Speaking of GravityLight’s low power solution, several people have written in to request more coverage in the blog on how transformers and power supplies for DIY projects work, and how to select them. Ladyada has a tutorial up on the Adafruit Learning System that addresses quite a few of the power supply options that pertain to the types of DIY projects most frequently attempted by our community:
What is a power supply?
A power supply is a device that supplies power to another device, at a specific voltage level, voltage type and current level. For example, when we talk about a 9VDC @ 500mA power supply can provideas much as 500mA of current and the voltage will be at least 9V DC up to that maximum current level. While it sounds simple, power supplies have a lot of little hang-ups that can be very tricky for the uninitiated. For example, unregulated supplies say they can provide 9V but really may be outputting 15V! The very common 7805 regulator datasheet claims it can regulate up to 1000 mA of current, but when you put a 15V supply on one side, it overheats and shuts down! This tutorial will try to help explain all about power supplies.
Why a power supply?
When you start out with electronics, you’ll hear a lot about power supplies - they’re in every electronics project and they are the backbone of everything! A good power supply will make your project hum along nicely. A bad power supply will make life frustrating: stuff will work sometimes but not others, inconsistent results, motors not working, sensor data always off. Understanding power supplies (boring though they may be) is key to making your project work!
A lot of people don’t pay much attention to power supplies until problems show up. We think you should always think about your power supply from day one – How are you going to power it? How long will the batteries last? Will it overheat? Can it get damaged by accidentally plugging in the wrong thing?