DESIGN OF ULTRASONIC DISTANCE-MEASURING INSTRUMENT

The report details the implementation of distance measurement system using the ultrasonic waves. As the human ear’s audible perception range is 20 Hz to 20 kHz, it is insensitive to ultrasonic  waves,  and  hence  the  ultrasound  waves  can  be  used  for  applications  in industries/vehicles  without  hindering  human  activity.  They  are  widely  used  as  range meters  and  proximity  detectors  in  industries  also  it  can  be  used  in  parking  assistance system. The distance can be measured using pulse echo and phase measurement method. Here the pulse echo method is used. The measurement unit uses a continuous signal in the transmission frequency range of ultrasonic transducers. Using HC-SR04 ultrasonic transducer module a 40 kHz ultrasonic signal is transmitted and once reflected by an obstacle it is received by the transducer receiver unit where the signal is detected. The pic 16f690 microcontroller accepts this signal, performs necessary processing and displays the corresponding distance on a 16x2 LCD display. The time delay of the transmitted and the received signal corresponds to the distance between the system and the obstacle. To improve accuracy of the distance measured, LM35 temperature sensor is connected to microcontroller and every time a command is issued to measure distance the temperature of the surrounding is taken and used to calculate the speed of sound at that particular temperature.

The design was first simulated using proteus software and then implemented on breadboard where it was later transferred on a PCB board. The project was found to calculate the distance based on the speed of sound at the present ambient temperature and using this system distance can be measured up to 500 cm with an accuracy of ±1 cm.

Keywords: ultrasonic waves, pulse echo, microcontroller, LCD display