Description LDR Sensor Module The LDR sensor module detects light and measures how bright it is. When there’s light, the output is high, and when there’s no light, it’s low. You can change how sensitive it is using a small dial (potentiometer). This light detection sensor has an M3 mounting hole for easy attachment and comes with an LDR for accurate readings. The LDR module also has a power LED and a status LED to show if it’s working, making it great for checking how bright the surroundings are.