using PIC microcontrollers
This system’s input is a temperature sensor’s output. In every 2 sec (Approx) microcontroller reads the temperature from sensor and either activate or deactivate buzzer based on the comparison result of current temperature value with the Maximum temperature value set by the user.
The system’s operation is based on the following algorithm. The system runs continuously until a reset occurs.
A TC74 Serial Digital Thermal Sensor is used to measure ambient temperature. The PIC and TC74 communicate using the MSSP module. The TC74 is connected to the SDA & SCL I/O pins of the PIC and functions as a slave. Every 2 seconds, the temperature is logged into the external EEPROM in a specific memory location. The data that is sent to the LCD is also sent to the USART through the RS-232 port to be displayed on a PC HyperTerminal.
The Moment Temperature reaches the TEMP_MAX buzzer is ON and as Temperature dips below than the TEMP_MAX value buzzer is OFF.
the source code of the project written in PIC Assembly is availabale with the author; incase you wish to have a look let me know by shooting a mail to email@example.com