Maybe an even better process for making hemispheres would be vacuum forming or pressure forming. Spent a hour watching the precess on the net.
May be premature but saw an add on Electronic Goldmine for 100 5 mm LEDs for$ 5.50. Brilliant white, 12,000 mcd , 3.4V, 30 mA, SN; G20224; offer good till noon 7-29-15

 

Maybe an even better process for making hemispheres would be vacuum forming or pressure forming. Spent a hour watching the precess on the net.
May be premature but saw an add on Electronic Goldmine for 100 5 mm LEDs for$ 5.50. Brilliant white, 12,000 mcd , 3.4V, 30 mA, SN; G20224; offer good till noon 7-29-15

With a high millicandella rating like that you usually have very narrow viewing angles and no diffusion.

 

This guy uses the TLC5940 in his video and it's a very thorough video and explanation of the chip and how he uses it. Some of his explanations do get a bit technical so if you haven't done programming in a really long time then your brain might get a bit fried like mine did. Now he uses RGB LED's which require two pins per LED. I'm just using white so I only need one pin and it has 16 outputs. You can also daisy chain them very easily for 32 outputs. Thus 30 LED's per globe easy. It has a current limiting pin that sets the whole chip resistance via what ever resistor you put on it. Thus none of the LED's need resistors on them. The programming is rather complex though. Hopefully I could find a free downloadable premade program I can customize to do what I want.

 

The 5MM just seem bigger then I want. The 1.8MM diffused and the 3MM diffused I think would be a better fit.

 

So I've decided to use the Arduino. I'm just trying to decide whether or not to use the UNO or the Mega. The UNO is obviously cheaper per board and if I do say 15 globes that could really help keep my costs down.

If I use the UNO I can wire up a 6 x 6 matrix and get 36 LED's per sphere. Then I could put in three random number generators, one for the columns and one for the rows. The first two numbers would determine which LED gets turned on. Then I would use the third to determine how long the LED stays on and maybe a 4th to create a random amount of pause before moving on to the next LED. I could also create a conditional that if the LED chosen is connected to a PWM pin then do a random fade in and out instead of blink.

If I use the Mega I could hook up to 53 LED's to each pin individually instead of a matrix. Not sure what the advantages and disadvantages of each design would be. Anyone have thoughts on this.