Beginner Parts Kit Identification Guide
The Voltage Regulators - 3.3V and 5V
Working behind the scenes in most circuits are the voltage regulators, ever-toiling to convert those unfriendly, unstable, high-voltage signals to something that keeps everything in the rest of the circuit happy.
The voltage regulators included in the Parts Kit are of the linear variety, they can be used to drop a large voltage down to either 5V or 3.3V. In exchange for this energy transfer, they'll produce anywhere from a slight warmth to searing, painful heat on the bottom, metal tab.
Each regulator has just three pins: an input voltage, an output voltage, and a common ground. The pinouts of the two regulators are annoyingly not the same, so take note of the picture below.