555 LED Blinker

Astable 555 oscillator blinking an LED at roughly 1 Hz.

Difficulty: Breadboard. Estimated build time: about 25 minutes. Estimated parts cost: about US$1.25. 8-part bill of materials with live supplier pricing. A free-running oscillator built around a single NE555 timer IC that toggles an LED on and off at approximately 1 Hz.