This is the door bell circuit with flashing LEDs to make the circuit more attractive. IC1 (NE555) is applied right here as being a clock generator. It is actually set up as an astable multivibrator whose frequency could be altered using the support of potensiometer VR1. The clock pulses received from IC1 are fed to pin 14 of IC2 (CD4017) that is a popular decade counter circuit module.

In this door bell circuit with flashing LEDs, the LEDs are connected in a rather different way. The LEDs flash sequentially from Q0 to Q9. The five trimmers of 100k each are joined to each pair of LEDs.

The IC3 is working as tune generator and then the Darlington set composed of transistors BC547B and SL100B is applied to boost its output so the circuit able to drive the loudspeaker. The frequency of IC3 is altered by potensiometer VR2. Each 100k trimmer (VR3 thru VR7) is fine-tuned to get a various tune based on personal decision. The 10 LEDs display is set up in this kind of a way that the first vertical column has orange LED1 through LED5 and then the second parallel column has green LED10 through LED6, as shown in the above circuit.

The circuit could very well be effortlessly constructed on a veroboard. Any good filtered 9V, 250mA DC power source is appropriate. Primary of the supply transformer may be joined towards the bell AC outlet factors.