Carl wants to go cruisin’
For Carl to use the PiCamera to line up with the dock at night, when the lights in the room are out, I need to wire up a couple LEDs. I purchased some 5mm white LEDs that have a 560 ohm current limit resistor in series, so each LED will draw around 9mA when driven by 5v.
I’m guessing (GoPiGo3 schematic) that the 820 ohm resistor on the AD1/AD2 port input/output line is to limit the max current to 6mA (5v / 820ohm).
Supposedly a single RPI GPIO pin could source 3mA, up to a max of 16mA, with a 51mA “all pins” limit, but I don’t really want to connect wires direct to the Raspberry Pi.
I could probably figure out the resistor(s) for an NPN switching transistor, but I’m not eager to go that route if the DI Grove LED board can do the job.
I found the schematic for it, but I don’t know how to analyze the current flow if I connected two of my “560ohm-LED” (in parallel) to the LED socket of the board.
Is it 5 / (220+560) or 6mA through each LED? Or the 220.10k are forming a voltage divider so I really don’t know how to calculate this.
Maybe I need to cannibalize back to raw LEDs, then it should be 5/220 or 23mA through each led, but there is that 10k across the LEDs so who knows how this works out?
Any EE types able to help me out?
I should just buy it and see how it works, but I like to understand things first.