First off I would like to say HI. I am new to the arduino community, And have started laying out the plans for my first project.
Project is a 16x8 RGB table.
My plans so far is to use an arduino uno, 7 x 74hc595 shift registers, 128 x RGB (cc) led's.
for the description I will label the 74hc595's as SR1, SR2, and so on.
OK now for the layout
SR1 would control red anode for column 1-8
SR2 would control red anode for column 9-18
SR3 would control green anode for column 1-8
SR4 would control green anode for column 9-18
SR5 would control blue anode for column 1-8
SR6 would control blue anode for column 9-18
SR7 would control cathodes 1-8
the SR's would be daisy chained with the data, clock, and latch going from pins 11,12,8 from arduino respectively starting in SR1.
I will be using an external power supply from a cannibalized desktop computer, and would be putting +5V to the arduino, (not sure if that would be enough power to run the LED's since I will be multiplexing with PWM).
I know I will need resistors coming from each of the data out pins going to each of the anode columns.
First question is, Would it be safe to go with 1k resisters on all the anode pins, Or would I need to put smaller ones on the green and blue.
the specs on the LED's are"
Color: Red/Green/Blue
Package: Round 5 mm (T-1 3/4)
Peak Wavelength [R/G/B]: 630 nm / 525 nm / 430 nm
Lens type: Diffused, milky-white translucent
Viewing angle: 30 degrees
DC forward current: 30 mA
Intensity (typical) at 20 mA [R/G/B]: 500 mCd / 600 mCd / 300 mCd
Forward voltage (typical) [R/G/B]: 2.1 V / 3.8 V / 3.8 V
0.055" (1.4 mm) lead spacing
Common Cathode configuration
Second question is, would I need to use transistors? And if so, what ones PNP or NPN? and would they be placed before or after the resistors? and would I also need resistors and transistors on the cathodes as well?
For the record I have no formal training in electronics, and I am learning as I go, That is the reason for the questions. I have been reading and trying to take in all that I can from reading and tutorials on the web. And like I said earlier this is my first project, and I am really impressed with the knowledge that I have seen on these boards so far.
I have a crude hand drawn schematic of what I have so far, It does not show any of the LED's because I was stuck at the transistor/resister part.
Here is a link to the schematic. It is hand drawn because for some odd reason whenever I try to get fritz to work, My schematics come out all garbled and everything is just a blob on the screen.
If i'm forgetting anything, or more info is needed, please let me know.
Any help, suggestions, comments would be appreciated.