go to ebay and take a look at LED power supplies. There should be about a thousand or so. Here's the link for the first one I found:http://www.ebay.com/itm/Led-Driver-6-12x2W-Inside-Driver-Power-Supply-for-E27-GU10-Led-Light-Lamp-2pcs-/110982585621?pt=Lamps_US&hash=item19d713dd15And, that was just a basic search. Alibaba, sourcingmap, etc have many, many of these at prices that made my jaw drop. I have two that I bought (quantity 1) for 3.95 free shipping. If I bought ten of them and redeemed the coupon I got I would have gotten them for about .80 cents each (still free shipping).
The ones I have supply a constant 350ma until the load resistance drops enough to cause it to shut down. On the high side, they max out at a little over 11V and don't go any higher. Carefully hooking it to the VIN on an arduino (UNO), they seem to work fine. The problems may come when the combination of arduino and other devices need more than the 350ma and the thing shuts down.
I haven't seen wall warts or small power supplies that were made anywhere else.
Has anyone else noticed that there are a ton of constant current power supplies out there for extremely low prices that are very small and quite powerful? I've got a couple I'm experimenting with that supply 6-11 volts at 350ma. I take it that that means they go as low as 6V and as high as 11V trying to supply 350ma to a fancy led or string of leds.Well, why can't we hook one of those up to an arduino and have it run just fine. There's already a regulator on the arduino that will take the incoming voltage and hold it at 5V for the board, so it shouldn't matter that the CCPS (constant current power supply, I just made that up) is varying its voltage as the current load changes.Right??? Thoughts.
The little transformers provide ("are supposed to provide") as much isolation as the traditional large "step down transformer." They can be smaller because they operate at a much higher frequency. You can think of a switch-mode power supply as modulating the high-voltage side of the supply so that the frequency and waveform are varied in a way that causes them to provide exactly the right amount of power needed by the load.