NE555 Monostable One-Shot Timer

Press a button, get a single calibrated pulse — the textbook 555 monostable circuit that times an LED, relay, or any logic input for exactly the duration you set with one R and one C.

Difficulty: Breadboard. Estimated build time: about 25 minutes. Estimated parts cost: about US$3.20. 8-part bill of materials with live supplier pricing. A one-shot timer that fires exactly one output pulse every time you press the trigger button.