luaks1493:
I´m looking for a method to turn some LED´s in a row behind each other on and off, as fast as the human eye can see. So it looks like the whole row is lighted, although only one LED is lighted at once.
The aim is to reduce the needed power supply to a minimum, due to only few lighted LED`s.
You seem to be confusing a technique used with ordinary LEDs with the usage of the WS2801. You will never see any advantage using your proposed scheme over just sending smaller data values to the WS2801.
Create a loop running at NUM_LEDS * F. (F can probably be 30 - 60 Hz). Step through your array data and only send the data for the current WS2801 while sending all zeros for all other WS2801s.
You will prove to yourself that there is no point in doing this.