Room Temperature Controller

The temperature controlling system maintains a user programmable room temperature where air conditionars are not provided. For this purpose we need a cooler and a heater. Cooler is used for decreasing temperature and heater is used for increasing temperature. This project also shows the real time temperature in degree centigrade. It can be used in any season.

Temperature controller

There are two relays for AC supply output to connect cooler and heater. Two buttons(up and down) are used to set a suitable temperature called as 'preset'. We can assume three cases to turn the relays in order to maintain the temperature to the user suitable temperature.

Case 1 :If the actual temperature is equal to this preset value, both relays remain OFF as the temperature is undercontrol.

Case 2 : When temperature rises above the preset value, the cooler turns ON and heater turnss OFF to decrease the temperature.

Case 3: When temperature falls below the preset value, the heater turns ON and cooler turns OFF to increase the temperature.


Components: MCU AT89S52, EEPROM AT24C02, Temperature sensor DS18B20, Relay12Volts, XL12MHz, 16x2LCD etc.

The MCU(AT89S52) is the brain of the circuit. It reads the temperature from sensor(DS1820) using one wire protocol. This temperature is compared with the preset temperature value inside the microcontroller and then switches the required function.Two toggle buttons are used to increase/decrease the preset temperature value. This value is saved in the eeprom(24C02), hence no effect of power failure. In the LCD connections there are two variable resistors of 10kΩ used to set the contrast & brightness.

Download the complete code.

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bodhesh choudhary
#27 bodhesh choudhary 2016-09-16 03:26
this aritcle blog is very much useful in domestic rooms without ac
Carlos Francisco
#26 Carlos Francisco 2015-07-23 23:56
Hi there I just like to join so I can learn about programming. Ive been in electronics for quite sometime but never been on any kind of programming. I saw this interesting project and would make it. Is there by any chance that someone can teach me of how and what are the thing I need to use the program code above...thanks very much and hope you could help me
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