IC 4017 CMOS-Decade counter/divider. When we build the 10 LEDs running light for hobby. Often use IC-4017. This really neat chip contains counter,decoder[...]
Here are LED light sequencer circuit that using IC-4017 and IC-555.
Simple Key code lock switch circuit using IC-4017 digital, uses 10 switch bottom to control output by Relay. No microcontroller so easier and cheaper!