An implementation of an ultrasonic device for the visually impaired

This paper describes a simple and inexpensive but yet reliable ultrasonic device to help the visually impaired to detect objects several meters away. There are a number of ways to design a device employing ultrasonic principles. In our approach the detection produces a change of duty cycle in the received signals, and then it is converted into a variable frequency, and eventually the user is alerted by the sound from a buzzer. The transmitter sends a continuous 40 kHz signal without modulation. The reflected ultrasonic signal collected by the receiver is very weak, and thus it needs to be amplified and rectified. Two Peripheral Interface Controllers (PICs) are employed in this design.