Recently, I found a good article about the LM317 so I decided to share it also here, as I am using this IC for current regulation with my LEDs and laser diodes.
A current source is the dual of a voltage source – it delivers a constant current, regardless of the voltage. While a resistor can be used as a rough current source, the current drawn will vary with the voltage. (Ohm’s law stipulates that I = V/R. The resistance is constant so if the voltage increases, current flow also increases. Same applies for decreases).This project is based on the common LM317T regulator, used as a constant current regulator. The circuit is ideal for driving LED arrays, laser diodes or any other circuit requiring a constant current supply. Alternatively, this could also be used as an electronic dummy load for testing small power supplies at relatively low current levels. Suggested applications and all calculations are explained in the article below.
The full article can be read here: CONSTANT CURRENT SOURCE/LOAD (LM317)