Temperature Controller Using PIC16F84A

This temperature controller is built around a PIC16F84A microcontroller along with an ADC, and a temperature sensor for measuring temperature and be displayed.

An inexpensive 8-bit temperature sensor TMP37 from Analog Devices is used by this module. An external ADC had to be used, since the data was analog and the PIC16F84 does not have an analog input. The ADC chosen was TLC549 from Texas Instruments which has the ability to communicate serially with the microcontroller while converting the temperature sensor readings into serially transmitted data. The module is done on a breadboard as it uses the Hitachi Controller HD44780 for a normal 16×2 LCD display and interfaced with 4 buttons.

An 8bit switched-capacitor successive-approximation ADC is used to build the TLC549 analog-to-digital converter which is designed for serial interface with a peripheral or microprocessor. It contains one data output line and two control lines. The TMP37 provides a voltage output that is linearly proportional to the Celsius temperature since it is a low voltage, precision centigrade temperature sensor. The ADC, temperature sensor, the LCD, and the input buttons are handled by the two PIC16F84 microcontrollers. The peripherals are distributed among the two microcontrollers.

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