Sunday, September 27, 2015

Supplemental Info for Constant Current LED Lighting Circuit

This post contains supplemental information for my YouTube video titled "LED Lighting in Passenger Car" at

Note that I am using one 47-ohm resistor (R1) across the Vout and Adj pins on my LM317T voltage regulator so it acts as a "current" regulator.  This is for my LED strip which has 150 ohm resistors built in to each group of LEDs and a total of 21 LEDs.  Your mileage may vary (ie you may need to adjust the resistor R1 for your circuit to get the desired brightness).

These are the pinouts for the LM317T Voltage Regulator I used in a TO-220 package.  Take careful note of the pinouts for your voltage regulator as it may be different.  Also assure the ADJ pin of the voltage regulator goes to DC + of your LED strip, not the Vout.

List of components used with DigiKey part numbers in brackets.  
Note the LED strip was from Amazon, not DigiKey.

22uH CHOKE [495-5557-1-ND]
470uF 50v CAPACITOR [P11260-ND]
1.5A LM317T Voltage Regulator [497-1575-5-ND]
5k TRIM POT [3362P-1-502LF]  (optional)
47 ohm ¼-watt resistor [adj per # of LED's]
LEDwholesalers 5 Meter Flexible LED Strip 12 Volt/Warm White/3100K/2026WW-31K [Amazon]