KY-018 Photoresistor

This module contains an LDR resistor whose resistance value decreases with brighter surroundings.

This resistance can be determined using a voltage divider, where a known voltage is divided across a known (10 kΩ) and an unknown (variable) resistance. Using this measured voltage, the resistance can then be calculated - the exact calculation is included in the code examples below.

Operating voltage	3,3 V - 5 V
Fixed known resistance	10 kΩ
Dimensions	21 x 15 x 6 mm

Pin assignment

Code example Arduino

Pin assignment Arduino

Arduino	Sensor
Pin A5	signal
5 V	+V
Ground	GND

The program measures the current voltage value at the sensor, calculates the current resistance value of the sensor from this and the known series resistance and outputs the results via the serial output.

int sensorPin = A5; // Declare the input pin here
 
// Serial output in 9600 baud
void setup()
{
    Serial.begin(9600);
}
 
// The program measures the current voltage value at the sensor,
// calculates from this and the known series resistance the current
// resistance value of the sensor and outputs the results to the serial output
 
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) );
         
    // ... and here output to the serial interface
    Serial.print("Voltage value:"); Serial.print(voltage); Serial.print("mV");
    Serial.print(", resistance value:"); Serial.print(resitance); Serial.println("Ohm");
    Serial.println("---------------------------------------");
 
    delay(500);
}

Example program download

KY018-Arduino.zip

Code example Raspberry Pi

Pin assignment Raspberry Pi

Raspberry Pi	Sensor
KY-053 A0	Signal
3.3 V [Pin 1]	+V
Ground [Pin 6]	GND

Sensor	KY-053
Signal	A0
+V	3.3 V [Pin 1]
GND	Ground [Pin 6]

Raspberry Pi	KY-053
GPIO 3 [Pin 5]	SCL
GPIO 2 [Pin 3]	SDA

Analog sensor, therefore the following must be considered: In contrast to the Arduino, the Raspberry Pi does not have any analog inputs or there is no ADC (analog digital converter) integrated in the chip of the Raspberry Pi. This limits the Raspberry Pi, if you want to use sensors, which do not output digital values, but a continuously changing value (example: potentiometer -> different position = different voltage value).

To avoid this problem, our sensor kit X40 contains the KY-053, a module with a 16-bit ADC, which you can use on the Raspberry to expand it with 4 analog inputs. This module is connected to the Raspberry Pi via I2C, takes over the analog measurement and transfers the value digitally to the Raspberry Pi.

Thus we recommend to connect the KY-053 module with the said ADC in between for analog sensors of this set. More information can be found on the KY-053 Analog Digital Converter information page.

The program uses the corresponding ADS1x15 and I2C Python libraries from Adafruit to control the ADS1115 ADC. These have been published at the following link https://github.com/adafruit/Adafruit_CircuitPython_ADS1x15 under the MIT license. The required libraries are not included in the download package below.

Please note that you need to enable I2C on your Raspberry Pi before using this example.

#!/usr/bin/python
# coding=utf-8

import time
import board
import busio
import adafruit_ads1x15.ads1115 as ADS
from adafruit_ads1x15.analog_in import AnalogIn
import math
# Create the I2C bus
i2c = busio.I2C(board.SCL, board.SDA)

# Create the ADC object using the I2C bus
ads = ADS.ADS1115(i2c)
voltageMax = 3.3
# Create single-ended input on channels
chan0 = AnalogIn(ads, ADS.P0)
chan1 = AnalogIn(ads, ADS.P1)
chan2 = AnalogIn(ads, ADS.P2)
chan3 = AnalogIn(ads, ADS.P3)



while True:
    resistance = chan0.voltage / (voltageMax - chan0.voltage) * 10000

    print("Voltage value: ",'%.2f' % chan0.voltage, "V, resistance: ",'%.2f' % resistance, "Ω")
    print("---------------------------------------------------")
    time.sleep(1)

Example program download

KY018-RPi.zip

To start with the command:

sudo python3 KY018-RPi.py

Code example Micro:Bit

Pinout Micro:Bit:

Micro:Bit	Sensor
Pin 1	Digital Signal
3,3 V	+V
Masse	GND
KY-053 A0	Analog Signal

Sensor	KY-053
Analog Signal	A0

Micro:Bit	KY-053
Pin 19	SCL
Pin 20	SDA
3,3 V	+V
Masse	GND

Analog sensor, therefore the following must be observed: The Micro:Bit has analog inputs or there is an ADC (analog digital converter) integrated in the chip of the Micro:Bit. However, these are only limited to 10-bit and therefore offer only a rather low accuracy for analog measurements.

To avoid this problem, our sensor kit X40 contains the KY-053, a module with a 16-bit ADC, which you can use on the Micro:Bit to expand it by 4 analog inputs. This is connected to the Micro:Bit via I2C, takes over the analog measurement and transfers the value digitally to the Micro:Bit.

Therefore we recommend to connect the KY-053 module with the mentioned ADC in between for analog sensors of this set. More information can be found on the KY-053 Analog Digital Converter information page KY-053 Analog Digital Converter.

The program uses the corresponding library from us to control the ADS1115 ADC. This has been published under the following link pxt-ads1115 under the MIT-License.

Sample program download

microbit-KY-018.zip