LED constant current source circuit diagram using LM317

This article introduces a circuit diagram of an LED constant current source using LM317. LEDs need constant current power supply, otherwise they are prone to aging and damage. You can use LM317. The principle is to use the 317's starting voltage to detect the constant voltage, and then remove the resistance to get the constant current value. You can connect as many lights as needed. Changing R1 can change the current, current = 1.25/R1. The circuit is shown in the figure below.