USB Hub as an iPod/iPhone Charger [solved]

[Man-wai Chang]

I found another USB hub that allowed me to short the D+ & D- pin AT THE
OUTPUT END.

It works as long as I don't plug the USB hub into a PC, but the
ACadaptor of the USB hub. If I did, the iPod would give me a yellow
triangle, and refuse to charge itself from the PC.

I don't even need to use any resistor at all.

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[Paul]

I found another USB hub that allowed me to short the D+ & D- pin AT THE
OUTPUT END.

It works as long as I don't plug the USB hub into a PC, but the
ACadaptor of the USB hub. If I did, the iPod would give me a yellow
triangle, and refuse to charge itself from the PC.

I don't even need to use any resistor at all.

Now where is the fun in that ? We need the resistors.
Resistors are good. Soldering is fun...

Paul

 

[Man-wai Chang]

Now where is the fun in that ? We need the resistors.

Resistors are good. Soldering is fun...

There are 3 other ports on that USB hub. I could attempt the resistor
thing later!

There is one problem I just learnt: the AM noise is back! I would try to
locate its source later, hopefully had nothing to do with the 2 shorted
pins.

I now wonder whether a 47K resistor over the 2 pins, rather than
shorting them directly, would remove the AM noise...



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[Paul]

I now wonder whether a 47K resistor over the 2 pins, rather than
shorting them directly, would remove the AM noise...

Not likely to happen.

Paul

 

[Man-wai Chang]

I now wonder whether a 47K resistor over the 2 pins, rather than

Not likely to happen.

Thanks. Is there a one-component solution to stop any AM noise?

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[Paul]

Thanks. Is there a one-component solution to stop any AM noise?

They make AC line filters. That is as close as I know of,
to a "single component". This one still needs line cord
attached to the end of it (a cord on the line side goes
to the wall, a cord on the load side goes to the adapter).
For the price of this box, you can buy an entire ATX
power supply instead.

http://classic-web.archive.org/web/20031114125934/http://corcom.com/pdf/rfi/N+Series.PDF

Paul

 

[Man-wai Chang]

It works as long as I don't plug the USB hub into a PC, but the

ACadaptor of the USB hub. If I did, the iPod would give me a yellow
triangle, and refuse to charge itself from the PC.

Another observation:

If I turned on the AC supply to the USB hub first,
then plugged the iPOD into the modified USB port using
the iPod cable, the yellow triangle appeared again
("Charging not supported on this device").

I have to first turned off the AC supply to the USB hub,
connected the iPod to the modified USB port,
and then turned on the AC. Then charging would happen.

So hot-plugging is NOT going to charge. Weird....

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[Paul]

Then how do the ATX power supply filter noise? By good design?

The ATX supply uses a slightly simpler filter. See T1 and T5
in the input section. You can compare this to the equivalent]
circuit of the Corcom box.

http://www.pavouk.org/hw/en_atxps.html

Paul

 

[Paul]

Another observation:

If I turned on the AC supply to the USB hub first,
then plugged the iPOD into the modified USB port using
the iPod cable, the yellow triangle appeared again
("Charging not supported on this device").

I have to first turned off the AC supply to the USB hub,
connected the iPod to the modified USB port,
and then turned on the AC. Then charging would happen.

So hot-plugging is NOT going to charge. Weird....

When the modified USB port is not powered, maybe
it is pulling down that shorted together junction ?
I have no idea how the Apple end is interpreting
the signal levels.

Paul

 

[Man-wai Chang]

I have no idea how the Apple end is interpreting

the signal levels.

I don't understand why Apple converted the 4-pin USB input into a wide
30-pin plug. Isn't it a waste of time?

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[Paul]

I don't understand why Apple converted the 4-pin USB input into a wide
30-pin plug. Isn't it a waste of time?

Probably multiple interfaces. Did you Google for a pinout,
to see if anyone knows what is on those 30 pins ?

Plenty of stuff has private interfaces. For example,
disk drives have a three pin interface for a TTL level
serial connection (RS232 but TTL levels). Sound cards
have some interesting private connectors as well. Once
you know of some of the generic approaches used, it's
fun to open up stuff and look for it. For example, when
my previous router broke, I started looking for a serial
interface on it, but couldn't be positive I'd found it.
The router was partitioned in two, and I couldn't tell
if the processor was running inside it or not. I was
hoping to find the serial interface, and see if it was
printing out a prompt or not (serially, over an RS232
like protocol).

Paul

 

[Man-wai Chang]

Probably multiple interfaces. Did you Google for a pinout,

to see if anyone knows what is on those 30 pins ?

You gave me a link. I am reposting it here:

http://pinouts.ru/Devices/ipod_pinout.shtml

Plenty of stuff has private interfaces. For example,
disk drives have a three pin interface for a TTL level
serial connection (RS232 but TTL levels). Sound cards

What Apple did was like converting the serial USB interface back to a
parallel one. Is it a joke?

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[Man-wai Chang]

The ATX supply uses a slightly simpler filter. See T1 and T5

in the input section. You can compare this to the equivalent]
circuit of the Corcom box.
http://www.pavouk.org/hw/en_atxps.html

Being not trained in elecronic engineering, this is beyond me. I was
hoping for a simple circuit mod to eliminate all AM noise!

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[Paul]

You gave me a link. I am reposting it here:

http://pinouts.ru/Devices/ipod_pinout.shtml


What Apple did was like converting the serial USB interface back to a
parallel one. Is it a joke?

That is a whole bunch of interfaces. From pin 1 to pin 30

Stereo_Audio, Composite_Video, S_Video (Luma, Chroma),
Serial_Data (could be TTL level), Power, Firewire (TPA pair, TPB pair),
USB (Data+, Data-).

Some of those functions might be nice on a dock.

Paul

 

[Man-wai Chang]

Stereo_Audio, Composite_Video, S_Video (Luma, Chroma),

Serial_Data (could be TTL level), Power, Firewire (TPA pair, TPB pair),
USB (Data+, Data-).

I think Apple was demultiplexing the signals by feeding the same 2-pin
input (data+, data-) into multiple 2-pin inputs of a chip.

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[Paul]

The ATX supply uses a slightly simpler filter. See T1 and T5
in the input section. You can compare this to the equivalent]
circuit of the Corcom box.
http://www.pavouk.org/hw/en_atxps.html

Being not trained in elecronic engineering, this is beyond me. I was
hoping for a simple circuit mod to eliminate all AM noise!

A different kind of adapter is likely the fastest solution.

Designing filters isn't that much fun. Especially making
coils for magnetics.

*******

You could look for an adapter with a three prong AC interface.

The EMI (noise) flows back in the safety ground. For this
to work, your wall output needs a safety ground pin as well.
This is similar in design to a laptop adapter, only it
puts out 5V @ 4A. That should be plenty of maximum current
level for charging. It's about $25 or so.

http://ca.mouser.com/ProductDetail/...=sGAEpiMZZMtpkqKkT5w3uqa0rkPN3QTQxHU8Ah9lTWc=

http://www.phihong.com/assets/pdf/PSAC30U.pdf

I gather from the product description, the output is floating,
so the shield of the DC output isn't joined to the safety
ground (like it would be on an ATX power supply).

Paul

 

[Man-wai Chang]

A different kind of adapter is likely the fastest solution.

I found that the AM noise seemed to come from that iPod cable.

Antennae effect?

Designing filters isn't that much fun. Especially making
coils for magnetics.

Thanks. Too much for an amateur.

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[Paul]

I found that the AM noise seemed to come from that iPod cable.

Antennae effect?


Thanks. Too much for an amateur.

If you really want to fix it, you'd want a transformer based
design, rather than a switching based design. That removes
the switching element, so there is no similar noise source
in the supply. You can find web pages that detail the construction
of such things. (If there was a "kit" with all the parts
you could put together, I'd point you at that, but I haven't
seen one for sale. None of the stuff I've seen so far, includes
the transformer.)

Transformer ---- bridge ------- filter ------ linear_regulator --- 5V @ 1A
120V 12V rectifier capacitor 7805 type

http://2.bp.blogspot.com/_1KIwZrxSy6A/S2JzbCrlu6I/AAAAAAAAAPg/LyPNU4wDNJg/s1600/-7805.JPG

That's the basic idea. The linear regulator idea
is not very power efficient. So it's not a very "green"
solution. Switching supplies are lighter in weight and
more power efficient, but they have the disadvantage of
making more electrical noise. The 7805 should have
a heat sink on it, if you want to use all 1 amps of
output.

I make my own supplies of that type here. The last one
I made was a couple months ago, and it powers my home
made stereo amplifier. The regulated DC output is adjustable
on that one, but is currently running at 12V @ 3A. The amplifier
is insensitive to the exact DC voltage, but makes more
sound level as you increase the voltage, up to 18V.

To reduce the complexity of that project a bit, you can
sometimes fine "unregulated" transformer based adapters,
and then connect a 7805 to the output of that, making
a "regulated" output. My label maker (prints text on adhesive
labels) uses such a transformer based power supply. That reduces
the circuit to something like this

Unregulated supply ---- linear_regulator --- 5V @ 1A
120VAC ~8VDC 7805 type

But if you're "adverse to working with resistors", that
is still too much project for your first one.

Paul

 

[Man-wai Chang]

On more new observation:

If the battery of the iPod was full, the yellow triangle would appear as
well (Charging not supported on this device).

 

[Man-wai Chang]

Another observation:

When the battery was charged to about 90% full, the yellow triangle was
shown again ("Charging not supported on this device"). Maybe the iPod
tried to find the PC again, failed and reported an error.

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