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.
Gerald On Mon, Jan 13, 2014 at 10:43 AM, <[email protected]> wrote: > 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)(R).. ? > > 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.. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
