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Hopefully, this will help some people, having trouble fast charging their USB rom modded Nexus7, who find this a much reliable and cheaper solution than just randomly pick any other dubious OTG hardware, from the usual dealers out there.

n7usbcharger.png


You will need:

1x oem Nexus 7 usb cable

1x plier

1x Stripping tool (a simple x-act or a small pocket knife will do)

1x Soldering Iron w/ a thin sharpened, clean tip

1x Thin Solder wire

1x Insulating tape

1x Regular solder paste flux

1x short 24AWG UTP cable or equivalent solid wire

1x male micro usb spare plug w/ plastic cover included. See here: http://www.ebay.com/itm/1set-USB-Male-plug-Connector-Micro-5pin-with-Cover-/180685352938?ssPageName=ADME:X:AAQ:US:1123

10x Calm and patient :)

Optional:

1x Heat shrink sleeve

1x Hot air gun

1x Female-to-female USB adapter

1x micro slide switch

Lets start:

Grab your ordinary, bundled Nexus 7 oem cable, which is already a trustworthy, quality build, and cut away the male micro usb end (not reusable you can trash it), with a plier tool. Strip the cable's outter insulation, for about 5mm (13/64 inches). Then, strip all of the colored wires for about 1,5 mm (1/16 inches), just enough to solder into the micro usb plug, backside pins. DO NOT cut the shielding wire, as it will be needed!

n7usbotg_1.png
n7usbotg_2.png


If you notice, the black (ground) and red (+5v) wires are much thicker than the "data" ones, which is nice and hard to find in a standard OTG cable.

Now grab the stripped wire tips and give them a small twist, as they are stranded and you'ill easily mess up if you don't do this. Plug in your iron and let it get hot enough, somewhere between lower/medium temperature. Give them tips a nice, quick tin cover, first on the Iron, then on the wires. Take your time, It's useless to rush any of these steps...

Give also a twist to the stranded shielding and tip it with some tin. Also, if you want to use some heat shrink sleeve to improve insulation of the shielding, inside the plug, or the cable itself, now is the time to stick it in...

With the help of a small pocket knife, a thin screw driver or any other similar tool, slightly spread some flux on the micro usb backside pins. Reach for your Iron and givem them alll a small tin cover, the flux will help the tin stick to the pins.

n7usbotg_5.png


n7usbotg_3.png


Now carefully solder all the 4 usb wires into the micro usb plug, starting with bottom facing up, from pin 5 to 1 (I found it easier this way), meaning, Black (ground), Green (data +) and Red (+5) on the bottom. And then the White (data -) on the top. See picture above.

Pick any cable leftovers you have laying around or get some UTP cable w/ 24AWG solid wire (stranded is ok too), from a local store. Cut one of the twisted pairs, about 50 mm (1.97 inches) long. Strip the wires for the same amount you prevoiusly did, on both ends. Solder both wires, one to pin 5/black (ground) wire and the other to pin 4. Shunt the other end of the pair.

n7usbotg_6.png


Add some sleeve to it, if you want, and shrink it with the hot air gun. Run this pair along the cable and sleeve it in or use some isulating tape around it, for a better insulated result. Leave out a short tip of those 2 wires, but you can tape them for now. You can always add some sort of tiny slide switch to them later, if you're planning on also using the cable for connecting the N7 to a PC or charge your smartphone or even other stuff:

42256553.jpg
switch_otg.png
switch_otg2.png


n7usbotg_7.png


n7usbotg_4.png


Lastly, find a nice spot to solder the cable's shielding on.

Seal the plug with the included black, plastic cover, for a neat finish (if you got it from ebay). Done! You should come up with something like this:

n7usbotg_9.png
n7usbotg_8.png


It is 100% reliable for fast charging and In-dash pojects. I tested this myself!

The other standard male USB connector, won't help much in conectivity, I know. For that I found it better to make use of a female-to-female USB adapter, whenever you need, rather than ruin another nice plug. They're really cheap and easy to find, like everywhere.

usb_ftof.png


WARNING: YOU SHOULD NEVER CONNECT YOUR N7 TO A PC IN OTG MODE (pins 5 and 4 shunted), especially if you have USB rom and WHILE "FAST CHARGING" IS ON! You may damage the USB ports and/or fry the N7 charger IC!

That's it, think I covered it all. Let me know if anything comes up...

Cheers

;)
 
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