Mr PostOfficeBuddy. Thank you for your input. After sleeping over it would like to make a summary of what I have learned about driving leds with Arduino:
I think your idea of using the 400+mA 4 ch http:// http://fi.mouser.com/Search/Refine.aspx?Keyword=STP04CM05
is the the best compromise in all respects if you want to make led room lighting with many channels. Want more light? put the leds in series (no common anode/cathode RGB leds then). Needs soft PWM/BAM, interrupts etc.
For something really huge (10-50A!) the 595 shift register mosfet solution might be the way to go. The mosfet FQP50N06L is $1 per channel so the price is really there. Not too bad, but that results in quite a big board if you go through hole. With surface mount components/board it would work ok. Needs soft PWM/BAM, interrupts etc. The current is defined by a 0.5-X Ohm resistor and you need one per channel so you cannot easily alter the current.
Dont like software PWM/BAM? Use TLC5940/TLC5947/MAX stuff, really easy to use with Arduino. Use the FET circuit we talked about for driving or if you do not have that many channels constant current sources might work for you and still keep your budget.
You like led cubes and matrices (low power stuff)? The Lightuino 3.0 Arduino Led driver with 70 sinks and 16 sources will drive your 1000+ leds and if you need more you can stack them. http://makersmarket.com/products/lightuino-led-driver-30-superstackable
. Out of stock but they just sent me one for $60 or so. Just connect the leds and you are ready to go.
How to power everything? For low power and/or high voltage (=some leds in series) normal 9-24V power sources are cheap enough and give you enough current.
For low voltage (=5V) and high power you can use FlexATX computer power supplies like HEC-120SA-7FX that are small and cheap and will give you a lot of regulated current with 5V and 12V.
Please correct me if I am wrong or you get new ideas!
ps PostOfficeBuddy - it would be nice to learn more about your (and other's) projects as I can see you have spent a lot of time working with these things.
ps2 One more thought about power losses. People seem to pay a lot of attention to power losses when driving these led things. I think this is illogical as long as we are not doing office lighting or 1000 street lights. I have maybe 500W of light bulbs lighting the house so 10+W of heat from my led mood lights is not really a problem or is it
And I do not even want to think about the new graphic cards for gamers.