Power Sources: Batteries, Supplies and Regulation
Every circuit you build needs energy pushed into it at the right voltage and with enough current available. A blinking LED, a spinning motor, and an Arduino brain all need power — but they need it delivered differently. In this lesson we meet the two great families of power: batteries (energy you carry) and wall supplies (energy from the mains). Then we learn how to turn a messy, drifting voltage into a clean, steady one using regulators, and finally how to choose the correct source for any project.
The big idea: A power source is judged by three numbers — its voltage (the push, in volts, V), the current it can supply (the flow available, in amps, A), and its capacity or energy store (how long it lasts, often in mAh). Match the voltage, make sure enough current is available, and pick a capacity that lasts long enough. Get those three right and almost any project runs happily.
What you will learn
- The main battery chemistries — their nominal voltage, whether they recharge, and where each is used.
- What capacity in mAh really means, and how to compute how long a battery lasts.
- How to combine cells in series (voltage adds) and parallel (capacity adds).
- Why a battery’s voltage sags under load — the idea of internal resistance.
- How a wall adapter turns dangerous mains AC into safe, smooth DC in four stages.
- How to read an adapter label and match a supply to a project (the amps-are-pulled rule).
- How USB became the universal 5 V standard.
- How regulators (linear 7805, LDO, and switching buck/boost) create a clean, fixed voltage.
- Why circuits need a common ground, and how to choose a source for a real project.