Light Sensor with Twilight Detection
This is not the first light sensitive circuit to be published in Elektor. This circuit however, distinguishes itself that in addition to light and dark it can also signal twilight. This lets you automatically turn on a light in the living room when it becomes dark and turn on a lamp in a dark hallway when dusk sets in. The circuit described here generates a logic signal on three separate outputs for light, twilight and dark. The transition thresholds are set with two trimpots.