Powering 16 super bright blue LEDs with Arduino

arduinoled

What is the best way to power 16 super bright LEDs using an Arduino Uno to achieve max brightness?

Each LED has the following characteristsics:

IF Typical (mA) = 20
VF Typical (V) = 3.2
IV Typical (mcd) = 3700
IF Max Continuous (mA) = 30
Preferred Series Resistor (ohms)
5VDC = 91
9VDC = 300
12VDC = 430

(http://www.jaycar.com.au/productView.asp?ID=ZD0132)

Output from Arduino pins = 5V.
Power suppply is 12V, while the final will be an Automotive ~12V rail.

I've used two LED calculators:

  1. http://led.linear1.org/led.wiz
    this site says I should use 16 LEDs in parallel with 100Ohm resistor on each one.

  2. http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator
    this site says I should use 16 LEDs in parallel with just one 5.625Ohm resistor.

The Arduino Uno has 14 digital pins outputting 5V.
I would like to use the least amount of 5V digital outputs, and the least amount of resistors necessary, while maintaining maximum brightness.

Hope you can help 🙂

Best Answer

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
30mAâ‹…8 = 240 mA
(5V−1.8V)/(30mA⋅8/10) = 133.33333 Ω

schematic

simulate this circuit – Schematic created using CircuitLab