In this article, we connect an KY-018 Photoresistor or LDR to a Raspberry Pi Pico, any Rp2040 type board will be suitable. We actually tested this with a Cytron Maker Pi Pico
We will use Micropython for these examples but of course you can use the Arduino IDE as well if you have Raspberry Pi Pico support enabled
The sensor looks like this
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.
| Name | Link | |
| Raspberry Pi Pico | ||
| 37 in one sensor kit | ||
| Connecting cables |
Schematic/Connection
| Pico | SENSOR |
|---|---|
| GPIO28 | S |
| 3.3v | middle pin |
| GND | – |
Code Examples
Basic example in thonny
from machine import Pin
import time
class LDR:
def __init__(self, pin):
self.ldr_pin = machine.ADC(Pin(pin))
def get_raw_value(self):
return self.ldr_pin.read_u16()
def get_light_percentage(self):
return round(self.get_raw_value()/65535*100,2)
ldr = LDR(28)
while True:
print(ldr.get_light_percentage())
time.sleep(1)
REPL Output
Run -c $EDITOR_CONTENT
31.31
30.99
31.11
57.09
67.28
23.32
14.8
14.55
14.77
13.92
13.68
13.92
Links
https://github.com/getelectronics/rp2040learning/tree/main/Sensor%20Kit/KY-018_PhotoResistor