Temperature Based Fan Speed Control And Monitoring Using Arduino
This project is a standalone automatic fan speed controller that controls the speed of an electric fan according to the requirement. Use of embedded technology makes this closed-loop feedback-control system efficient and reliable. The microcontroller (MCU) ATMega8/168/328 allows dynamic and faster control and the LCD makes the system user-friendly. Sensed temperature and fan speed levels are simultaneously displayed on the LCD panel.
The project is very compact and uses a few components only. It can be implemented for several applications including air-conditioners, water-heaters, snow-melters, ovens, heat-exchangers, mixers, furnaces, incubators, thermal baths and veterinary operating tables. The project will help save energy/electricity.
Circuit and working
Circuit diagram of the temperature fan speed control and monitoring is shown in Fig. 1. It is built around Arduino Uno board (Board1), 16×2 LCD (LCD1), temperature sensor LM35 (IC1) and a few other components.
Arduino is at the heart of the circuit as it controls all functions. LM35 is a precision integrated circuit whose output voltage is linearly proportional to Celsius (Centigrade) temperature. It is rated to operate over a -55°C to 150°C temperature range. It has +10.0mV/Celsius linear-scale factor.
Fig. 2: Screenshot of the source code on Arduino IDE
Temperature sensor LM35 senses the temperature and converts it into an electrical (analogue) signal, which is applied to the MCU through an analogue-to-digital converter (ADC). The analogue signal is converted into digital format by the ADC. Sensed values of the temperature and speed of the fan are displayed on the LCD. Temperature and monitoring using Arduino The MCU on Arduino drive the motor driver to control fan speed.
Fan speed control technique
A low-frequency pulse-width modulation (PWM) signal, usually in the range of about 30Hz, whose duty cycle is varied to adjust the fan’s speed is used. An inexpensive, single, small pass transistor can be used here. It is efficient because the pass transistor is used as a switch.
One disadvantage of this approach, however, is that it can make the fan noisy because of the pulsed nature of the signal. The PWM waveform’s sharp edges cause the fan’s mechanical structure to move (like a badly-designed loudspeaker), which can easily be audible.
Construction and testing
Fig. 3: Actual-size PCB pattern of the temperature-based fan speed control and monitoring circuit using Arduino
Fig. 4: Component layout of the PCB
CON2 and CON3 are used to connect Board1 (Arduino UNO board) through external connectors. A 12V battery is used to drive the 12V DC-operated fan.
Software
Software for the automatic temperature controller and monitor circuit is written in Arduino programming language. Arduino Uno is programmed using Arduino IDE software.
ATmega328P on Arduino Uno comes with a pre-programmed bootloader that allows users to upload a new code to it without using an external hardware programmer.
Connect Arduino board to the PC and select the correct COM port in Arduino IDE. Compile the program (sketch). Then select the correct board from Tools Board menu in Arduino IDE and upload the sketch (abfc.ino) to Arduino through standard USB port.
Code
//Include necessary libraries
#include <OneWire.h>
#include <DallasTemperature.h>
//Define temperature sensor pin
#define ONE_WIRE_BUS 2
//Create OneWire instance
OneWire oneWire(ONE_WIRE_BUS);
//Create DallasTemperature instance
DallasTemperature sensors(&oneWire);
//Define fan pin
int fanPin = 3;
void setup() {
//Initialize serial communication
Serial.begin(9600);
//Initialize temperature sensors
sensors.begin();
//Set fan pin as output
pinMode(fanPin, OUTPUT);
}
void loop() {
//Call sensors.requestTemperatures() to get temperature readings
sensors.requestTemperatures();
//Read temperature in Celsius
float temperatureC = sensors.getTempCByIndex(0);
//Convert Celsius to Fahrenheit
float temperatureF = (temperatureC * 1.8) + 32;
//Print temperature in Celsius and Fahrenheit
Serial.print("Temperature: ");
Serial.print(temperatureC);
Serial.print("C / ");
Serial.print(temperatureF);
Serial.println("F");
//Control fan speed based on temperature
if (temperatureC >= 30) {
analogWrite(fanPin, 255); //Set fan speed to maximum
} else if (temperatureC >= 20) {
int fanSpeed = map(temperatureC, 20, 30, 0, 255); //Map temperature to fan speed range
analogWrite(fanPin, fanSpeed); //Set fan speed based on temperature
} else {
analogWrite(fanPin, 0); //Turn off fan
}
//Delay for 1 second
delay(1000);
}
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