Using the Microcontroller Atmel 89C52, The Temperature sensing IC DS1621, The LCD and The Matrix Keyboard and establishing the serial communication between the two ICs and interfacing the ICs and the LCD the task of the temperature controlling is performed.
This is the microcontroller based Temperature Controller that displays the temperature in the range of -55 0 C to 125 0 C .
Besides AT89C51 microcontroller, it used a temperature sensor chip ,LCD module & matrix keyboard.
The controller outputs the calibrated the data in digital form.
The program for the microcontroller is written in assembly language.
FEATURES: • Temperature measurements require no external components • Measures temperatures from –55°C to +125°C in 0.5°C increments. Fahrenheit equivalent is –67°F to 257°F in 0.9°F increments • Temperature is read as a 9–bit value (two byte transfer) • Wide power supply range (2.7V to 5.5V) • Converts temperature to digital word in 1 second • Thermostatic settings are user definable and nonvolatile • Data is read from/written via a 2–wire serial interface (open drain I/O lines) • Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermal sensitive system. • 8–pin DIP or SOIC package (150 MIL and 208 MIL)
SDA – 2–Wire Serial Data Input/output
SCL – 2–Wire Serial Clock
GND – Ground
TOUT – Thermostat Output Signal
A0 – Chip Address Input
A1 – Chip Address Input
A2 – Chip Address Input
VDD – Power Supply Voltage
Instruction Description Protocol Read Temperature Read last converted temperature value from temperature register. Aah Read counter Reads value of count remaining from counter A8h Read Slope Read value of the slope accumulator A9h Start Convert T Initiates temperature conversion EEh Stop Convert T Halts temperature conversion 22h Access TH Read or write high temperature limit value into TH register. A1h Access TL Read or write low temperature limit value into TL register A2h Access Configuration Reads or write configuration data to configuration register Ach
Start Initialize Lcd & show welcome Msg Th __ Tl___ Enter for Cont. Is Enter Pressed? Is Clr Pressed? Th __ Is Th < 125d Tl __ Is Tl < Th Show error & again get Th value Show error & again get Tl value Go to #2 #2 Set Ds1621 with Th , Tl & other settings Temperature ____ No Yes No Yes Yes No No Yes