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I used the 8bit-counter 74HC4022 to build this simple running light circuit which makes out of one blinking LED (e.g. HDD-LED or NIC ACT-LED) eight LEDs blinking in turns. The "data-input" has to be connected via an optocoupler. This is because you never know exactly what kind of signal the board gives to the LED. The signal provided by my board can't be feeded directly to the counter chip. Most NICs provide a very low-powered signal. Because of this the optocoupler you use mustn't have a too low amplification factor. The circuit works with an 4N 36 (factor 100%) at the HDD-LED connector but not at a NIC. With the only inessential more expensive 4N 33 (factor 500%) it works with both. The unlabeled resistor in the circuit has 68kOhm. Because there can be only one LED alight at a time they can be connected via one common resistor.
