CD4017 10-LED Knight Rider Chaser

A 555 clock and a CD4017 decade counter give you a marquee chaser of ten LEDs in sequence.

Difficulty: Through-hole. Estimated build time: about 40 minutes. Estimated parts cost: about US$4.50. 9-part bill of materials with live supplier pricing. A classic showcase of CMOS digital logic: a 555 timer running at a few hertz feeds clock pulses into a CD4017 decade counter, and the CD4017's ten outputs Q0–Q9 light up sequentially, one at a time, in a marching pattern.