Power Supply Selection

I am about to embark on a fairly expensive project and I want to know I have my theory down pact, before I spend the money.

I want to be able to control a sure electronics dot matrix board (64*16 LEDs): http://www.sureelectronics.net/goods.php?id=418

The data sheet states the following power consumption for the 64*32 flavour:

Maximum Current 5.26 A. Every LED in row lit up of both halves(64 LEDs2)
Average Current 1.64A. 16 LEDs in row lit up of both halves (16
2 LEDs)

the 6416 is basically half of the 64*32. Can I cut the current usage by half? Therefore my max current would be 2.63 and avg would be 0.82

Also I was looking into a power supply to power the whole project. I will be powering the above board, a duminalove upgraded to 328 and an ethernet shield.
Would this power supply do (12V 3.25A)?
http://www.sureelectronics.net/goods.php?id=371

I do know I would need a regulator that is capable of supplying the amps needed for the matrix

Also, if in the future I want to expand my matrix and daisy chain another row, is it possible to use that power supply? The power supply is rated for 12V 3.25A, while two of these LED matrices would be around 5V 5.26A. The 12V 3.25A supplies enough watts, is there a solution to up by 3.25A to 5.26A? I've only every worked with voltage regulators and as far as I know they can't supply more than the input current.

First the good news:-

Can I cut the current usage by half?

Yes that is OK.

Would this power supply do (12V 3.25A)?

Yes but 12V is more than twice the voltage you need therefore you will be burning up a lot of power to get it down to 5V. Actually it will burn 12-5 = 7V at 3.25A will give 22.75 watts to get rid of. Remember 25Watts is about the power of a medium size soldering iron.

So you probably don't need a liner regulator chip but a switching regulator module. These are normally about 90% efficient and would allow you to increase your current output above that of the supply. However they are expensive.

EDIT
Do you know that this is just the display, you are going to have to multiplex it with the arduino. It will take 1024 bits of memory to store the one frame image, that is one eighth of the total memory on an ordinary arduino.

Wow I didn't even think of that! Unfortunately i can't seem to find a switching voltage regulator that is cheap enough, yet powerful enough to supply the amps I need.

What about a PC Power Supply? I have one lying around that is close to these specs:
http://www.compusa.com/applications/SearchTools/item-details.asp?EdpNo=935375&CatId=1076

The one I linked to can supply 14A at +5V. Is this power regulated?

Or do I now have to go buy a switching power supply? Are there any specs I should be aware of when buying a switching power supply?
http://www.meanwell.com/search/s-145/default.htm

The one I linked can supply 25A at +5V and is regulated. It costs about $20.

Yeah I know memory is going to be an issue with the Arduino. I am hoping upgrading it to the 328 will fix my issues. I originally wanted to go with the illuminato, but the Ethernet library doesn't work with it.

Someone already has interfaced the Arduino with this board. When I compiled the program to test mem usage it used about 5K of the flash. This also includes storing all the alphabet as structures and the corresponding bits in PROGMEM. The Ethernet Library is another 7K. I don't plan on storing any strings in the Arduino. I am hoping to use the Ethernet Library to poll a webpage, extract a long string and store it in PROGMEM. Then I plan on using the Arduino and my character library to scroll the string on the display.

I really don't know if this will work. I am worried about running out of RAM.

The Ethernet Library is another 7K.

Look at the Ethernet2 library which should be functionally identical but takes ~2.5KB less space.

extract a long string and store it in PROGMEM.

You won't be able to store it in PROGMEM, only EEPROM.

--Phil.

oh I forgot you can't right to flash when the program is running... 2k SRAM should be enough though, after assigning all my other variables (Ethernet Library, loop counters, etc.), I should have atleast 1k for string management.

Does the Ethernet library act like the Serial library? Wehn you did a Serial.read it imported a character and waited for the next one, does the ethernet library work the same way? If thats the case, I can create a 16 character array queue and push and pop new and oldcharacters. That should save me some memeory right?

What about a PC Power Supply?

Yes that would work. On some you have to short out a pin to ground before it will deliver any power (it's a safety feature) but these are switch mode and regulated.

This thread has info (links) about using a PC power supply:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236047773/0

You have to do a couple things to the power supply to make it work. But it is a very good and cheap way to get a lot of amps at 5 and 12 volts.