Why didn't you just use a cheap PC power supply and tap off the 5v rail?
Would've been a lot cheaper...not to mention easier.
You got 12v, need 5v @ 4amps. Assuming a linear regulator (eg. 7805), you've got 20watts (5v @ 4amps) going out, 48 watts coming in (12v @ 4amps). You have to dissipate over 28 watts of power. A ridiculous amount of heat in anybody's book.
I'll need to buy the PC power supply as well (also on the list
). But yea, the heat dissipation is the worry, 7805 might be okay for something low power in a pinch, but not really heavy duty.
You can however go with a switching regulator dc-dc converter, which has a much higher efficiency, usually above 85% .. the cheap 5A (or higher) dc-dc converters on eBay will work just fine to drive leds.
Here's one example, or another or another.
Nice, thanks for those links. I think I'll get one of those cheap step downs, that might do the job! I think I'll get the LTC3780 as well. After looking online a bit, it seems that it's a bit pricey is because it can do both step up and step down which will be useful for me to build a bench power supply.
You indicated that your RGB LED Matrix "requires 5V at at least 4A current". But I thought these types of LED arrays require constant current regulation, which is a more stringent requirement than making some minimum amount of current available. (You may well already know this, but I wasn't sure since it wasn't explicitly stated.)
I figure if I get a power supply with at least 5A, it should be sufficient for my needs? Most of the documentation seems to suggest that 2A is also good enough, but better have at least 4A if you intend to use all the LEDs. The RGB matrix I have is similar to
Adafruit's RGB LED matrix. Do you think this might not work?
How about you just change the feedback resistors on the 220-12v supply so it instead outputs 5v?
I could try that, but I have no idea where to begin
. I checked online there isn't too much info on how to do this for my power supply, do you have any suggestions? In any case, the 5V 10A power supply is only 9 bucks with shipping, so I figure I might as well buy it.