On this page, I will introduce the alarm equipment which arranged "Ultrasonic Alarm (1)". In case of ultrasonic alarm (1), it detected that object was included in the set distance. However, in case of the ultrasonic alarm (2) to introduce here, it gives the alarm when the object which is in the set distance passes away. This alarm device transmits the ultrasonic and it confirms a reflected wave from the obstacle. If there is object within the set distance, it doesn't give the alarm. When there is no object within the set distance, it gives the alarm. The distance which can be set is from about 40 cm to 5-6 m. For example, when making a setting distance 5 m, it gives the alarm when the reflected wave from 40 cm to 5 m passes away.
The ultrasonic detection unit amplifies(About 1000 times) and detects the ultrasonic that a reflected wave from the object. At the circuit this time, transmitter and receiver(Transducer) and detector are incorporated into another printed board. The transmitter transmits the 40 kHz ultrasonic with the 1 millisecond in the about 64 milliseconds interval. The receiver checks whether or not there is a reflected wave during the 64 milliseconds. The detector detects the reflected wave which exists in the set time. Ultrasonic Alarm (1) gives the alarm when there is a reflected wave in the set time. The circuit this time gives the alarm when the reflected wave passes away. The transducer circuit is similar to Ultrasonic Alarm (1). This circuit can be used generally. Therefore, I made a transducer with the independent printed board.