The main part of this circuit Doorbell two timer NE555 ICs.When someone hit the switch S1 momentarily, the speaker emits a sound of the bell, if the time period of the monostable multivibrator built around IC1.
When the switch S1 pressed, IC1 is enabled in your pin 2 and pin 3 output is high for a period of time previously set by the values of R4 and POT POT R5.When ofIC1 restores the IC2 output is high and starts to swing to make a bell sound through the speaker.The IC2 is configured as an astable multivibrator whose oscillation frequency can be varied with the help of POT R5.By adjusting the values of R4 and R5, changes in tone are possible
Notes.
- The circuit has to assembled on a good quality PCB or common board.
- The IC1 & IC2 has to be mounted on IC holders.
- Power the circuit from a 9V battery or 9V DC power supply.
- Switch S1 is push button switch.
