Is a USB Charger Universal?

[Talal Itani]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

 

[D from BC]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

Seems to me that a 5V smps wallwart and a USB cable will do..
http://www.cui.com/pdffiles/EPS050100-P6P.pdf
~$6.00 from Digikey.
Useful only off 120VAC like in the US or Canada.

See Ebay 5V adapters for travel or directly look for products for
charging USB ported mp3 players.

Try to avoid buying a bulky surplus computer power supply for $10.00.



D from BC

 

[John Popelish]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Since all computer USB ports supply 5 volts, I think any 5
volt supply with a USB socket will work.

The top two on this catalog page are examples:
http://www.mouser.com/catalog/631/1793.pdf

 

[Nonya]

Since all computer USB ports supply 5 volts, I think any 5 volt supply
with a USB socket will work.

The top two on this catalog page are examples:
http://www.mouser.com/catalog/631/1793.pdf

Better make sure it is low amps. Or you will fry it. USB outout is very low
amps.

 

[Martin Griffith]

likeOn Sat, 27 Oct 2007 04:58:09 GMT, in sci.electronics.design "Talal

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

like this?
http://store.theonion.com/app/webroot/media/gotcha-pics/BoxUSBTOASTER.jpg


Martin

 

[Tom Bruhns]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

You probably won't have any trouble with your mp3 player. I have an
iAudio unit that charges just fine from any USB port and matching
cable I've tried it with.

HOWEVER...the same is NOT true of my Verizon/Motorola cell phone! @#$
%& thing will charge only from a USB cable/supply designed for the
phone, or if I have the Motorola mobile phone software installed on
the computer; otherwise I get an error message on the phone. Nutz.

Cheers,
Tom

 

[Ecnerwal]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

depending what ese you are doing, you might want to buy a USB battery
supply ($10 or so) and an AA battery recharger....

 

[Paul Hovnanian P.E.]

Hello,

Rechargeable MP3 players recharge from the PC's USB port. I want to buy a
wall charger, for travel, for MP3 players. Do I have to buy a charger
specific for my MP3 player?

Thanks,
T.I.

As others have stated, a 5V supply (500 mA minimum) with a USB cable
will probably suffice.

However, the USB standard describes a handshaking protocol that a well
behaved USB client must engage in to draw more than 100 mA. If your
player is well behaved, it may not kick into charging mode until it gets
the go-ahead from a smart host. Wall warts, not being very smart, will
never send this signal, so the client may remain in low power mode.

 

[Tom Bruhns]

As others have stated, a 5V supply (500 mA minimum) with a USB cable
will probably suffice.

However, the USB standard describes a handshaking protocol that a well
behaved USB client must engage in to draw more than 100 mA. If your
player is well behaved, it may not kick into charging mode until it gets
the go-ahead from a smart host. Wall warts, not being very smart, will
never send this signal, so the client may remain in low power mode.

Interestingly, although I think my iAudio MP3 player will charge fine
from a dumb wall-wart with USB cable, when I connect it to my Motorola
phone charger (same mini-USB connector), it says, "Connected" --
apparently because the phone charger is "smart" to tell the phone it's
OK to charge through it. The phone WON'T charge from a dumb wall
wart--nor will it charge from a computer without the right software.
Anyway, I believe in the "connected" state, the MP3 player won't
charge; it's expecting to look like an external hard drive to a
computer at that point. This is kind of the other side of the coin
Paul was describing. Not everything that looks like it should work
together -- does.

Cheers,
Tom

 

[Jeff Bradt]

Better make sure it is low amps. Or you will fry it. USB outout is very
low amps.

If you mean, make sure the power supply has a low amperage rating, that
makes no sense. The amperage rating of the power supply only needs to be
high enough; as long as it's above the amount you need, you're fine - unless
the voltage goes too high. If you need 5V, and you're trying to get, say
100mA (I have no idea if that's realistic but it's just an example), you'll
get 100mA unless the power supply is not able to push that current. You
won't get more. So even if the supply is rated for 5A, you're fine unless it
tries to put out a higher voltage. You'll still only draw those 100mA. See
what I mean:
Ohm's Law:
V=IR where R is the resistance of the load (the MP3 player), which won't
change beyond a certain specified point. So consider R a constant.
So, I, the current drawn, is directly proportional to V. If you want to get
a higher current I, you'll have to bring up V. A power supply won't push up
the voltage in order to give more current.
(Sorry if I'm verbose, it's my first post; I just got excited. I'll die
laughing if I just misunderstood your post!)