USB Power?

I have seen it done with four passive components. Complete USB specifications are available if you search google.

I use a dumb transformer driven USB port to charge my iPhone. My sons iPod also works with this. There is no software handshake. Also, I use a USB battery pack for charging on aircraft. Again, no software handshake. Go ahead and remove a little misery ;-)

Thanks all. I'll keep looking into it.

I've seen several simple "dumb" circuits online that supposedly can do the trick. Apparently it may or may not be critical to not leave the two data lines floating. Seems the consensus is they must reference to + & - via resistors.

I wonder if perhaps those folks making their own USB charging thingamahickies and getting bad results aren't doing this. Or perhaps they're not adequately regulating the 5V output. For all I know iPods or other devices get all cranky when supplied with a value close to but not exactly 5V.

Guess I'll have to tell my boss that I need to go out and buy a slew of gizmos to test with!

I just finished building a "dumb" USB charger, by using a 5V wall supply and a stacked USB connector from an old computer motherboard. Unfortunately, my Motorola phone is not happy with this arrangement. Some web searching later, I learned that the phone will only charge on a computer if the proper driver is installed, and will only charge from a stand-alone charger that has the data pins shorted, and another line tied to ground through a 200K resistor. They use the same mini-USB connector that many other products use, they just HAD to do it differently. It couldn't be because they wanted to make more money selling chargers, could it?

I would go with the passive approach. If someone does try to charge a device that has "other" requirements, you're probably better off not trying to address those, cause when the customers "toy" goes "poof", and the toy maker says "you didn't use a genuine Acme charger, no warranty!", you'll have an unhappy customer on your hands. Good luck.

Tom

Hi,

You are correct the usb port can provide 5v+/-.25v @ 500mA no software should be needed I have a small fan that run off usb. It has no software interaction.

I have been away so it is probably too late for this to get read, but you can buy all of the USB chargers that your little heart desires. http://www.tigerdirect.com/applications/SearchTools/search.asp?keywords=usb+charger

Sorry, I did not read the date on the CR4 so I did not realize that I was reading the most recent one in my mailbox, not the oldest.

How interesting Dragonfly! I can spend $4.99 to turn my $3000 laptop into a AAA battery charger! How the worm has turned!

This post piqued my interest. My Smartphone sits in a USB cradle. The little beastie refuses to charge unless the software is running. Never knew that.

Checked out a handful of other items but all are OK without Da Master Pea Sea.

For the Xmas period I have discovered a plethora of weird and wonderful wacky widgets to fill the portals of my USB, and no doubt the pockets of some devious smart oriental. All I need is another 348 USB ports, and a Toyota Prius as a portable battery charger, and I can run my life with LED ease.

I'm starting another forum - wackiest use for a USB port.