Door bell circuit using NE555

Description.The main part of this doorbell circuit are two NE555 timer ICs. When someone presses switch S1 momentarily ,the loud speaker sounds a bell tone as long as the time period of the monostable multivibrator built around IC1.When the switch S1 pressed, IC1 is triggered at its pin 2 and output pin 3 goes high for a time period previously set by the values of POT R4 and POT R5.When the output ofIC1 goes high it resets IC2 and it starts to oscillate 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 & R5, modifications on the tone are possible.

Circuit diagram with Parts list.

   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.