# 3.27 Auto-fan

## 3.27.1 Overview

The weather is getting hotter in summer, so some public places will be equipped with some auto-fans that sense the ambient temperature value. When the temperature reaches a set value, he fan turns on. We add a PIR motion sensor to lower energy consumption. Thus, the fan will turn on only when the temperature reaches the value and someone is sensed nearby. 

Now let's do it!

## 3.27.2 Test Code

**Code Flow:**

![6-27-2-1](./media/6-27-2-1.png)

**Code:**

In Files, open **3-27-autimaticFan.py** and click ![](media/run.jpg).

```python
'''
 * Filename    : 3-27-autimaticFan
 * Thonny      : Thonny 4.1.4
 * Author      : http://www.keyestudio.com
'''
#import I2C and Pin from machine module
from machine import I2C, Pin
#import AHT20 from aht20 library
from aht20 import AHT20
import time
#create an I2C object and add SDA and SCL pins
i2c = I2C(scl=Pin(22), sda=Pin(21))
#create an AHT20 object, initialize I2C object to communication with AHT20 sensor via I2C bus
sensor = AHT20(i2c)

pir = Pin(19,Pin.IN)
#set the motor pin A to IO18
MA = Pin(18,Pin.OUT)
#set the motor pin B to IO17
MB = Pin(17,Pin.OUT)

while True:	
    try:
        #store the temperature and humidity to variable temperature and humidity
        temperature, humidity = sensor.read_temperature_humidity()
        Pir = pir.value()
        #Determine whether the PIR detects persons and temperature are greater than 28 degrees. If yes, the motor rotates; if not, the motor will not rotate
        if Pir == 1 and temperature > 28:
            MA.on()
            MB.off()
        else:
            MA.off()
            MB.off()
    # detect and read value, print “Failed to read from sensor:” if an error occurs
    except RuntimeError as e:
        print("Failed to read from sensor: ", e)
    time.sleep(1)	#delay 1S

```

 **Result:**

After uploading the code, when the temperature value is higher than 28 and the PIR motion sensor detects someone, the fan turns on. If one of the two conditions are not satisfied, the fan will not rotate.