If you do a fair amount of tinkering with electronics, then there's a good chance that at some point you've found yourself needing a good way to get power to your project. Sure, you can use batteries, but if you're only using them for testing purposes, you can burn through a lot of them. Another option is to buy a desktop power supply, which lets you route power at a specific voltage and current to whatever you're working on. The downside to these is that they can cost more than you're wanting to spend. The third option would be to build your own desktop power supply.