16.1. Simple Voltage Regulators

Often your project will need regulated power beyond what can be tapped from the Arduino board itself. One of the simplest ways to achieve this is through the use of a three-terminal regulator. The most common of these are the 78xx series parts where xx is the output voltage—05, 06, 08, 12, 15 for 5V, 6V, 8V, 12V and 15V outputs, respectively.

Figure 16-1 shows a simple 5V supply based on a 7805. Most of the components other than the regulator and 0.1μF capacitor are optional. We include them because it represents good design practice. The capacitors all serve to help the circuit deal with transient demands from the connected circuitry. The 0.1μF part helps the regulator remain stable, so it's good practice to install it and have it as close as reasonably possible to the regulator itself. The diode back across the regulator limits how much current will flow back into the regulator from the capacitors on the output side when the input power is removed.