Morning Or Light Activated Alarm using UM66 IC

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4 Morning Or Light Activated Alarm Circuit

In this project, we are going to make one of the most interesting DIY circuits which is the Morning Alarm or Light Activated Alarm Circuit. This circuit works in the presence of light and produces a melody. To detect the light we are going to use an LDR, it is a variable resistor and its resistance depends on the intensity of light falling onto it, in Dark its resistance gets maximized therefore it stops all the currents going into the circuit, and as the light’s intensity increases its resistance decreases (100 ohms or less in full light).

For the purpose of generating melody, we are going to use UM66 IC which is a melody generator CMOS IC that comes in a TO-92 transistor package. This IC has a lot of variety, each IC comes with a code for the melody programmed by the manufacturer. A variable resistor is also used to produce the melody on the desired amount of light, you can adjust it accordingly and this circuit will produce the same amount of melody every day.

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Hardware Components

The following components are required to make Morning Or Light Activated Alarm Circuit

S.no	Component	Value	Qty
1.	Battery	3v	1
2.	LDR	–	1
3.	Resistors	1K, 220 ohm	1, 1
4.	Variable Resistors	500K	1
5.	Transistor	BC547, 2N3904	1,1
6.	IC	UM66	1
7.	Speaker	8Ω	1

UM66 Pinout

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

2N3904 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3904

Morning Or Light Activated Alarm Circuit

Working Explanation

When the light falls on the LDR its resistance will decrease and it will turn the transistor ON, the voltage that will pass through the transistor will now enter the UM66 IC. UM66 has three pins, GND (1), For input VCC (2), and Melody output (3). The melody will generate by the corresponding electrical signals at Pin 3. This melody will be amplified through the second transistor 2N3904 which will later drive an 8 ohms speaker.