need some help

[Ozaibi]

Heey first time to write here, first time to post in any electric forum, i love electronics and i am still a noob, hopefully i will stay in this site only and really learn from here

anywaz my questions is how does the picture i sent u work?
basiclly it increase the output of the voltage to 2.1... a usb port on a pc usally is 5 volts, ...
i am confused while writing this ... i just dont get the picture i sent ... :S

 

[MagicMatt]

It's bad advertising, something has clearly been mis-translated. It can also damage your USB ports, so I wouldn't use it.

There are a variety of these things around, some of which seem to short out the USB port - some computers are happy with that, some end up with broken USB ports. Just use the proper charger.

A USB port is designed to deliver 5V at 500mA, no more. Trying to force it to drive more is a risk I wouldn't want to take given the cost of the computer vs. the cost of a charger.

Note that the NEWER MacBook etc. have USB ports that are able to deliver much higher current, because Apple designed their USB ports to work above the USB specification so they would charge iPads etc.

 

[MagicMatt]

Found the charging specification - iPad2 requires 2.1Amps at 5V to charge, so it's likely this is claiming to increase your output CURRENT (not voltage) to 2.1Amps (not volts).

Anything that tries to force a circuit designed ot run at 500mA (0.5A) max to output 2.1A is probably to be avoided... if indeed it works at all... which is doubtful. It's more likely to disconnect the data lines so the iPad thinks it's connected to a charger and charges anyway, but it wouldn't magic an extra 1.6A out of thin air.

 

[Ozaibi]

i agree

i thought so ...
so lets me return to my major issue...
because i thought that was a supposed answer and wanted to reverse engineer it to see how it works , so i will scrap that idea...

i am trying to a build a usb Hub that charges the ipad, even powered usb hub dont work well enough for the ipad due to the limited current and voltage ..

 

[MagicMatt]

even powered usb hub dont work well enough for the ipad due to the limited current and voltage ..

Actually that depends on the hub. My 7-Port DLink USB hub can charge an iPad, MP3 and mobile phone, but it has a 5V 3Amp power supply, and doesn't seem to limit the outputs. My cheap Novatech powered hub can too, but only if I substtute the 1A PSU it came with for a 2.5A PSU that was for my old Zip drive.

As far as I can tell you just need a 5V 2.1A power supply to the iPad.

You have 4 pins on USB,
1 - VCC (Red) +5V
2 - D- (white) Data -
3 - D+ (green) Data +
4 - Gnd (Black) Ground

All you need to do is make a USB power "booster" yourself:
* Pass the data lines direct through so that the unit is totally transparent to the iPad and PC.
* Tie your power supply Gnd, and USB Gnd together, so everything has the same Gnd reference
* BREAK the VCC line.
* Tie computer end of the VCC line through a resistor to GND - I suggest something like 100k so the computer sees power usage, but only a small amount. If you leave the line floating, some computers wont think there's anything connected.
* Connect your PSU +5V to the outgoing USB VCC (the one going to the iPad)

In theory, that would do it, since it's the computer that shuts down the USB power when the port is over-stressed, or the iPad that quits if the voltage drops too much.

 

[Ozaibi]

That's interesting point let me tell u my project in whole ....
U know there is a camera connection kit to the iPad to connect mmc and any USB flash drive.
U know there is a connection for the hdmi/vga to any display / tv
Another connection to connection a headset
Keyboard connection
I Wana put all that into a an iPad cradle ...
Alittle complicated I am sure
But thats my major project ....