Sure, there are some times when you can get away with using unregulated voltage. But if you want your project to work reliably, you need to provide a reliable power source. If you ask me, the easiest and least expensive way of doing this is to use a linear voltage regulator. You’ll need just three parts, but you might roll in a few more to add features. And the good news is that these regulators are available with many different voltage output levels.
I’m going to illustrate their use with a 7805 regulator. It puts out 5V and you can buy it at Radio Shack or order if from your favorite parts supplier. If you look hard enough you might find one to salvage in your junk bin. I’ll get started on it after the break.