An ultrasonic ranging system for the blind

A mobile ultrasonic ranging system was developed for the blind. Currently, the most common method of range detection used by blind people is the walking stick The limitation of the walking stick is that a blind person must come into close proximity with their surroundings to determine the location of an obstacle. In this project, a commercially available ultrasonic sensor, the Sona Switch(TM) 1700 (Electronic Design and Packing, Livonia, Michigan) was used to expand the environmental detection range of blind individuals. This sensor has a DC voltage output proportional to distance measured and an internal solid state snitch. The DC voltage changes inversely with respect to changes in object distance. By using a monolithic voltage-to-frequency (V/F) converter, the DC voltage from the sensor is converted into an AC frequency that produces an audible frequency of chirps in two small headphones. The larger the DC voltage input into the V/F converter, the higher the frequency of chirps output. The result is a system that produces a varying frequency of chirps that is inversely proportional to the distance measured. The sensor is mounted on a lightweight helmet allowing the user to obtain a reading in whichever direction their head points. The power source and corresponding circuitry are each encased in a plastic experimenter's box and attached to the user's belt. The ultrasonic ranging system has been tested on a blind student. The blind student's response was that the system enhanced his visualization of the surrounding environment, and further improved his ability to maneuver in a general environment.