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Intelligent temperature monitoring and control system using AVR microcontrollerAugust 6, 2012

Controlling temperature has been a prime objective in various applications including refrigerators, air conditioners, air coolers, heaters, industrial temperature conditioning and so on. Temperature controllers vary in their complexities and algorithms. Some of these use simple control techniques like simple on-off control while others use complex Proportional Integral Derivative (PID) or fuzzy logic algorithms. In this project Shawon Shahryiar discusses about a simple control algorithm and utilize it intelligently unlike analogue controllers. Here are the features of this controller:

  • Audio-visual setup for setting temperature limits.
  • Fault detection and evasive action.
  • Temperature monitoring and display.
  • Audio-visual warning.
  • System status.
  • Settable time frame.
  • Data retention with internal EEPROM memory.

The hardware consists of a four-button interface, four LEDs, a piezo tweeter or sounder, a 4×20 LCD, a LM35 temperature sensor, an AVR ATMega32L microcontroller and some other passive parts. Two LEDs connected to PORTD0 and PORTD1 pins simulate on and off operation of relay switches that are actually present in actual applications to control a heater and an air conditioner. The hardware is powered by a 5V source preferably with a 5V regulator like 7805. If relays are used then a 12/24V source will also be needed to power the relays. The AVR micro’s AVREF and AVCC pins should be both connected to the 5V source. The distance between the LM35 sensor and the AVRs ADC pin must not be greater than 10-12cm for proper temperature reading. Though I did this project in a prototyping board made with a strip board, a PCB version is more preferred. Two additional LEDs connected to PD2 and PD3 indicates the failure or malfunctioning status of the air conditioner and the heater.

Via: Electronics Lab , Source: Embedded Lab

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