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2 in 1 Doorbell


Anjali Sethiya
The doorbells are used to produce a ringing alert sound so that the resident comes to know that a visitor is there on the door. Many homes have two doors for entering. So at times it is confusing for the resident to find out on which door is the visitor present. This project on doorbell circuit produces two different sounds can be used simultaneously on both the doors. The circuit is based on UM3561 IC whose details are shown in the image below:
UM3561 IC




The project about doorbell circuit is made up of CMOS LSI designed UM3561 IC which consumes less power. It is commonly used in toys and alarm watches because of its low cost. A compact sound module can be constructed using this IC. It includes oscillator and selector circuit and only few components are required to be added externally. It also contains a programmed ROM to produce siren sound.


When the switch S1 or S2 is pressed, the pin1 or pin5 of the IC1 receives the high signal which is used to drive the transistor that is connected to pin3 of IC1. Hence the speaker gets the supply and IC1 produces the sound of siren so as to indicate the presence on the door. A transistor is used for the process of amplification as the output of pin3 is very low.
Many other different sounds can be produced by referring the datasheet of UM3561. Similarly many other ICs are there to produce different sounds i.e. UM3481, UM3484, and UM34811. 


Circuit Diagram


Resistor Image

Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits.

Capacitor image

Capacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycle of charging and discharging in AC circuits where the voltage and curre...

BC548 | Transistor BC548
Transistor BC548

BC548 is general purpose silicon, NPN, bipolar junction transistor. It is used for amplification and switching purposes. The current gain may vary between 110 and 800. The maximum DC current gain is 800.

Speaker Image
A loudspeaker (or "speaker") is a transducer that converts electrical energy into acoustical energy. When an electric signal is applied to the input pin of speaker, it generates sound waves. The other pin is connected to ground. A speaker is commonly used to produce sound in response to a sensor output. For example, in an...


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