Introduction
A dark Dark Detector Using BC547 circuit, capable of sensing darkness or absence of light, finds utility in applications like night detection and light control. Using a BC547 transistor, this circuit design enables the automatic activation of street lights during nighttime. When light strikes the LDR (Light Dependent Resistor), it alters the potential difference across it, regulating the base current of the transistor. Once the potential difference drops below a specific threshold, the transistor activates, illuminating the LED.
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Components Required
In this Dark Detector Using BC547 project we are making a night-light that turns on in the dark. And the project is based on Light Dependent Resistance (L.D.R.). These resistors are commonly used as light sensors. Whenever the sensor is exposed to light, its resistance decreases. When it is dark, its resistance is maximum.
What is resistor
An electrical resistor is a device that restricts the flow of electric current. It is composed of an insulating material, such as carbon or ceramic, and metal wire, and is used to limit the current flowing in a circuit. Resistors are important components in many electrical applications, ranging from regulating voltage levels to controlling signals.
Variable resistor
A variable resistor, also known as a potentiometer, rheostat, or preset, is an electronic component with an adjustable resistance. It finds its purpose in controlling the current in a circuit and can also function as a voltage divider. Variable resistors are widely utilized in audio systems for volume control and in adjusting the brightness of lights.
LDR light dependent resistor
Light dependent resistor (LDR) These devices depend on the light. When light falls on the LDR, its resistance decreases. When it is dark, its resistance is maximum. You can place it (LDR) at the top (near +Vs) or at the bottom (near 0V), depending on when you want a large output voltage:
LDR made up of semiconductor materials that have high resistance. There are many different symbols used to identify a photoresistor or LDR. The two most used symbols are shown in the figure above. The arrow indicates where light falls.
Circuit Diagram
Swapping the resistor and LDR
If you swap the resistor and LDR, the voltage divider will reverse its action. The resistance of an LDR is high when it is dark and low when it is bright:
- In bright light, the LDR at the top (near +Ve) makes Vout high.
- In the dark, the LDR at the bottom (near -Ve) makes Vout high.
LEDs emit light only when current flows through them. This can only happen if there is a path between the positive terminal and the negative terminal of the battery. We are using an LDR whose resistance decreases in the light and increases in the dark.
Let’s Build the circuit on the breadboard
Learn More about Transistor
