The Control module
consists of a microcontroller (AT89S52). It is connected with a crystal
oscillator (11.0592MHz) to the pins 18 & 19. Additional two capacitors are connected to
filter any noise or unwanted particles in it.
A reset circuit is
connected to the 9th pin with a capacitor & resistor. At power ON
condition, this capacitor sends a high pulse to this pin to make it reset all
its I/O pins. Additionally a switch is connected as a reset switch. In system
hang-up conditions, this switch can be used to reset the unit.
A LCD is connected to
the microcontroller to display the input & output operations to the user.
The control pins of the LCD are connected to two pins of Port 3 and the data
pins are connected to Port 1.
Control module: ATMEL89S52 microcontroller
Communication Modules: GSM Modem