Automatic Bell System for Institutions or Schools
Usually, conventional methods require a pawn or bell operator to assist and operate the bell system for each period and interval in schools and institutions. Such systems need sufficient human effort to do so, and require an advance to be automated - those that minimize human effort. As the bell system is important in schools, homes and industries, the automatic operation of this instrument must have to be performed with a precise time controller in an economical manner.
This automatic school bell timer system is designed using a basic 8051 microcontroller to manage time intervals. The read / write memory is also required to store bell timings, but for less number of times this memory is not required. This system also provides the display of seven-segment timing information for a user interface purpose.
This system uses a power supply block to drive all components of the circuit, an 8051 microcontroller to control and manage bell timings, a real-time clock for precise timing operation, a matrix keyboard to enter and configure the timing Bell and a segment of seven segments Display to show the time and information. The operation of this system can be easily understood from the above block diagram, in which the times entered on the keyboard are stored in the microcontroller, which are responsible for operating the bell based on the microcontroller program.
Microcontroller-based school timer circuit operation
• The regulated DC power supply is supplied to the microcontroller by means of a supply block (in the circuit, it is not indicated except in the block diagram). This power supply block consists of a transformer reducer, a rectifier girlfriend, a filter and an IC regulator. The 230V supply of the network is reduced to 12V AC by the transformer. This AC is rectified to a DC source by bridge rectifier and capacitor filters to a pure DC, and then by a regulator regulating the power to a constant DC to 5V. This power supply drives the entire circuit except the relay and bell devices.
• To make a precise and precise time controller, the DS1307 serial RTC (Real Time Clock) is connected to the microcontroller. This RTC is a low power decimal clock, fully binary coded, with 56 bytes of SRAM. This clock displays information for year, month, date, day, hours, minutes and seconds. In this clock, the data and the address are transferred in series by the bi-directional bus I2C. It also has a built-in backup source to maintain continuous time operation in times of power failure as shown in the figure.
• The matrix keyboard is connected to the microcontroller to adjust and store the timing values. In this keyboard, several keys are used to set hours and minutes in real time, ring synchronization operations and to store and erase timbres and real times.
• The seven-segment display is connected in common anode mode and connected to the microcontroller to display the timing information.
• The buzzer is switched using a relay and the relay coil is energized by the microcontroller.
• The microcontroller has built-in EPROM flash memory to store data that remains even after a power failure.
• The microcontroller is programmed in such a way that it accepts the actual timing and bell times and correspondingly sends the control signals to the seven-segment display and also to the transistor connected to the relay coil.
• When the relay transistor is enabled, energize the relay coil so that the track is closed to feed the bell device.
• Before working with this system, we must configure the real time and ring time values using an array keyboard. The procedure for the configuration is given below:
Enter the current real time using the keyboard.
Press '#' to store the real time.
Press the '*' screen that shows all the hyphens.
Enter the start time of the first bell.
Press '*' to save the start time of the first bell.
Continue this procedure for 5 bells.
Press '*' to get the real time
In this way, one can build a school bell timer using the simple microcontroller.