Basic Adjustable Power Supply Based on LM317

Overview

The LM317 adjustable voltage regulator is used in this project to produce a power supply that can be used for testing and debugging purposes.

Explanation

The voltage regulator contains 1N4001 protection diodes in order to protect the device against input short circuit while another diode protects against output short circuit for discharging capacitors. It should be noted that the LM317 is not connected to ground at any pin. Along with the voltage regulator are the capacitors with 10V rating or can be larger. There are also resistors and the 5K potentiometer can be replaced with 1K for this project with thumbwheel feature. The 9V battery pack has a switch and a red LED may be optional.

During the assembly, all the necessary parts should be available. First to be soldered are the resistor, potentiometer, the LM317T, and the 9V battery pack. The two pins of the 5K potentiometer must be shorted where the left pin and the middle pin are tied together in this case. The voltage between the left and middle pin of the LM317 should be measured and should be almost exactly 1.25V and turning ON the potentiometer could reach 7V.