I made a new cube using some SMT RGB LEDs, Im using these 5050 SMT LEDs I found on ebay.
This is the specs i have on the LEDs, I've written the ebayer, but they wont be back for a couple weeks.
RGB PLCC -6 5050 3-CHIPS SMT SMD LED Light
VF Forward Voltage
Min2.9 Max 3.6
Luminous Intensity
Min 4000 Max 5000 mcd
Power Dissipation 200 mW
DC Forward Current 60 mA
Reverse Voltage 5V
I've built the cube using common cathode, assuming thats how most of other rgb cubes are setup.
The LEDs have 6 leads, so I could build it either way, or even use them in series.
I had planned on making a matrix, but it turned out to be too difficult to solder up, and i found that I can just buy a nice SMT RGB LED matrix for under $10 so I abandoned that idea, but I made up a 32 bit shift register out of 4 74hc595s.
I figured i'd use it with this cube, but then I realized that I will need to control one plane (48 LEDs) with it, and 32 bits wont work unless I cut the planes in half, which would be difficult. Had I made 2 1/2 cubes, and set them next to each other, it would work... but I have 1 cube.
So, I built a big 56 bit shift register tower (7 chips tall) I figure I will use 48 bits for the LED anodes, and 4 bits for the planes (cathodes), and have 4 dummy bits (but they could be used for additional features).
If I use shift registers, i will need resisters, and im not exactly sure what the forward voltage is on these leds since the only info I have lists one voltage. I tested the leds with 3 volts, and the red ones were really bright, too bright, but the didnt blow from quick testing 3v. Based on looking over specs on several 5050 leds, my guess is the forward voltage is 2.2v Red, 3.2v Blue, 3.2v Green
From 5 volts, 100ohm should get me close on the blue/green ones, and 150 on the red.
Since I dont really know what these LEDs should use, I figure i can experiment with resisters on a spare LED to try to dial in the right resisters for each color, but maybe there is a better way?
I have also been revisiting the idea of running the shift registers at 3.3v instead of 5, reduce the 5vs to 3.3, and resister the data pin so that it gets 3.3v from the arduino. I was thinking maybe having a voltage regulator (like an lm317) drop the voltage from 5 volts to 3.3. Then I would have to resister the red LEDs, and run the other leds on 3.3v
Is that a reasonable solution?
Im also considering just using LED drivers instead, just to be easy... There seem to be many good LED drivers, which would be a good one, and why?
I've read some posts here that mention TLC594?, max232,ws280?
I have an uno for developing it, but I plan on running it off of a nano, and hopefully a small inexpensive power supply (like used for charging cell phones)
I also have a real nice power supply from a DVD player, it puts out 5, 12, and 24v, but i was hoping to save it for something that needs a lot more current (like a burning laser!)
So... im interested in ideas about how to control the cube best, I have shift registers, and can maybe scrounge up resistors (or just order some online...), but I will probably have to order resisters online, and maybe i should just order some inexpensive driver chips instead?
Oh, i just realized that I have some ULN2003 chips (they are in circuits, but I can unsolder them.)