ARDUINO MOODLAMP

Hi, I have decided to buil my own Mood Lamp using Arduino. I have used high intensity LEDs (5 green, 5 blue and 5 red). Since Arduino outputs can source only 5 mA I have used NPN BD137 transistors in order to amplify current. In addition I have designed the circuit so that only 20 mA can go through any of the diodes (considering forward voltage for any kind of LED).

In order to power the circuit I am using a 5V 1A power suply connected directly to the Arduino. Everything works fine but I wanted to ask if you think there is anything that could be improved and specially in you think that the circuit will burn because any failure in its design. As you can see in the schematic I am attaching 5 leds of each color are controlled at the same time. I have chosen analogic outputs of Arduino so that I can control the intensity of the diodes. Thanks for your help!!

Might have to lower the 1K base resistors if you are not getting the brightness you expect. If you assume the BD137 will have 0.7V from base to emitter when on, then you have 4.3V across the resistor. 4.3/.02 = 215 ohm, so you could safely go down to 220.

Arduino can safely do 20mA, 5 is pretty safe to design to.

LED on full will be 300mA, so 1A source seems like plenty of margin.