This is a light controlled relay, you can set the relay on/off when the luminance is higher/lower than the illuminance you set.The peak voltage capability is up to 250V at 10A when AC and 30V at 10A when DC. With this module, it will be much more easy to implement applications that needs auto power up/down with the illuminance varies.This module uses the LDR to detect the light, which has a more stable directivity than the ordinary photo resistance. Adjust the on-board potentiometer to adjust the sensitivity. The relay would ON/OFF when the luminance is higher/lower than the threshold set by the potentiometer.