Here is a circuit of a LED sequencer / chaser using CD 4017 and NE555 IC. CD 4017 is a CMOS counter IC consist of 16 pins. This IC gives 10 outputs according to the clock pulse it receives from the clock input, which is pin 14. The another IC used in this circuit is NE555 which is a timer
IC. NE555 is a very famous IC and used in wide verity electronic projects to perform different tasks. In this circuit it is working as an astable multivibrator and its providing continuous clock pulses to the CD 4017 IC. Due to which CD 4017 produces very beautiful looking chasing light effects.