DIY Doorbell Circuit for Homes - Electronics Projects

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In this tutorial, we are going to demonstrate how to make a Doorbell circuit for your home. This project is beginner-friendly because it is very simple. The main purpose of this circuit is to convert electrical signals into audio signals. The IC used in this circuit is UM66 which is a melody generator CMOS IC. It consumes less power, therefore, can be used in smaller circuits, it has three pins GND (1), Vcc (2), and Melody Output (3).

The tones are generated by corresponding electrical signals at Pin 3.
Different versions of this IC are available, each IC comes with the code for the song or melody programmed by the manufacturer. You can choose the IC according to your desired song through those codes. For example, UM66T05L contains a “Home sweet home” melody.

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Hardware Components

The following components are required to make Doorbell Circuit

S.no	Component	Value	Qty
1.	Step down Transformer	230V/5V 200 to 500mA	1
2.	Switch	–	1
3.	Diode	1N4007	4
4.	Resistor	100Ω, 220Ω	2, 1
5.	LED	–	1
6..	Zener Diode	3.3V	1
7.	IC	UM66	1
8.	Speaker	8Ω	1
9.	Capacitor	220µF, 0.1µF	1, 1
10.	Transistor	2N3904	1

UM66 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of UM66

Doorbell Circuit

Working Explanation

The voltage is stepped down to 5V which is then rectified by the diode bridge of 1N4007 and filtered by the capacitor 220µF. Because the minimum operating voltage of the IC is 4.5V DC, a Zener diode is used to further step down the voltage to 3.3V. The melody output generated at Pin 3 of IC is amplified through transistor 2N3904 to drive the Speaker. Resistors are used to limit the base current, and the capacitor is used to suppress the noise at the output.

To make this process simpler, there is another circuit diagram. Figure 2 shows how you can replace the power source with any cellphone charger you have in scrap. All the components and working will be the same except the transformer and the diode bridge will be replaced by a cellphone charger.