Powering 16 super bright blue LEDs with Arduino
8 parallel strands of 2 LEDs each and a 150ohm resistor. All loose anodes should be connected to V+. The loose cathodes should be connected to the collector of a TIP31 NPN transistor. The emitter should be connected to ground. The base should be connected to a 100ohm resistor, and the other side of the resistor should be connected to a digital output. 16 LEDs, 9 resistors, 1 transistor, 1 digital output.

(12V−(3.2V⋅2+1.2V))/30mA = 146.66667 Ω
30mA⋅8 = 240 mA
(5V−1.8V)/(30mA⋅8/10) = 133.33333 Ω







simulate this circuit &ndash; Schematic created using CircuitLab