NE555 school bell automatic controller circuit diagram

The working principle of this circuit : ringing - 10 minutes - ringing - 45 minutes class - ringing - 10 minutes

IC1~IC4 are trigger delay circuits, and the delay time can be corrected by adjusting the time constant RC as needed. For example, the delay of IC1 is td1=1.1(R2+RP1)C1, and the other delays are similar.

IC5 is the ringing time timing control circuit. The delay time td5=1.1R13C12 is about 10 seconds. The output of the ring program timer IC1 and IC4 is added to the AND gates D1 and D2. After C11 triggers IC5, after triggering, pin 3 At high level, turn on the DL power supply of the electric bell.