# Doorbell Circuit using IC 555 and CD4017

Doorbell Circuit using IC 555 and CD4017: The bell is a very common and useful electronic device used in houses, offices, etc. Among electronics students and hobbyists, the doorbell circuit project is very popular. So in this tutorial, I am going to build a doorbell with 555 (timer) IC. The main feature of this doorbell is that we can control the time duration for which it keeps ringing upon pressing the switch those transistors are repaired and coverage warranty are taken by action ac repair heating San Diego. Also, we can control the oscillation frequency of Door Bell With a change in resistor and capacitor.

## Doorbell Circuit Diagram Using IC 555 and CD 4017

Full circuit Diagram of this doorbell circuit is given below. All componnets are showen in the diagram with fully connection.

## Doorbell Circuit component list

• 1  CD4017 decade counter IC (IC1)
• 1  555 timer IC (IC2)
• 1  1uF / 250V capacitor (C1)
• 1  47nF / 250V capacitor (C2)
• 1  100uF / 12V capacitor (C3)
• 1  470 K resistor (R1)
• 1  220 K resistor (R2)
• 1  15 K  resistor (R3)
• 1  10 K resistor (R14)
• 1  150 ohms resistor (R13)
• 1  220 ohms resistor (R15)
• 10  100 K potentiometer
• 10  1N4148 or 1N914 diodes
• 1  2N2646 Unijunction Transistor (UJT) (T1)
• 1  2N2222 NPN bipolar transistor (T2)
• 1  Normaly Open (NO) contact button (PB)
• 1  8 ohms miniature speaker

## Working Of Door Bell:

The 555 timer IC is set up as an astable multivibrator. The UJT is used for the relaxation oscillator. To chnage from one note to the next note we use the CD4017 IC and to drive the speaker we use a NPN transistor 2n222. Doorbell circuit generates 10 notes, Doorbell sounds can be modifiy futher if you want by using potinomiters.

Relaxation oscillator having a frequency depends on the values of the Capacitor C2  and the resistor R14 plus the value of the corresponding potentiometer connected to each of the outputs of the CD4017.