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Arduino and KY-018 Photoresistor

by arduinoguy71

In this article, we connect a KY-018 Photoresistor or LDR to an Arduino Uno

The KY-018 is a Photoresistor module which can be used to measure light intensity.

The resistance will decrease in the presence of light and increase in the absence of it. The output is analog and determines the intensity of light.

The module consists of a photoresistor, a 10 k in-line resistor and header.

This resistance can be determined using a basic voltage divider, where a known voltage is divided across the 10k resistor and the unknown resistance from the LDR. Using this measured voltage, the resistance can then be calculated. This is the basic idea

 

Parts Required

You can connect to the module using dupont style jumper wire.

This should work with other Arduino board – I have tried an Uno and Mega

Name Link
Arduino Uno
37 in one sensor kit
Connecting cables

 

Schematic/Connection

Code Example

The following code example will

Example 1

int sensorPin = 1; //define analog pin 1
int value = 0; 

void setup()
{
  Serial.begin(9600); 
} 

void loop() {
  value = analogRead(sensorPin); 
  Serial.println(value, DEC); // light intensity
                // high values for bright environment
                // low values for dark environment
  delay(500); 
}

 

Example 2

int sensorPin = A1; // Declare the input pin here
 
void setup()
{
    Serial.begin(9600);
}
 
void loop()
{      
    // Current voltage value is measured...
    int rawValue = analogRead(sensorPin);
    float voltage = rawValue * (5.0/1023) * 1000;
    float resitance = 10000 * ( voltage / ( 5000.0 - voltage) );
    
    Serial.print("Voltage value:"); 
    Serial.print(voltage); 
    Serial.print(" mV");
    Serial.println("");
    Serial.print("resistance value:"); 
    Serial.print(resitance); 
    Serial.print(" Ohms");
    Serial.println("");
    Serial.println("---------------------------------------");
 
    delay(500);
}

 

Serial Monitor Output

Example 1

177
171
172
178
759
828
929
949
373

Example 2

Voltage value:3699.90 mV
resistance value:28458.65 Ohms
—————————————
Voltage value:938.42 mV
resistance value:2310.47 Ohms
—————————————
Voltage value:923.75 mV
resistance value:2266.19 Ohms
—————————————
Voltage value:982.40 mV
resistance value:2445.26 Ohms
—————————————
Voltage value:3543.50 mV
resistance value:24328.86 Ohms

Links

https://github.com/getelectronics/ArduinoCode/tree/main/37%20Sensor%20Kit/KY-018_PhotoResistor

 

 

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