By Allan Robinson
Updated Mar 24, 2022
Image credit: golubovy/iStock/GettyImages
A voltage stabilizer, commonly known as a voltage regulator, maintains a constant output voltage regardless of variations in input voltage or load. Among the many types available, linear IC regulators like the 7805 are the most widely used for small‑scale projects. This guide walks you through wiring a 7805 5‑V regulator to a 9‑V battery, so you can power a low‑current load such as a miniature lamp with a steady 5 V supply.
The 7805 is a three‑pin device. When the leads are oriented with the flat side facing you, the pins from left to right are: Input (VIN), Ground (GND), and Output (VOUT). The label “7805” on the package indicates a positive regulator that delivers 5 V.
Insert each of the regulator’s pins into a dedicated hole on a perfboard or prototyping board, ensuring the pins are aligned in a single column but in separate rows. This arrangement keeps the connections tidy and reduces the chance of short circuits.
Attach the load (e.g., a small incandescent bulb or LED) to the regulator. Wire the load’s positive lead to the same row as the regulator’s output pin, and its negative lead to the same row as the regulator’s ground pin.
Connect the positive lead of a 9‑V battery holder to the same row as the regulator’s input pin. Connect the battery’s negative lead to the same row as the regulator’s ground pin and the load’s negative lead.
Insert a 9‑V battery into the holder. The 7805 will regulate the voltage down to a steady 5 V, delivering that voltage to the load. Because linear regulators dissipate excess voltage as heat, ensure the regulator’s thermal envelope is not exceeded—use a heat sink for higher currents.
For more detailed specifications, consult the TI 7805 datasheet.
