How to make automatic night light circuit LDR

Introduction:

An LDR circuit uses an LDR to detect changes in ambient light levels. It is made up of an LDR, a resistor, and a load, and can be used to turn on or off a load when the ambient light level falls below or rises above a certain threshold. LDR circuits are easy to build and can be used in a variety of applications, such as automatic night lights and light-sensitive alarm circuits.

By using the some basic components I am going to make the LDR circuit components we need for making this circuit.

• BD139
• 3.3K Resistor
• LDR
• 3.7V LED
• 5V Power Supply (You can use powered supply)

An automatic USB night light circuit can be built using a BD139 transistor, an LDR, or a 3.3k resistor. The circuit is designed to turn on a light automatically when the ambient light level falls below a certain threshold. This can be a useful feature in situations where you need a night light in a dark room.

The BD139 transistor is used in the circuit as a switch that turns on and off the LED light. The LDR, or light-dependent resistor, is used to detect changes in ambient light levels. When the ambient light level falls below a certain threshold, the resistance of the LDR decreases, allowing current to flow through the transistor, turning on the LED light.

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let's continue to our topic Alternatively, a 3.3k resistor can be used instead of an LDR in the circuit. This resistor serves as a voltage divider, allowing the voltage at the base of the transistor to be adjusted according to the ambient light level. As the ambient light level decreases, the voltage at the base of the transistor decreases, allowing current to flow through the transistor and turning on the LED light.

To build this circuit, I am providing you a schematic diagram:

Overall, the automatic USB night light circuit using a BD139 transistor, LDR, or 3.3k resistor is a simple and useful project that can be easily built by electronics enthusiasts. It provides a convenient way to have a night light that turns on automatically when it gets dark, making it a great addition to any bedroom, hallway, or other space where you need a bit of extra light at night.

By the way you can also watch the making video