ATMEGA ULTRASONIC RANGE FINDER FAKHRUL ADLEE BIN ...

23The echo signal received by the receiver sensor after reflection is very weak.It is amplified by operational amplifier. The rectifier functions, unlike a simplediode, even for signal voltage of less than 0.6V. The output is filtered to accept40kHz frequencies and fed to pin 12 of microcontroller, which is an analogcomparator.Microcontroller AT89S51is at the heart of the circuit. Port-1 pins P1.7through P1.2, and port-3 pin P3.7 are connected to input pins 1 through 7 of currentbuffer, respectively. These pins are pulled up with a 10-kilo-ohm resistor network.They drive all the segments of the LCD module display with the help ofinverter.Microcontroller AT89S51 provides the segment data and display-enablesignal simultaneously in time-division multiplexed mode for displaying a particularnumber on the LCD module.Segment data and display-enable pulse for the display are refreshed every5ms. Thus the LCD module appears to be continuously display. Using switch S1 wecan manually reset the microcontroller, while the power on reset signal for themicrocontroller is derived from the combination of capacitor and resistor.A 12MHzcrystal is used to generate the basic clock frequency for the microcontroller.The comparator is inbuilt in microcontroller AT89S51. The echo signal willmake port-3 pin 3.6 low when it goes above the level of voltage set on pin 13. Thisstatus is sensed by the microcontroller as programmed. When port-3 pin P3.6 goeshigh, we know that the echo signal has arrived, the timer is read and the 16-bitnumber is divided by twice the velocity of sound and then converted into decimalformat.