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DIY TF101 charger and other charging methods

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By DevCake, Senior Member on 19th May 2011, 09:05 PM
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!UPDATE!

Starting a Barrel Charger keyboard Dock MOD Thread. If you want yours done for free I'm looking for a volunteer to send me a keyboard dock to modify with standard barrel charging adapter. Stay tuned for the tread link


Covering 3 popular charging topics

1. Why you can't use a USB 2.0 extension cable with the factory charger
2. Testing data proving the Tablet needs 11V or higher to chartge
3. Off the shelf parts and spare parts to make a Wall charger
4. Off the shelf parts and spare parts to make a Car Charger

1.Why you can't use a USB 2.0 with the factory charger

Because the charger is looking for termination of Pin 7 from the Tablet to start sending 15 Volts. Pin 7 is a USB 3 pin, not available in usb 2.0 so the charger never sees termination and continues to send 5V. This is why if you connect your phone or other 5V usb device to the charger it will charge at 5V.

The only way to trick the charger into always sending 15V so that you can use a 2.0 extension cable is to take it apart and bridge ground with pin 7. But you will not be able to use the charger for any other device, not worth it IMO.



Here you can see that pins 5-9 are USB 3.0 only.

2. Testing Data

-The Tablet looks for more than 11V to start charging
-With a source other than from the ASUS charger I supplied pins 1 (RED HOT)and 2 (Black Ground) with 13.5 volts and it charges. My source was a 12V AC to DC power supply I use for testing DC devices.
-My power source was pushing 1.5 Amps during the charge
-All other pins were disconnected on the USB extension.

Its all about voltage. Any AC to DC adapter that supplies at least 11 Volts that has a female usb adapter with ground to pin 1 (RED HOT)and 2 (Black Ground)

CONFIRMED: I Connected my 13 V source to pins 1 and 4 on a USB 2.0 extension cable and it worked.

The Asus charger does need a 3.0 cable extension to work. But with a DIY charger you don't need USB 3.0 cables or connectors.

WARNING! Please know your technical limits and understand that any instructions you follow in this thread are at your own risk.

DIY ADAPTERS
--------------
Wall charging - Any Voltage selectable DC wall adapter that supports at least 11 Volts 1 Amp will work. You will need to add a female DC barrel to USB Female cable which are available cheap or can be made which I will post pics.

Off the shelf Parts $13.99 Total


!IMPORTANT! PLEASE BE AWARE OF POLARITY WHEN USING THESE UNIVERSAL ADAPTERS. YOU WILL DAMAGE YOUR TABLET IF THE POLARITY IS WRONG.

Check this SITE for information on setting up the tips for the correct polarity.

I check polarity every time I connect and disconnect my tablet when testing. If you have basic voltage meter and one USB cable you can sacrifice I suggest you test the polarity by creating a test cable. Cut the cable, expose the bare wire on red and black then test with your meter while connected to your generic charger. If your meter shows a "-" while showing the voltage your polarity is WRONG. If it doesn't show a "-" or in some cases a "+" your polarity is right.

Adjustable Voltage DC wall charger -EBAY $11 shipped.



UK Equivalent
Generic AC/DC Adapter Up to 12V and 1500Amps

5.5mm DC Female Barrel to USB Female cable - EBAY $2.99 Shipped EBAY UK LINK

EBAY UK LINK

Plug the adapter cable into the 5.5 connector on the DC adapter, set it to 12V , connect the factory Asus cable to the adapter cable and you are charging. Your 3.0 extension cable will work with this as well as any 2.0 extension cable. I'm waiting for the adapter cable and will post pics of the components connected together.

Or you can get an adjustable charger that comes with a USB Female adapter like this one



Building with spare parts

I'll be taking a 12 or 14 volt DC adapter I have and wiring a USB end directly to it. If you are a gadget person you might just have some spare DC adapters. Pictures soon. I'll also be making a version that includes the adapter cable from above.

Charging in the Car - Any Voltage selectable Car DC adapter that supports at least 11 Volts 1 Amp will work. You will need to add a female DC barrel to USB Female cable which are available cheap or can be made which I will post pics. You will be able to use the same adapter cable as above, you just need the car adapter


Off the shelf Parts $10.98 Total


Auto DC adapter Adjustable starting at 15V - EBAY $7.99 Shipped



5.5mm DC Female Barrel to USB Female cable - EBAY $2.99 Shipped

Plug the adapter cable into the 5.5 connector on the DC car adapter, set it to 12-15V , connect the factory Asus cable to the adapter cable and you are charging. Your 3.0 extension cable will work with this as well as any 2.0 extension cable. I'm waiting for the adapter cable and will post pics of the components connected together.

Multi function Car & Wall charger,

This is interesting, it has input for AC and DC so you can use it in the Car and at home.



Generic adjustable Car and Wall charger

For charging on a PC. - Not possible, There is no way to double the voltage from one power supply, connecting 2 cables together will not increase volts only AMPS.

OTHER KNOWN CHARGERS THAT WORK
Dynex DX-UA - Universal laptop/camera charger. $29
Radio Shack 12V adapter Comes with a free USB tip $30
X1 PST-1200UF NOTE: Even though this one comes with a USB tip you still Need to add the USB adapter cable because the manufacturer limits 5V to that one USB tip in the package.

UNTESTED BUT SHOULD WORK
PowerLine 90304 Need to add USB adapter cable
Generic adjustable Car and Wall charger Need to add USB adapter cable

My mess of a test bench =]



~DC
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26th May 2011, 03:34 AM |#2  
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Just updated the OP and man this is frustrating, the charger is very sensitive.
26th May 2011, 03:56 AM |#3  
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try to get a scope, it is possible that the charge controller is in the tf while the charge circuitry is in the charger. the two middle pins might be control signals which would explain why touching them stops the charger. the lack of signals on the middle pins may explain why when using the dynex charger you lose the battery meter.
26th May 2011, 04:10 AM |#4  
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Quote:
Originally Posted by Rumbleweed

try to get a scope, it is possible that the charge controller is in the tf while the charge circuitry is in the charger. the two middle pins might be control signals which would explain why touching them stops the charger. the lack of signals on the middle pins may explain why when using the dynex charger you lose the battery meter.

DONE

It's voltage people, all voltage. No fancy communicating with the charger. Right now I have a DC power supply use for powering DV voltage devices connected directly to pins 1 and 4 supplying it with 13.8 Volts and it is charging. All other pins are disconnected. This is why the Dynex works, because it is 11 V.

Back to the OP with a follow up.
26th May 2011, 04:32 AM |#5  
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Something is still missing. If only pins 1 and 4 are used by the charger, then a usb 2.0 cable with four pin/conductors should work as an extension, but it doesn't.
26th May 2011, 04:50 AM |#6  
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would something like this work to charge from 2 usb ports?

http://www.amazon.com/Apricorn-Power...6378019&sr=8-1
26th May 2011, 04:53 AM |#7  
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Quote:
Originally Posted by Rumbleweed

Something is still missing. If only pins 1 and 4 are used by the charger, then a usb 2.0 cable with four pin/conductors should work as an extension, but it doesn't.

True but my goal is to come up with more charging options. I've been charging my tablet for about 45 mins now, voltage and amps have been steady, 13.8 and 1.6.
26th May 2011, 04:56 AM |#8  
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Quote:
Originally Posted by skchan2

would something like this work to charge from 2 usb ports?

http://www.amazon.com/Apricorn-Power...6378019&sr=8-1

Possibly, I'm testing the 10V theory now.
26th May 2011, 05:14 AM |#9  
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Quote:
Originally Posted by skchan2

would something like this work to charge from 2 usb ports?

http://www.amazon.com/Apricorn-Power...6378019&sr=8-1

Scratch the hole 2 USB connectios theory, you cant combine 2 voltage from one power source in series. But i'm looking into what those dual cables actually do.
26th May 2011, 05:19 AM |#10  
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Someone should disassemble there Asus charger, i couldn't figure out how to pry it open, so i gave up before i broke the plastic shell

Someone needs to get an oscilloscope going on the cable , there has got to be a reason Asus chose USB 3.0 connectors, which i think it is for some accessories down the road, who knows
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26th May 2011, 05:26 AM |#11  
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Quote:
Originally Posted by SlimDan22

Someone should disassemble there Asus charger, i couldn't figure out how to pry it open, so i gave up before i broke the plastic shell

Someone needs to get an oscilloscope going on the cable , there has got to be a reason Asus chose USB 3.0 connectors, which i think it is for some accessories down the road, who knows

Not going to argue with you on that one. The dynex is working for people and so is my rig.
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