74HC595 Shift-Register 8-LED Bar Graph

Three Arduino pins drive eight LEDs through a shift register — your first lesson in trading I/O lines for serial-to-parallel conversion.

Difficulty: Breadboard. Estimated build time: about 35 minutes. Estimated parts cost: about US$4.80. 5-part bill of materials with live supplier pricing. An 8-LED bar graph driven through a 74HC595 8-bit serial-in / parallel-out shift register, controlled from just three Arduino pins (data, clock, latch).