Ultrasonic Range Finder SRF04:
The SRF04 is a superior quality ultrasonic ranger that is utilized in many robotic applications for simple detection of obstacles. It takes 10 microseconds to reach the trigger state. Once triggered, it will generate 8 pulses of ultrasound, at a frequency of 40 KHz and simultaneously raises its echo line to HIGH.
Once it receives the reflected signal or echo, it lowers the echo line to LOW. The width of the echo pulse, in this case, determines the depth or distance from which water levels can be measured.
PIC Microcontroller PIC16F84A
It really is a CMOS compatible, 8-bit, 18 pin Flash Microcontroller with just one 8-bit Timer and an 8-bit programmable prescaler. The Timer operation is controlled making use of the registry entries that are OPTION_REG, TMR0, and INTCON.