Como HACER un SENSOR de OSCURIDAD con LDR + TRANSISTOR

Summary

In this tutorial video, viewers learn how to build a light-sensitive sensor circuit using basic electronic components, such as an LED, a photoresistor (LDR), an NPN transistor, and resistors. The circuit turns the LED on or off based on light intensity. The video also covers a variation of the sensor, incorporating a potentiometer to adjust the sensitivity, allowing users to control how much darkness is needed for the LED to turn on. The step-by-step guide provides a clear explanation of the assembly process and the working principle behind the sensor's operation.

Takeaways

• 😀 The project is about creating a light/darkness sensor and its variation.
• 😀 Key components used include a breadboard, a 9V battery holder, a 5mm LED, and a photoresistor (LDR).
• 😀 Proper polarity is important for the components, especially for the LED.
• 😀 The schematic shows how the components are connected: the LED, transistor, resistors, and photoresistor.
• 😀 A 220-ohm resistor is used to protect the LED, and a 100k resistor adjusts the sensitivity of the sensor.
• 😀 The transistor serves as a gate that controls the LED based on the amount of current it allows through.
• 😀 The photoresistor changes its resistance depending on the amount of light it receives.
• 😀 When no light is received, the photoresistor has a resistance of up to 200k ohms, and with light, it can drop to around 500 ohms.
• 😀 The circuit works by adjusting the voltage between the 100k resistor and the photoresistor, which impacts the transistor's behavior.
• 😀 A variation of the sensor circuit uses a potentiometer to control sensitivity by adjusting the resistance in series with a 15k resistor.
• 😀 With the potentiometer, the sensor's sensitivity can be adjusted: higher resistance requires more darkness for the LED to turn on, while lower resistance makes the sensor more sensitive to light.

Q & A

What is the main objective of the video?

The main objective of the video is to demonstrate how to build a light/darkness sensor using various electronic components such as resistors, a transistor, a photoresistor, and an LED.

What components are required to build the sensor?

The components required are a breadboard, a 9V battery holder, a 5mm LED, a 100k ohm resistor, a 220 ohm resistor, an NPN transistor (like 2N2222), and a photoresistor (LDR).

What is the role of the photoresistor (LDR) in the circuit?

The photoresistor (LDR) changes its resistance based on the amount of light it receives. The resistance decreases in light and increases in darkness, affecting the current passing through the circuit and controlling the LED.

How does the transistor function in this circuit?

The transistor acts as a switch or gate, controlling the flow of current to the LED. It allows or blocks the current depending on the voltage it receives, which is influenced by the photoresistor.

What does the 100k ohm resistor do in the circuit?

The 100k ohm resistor determines the sensitivity of the sensor. It works in conjunction with the photoresistor to regulate the current flow, controlling when the LED turns on or off based on light levels.

Why is polarity important when connecting the LED?

Polarity is important because the LED will only work when connected in the correct direction. The longer leg of the LED should be connected to the positive line, and the shorter leg to the negative line.

How does the circuit respond to varying light conditions?

When the photoresistor receives light, its resistance decreases, allowing more current to pass through the transistor, which turns the LED on. In darkness, the resistance increases, reducing the current and turning the LED off.

What is the difference between the standard sensor and its variation in the video?

The variation in the video introduces a potentiometer and a 15k ohm resistor to adjust the sensitivity of the sensor. This modification allows the user to control how much darkness is required to turn on the LED.

How does the potentiometer affect the sensor's sensitivity?

The potentiometer, in combination with the 15k ohm resistor, adjusts the total resistance in the circuit. By rotating the potentiometer, the user can control the sensitivity, requiring more or less darkness to activate the LED.

What happens when the potentiometer is set to a higher resistance?

When the potentiometer is set to a higher resistance, more darkness is required to turn on the LED, as the overall resistance in the circuit is higher, limiting the current flow.