really small arduino power supply

http://www.ebay.com.au/itm/New-20-50W-AC-220V-12V-LED-Power-Supply-Driver-Electronic-Transformer-bae-/221059782295?pt=AU_B_I_Electrical_Test_Equipment&hash=item3378309697

Input Voltage: AC 220V 50/60HZ
Output Voltage: AC 12V
Output power: 20-50W Max
Ta: 50°C Tc: 70°C
Dimension: approx. 52 x 27 x 22 mm(L x W x H)
Input and Output Cable length: approx. 10 cm

Package Included:
1 x Electronic Transformer

12v is a lot more managable, I think the regulator of a standard arduino accepts up to 17v's so a 12v supply would be perfect as it would then supply you both
your 3v 5v rails and 5v logic pins.. but, you also have a high power source 12v with a high current you can use the lower 3-5v to switch on and off with power mosfets
and Power Transistors.

[edit] just noticed it's an AC out, even better, use 2 diodes to rectifiy the signal to dc, and you'll have something more like 9-10volts DC out, almost perfect voltage for a typical
arduino board (2 diodes, 20cents each..)

Any voltage you need, just buy a regulator for that voltage?...

Or am i missing it?

$.99 including shipping.

http://www.ebay.com/itm/USB-Adapter-Adaptor-Wall-Charger-For-iPhone-3G-4-4G-iPod-Touch-nano-Colors-NEW-/271042037188?pt=LH_DefaultDomain_0&var=&hash=item3f1b5d45c4

Zoomkat, fair enough and how many Watt rating is that?

5v * 1amp = 5watt power supply
vs
20-50W Max (so i'll reflect the min/max)
10-11v (after rectifier DC output and cap)

20W/11.5v = 1.73amps
50W/11.5 = 4.34 amps

20W/(11.5v > Regulator > 7V) (Recommended regulator voltage , which drops it down to 3/5v for the board) = 2.8amps
50W/(11.5v > Regulator > 5V) (not so good, as it stresses the regulator out) = 10 amps

?? 10 amps? am i doing this right..

20w/7v = 2.8?
50w/5v = 10amps.

sounds kinda right, but that's a lot of power for AU $2.19 (Free postage)

I thought the need was for 100mA? 0.5W total?

Why settle for a ford mondeo when for an extra few bucks you could buy a ford GT ..

is it not better to "have" than have not?

Careful, there are a lot of dodgy USB "chargers" out there these days. Typically they'll have poor regulation that might be ok for most phone's charging circuits, but not so good for powering ics directly.

how hard would it be to mke something like tht from scratch

The answer would depend on how complicated "that" is.

In the simplest form, it can be a rc network. In a more reasonablly engineered form, it could contain an isolated switching mode power supply, with good common mode filtering and power factor correction, and low idle power -> you may find a mcu far more powerful than you arduino reside in one of them.

The cheapos you get off ebay probably are a lot closer to the dangerously simple types.

That's comparable to the Recom part I linked to from Mouser.

5V, 200mA unit is a few dollars cheaper.

Here is the teardown comparison

Here is the teardown comparison

Is he sure that he was tearing a real Apple charger? The "genuine" one he took apart looked to me of lower quality than the "fake" ones he linked on the sme page.

cjdelphi:
Why settle for a ford mondeo when for an extra few bucks you could buy a ford GT ..

is it not better to "have" than have not?

The origional request seems to read "Probably atleast 100ma". For only $1 shipped it would be worth a try. Bigger and more expensive may not be better. Why buy a ford GT when all the kids won't fit in when going to the store?

Recommended "cheaper than apple" tiny USB supplies seem to include the kindle charger ($10 http://www.amazon.com/Kindle-Power-Adapter-included-Paperwhite/dp/B005DOK8NW )
and the samsung charger ($6 http://www.amazon.com/gp/product/B005OSURT2/ )
Beware counterfeits!

It would be worthwhile to measure the output voltage of a suspect supply before connecting it to your expensive Arduino project...

For small quantities, check out a thrift store. "Orphaned" power supplies (ie from cellphones) frequently seem to end up there, sold for very cheap. Most of these are approx 5V, these days.

westfw:
Here is the teardown comparison

IPhone Charger Teardown Shows Astounding Miniaturization. | Hackaday

That's a nice article -- the one at Ken Shirriff's blog. I'm far from an Apple fanboi, but they do, in most cases, build very good hardware. I'm now curious what the guts of my LG charger look like. It sure isn't a $30 item.

The requirement was definetly a minimum, more the merrier, this is for a design for somethi that is going to be behind regular house outlets and switches(probably in the same box, so im trying to keep it cool and small as possible, basically going to be powering an attiny84/85, relays, leds, perhaps some other comm peripherals
so while quality isn't the most important, reliability definetly is, something that could be expected to last perhaps atleast 3 years by itself in a closed enviroment, without gtting hot or posing a fire hazard lol

The little recom units or the same at digikey would seem to be good for that.

Hmm fter looking at it I kinda like that digikey item, have you used one before?

No. I am using a Recom 24DC to 5VDC unit on a card. 24V drives motors, 5V drives the uC & logic.
I think boffin1 down in South Africa is using a mains to 5VDC module like I recommended.