Hello, i found an Trafo from my model railway and dont know if i can use it as power source for the Arduino Uno board to.
0 - 12 Volt --> 6 VA
I wouldn't advise so.
This power supply isn't as you stated 0 - 12 volts, it's actually -12 0 +12 volts.
As it is made to control speed and direction of your locs, it doesn't need any accuracy.
Therefore you can be sure it will output a DC voltage, but it's unlikely to be any kind of stable (simply because threre's no need for that in the application it is meant for).
That means, it could be outputting a pulsing DC voltage (which is still DC) because your motors do not care about a flat line or some pulses.
Your Arduino does care about that, and will probably need some additional electronics.
Of course you could test the accuracy of that power supply using an oscilloscope to be sure.
Possibly not - those sorts of power supplies tend to just be
rectified AC, no smoothing or regulation, and the control circuit may just be a rheostat.
You'd have to investigate it.
Thank you very much for your reply. 