Hello friends! Today we will make six LEDs light in a back-and-forth sequence using a 555 timer and a CD4017 decade counter. This extends our multiple LED flasher : instead of switching two whole banks, we will select a different position after each clock pulse. The timer controls how quickly the pattern advances. The counter decides which of ten states is active, and an output-mapping network converts those ten states into a six-position outward-and-return pattern. Separating those jobs makes the circuit easier to understand and troubleshoot. The original screenshots and download remain below. We will correct the description of the 4017 and replace the old output-combining method with diode isolation. Resistors between opposing outputs do not turn those outputs into a proper logic OR func ...