1. 12 V input as sensor for relay board regulator transistor The 12 V supply is used as the sensor input for the relay board’s regulator transistor, improving stability and overall reliability. 2. Onboard optocoupler isolated relay An optocoupler-isolated relay protects the control circuitry and the IC, delivering robust protection and more reliable operation. 3. Adjustable sensitivity and trigger threshold A potentiometer sets the relay trigger threshold. When ambient light falls below this threshold, the module energizes the relay; the same setting governs relay release. 4. Photocell based light sensing A photoresistor directly senses ambient light and drives the relay, enabling automatic switching based on light level. Typical applications - Automatic lighting control: connect outdoor or indoor lights to the relay so they turn on when it gets dark and turn off when it brightens. - 12 V automation: use the relay to switch fans, indicators, or small motors in response to ambient light, within a 12 V system. - Environment or display control: automate backlighting or signage by sensing light levels and triggering the relay accordingly.