AC to USB Power Adapter

[McBainUK]

Looking to get a AC -> USB Power Adapter like this one or this one, that I can just plug in to the wall without the need for a PC. First thing I would use it for is this Samsung MP3 player but in the future there maybe other devices also.

If anyone knows anything about them...

• Are they safe?
  
• Do they "stop" when the device is fully charged?
  
• Are they all the same or do I have to match the output rating and so on t the device?
  

Thanks

[martint123]

• Are they safe?
  
• Do they "stop" when the device is fully charged?
  
• Are they all the same or do I have to match the output rating and so on t the device?

(1) The ones I have seem to be.
(2) No, they emulate USB and supply the normal 5V as a USB socket does.
(3) Not really, a laptop doesn't give much power via USB

Both have info on power from USB.
http://pinouts.ru/Slots/USB_pinout.shtml
http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power

I may be getting a number of them in a few days as part of a lot of duff slide/negative scanners, there may be one or two free if I fail to get them all working.

[whurlston]

I've used USB power adapters on multiple devices and I usually mix and match and it's never been a problem. I've used the one for my iPhone to charge my GPS, Logitech and Acoustic Research remotes and a PDA for example. Never had any issues. They don't "stop" when the device is charged but all the devices were "smart" and stopped charging themselves so it was never an issue for me.