School Bells Analog Circuit

Published:2011/7/16 7:15:00 Author:Sue | Keyword: School Bells, Analog | From:SeekIC

T1,T2 will compose oscillate circuit. The signal will be coupled to T3 through the capacitor C3, which will be sent to the loud speaker after the signal is amplified. The circuit's T3's right terminal is connected to a normally open contactor of the relay. When J1-1 is connected, the power will charge C4. Then J1-1 is disconnected, C4 will be discharged through Y,T3. Discharging T3,C4 will be equal to a power supply so a weakening bell will be heard. The integrated circuit 555 will compose oscillate circuit with a period of about 1s. If its pin 3 is high level, the current will charge C1 through R1. When the potential of pin2, 6 is higher than 2/3Vcc, pin 3 has low level. C1 will then be charged through R1, and potential of pin 2,6 will be lower. When it is lower than 2/3Vcc, pin 3 has high level again. By controlling J's connection and disconnection, the interval of the bell can be controlled. When the sound from the loud speaker is good, the loud speaker can be moved. Then use a wire to short, and R5 will output U0. U0 will be sent to the loud speaker to drive the high tone loud speaker to make a loud and vivid sound. R6 can choose from 68-200Ω. The larger R6 is, the longer the aftersound is. R2,C2 are decided by the tone.



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