LM393 Comparator Dark Detector

Single LM393 comparator with an LDR and threshold pot — LED snaps on cleanly when the room gets dark.

Difficulty: Breadboard. Estimated build time: about 25 minutes. Estimated parts cost: about US$1.10. 6-part bill of materials with live supplier pricing. A clean digital dark-detector that introduces the comparator — a part the LM393 is built for and the LM358 op-amp is not.