But because LED`s take too much energy, i would need this?
Maybe a led strip takes too much energy, but how about just one LED?
From the documentation here:
The GPIOs of the Omega have:
Maximum drive: 24 mA
So, anything less is safe to use. I can't recommend a particular circuit, but others with more electronic knowledge can (and surely someone already did).
I don't have the Omega (1) to test, but I guess that you could use the ON-BOARD OMEGA LED if it's not obstructed by your OLED module. The above documentation says it is wired to GPIO27.
I also thinked about this, but it just does not look good (or that goog) c:
@MultiDJRoni While the display you reference (http://ebay.eu/2brESNp or http://ebay.eu/2bYf3pA) communicates via I2C and is potentially controllable from the Omega, I don't know whether or not the chip/display it uses is the same as or compatible with that used in the OLED expansion. If it is not, you may be up for additional coding work to control it from the Omega (not a totally trivial task).
I still think you would be better of using a Prototype Expansion (http://www.robotshop.com/en/proto-expansion-for-onion-omega.html) between your Expansion Dock and OLED Expansion and wiring the Prototype Expansion to provide access to the I2C lines (GPIO 20, GPIO 21, 5v, Gnd) and other pins you need for access to your other devices.
I will try :) Thank you both for the tipps!