This circuit produces a running led effect without using microcontrollers. All you need are two CD4017 counters, a NE555 timer and some basic skills in electronics. At the start condition the clock enable (pin 13) of the IC1 counter takes the direct negative signal from the last output of that counter. Such negative signal is inverted by the Q17 transistor and sent to the clock enable of the IC2. So the first counter drives the led from 1 to 8, while the second one keeps on the first output, which is not connected.
When the last output of the first counter turns on, the second counter drives the led from 8 to 1 and its last output gives off the reset signal.
The speed of the led effect can be adjusted by a trimmer.
Thehttps://www.youtube.com/watch?v=eXJgwhYXZH8CD4017https://www.youtube.com/watch?v=eXJgwhYXZH8counter is a CMOS integrated circuit, so it is very sensitive to electrostatic charges.
The circuit schematic is available here:
