Running LEDs

Parts List

R1, R2, R3Resistor 10 kΩThree standard resistors
C1Capacitor 4.7 µFPolarized capacitor
L1 to L10LEDStandard light-emitting diode
U1NE555555 Timer IC
U2CD4017BE4017 Decade Counter


The 555 timer circuit decides how fast the LEDs are “running”. Specifically R1, R2, and C1.

Since the 4017 chip only supports up to 2-3 mA of current out of its outputs, be sure to limit the current sufficiently with R3. 10 kΩ will limit the current to less than 1 mA.