultrasonic|

**Code**

.. note::

    * You can open the file ``6.1_ultrasonic.ino`` under the path of ``kepler-kit-main/arduino/6.1_ultrasonic``. 
    * Or copy this code into **Arduino IDE**.
    * Don't forget to select the board(Raspberry Pi Pico) and the correct port before clicking the **Upload** button.


.. raw:: html
    
    <iframe src=https://create.arduino.cc/editor/sunfounder01/631a1663-ce45-4d46-b8f0-7d10f32097a9/preview?embed style="height:510px;width:100%;margin:10px 0" frameborder=0></iframe>


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


**How it works?**

About the application of ultrasonic sensor, we can directly check the
subfunction.

.. code-block:: arduino

    float readSensorData(){// ...}

``PING`` is triggered by a HIGH pulse of 2 or more microseconds. (Give a
short ``LOW`` pulse beforehand to ensure a clean ``HIGH`` pulse.)

.. code-block:: arduino

    digitalWrite(trigPin, LOW); 
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH); 
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW); 

The echo pin is used to read signal from PING, a ``HIGH`` pulse whose
duration is the time (in microseconds) from the sending of the ping to
the reception of echo of the object.

.. code-block:: arduino

    microsecond=pulseIn(echoPin, HIGH);

The speed of sound is 340 m/s or 29 microseconds per centimeter.

This gives the distance travelled by the ping, outbound and return, so
we divide by 2 to get the distance of the obstacle.

.. code-block:: arduino

    float distance = microsecond / 29.00 / 2;  


Note that the ultrasonic sensor will pause the program when it is working, which may cause some lagging when writing complex projects.