22-10-2012, 05:21 PM
Automatic College Bell
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INTRODUCTION
This project is an innovative idea which can be developed and implemented to Automatic College Bell. As we all know that communication is the vast developing field and we are the witness of several such developments. Day today in our life we experiences these development and only because of the communication our life style, mode of living, culture etc had been changed. As explained before our project is based on electronics and it’s titled as “Automatic College Bell”.
In today’s life, everyone gives importance to time. Time does not wait for anybody. Everything should be performed in time & accurately. Now a day’s school/college bells are manually operated. Hence there is a big question of accuracy. Also there is necessity of manpower and money. Hence here we should use automatic control system, which saves our manpower and money & also highest accuracy. Hence we have selected the project.
Manual operation of College bell creates lot of disturbances caused by human errors. If the bell operator forgets to ring the bell for a specific period, or delayed to ring the bell, it creates disturbances for entire the institution. All the classes on that day will be completely disturbed. This problem is more present if the bell operator is on leave. Our Project takes over the task of Ringing of the Bell in Colleges. It replaces the Manual Switching of the Bell in the College. It has an Inbuilt Real Time Clock which tracks over the Real Time. When this time equals to the Bell Ringing time, then the Relay for the Bell is switched on. The Bell Ringing time can be edited at any Time, so that it can be used at Normal Class Timings as well as Exam Times. The Real Time Clock is displayed on LCD display. The Microcontroller AT89S52 is used to control all the Functions, it get the time through the keypad and store it in its Memory. And when the Real time and Bell time get equal then the Bell is switched on for a predetermined time.
In the circuit shown above, we provide 230V A.C. power supply to the “Step-Down Transformer” which converts 230V A.C. into 5V DC with the help of “Full Wave Rectifier”. Two different voltage levels are required for our circuit – One is 12V D.C. to operate relay switch. Second is 5V D.C. supply to operate microcontroller “AT89S8252”. For this purpose we will use voltage regulator “LM7805” which can take 8V -25V as I/P & provide 5V constant voltage.
Here we have used “Atmel AT89S8252” microcontroller to control various timing of the ringing. Here we also use a “12MHz Crystal” which will provide the microcontroller a reference time.
We have used “Assembly Language” to program this microcontroller and we have also used a microcontroller programmer. We have used different types of capacitors and resistors in this circuit. We have used two 33pF capacitor which are acting as a High Pass Filter [H.P.F.]. The 10KΩ resistor is used for RESET circuit to provide negative potential to RESET pin of microcontroller. We have used IC DS 1307 which is a low-power clock/calendar with 56 bytes of Battery-backed SRAM. It uses an external 32.768 kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate.
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was trimmed.
We have used 16x2 LCD display for the displaying the real time. The microcontroller can operate on 5V and 10mA current maximum but we have to operate 12V relay switch which consume more than 100A current. So, we have to amplify this current and voltage. For this purpose we are using transistor.