USB Hub as an iPod/iPhone Charger

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Man-wai Chang

This person just shorted Data+ and Data- pin! Didn't use any resistor at
all. Comments?

http://carlhutzler.com/blog/2009/07/28/usb-hub-as-an-ipodiphone-charger/

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Man-wai Chang said:
This person just shorted Data+ and Data- pin! Didn't use any resistor at
all. Comments?

http://carlhutzler.com/blog/2009/07/28/usb-hub-as-an-ipodiphone-charger/
Click to expand...

Well, download the 500 page USB2 spec, analyse it, and see what the
consequences would be ? :-)

I think the various "weak resistor" circuits you've been looking at,
are safer. All the hacks require soldering, so you might as well
solder resistors to your charging connector. I think your three
resistor circuit (giving 2.5V on one lead and 2.0V on the other)
has some merit, and might be your best option. By using high resistance
values, as those circuits have been using, there is virtually no chance
of damage. I can't tell you, right off hand, how the USB I/O pad
would respond to a short circuit from D+ to D-. I don't know what
that would do, if the USB I/O pad decided to drive the signals for
any reason. (Like trying to drive out a chirp.)

(Picture of chirp sequence on page 15)

http://ep-div-ed.web.cern.ch/ep-div-ed/Documents/Mikes_USB.pdf

Paul
 
of damage. I can't tell you, right off hand, how the USB I/O pad
would respond to a short circuit from D+ to D-. I don't know what
that would do, if the USB I/O pad decided to drive the signals for
any reason. (Like trying to drive out a chirp.)
Click to expand...

OK, I took the plunge and mod a malfunctioning USB hub. The iPod Touch 3
powered up itself when I plugged in the iPod cable, BUT there was NO
CHARGING!!

DAM! :)

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Man-wai Chang said:
OK, I took the plunge and mod a malfunctioning USB hub. The iPod Touch 3
powered up itself when I plugged in the iPod cable, BUT there was NO
CHARGING!!

DAM! :)
Click to expand...

Did you use the three resistor circuit ? Have you verified
you connected it up so that the D+ and D- got the voltages
others have used ?

Paul
 
OK, I took the plunge and mod a malfunctioning USB hub. The iPod Touch
Did you use the three resistor circuit ? Have you verified
you connected it up so that the D+ and D- got the voltages
others have used ?
Click to expand...

I just shorted D+ and D- directly, not using any voltage divider.

BTW, this afternoon, I tried to salvage a few 10K resistor from the dead
power supply and burnt my finger tip with the soldering iron. :)

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Man-wai Chang said:
I just shorted D+ and D- directly, not using any voltage divider.

BTW, this afternoon, I tried to salvage a few 10K resistor from the dead
power supply and burnt my finger tip with the soldering iron. :)
Click to expand...

To salvage components, you need:

1) Solder wick. This draws up the excess solder. When done properly,
there will be very little holding the component in place. Note that
solder wick comes in different thicknesses, and retailers like this
one will sell the "fat useless" type. You have to search around to
find a roll of "fine" wick.

http://www.thesource.ca/estore/prod...line&category=Soldering+Tools&product=6402090

In the example here, 0.030" wide or 0.050" wide are available. I
may have even had some 0.025" in the tool box at one time.

http://www.chemtronics.com/literature/americas/flyers/Soderwick Brochure_LR.pdf

http://parts.digikey.com/uk/1/121774-solder-wick-rosin-030-25-50-1-25.html

The thin solder wick is easier to heat with the soldering iron.
If the wick contains "resin", that helps promote the flow of
molten solder into the wick. The dry wick they sometimes sell
for usage on ROHS assemblies, is kinda useless. At least, the
wick I've bought in the last few years, hasn't worked very well
for me. Only the older stuff I've got, works good.

2) Hobby knife blade, to use to move a component when it is hot.
The nice thing about the knife blade, is if you burned it, you
can get more blades for the knife, cheaply.

3) Pair of needle nose pliers, to hold a component or to provide a
heatsink, to prevent heat from going places where it will melt the
plastic. If you place a flat elastic band around the handles, the
pliers can be made to grip an item.

http://www.active123.com/_static/webUpload/731/26_100-012_none_3.jpg

When you own enough tools, there is hardly ever a reason to
stick your fingers in there :-)

http://www.micromark.com/RS/SR/Product/84454_R.jpg

Paul
 
When you own enough tools, there is hardly ever a reason to
stick your fingers in there :-)
http://www.micromark.com/RS/SR/Product/84454_R.jpg
Click to expand...

The board in the dead power supply is a lot larger.

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Man-wai Chang said:
The board in the dead power supply is a lot larger.
Click to expand...

I still think the mixed pack of resistors is your best bet.
You can likely find three resistors close enough in value,
to do your charger project.

http://www.thesource.ca/estore/prod...log=Online&category=Resistors&product=2719018

The only time I salvage resistors, is when they're the big ones.
Even at work, when we needed to build a dummy load, one
of the guys walked down the street to a surplus electronics
place and bought some used power resistors. That was a lot
cheaper, than trying to buy them brand new. But for the
tiny $0.05 resistors, it's better to just buy a pack and
put them in bins.

https://getzequipment.com/oscommerce/images/Parts-Cabinet-20-Drawer-WS1.jpg

For my parts cabinet, I only sort them to the nearest decade.
So 100-999 ohms goes in one drawer, 1000-9999 ohms goes in
the next drawer, and so on. It means having to sort through
them, but isn't quite as bad as having them all jumbled
together.

If you put each resistor value in its own drawer, the storage
requirement would be huge.

Paul
 
I still think the mixed pack of resistors is your best bet.
You can likely find three resistors close enough in value,
to do your charger project.
Click to expand...

There is no such deal in Hong Kong. Haven't seen any shop offering it.
If you put each resistor value in its own drawer, the storage
requirement would be huge.
Click to expand...

They are just a few Hong Kong cents a piece. I can afford that.

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Did you use the three resistor circuit ? Have you verified
you connected it up so that the D+ and D- got the voltages
others have used ?
Click to expand...

After reading the documents you posted here, I learnt that no current
would be released unless D+ is 2.5V and D- is 2.0V. So, I guess I have
to do the voltage divider circuit after all.

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Man-wai Chang said:
After reading the documents you posted here, I learnt that no current
would be released unless D+ is 2.5V and D- is 2.0V. So, I guess I have
to do the voltage divider circuit after all.
Click to expand...

Now, you're a resistor expert *and* a hobbyist :-)

Only a hobbyist would go to this much trouble :-)

Paul
 
Now, you're a resistor expert *and* a hobbyist :-)
Only a hobbyist would go to this much trouble :-)
Click to expand...

As long as I have the time... :)

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