LM317 as Constant Current Source
Category: Linear Power Supplies
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This schematic and simulation is also made in Proteus 7.10. So if you want to do more experiment you should have Proteus 7.10 installed in your computer or laptop. In this circuit you will learn how to use LM317 (a variable voltage regulator) as a constant current source. 1. LM317 is a 3 pin device. 1st pin ADJ, 2nd pin Vout and 3rd pin Vin. 2. LM317 can be used as constant current source by connecting a current limit resistor between pin 1 and pin2. 3. Load should be connected at pin 1 with respect to ground. 4. Resistor can be calculated using this equation R1 = 1.25/Iout 5. You see in picture that current remains same irrespective of number of LEDs. Download these files to perform more experiments. See the datasheet of LM317 for more understanding.