resistor values

I’m confused about the resistor values used on the user LEDs on the BBB. The first question is, the power LED (D1) is on a 3v3 circuit. The datasheet for that LED says the fwd voltage is around 3V @ 20mA. No matter how I spin it, i can’t figure out how in the world they came up with an 820 ohm resistor?? (3.3 - 3.0) = (0.020)®… ?

The second question is, the USER LEDs (D2. D3. D4. D5) are on a 5V circuit. Yet guess what, they still somehow figured on an 820 ohm resistor?? So confused…

These are low current very bright LEDs. I had to increase the value in order to dim them because people were complaining they were too bright. The power LED, that is also the same value, 4.75K, not 820 ohms… Check the latest schematic. The transistor has some voltage drop in it, so even at 5V, the LED brightness is about the same.


ok, thank you! I’m definitely a hardware newbie, so I am easily confused :slight_smile:

Not an issue.