[Joeaksa]

Island is somewhat correct about the voltage.

I have done what you are talking about with no problems. Take a digital VOM and read the output on the transformer. Usually a 5v output on a small transformer like this will read 6.5 or even 7v under no load, but drop down closer to its rated 5 volt output when placed under a load.

Depending on your application I would get one that is very light duty, like 200 or 300 miliamps, or try one that size at first. The ones that are higher duty (say 500 miliamps) tend to go even higher on the unloaded voltage.

Another option for power in this range is to find an old desktop power supply. They output 12 and 5 volts and are much more stable. Most of us electronic nerds have one or two of these around the house.