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.. _ar_analog_read:

1.5 Analog Read
===============

Overview
------------

You can use the analogRead() command to read analog input from the
physical world through an analog pin, which is suitable for analog input
elements such as potentiometers, photoresistance, water level detection
sensors, and so on. This article will take the potentiometer as an
example to read the analog value of its output.

Components Required
--------------------

.. image:: img/list_1.5.png

* :ref:`cpn_mega2560`
* :ref:`cpn_breadboard`
* :ref:`cpn_wires`
* :ref:`cpn_potentiometer`

Fritzing Circuit
----------------

In this example, we use the analog pin (A0) to read the value of the
potentiometer. Connect the pins at both ends of the potentiometer to 5V
and GND respectively. Connect the middle pin to A0.

The voltage of the middle pin will be output to the Mega2560 board as an
analog value. By rotating the axis of the potentiometer, you can change
the voltage on the middle pin, thereby changing the analog value of the
pin obtained by A0.

.. image:: img/image45.png


Schematic Diagram
-----------------

.. image:: img/image406.png


Code
----

.. note::

    * You can open the file ``1.5_analogRead.ino`` under the path of ``sunfounder_vincent_kit_for_arduino\code\1.5_analogRead`` directly.
    * Or copy this code into Arduino IDE.




.. raw:: html

    <iframe src=https://create.arduino.cc/editor/sunfounder01/5003d35b-2bb2-47ec-9a87-cf259311c8c5/preview?embed style="height:510px;width:100%;margin:10px 0" frameborder=0></iframe>

After the code is uploaded to the Mega2560 board, you can open the
serial port monitor to view the reading value of the pin. When the shaft
of the potentiometer is turned, the serial port monitor will print the
value that changes between "0" and "1023".

Code Analysis
-------------

To enable Arduino IDE to print the value transmitted from electronic
component to the Mega2560 board, you need to start serial communication
in setup() and set the data rate to 9600.

.. code-block:: arduino

    Serial.begin(9600);

Use the analoglRead() statement in loop() to read the level state acquired by analog pin A0 and declare a variable to store the level state.

.. code-block:: arduino

    int sensorValue = analogRead(A0);

Print the value stored in the variable on the serial monitor.

.. code-block:: arduino

    Serial.println(sensorValue);

Use delay() statements to make printing results easy to observe.

.. code-block:: arduino

    delay(1);

※ Analog-to-Digital Converter
------------------------------

The Arduino have a circuit inside called an analog-to-digital converter
or ADC that reads this changing voltage and converts it to a number
between 0 and 1023. When the shaft is turned all the way in one
direction, there are 0 volts going to the pin, and the input value is 0.
When the shaft is turned all the way in the opposite direction, there
are 5 volts going to the pin and the input value is 1023. In between,
analogRead() returns a number between 0 and 1023 that is proportional to
the amount of voltage being applied to the pin.

Phenomenon Picture
------------------

.. image:: img/image47.jpeg