When building a project and instead of using a bench power supply to always power your newfangled device you would use typically batteries or a power supply of some sort. There is one type that is cheap and easy to use, it even has many names such as AC Adapter, Wall Wart and Power Brick. These are typically unregulated and a bit tricky to figure out at times. I have a collection so to speak of these that I use at times but it’s not just as simple as reading the label and plugging it in. Reason being since they’re unregulated and you probably didn’t add a regulator to your device you might over power the device and cause issues or even destroy the device. I’m not saying to use one with out a regulator, if you plan to use a Wall Wart I would recommend to adding a regulator to what ever project you’re powering but if you’re in a pinch you can get by with out one as long as your Wall Wart is the correct voltage value. I typically will test a Wall Wart and get the exact voltage rating and use some masking tape and marker to label it. I’ve came across some that say 12 volts on the label but in fact are 17 to 20 volts.
Now if you thinking that a regulator isn’t needed then you might need your head checked. The power supply is unregulated so if you’re getting the correct voltage you need you’re still not out of water. Say there’s a voltage spike. Voltage spikes happen when you loose voltage and when it comes back with a surge of extra power so if your outlet runs 120 AC and a voltage spike hits that lowers the voltage to say 105 volts and quickly switches up to 130 volts for a few seconds and decreases back don to 120. With that extra 10 volts it can increase the DC voltage of the wall wart from 12 volts to 20 volts. This could fry your project with out proper protection. Even if you use a surge protector you can still fry the device. It’s better to burn up a regulator then a whole circuit board.