Update: Charging MP3 Player, Coby MP620-4G

[[email protected]]

Hi,
Since my original post, I bought the Coby MP620-4G MP3 player.
The OM says to use a "high power" USB port (computer). There is
no other information in the OM or at their web site on a recommended
charging current if using a different source.

I can set the maximum current limit on my lab quality regulated
power supply. Note: There is no connection to the USB "data" pins
with this setup. The MP3 player display indicates that it was "charging".

When I first charged this MP3 player at 200 MA max, which didn't take
very long before the display said the battery is "charged", I loaded it with
several hundred songs (MP3). It played for a little over an hour then the
player "died" (no warning).

I recharged it at 100 MA max and it played over 5 hours, but I didn't run
it until it "died". Again, when I charged it at 200 MA max, which didn't take
long, it played for 1hr and 10 minutes, then "died".

For the second time, I charged it at 100 MA max, and it plays a long time.

John

PS, Remove "ine" from my email address

 

[JW]

A USB port is supposed to provide 500 mA max.

According to the specification, yes. However, I've seen motherboards that
connect +5V directly to the USB port.

 

[JW]

IBM did that with the keyboard on their original XT motherboard, with
no fuse. I had a customer's keyboard cable short at the keyboard. If
he hadn't been at the computer when it happened, it would have set his
house on fire. There was nothing but a few pieces of bare, burnt wire
left.

Keyboard cables with 24/26ga wire make nice resistors.
I'm surprised that IBM would have missed something like that.

Do those motherboards have self resetting fuses? If not, there is no
way I would use them or let anyone else get their hands on them.

I'm not sure if they did or not. I'd take a look now, but I can't remember
which one of the dozens we have around here was the one wired in that
way... All I know is that the resistance between +5 and the USB socket was
less than an ohm. Usually there's a switched FET and it will read open.