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usb hub to iphone help

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usb hub to iphone help

Postby mitchdublin » Fri Apr 20, 2012 12:52 pm

Hi, Im new to this forum. Based in Dublin, Ireland.
Im building a mobile phone charging unit to bring to outdoor festivals. Phone charging for about 800 phones. I bought usb hubs with 24 usb outlets. These are self powered and for most phones that works great.
Problem is that the iphone needs a usb input signal to hub from a pc to work. other than having to bring about 4 pcs (127 max usb to pc). I trying to find a workaround for the hub.
I found a couple of sites that said that if i split the input usb lead the pinouts should read 1=5v, 2=data, 3=data, 4= ground.
That i need to add +5v to 2 using a 49.9k R3 and 75k R4 resistors
And +5v to 3 using 75K R2 and 49.9k R1
and ground both 49.9k resistors.
This will send 2v to both data cables into hub and should fool hub into thinking it is connected to pc.
Im not sure if this will effect other items connected to hub or will just tell hub to output full 500ma charge.
Appreciate any help out there.
mitchdublin
 
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Re: usb hub to iphone help

Postby I_Daniel » Thu Apr 26, 2012 2:35 pm

Play it safe and do not connect cellphones to the USB's that have been modified to cater for the iPhones. I do not know exactly how the cellphones use the charger but if the data pins are powered I haven't the foggiest idea if it could adversely affect the cellphones.

I have seen a charging schematic for iPhones using a standard USB connector where much higher resistances are used. 150k Ohm resistor in series with a 120K resistor. The 150 K is connected to the +5 Volts and the other side - the 100 K to the negative/ground.
Pin 1 is +5 volt and pin 4 is ground.
Pin 3 is Data+ and is connected to the center of this voltage divider.
You then have a second pair of 150K and 120K resistors but here the 120 k is connected to +5 volt and the 150 K to ground.
Pin 2 (Data-) is connected to the center of this voltage divider.
The total parallel resistance is thus 135 K and the current drawn by the voltage dividers is a few micro amps (5 Volts divided by 135000 Ohm) so there should not be any adverse affect on the power supply.
I_Daniel
 
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