[sdiy] get 5V from 12V - DC-DC converter or 7805?

[Tony Allgood]

The OKI-78SR-5/1.5-W36-C is pin compatible with a traditional 7805 
linear regulator. The disadvantage is that it is more expensive and 
creates a small amount of high frequency noise that is both radiated and 
into the power rails. The amount of noise depends on the current draw 
from the +5V line, with greater currents creating more noise.

If the current draw is less than 100mA, I'd be tempted to use a 78M05.

Tony