A doorbell circuit with a blinking LED

This is a doorbell circuit with flashing LED to make the circuit more attractive. IC1 (NE555) is used here as clock generator. It is actually set up as an unstable multivibrator, the frequency of which can be changed using the support of potentiometer VR1. The clock pulse received from IC1 is fed to pin 14 of IC2 (CD4017) which is a popular decimal counter circuit module.

In this doorbell circuit with blinking LED, the LED is connected in a completely different way. The LEDs flash from Q0 to Q9 in sequence. Five 100k trimmers are connected to each pair of LEDs individually.

IC3 is used as a tone generator, and a Darlington bank consisting of transistors BC547B and SL100B is then applied to boost its output, enabling the circuit to drive a speaker. The frequency of IC3 is changed by potentiometer VR2. Each 100k spinner (VR3 to VR7) is fine-tuned to allow various adjustments based on personal decisions. The 10 LED displays are set up in such a way that the first vertical column has orange LED1 to LED5 and then the second parallel column has green LED10 to LED6 as shown in the above circuit.

The circuit can be easily built on veroboard. Any good filtered 9V, 250mA DC power supply is suitable. The primary of the power transformer can be connected to the bell AC outlet factor.