Another arduino led cube question.

Im sure most of you are tired of seeing these. But Im going to do a 3x3x3 and 4x4x4 before taclking the massive task of the 8x8x8.

I want to make sure Im doing it right, And I drew up some very basic schematics as for what I need to do. Im hoping these are at least somewhere in the ballpark.

3x3x3

4x4x4

So yeah, thats what I have so far, as for led's heres the specs: Life Rating : 100,000 Hours Emitted Colour : Blue Size (mm) : 5mm Lens Colour : Water clear Peak Wave Length (nm) : 460 ~ 470 Forward Voltage (V) : 3.0 ~ 3.4 Reverse Current (uA) : <= 30 Luminous Intensity Typ Iv (mcd) : 6000(Typical) ~ 8000(Max) Viewing Angle : 20~25 Degree Max Power Dissipation(PM): 80mW Max Peak Forward Current(IFP): 75mA Lead Soldering Temperature : 240 Degree (<5Sec) Operating Temperature Range : -25 ~ +85 Degree Preservative Temperature Range : -30 ~ +100 Degree

Not sure what resistors I need though.

Conceptually it looks OK to me. A real schematic drawing would be more useful of course. It looks like you forgot that the three transistors will each require a series resistor from the arduino output pin to the base terminal of each transistor. As far as resistor size you can start off with, 100 ohms would limit the current through any led at any time to 20ma, however the fact that you will be scanning at given duty cycle you may be able to lower that value to gain brightness, say 50 ohms. The transistor base resistors can be 200 ohms or so to ensure the transistors are saturated fully on.

One recommendation I would make for led cubes (having built a 5x5x5) is to not use " Lens Colour : Water clear" types but rather diffused lens types, this will give a more even light at more angles of view Vs the clear types. You can simulate diffused lens by sanding your clear ones.

Good luck

Lefty