Chapter 5. Power Sources

All electronic or electrical and electronic devices, from the simplest flashlight to the control systems on a modern aircraft, need one thing in common: power. Without a source of electrons, it’s all just a pile of inert metal, plastic, and silicon (among other things).

This chapter presents an overview of power sources for both DC and AC, ranging from batteries to linear and switching power supplies. Special attention will be given to batteries and inexpensive DC power supplies you can use to power your project that plug into a standard AC wall socket (so-called wall warts).

We’ll wrap up the chapter with a look at fuses and circuit breakers, essential but often overlooked devices that can save the day if used correctly. To that end, there is a brief discussion of how to select an appropriate rating for these essential protection devices.


Batteries are the simplest source of DC power, and they are essential when portability is a major consideration. Unfortunately, a battery will last only so long before it must be either replaced or recharged.

There are numerous types of batteries available, ranging from the tiny types used in things like hearing aids, all the way up to huge arrays that are found in solar power installations and in the back-up power systems for large computer installations. Some batteries are rechargeable, such as the types used in cell phones and automobiles, while others are single-use and must be disposed of when they are ...

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