| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a human body detector capable of detecting the mutual interference due to respective ultrasonic sensors even when a plurality of ultrasonic sensors are arranged in close vicinity to each other, reduced in erroneous detection and capable of detecting matter within an area to be detected as a human body with high reliability. SOLUTION: In a human body detector for detecting matter within area to be detected as a human body, a zero cross comparator, an N frequency divider circuit and an ultrasonic sensor control unit are provided. The zero cross point of a commercial AC power supply is detected by the zero cross comparator to form the rectangular wave signal synchronizing to the zero cross point and the formed rectangular wave signal is divided in frequency by N by an N frequency divider circuit so that the signal cycle thereof becomes equal to the interval of an arbitrary ultrasonic transmission time and the rectangular wave signal divided in frequency by N is used as an ultrasonic transmission synchronizing signal by the ultrasonic sensor control apparatus to take the synchronism of the ultrasonic transmission time interval of respective ultrasonic sensors.</p> |
