THEORETICAL STUDY OF ALARM SYSTEM FOR BLIND MAN
journal of kerbala university,
2010, Volume 6, Issue 3, Pages 259-268
AbstractIn This paper we discussed the usage of ultrasonic sensor to alerts a blind man from hitting an object depending on the principle of SONAR and generate an audible signal to alert the blind man that there is an object in front of him at a detection range (0.31- 3.1) m. The device could be mounted at the belt of the blind man. The ultrasonic pulses is transmitted by transducer, this pulse reflects off an object is received by another transducer. We use the 40 kHz ultrasound transducer enabling the same transducer to be used both as a transmitter and as a receiver . The sound waves frequency which is used beyond our range of hearing ( human hearing is between 20Hz – 20kHz ) . By using the known speed of the sound wave (346.3 m/s) and the time between the transmitted pulse and the received pulse we could calculate the distance. The determination of the distance will depend on two modes of operation ( calibration mode and speed detection mode ) , The calibration mode is useful because the sound wave speed varies with altitude and the atmospheric conditions , while the speed detection mode is useful to determine the speed of the user moving toward or away from an object .
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