The aim of the project “REAL TIME COLLEGE ALARM USING PC ” is to design a system using which the college alarm can be automated through a PC using the microcontroller 8051. Manual operation of school bell / college bell is a mundane task prone to human errors. If the bell operator forgets to ring it for a specific period, or delayed to ring the bell, it will create disturbances for the entire institution. Automatic Periodic College Bell is the only solution to avoid all these problems. This project is very useful in schools, colleges and educational / academic institutions for automation of periodic class bell. This bell rings only at preprogrammed timings. The project is designed in such a way that the controller is interfaced to PC using serial communication technique. Serial communication is often used either to control or to receive data from an embedded microprocessor. In serial communication the data is sent as one bit at a time. Serial communication is a form of I/O in which the bits of a byte being transferred appear one after the other in a timed sequence on a single wire. Serial communication is commonly used in applications such as industrial automation systems, scientific analysis and certain consumer products. Here the serial communication is established between the PC and the controller by a line driver IC max232 which acts as a voltage converter. User set the alarm in software. According to that set values alarm will on. Microcontroller is connected to PC through serial communication. C# application always interact with serial port and according to alarm set values application gives signals to microcontroller. Microcontroller takes values from serial port and generates alarm through buzzer (or relay). This project uses regulated 5V, 500mA power supply. Unregulated 12V DC is used for relay.7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of secondary of 230/12V step down transformer.