Here we are going to make a temperature controlled DC fan. DHT22 sensor is used to sense the room temperature and then we adjust speed of a DC fan/motor accordingly using PWM (Pulse Width Modulation). Arduino Uno is the heart of this project and a L293D driver IC is used to drive the DC fan/motor.

Components Required

• Arduino Uno
• L293D Motor Driver IC
• DHT22 Sensor
• 16×2 LCD Display
• DC Fan/motor
• 9V Battery
• 10KΩ Potentiometer
• 220Ω Resistor
• Breadboard

Circuit Diagram

Explanation

First we can connect L293D motor driver IC to Arduino as below. You can read articles L293D Motor Driver IC and H-Bridge Motor Driving for more information about the working of L293D.

• Connect pin 1 (Enable 1) of L293D to pin 5 of Arduino.
• Connect pin 2 (Input 1) of L293D to the pin 4 of Arduino.
• Connect pin 3 (Output 1) of  L293D to one terminal of the DC motor.
• Pins 4 and 5 of the L293D are ground pins, connect these to common ground (battery ground + arduino ground).
• Connect pin 6 (Output 2) of L293D to the remaining terminal of the DC motor.
• Connect pin 7 (Input 2) of L293D to the pin 3 of Arduino.
• Pin 8 is Vcc2, which is the driver/motor power input, connect it to positive of the battery.
• Pin 16 is Vcc1, which is logic voltage input (voltage level of control signals provided by Arduino). Connect it to 5V output of Arduino.

After that connect DHT22 sensor to the Arduino, it is using a single wire bus for communication.

• First pin is VCC power input, connect it to 5V output of Arduino.
• Second pin is DATA output, connect it to pin 6 of Arduino.
• Third pin is NOT USED.
• Fourth pin is Ground, connect it to ground.

Now we can connect 16×2 LCD to the Arduino.

• Pin 1 is VSS, connect it to ground.
• Pin 2 is VDD, connect it to 5V output of Arduino.
• Pin 3 is VEE, for adjusting display contrast. Connect it to the variable terminal of a potentiometer whose fixed terminals are connected to ground and 5V.
• Pin 4 is RS (Register Select), it is used to select data or command register. Connect it to pin 12 of Arduino.
• Pin 5 is R/W (Read/Write). Connect it to ground since we are only writing data to LCD in this project.
• Pin 6 is EN (Enable), it is used to indicate a valid data/command in data lines (D0 ~ D7). Connect it to pin 11 of Arduino.
• Pin 7 ~ 10 are data pins (D0 ~ D3), used to transmit data/command to LCD controller. But these pins are not used in 4 bit LCD interfacing, so connect it to ground.
• Pin 11 ~ 14 are data pins (D4 ~ D7), used to transmit data/commands to LCD controller. Connect it to Arduino pins 10, 9, 8 and 7 respectively.

Read More:  Temperature Controlled Fan using Arduino