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3.1.4 Smart Fan
=================


.. note::

   .. image:: ../img/mcp3008_and_adc0834.jpg
      :width: 25%
      :align: left
    

   Depending on your kit version, please identify whether you have **ADC0834** or **MCP3008** and proceed with the matching section.


Introduction
-----------------

In this course, we will use motors, buttons and thermistors to make a
manual + automatic smart fan whose wind speed is adjustable.

Components
------------------

.. image:: img/list_Smart_Fan.png
    :align: center

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

============ ======== ======== ===
T-Board Name physical wiringPi BCM
GPIO17       Pin 11   0        17
GPIO18       Pin 12   1        18
GPIO27       Pin 13   2        27
GPIO22       Pin 15   3        22
GPIO5        Pin 29   21       5
GPIO6        Pin 31   22       6
GPIO13       Pin 33   23       13
============ ======== ======== ===

.. image:: img/Schematic_three_one4.png
    :width: 500
    :align: center

Experimental Procedures
-----------------------------

**Step 1:** Build the circuit.

.. image:: img/image245.png
   :width: 800
   :align: center

.. note::
    The power module can apply a 9V battery with the 9V Battery
    Buckle in the kit. Insert the jumper cap of the power module into the 5V
    bus strips of the breadboard.

.. image:: img/image118.jpeg
   :width: 2.80694in
   :height: 0.94375in
   :align: center

**For C Language Users**
^^^^^^^^^^^^^^^^^^^^^^^^^

**Step 2**: Get into the folder of the code.

.. raw:: html

   <run></run>

.. code-block:: 

    cd ~/davinci-kit-for-raspberry-pi/c/3.1.4/

**Step 3**: Compile.

.. raw:: html

   <run></run>

.. code-block:: 

    gcc 3.1.4_SmartFan.c -lwiringPi -lm

**Step 4**: Run the executable file above.

.. raw:: html

   <run></run>

.. code-block:: 

    sudo ./a.out

As the code runs, start the fan by pressing the button. Every time you
press, 1 speed grade is adjusted up or down. There are **5** kinds of
speed grades: **0~4**. When set to the 4\ :sup:`th` speed grade and you
press the button, the fan stops working with a **0** wind speed.

.. note::

    If it does not work after running, or there is an error prompt: \"wiringPi.h: No such file or directory\", please refer to :ref:`install_wiringpi_pi5`.


Once the temperature goes up or down for more than 2℃, the speed
automatically gets 1-grade faster or slower.


**Code Explanation**

.. code-block:: c

    int temperture(){
        unsigned char analogVal;
        double Vr, Rt, temp, cel, Fah;
        analogVal = get_ADC_Result(0);
        Vr = 5 * (double)(analogVal) / 255;
        Rt = 10000 * (double)(Vr) / (5 - (double)(Vr));
        temp = 1 / (((log(Rt/10000)) / 3950)+(1 / (273.15 + 25)));
        cel = temp - 273.15;
        Fah = cel * 1.8 +32;
        int t=cel;
        return t;
    }

Temperture() works by converting thermistor values read by ADC0834 into
temperature values. Refer to :ref:`2.2.2_thermistor_c_pi5` for more details.

.. code-block:: c

    int motor(int level){
        if(level==0){
            digitalWrite(MotorEnable,LOW);
            return 0;
        }
        if (level>=4){
            level =4;
        }
        digitalWrite(MotorEnable,HIGH);
        softPwmWrite(MotorPin1, level*25);
        return level;    
    }

This function controls the rotating speed of the motor. The range of the
**Level**: **0-4** (level **0** stops the working motor). One level
adjustment stands for a **25%** change of the wind speed.

.. code-block:: c

    int main(void)
    {
        setup();
        int currentState,lastState=0;
        int level = 0;
        int currentTemp,markTemp=0;
        while(1){
            currentState=digitalRead(BtnPin);
            currentTemp=temperture();
            if (currentTemp<=0){continue;}
            if (currentState==1&&lastState==0){
                level=(level+1)%5;
                markTemp=currentTemp;
                delay(500);
            }
            lastState=currentState;
            if (level!=0){
                if (currentTemp-markTemp<=-2){
                    level=level-1;
                    markTemp=currentTemp;
                }
                if (currentTemp-markTemp>=2){
                    level=level+1;
                    markTemp=currentTemp;
                }
            }
            level=motor(level);
        }
        return 0;
    }

The function **main()** contains the whole program process as shown:

1) Constantly read the button state and the current temperature.

2) Every press makes level\ **+1** and at the same time, the temperature
   is updated. The **Level** ranges **1~4**.

3) As the fan works ( the level is **not 0**), the temperature is under
   detection. A **2℃\ +** change causes the up and down of the level.

4) The motor changes the rotating speed with the **Level**.