Design with Photoresistor (LDR) Sensor (Wokwi Compatible) in Cirkit DesignerA Photoresistor, also known as a Light Dependent Resistor (LDR), is an electronic component whose resistance varies with the intensity of light it is exposed to. It is widely used in applications that require the detection of light levels, such as in light-activated switches, alarm systems, and ambient light sensing for display backlight control.
This circuit uses an Arduino UNO to read the output from a photoresistor (LDR) sensor and display the light status ('Light!' or 'Dark') on a 16x2 I2C LCD. The Arduino reads the digital output of the LDR and updates the LCD accordingly.
Open Project in Cirkit Designer
This circuit is a street light control system using an Arduino UNO, LDR sensor, and two PIR sensors. The LDR sensor determines day or night, turning on three LEDs at night via a transistor switch, while the PIR sensors detect motion to activate an additional LED.
Open Project in Cirkit Designer
This circuit utilizes a Photoresistor (LDR) sensor to measure ambient light levels and display the results on a 16x2 I2C LCD. The Arduino UNO processes the sensor data and updates the LCD to indicate whether the environment is 'Light' or 'Dark' based on the calculated lux value.
Open Project in Cirkit Designer
This circuit is a street light control system using an Arduino UNO, LDR sensor, and two PIR sensors. The LDR sensor detects day or night to control three LEDs via a transistor switch, while the PIR sensors detect motion to turn on an additional LED for enhanced illumination.
Open Project in Cirkit DesignerThe LDR sensor typically has two terminals, which are non-polarized:
| Pin | Description |
|---|---|
| 1 | Terminal 1 |
| 2 | Terminal 2 |
To use the LDR sensor in a circuit, you can create a voltage divider by connecting it in series with a resistor to the supply voltage. The voltage across the LDR will vary with light intensity, which can be measured using an analog input on a microcontroller such as an Arduino UNO.
// Define the LDR pin
const int ldrPin = A0;
void setup() {
// Initialize serial communication at 9600 baud rate
Serial.begin(9600);
}
void loop() {
// Read the value from the LDR
int ldrValue = analogRead(ldrPin);
// Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V)
float voltage = ldrValue * (5.0 / 1023.0);
// Print out the value in the Serial Monitor
Serial.print("LDR Value: ");
Serial.print(ldrValue);
Serial.print(" - Voltage: ");
Serial.println(voltage);
// Wait for a bit to avoid spamming the serial output
delay(500);
}
Q: Can I use the LDR with a digital input?
A: The LDR is an analog sensor, so it is best used with an analog input to get a range of values. However, you can set a threshold to create a digital (on/off) signal.
Q: How do I calibrate the LDR for my application?
A: Measure the resistance of the LDR at known light levels and create a lookup table or function in your code to translate the analog readings to light levels.
Q: What is the lifespan of an LDR?
A: LDRs can last many years if used within their specified ratings and environmental conditions. However, they can degrade over time, especially if exposed to high-intensity light for extended periods.