Temperature Controlled DC Fan by using 8051 Microcontroller

Nowadays, the humankind is moving towards the new technologies by replacing the manual operations to automatic controlled devices. One of the basic requirements of the people during hot weather is a cooling fan. But, the speed of the fan can be controlled by manual operation using a manual switch namely fan regulator or dimmer. By turning the dimmer, the fan speed can be altered. It can be watch in some places like where the temperature is high during the morning though the temperature falls down radically at night time. The users do not understand the difference in temperature. So to overcome the speed of the fan here is a solution to vary according to temperature. This concept is particularly applicable for the areas like where temperature changes radically during day and night time. This project will convert the manual fan into automatic fans. The automatic fans will change its speed according to the temperature in the room.This article discusses about temperature controlled fan block diagram, working of each block and properties.

Temperature Controlled DC Fan using Microcontroller

The proposed system temperature controlled fan using microcontroller is used to control the speed of the fan according to the temperature and specify the temperature in the display. The required components are microcontroller, temperature sensor, motor; seven segment display, ADC, power supply, operational amplifier.

Temperature Controlled DC Fan
Temperature Controlled DC Fan

The block diagram of the temperature controlled fan using microcontroller is shown in the above figure. The block diagram includes power supply, RST circuit, 8051 microcontroller, LM35 temperature sensor, 8 bit ADC, L293D motor driver, DC motor, 7-segment display, i/p switches.

Temperature Sensor

The temperature sensor used in the proposed system is LM35. The o/p of this temperature sensor is linearly proportional to the Celsius scale. This IC doesn’t need any external calibration to give accuracies. The main function of the temperature sensor in the proposed system is to detect the temperature of external environment of fan.

Temperature Sensor
Temperature Sensor

8051 Microcontroller (AT89C51)

The 8-bit microcontroller AT89C51 belongs to 8051 family. It consists of 128 bytes of RAM, 16-bits of addresses, 16 bit timer/ counter-2, 6 interrupts, ROM- 4k bytes. The main function of the microcontroller in the proposed system is to analyze the temperature which is sensed by the temperature sensor. Based on the temperature, the microcontroller should change the speed of fan.

AT89C51 Microocntroller
AT89C51 Microocntroller

ADC (0808)

An ADC (analog to digital converter) needs to be interfaced with 8051 microcontroller to allow analog i/p for processing of data. Here serial I/O port is used to make the flow of data between controllers and also other devices. Here, an 8 bit parallel ADC0808 IC has been used. It works with +5V and has an 8-bit resolution. This ADC converts the input analog signal into equivalent digital signal by using the reference voltage.


Seven Segment Display

A 7-segment display is a one kind of electronic display used for displaying the decimal numerals. The applications of these displays mainly include electronic meters, digital clocks, and various electronic devices for displaying the information in the form of numerical. But these displays uses hex code for displaying alphanumeric code.

7-Segment Display
7-Segment Display

Temperature Controlled DC Fan Working

All the modules used in the above block diagram are integrated. The fan speed can be monitored by the variation of temperature. Basic concept of this project is to getting the temperature, displaying the temperature and temperature change is reflected as vary in fan’s speed. Here temperature sensor used in the project is LM35 and the o/p of this sensor is given to analog to digital converter. The complete working is allowed or not can be decided by external interrupts.

Temperature Controlled DC Fan Block Diagram
Temperature Controlled DC Fan Block Diagram

Temperature sensor LM35 is interfaced with the 8051 microcontroller’s analog pin because, temperature sensor changes temperature into voltage. Here temperature sensor should be interfaced correctly to the microcontroller in order to get correct reading. The speed of the fan can be decided by the temperature examine by the microcontroller.

Microcontroller controls the DC fan using the IC L293D motor control. This IC L293D is a dual H-bridge motor driver used to control the speed and direction of DC motor. It also offers isolation between microcontroller and motor. Motor speed can be controlled by using the pulse width modulation (PWM) technique.

The proposed system is also provided with auto or manual switch which gives the option to user to control the speed of fan. When the button is pressed, the speed can controlled by manually that means user can control the fan speed manually. An LED can also be connected at RC1 to demonstrate the status of auto or manual switch. If light emitting diode is blinking, it means the fan control is manual.

So finally we can conclude that, when the power supply is given to the entire circuit then the microcontroller reads the surrounding temperature of fan. The analog value of the temperature is given by the sensor and applied to the ADC pin of microcontroller. The value of analog is changed to the digital by the microcontroller internally. If the temperature is superior to the threshold value, then microcontroller sends a signal to the controller to turn ON the motor. Thus fan starts rotating.

Properties of Temperature Controlled Fan

The properties of temperature controlled fan mainly includes the following

  • When the temperature surpasses 35 ᵒ C then fan should run at max speed.
  • When the temperature drops below 15 ᵒ C then fan should be at min speed.
  • The fan speed should be change according to the ranges of temperature from 15 ᵒ C to 35 ᵒC,
  • Auto-manual switch should be built-in which would give user the freedom to control the speed of fan on manual or auto.

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The applications of the temperature controlled fan includes where the consumption of power has to be controlled such as firms, institutes, organizations, home appliance, in computers to cool the processor. Furthermore this project can be enhanced by interfacing it with air conditioners.

Thus, this is all about temperature controlled fan using microcontroller. We hope that you have got a better understanding of this concept. Furthermore any queries regarding this concept or microcontroller based projects, please give your feedback by commenting in the comment section below.Here is a question for you, what is the function of 7-segment display?

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  1. Manthan rs says:

    Can i please get the c code for temperature controlled fan(sst)

    1. Hi Manthan ss
      As per your query, I can suggest you that, we provide you DIY (do-it-yourself) kits. With these kits, you can get practical knowledge. once you purchase the project from our website http://www.edgefxkits.com/, you will be provided with all support documents, source code, components, soldering kit, and video tutorials.
      please visit our domestic website http://www.edgefxkits.com/
      For more details please contact to Mr. Sathish on +91 8885507011 (toll-free) or you can email us on info@edgefxkits.in

  2. Could you please tell me the code for the temperature controlled dc fan project

  3. mankesh poonia says:

    please post the circuit diagram

  4. sindhujaa ea says:

    i have a miniproject on temprature controoled dc fan by using 8051 architechture .could you please say about the connection

  5. could i use lm35 to stop my robot before fire or any hot object so that it cant get damage?

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