Hey all..
I have my tab installed in my dash of my car. I am running Jt's CM7 and am also running the tasker app.
Right now i have it all set where then the car starts up power goes to the charger and it switched to an AC mode profile. When off it switches to non Ac mode and i have it set to screen timeout to 7 seconds and to turn on airplane mode.
tasker can also sense when it is in usb charge mode.
I would love to be able to make a charging cable that will charge at AC mode or full current.. then when the car is off make the charger charge at usb mode or low current charge
Has anyone got any ideas? I was thinking about the hacked charging usb cables that allowed the non samsung cables to pull full current.
If i got 2.1 amp usb charger, then built the resistors into the usb cable to fool it into full current mode it should work in AC mode, put a relay on the 2 wires with the resistors to break the connection when the car is off, forcing usb charge mode.
Would this work? Any one else got any other ideas?
kamakazie2 said:
Right now i have it all set where then the car starts up power goes to the charger and it switched to an AC mode profile. When off it switches to non Ac mode and i have it set to screen timeout to 7 seconds and to turn on airplane mode.
I would love to be able to make a charging cable that will charge at AC mode or full current.. then when the car is off make the charger charge at usb mode or low current charge
Click to expand...
Click to collapse
I don't understand.... if when the car is off, no power is supplied to the charger (lighter port?), how/where will you get power to provide for the usb, low current charging mode.
Also if you can supply power when the car is off, why bother switching to a low current mode? The gtab will charge (at high current), until it is fully charged, at which point it will stop charging and little further current will be drawn.
Also, you don't want resistors in the circuit, a current limiter would be better, but also I believe that the gtab switches charging mode NOT based on current capacity, but on whether data lines in the USB cable are shorted... I'm hazy on this but will check it later...
Overall, I don't understand your project...
from another post:
There is a little trick actually in original Samsung Tab charger: lines D+ and D- (contacts 2 and 3) are short-circuited, and there are 2 resistors between them and +5 and GND contacts. 30 KOhm between +5 and 2/3, and 10 KOhm between 2/3 and GND. When you connect the charger (or USB port of PC) to the Tab, it first checks contacts 2 and 3 - if they are shortened, then it "thinks" that some charger is connected to it, not PC port. Then it measures voltage between 1 - 2/3 and 2/3 - 4, and if there is a predefined ratio, it "understands" that it is connected to AC charger and gets full power from it. I made this dongle myself in 15 minutes using standard USB cable (male/female), good knife (to peel off plastic from cable connectors), 2 resistors and soldering iron. Now my Tab can be smoothly charged from any 3-rd party iPad charger and original HTC Hero charger. A charger must be rated for output current not less than 1 A.
Click to expand...
Click to collapse
Thanks for the post.. let me clarify the purpose
In the current setup i use the change of status from no power to ac charging to trigger the tablet to wake up and sleep using the tasker application.
AC Mode happens when the car is on and powers up the charger. when this happens tasker will wake up the tablet.. set screen time out to never and disable airplane mode.
No power mode happens when the car is off and the charger is no longer powered. Tasker will set timeout to 7 seconds and turn on airplane mode.
Currently this setup works well, however i would like to have slacker radio auto refresh overnight when im home and connected to wifi. the problem is slacker will no refresh when there is no charger active. also it i dont drive the car for a few days eventually the battery will drain. I would also like to have wifi and 3g on so i can remotley sync mp3's with the device when i am home.
My attempted solution would be to always have power going to the tablet. But i still need a trigger to tell the tablet to wake up and shut down.
My idea would be to have a charger that will charge like the official samsung charger where the tablet recogcnizes it is being charged by a high current charger and not by an unsupported charger where it charges with the small lightning bolt in the battery icon which is the usb low current charger.
What i have read is that you can build a usb charge cable that will force the high current charge if you take a usb cable and place a 33k and 10k ohm resistor on the data + and - wires and connect them to the power and ground wires as in the sticky post.
http://forum.xda-developers.com/showthread.php?t=975558
If i can get a relay that will take the same car charger and have 2 states by opening and closing the resistor circuit.
1. the charger will operate with the resistors on the data lines causing high current mode and triggering AC mode
2. the charger will operate without the resistors on the data lines causing low current mode and triggering usb power mode.
Then i can use tasker to read the different state and power on and off the tablet when the circuit is active.
thus i can keep the teblet always charging as it needs and still retain my triggers to wake and sleep the tablet.
Unless there is some other trigger i can use.. possibly make a bluetooth device that will connect when the car is on.. then i can use that trigger to wake and sleep... I need to think out of the box on this one
-----
Now that i think about it.. if i just keep the charger plugged in without modification i can use a switched bluetooth device to trigger a state change. Tasker can read if a specific bluetooth device is paried then i can switch profiles.
So then i need to find a bluetooth device that i can have power up when the car is on then shut off when the car is off. solving my problem.
I know this thread is a little old but below is a schematic that should do what you want, i.e. provide full charging when car ignition is on and trickle charge when ignition is off. This circuit requires a 12v single pole, double throw relay, 2ea 22k resistors, and 1ea 33k and 10k resistors (1% tolerance). The 33k and 10k resistors provide a 1.25v voltage divider while the 2-22k resistors provide a 2.5v voltage divider (they might not be needed but on a non-Samsung charger D+ is ~2.7v while D- is ~2.0v). Note that the light blue lines between the normally closed terminal (NC) and the common terminal (COM) of the relay and the coil represent the wiper arm and armature and are not connections you make.
The relay coil gets 12v from the car's ignition only when the key is on and the ground for the coil comes from the car's body or a ground wire. The power (+5v) & ground (GND) for the voltage dividers come from the 2amp car charger as does the power for the 30 pin connector.
Radio Shack relay p/n 275-248 should work, and all can be mounted on multipurpose circuit board p/n 276-150 which should fit in project box p/n 270-1801. Unfortunately Radio Shack doesn't carry 1% tolerance resistors so some place like Digikey or Newark Electronics would be a good source.
Code:
VCC = +5v from car charger
VDD = GND from car charger
[COLOR="Red"]┌─ ──[RELAY]── ─┐[/COLOR]
┌─────────────────────Θ [COLOR="Red"]|[/COLOR] ─Θ VCC {RED}[COLOR="Green"]\[/COLOR]
┌─▒▒▒─┴─▒▒▒─┐ [COLOR="Red"]|[/COLOR] (NC)[COLOR="DeepSkyBlue"] \[/COLOR] [COLOR="Red"]|[/COLOR] [COLOR="Green"]\[/COLOR]
│ 22k 22k │ [COLOR="Red"]|[/COLOR] [COLOR="DeepSkyBlue"]|\[/COLOR] (COM)[COLOR="Red"]|[/COLOR] ┌─Θ D- {WHT} [COLOR="Green"]\[/COLOR]
VCC Θ─┤ ├─Θ VDD [COLOR="Red"]|[/COLOR] [COLOR="DeepSkyBlue"]|[/COLOR] Θ────────┤ [COLOR="Green"]> TO 30 PIN[/COLOR]
{RED} │ 33k 10k │ {BLK} [COLOR="Red"]|[/COLOR] [COLOR="DeepSkyBlue"]|[/COLOR] [COLOR="Red"]|[/COLOR] └─Θ D+ {GRN} [COLOR="Green"]/[/COLOR]
└─▒▒▒─┬─▒▒▒─┘ [COLOR="Red"]|[/COLOR] (NO) [COLOR="DeepSkyBlue"]|[/COLOR] [COLOR="Red"]|[/COLOR] [COLOR="Green"]/[/COLOR]
└─────────────────────Θ[COLOR="DeepSkyBlue"]|[/COLOR] [COLOR="rED"]|[/COLOR] ─Θ VDD {BLK}[COLOR="Green"]/[/COLOR]
[COLOR="Red"]|[/COLOR] ┌──[COLOR="DeepSkyBlue"]|[/COLOR]───┐ [COLOR="Red"]|[/COLOR]
[COLOR="Red"]|[/COLOR] ┌─┤ COIL ├─┐ [COLOR="Red"]|[/COLOR]
[COLOR="Red"]|[/COLOR] │ └──────┘ │ [COLOR="Red"]|[/COLOR]
[COLOR="Red"]|[/COLOR] Θ Θ [COLOR="Red"]|[/COLOR]
[COLOR="Red"]|[/COLOR] +12v GND[COLOR="Red"]|[/COLOR]
[COLOR="Red"]| [COLOR="DarkOrchid"](car ignition)[/COLOR]|[/COLOR]
[COLOR="Red"]└─ ── ── ── ── ─┘[/COLOR]
Related
Hello Friends,
i made myself a Carholder with Charger and Audio-Connection for my Wizard100. I took a Lm7805 to create +5V out from 12V of the Car Battery. I also took a normal Mini USB Plug, and connected the two wires who leads the Voltage to the unit with my 5V Regulator. When i turn on ignition in my car i could measure the 5Volts at the Cradle and when i plug in my Device the Charging LED goes Red and the Symbol in my Today Screen shows the charging. But when i pull out my Device after a while the batterypower goes down very fast and rapid. Why? Is there any conection that has to be done? How many pins are used to charge the Wizard by USB?
Charging current...
How much current is your rig capable of, the stock charger puts out 1 Amp. I know that the wizard is rather finicky 'bout its charging method. Hope this leads you in the right direction...as for pins, i would think that if it says its charging, then your pin outs are ok. It would most likely be about the amperage
The L7805 Regultaor IC fits up to 1.5A .Thats enough i suggest. Now i´ve ordered a real car charger and put the electronic in my carholder. What about grounding? Is ist allowed to put the Audio Ground together with the charging ground or must I divide both grounds?
Thanks so far for your replys...
Hello, I've just bought an emergency charger for my Kaiser. It takes the power from an AA battery and gives the USB voltage in the output. It works great with my Mio A 501, but doesn't work at all with the Kaiser. I did a quick search and found this in a discussion about car chargers:
Are you using the HTC charger or an OEM one?
The HTC charger works all the time the OEM ones don't - the reason being that if you use a normal Mini USB cable, the handsets will only take a charge if there is an indication of a data connection (either than gprs or the cable) - otherwise it won't take a charge.
You can apparently solder a couple of wires together on a normal mini USB cable - but I wouldn't know where to start on that!
Click to expand...
Click to collapse
Now I've already heard of that, for example, a Play Station Portable needs the data wires in the USB grounded in order to charge. Is it the same with Kaiser? (putting three wires together isn't a big deal) Or is there an easier way how to make it charge?
So, I gave it a try and soldered the data wires with the ground wire. But when I try to charge the Kaiser, a yellow led starts to glow (which it didn't with the original cable) and, after a minute or two, the led goes off and Kaiser stops charging. When I turn the Kaiser off and then plug the cable in, the yellow led doesn't go off. However, when I turn Kaiser back on to check the battery meter (after about half an hour), I find out that the battery didn't take any charge at all. So, could anyone tell me what the problem is?
thanks, Mike
PS.: Adding some photos of the wires...
Probably because of the voltage...
Hey!
Have you checked the output voltage of this charger? Standard charger outputs 5V. If yours outputs less - the battery won't charge; if outputs more - you may "burn" your PDA chipsets
5V - 5.5V is safe range.
I found this on thinkgeek.
http://www.thinkgeek.com/gadgets/cellphone/b43f/
It says for iPhone, but sure it would work just fine with other devices that have issues.
had a same problem but using it in the car...
when i got my tytn2 i immediately bought a car charger and the salesman told it's an original one, said output 5v 1A.. when using in the car it charged for a minute or two and went off... than i got from ebay a micro usb 1A charger (used for iPhone too) and tried in the car-> it work flawlessly
Hi. I've solved the problem of using other chargers with GT.
Like Apple, Samsung used a little trick with their chargers.
To charge your GT with any usb charger you have to make a little adapter.
Usb pinout:
gnd d- d+ 5v
To work you must short d+ and d-.
From 5v use a 33k resistor to d+/d-.
From gnd use a 10k resistor to d+/d-.
If you have multimeter you should obtain ~4v between 5v and d+/d-; and ~1v between gnd and d+/d-.
I tested it and it's working.
Hi, it's not a trick but a standard. You only need to short d+ with d-, the resistors are not needed. Just be sure that the charger outputs closest to 5v possible, around 5.2~3 usually work for everything. About 5.6v and it start not to work on some devices, like apple..
Maybe, I have to test that
I know it's not a trick, I should wrote "trick".
For example GT adapter outputs 5.31v.
Apple adapter worked with 1 22k resistor between d- d+.
WarlockM said:
Hi. I've solved the problem of using other chargers with GT.
Like Apple, Samsung used a little trick with their chargers.
To charge your GT with any usb charger you have to make a little adapter.
Usb pinout:
gnd d- d+ 5v
To work you must short d+ and d-.
From 5v use a 33k resistor to d+/d-.
From gnd use a 10k resistor to d+/d-.
If you have multimeter you should obtain ~4v between 5v and d+/d-; and ~1v between gnd and d+/d-.
I tested it and it's working.
Click to expand...
Click to collapse
WarlockM said:
To charge your GT with any usb charger you have to make a little adapter.
Click to expand...
Click to collapse
How can you do that? You need an extra device adapter? Please explain.
I've tested with d-/d+ shorted and it's not working.
@MizGarfield if u have 1 usb extension cable u can cut it on half.
Tie together white and green wires.
Tie black wires and conected to that 1 end of 10kohm resistor, the other end tie it to green/white wire.
Same to red wires but use 33kohm resistor.
See att. Sry for drawing.
bookmarking this for later use
WarlockM said:
I've tested with d-/d+ shorted and it's not working.
@MizGarfield if u have 1 usb extension cable u can cut it on half.
Tie together white and green wires.
Tie black wires and conected to that 1 end of 10kohm resistor, the other end tie it to green/white wire.
Same to red wires but use 33kohm resistor.
See att. Sry for drawing.
Click to expand...
Click to collapse
You don't need that for modern devices has i told you. It did not work because you did it wrong. I have all my usb chargers working the new way, you even have wikipedia talking about it. You have to cut the data + and - on the power supply from the female usb port and short only the female d+ and d-. Trust me it works and it is alot simpler.
Edit : from wikipedia "The Dedicated Charging Port shorts the D+ and D- pins with a resistance of at most 200 Ω. The short disables data transfer, but allows devices to detect the Dedicated Charging Port and allows very simple, high current chargers to be manufactured. The increased current (faster, 9 W charging) will occur once both the host/hub and devices support the new charging specification."
""As of June 14, 2007, all new mobile phones applying for a license in China are required to use the USB port as a power port.[35][36] This was the first standard to use the convention of shorting D+ and D-.[37]""
http://apple.slashdot.org/story/10/08/03/1743240/Hardware-Hackers-Reveal-Apples-Charger-Secrets
""We all love to call out Apple when they design deliberate incompatibility into their devices, but there is a perfectly valid technical reason for what Apple is doing here, and, in fact, they are following a USB specification (which LadyAda unfortunaterly didn't even test).
Without data communications or when suspended, devices may legally draw no more than 2.5mA from a host, which is useless for charging. In fact, even if you're generous and pretend they're connected, devices are not allowed to draw more than 100mA without negotiating for a higher current, which requires actually talking to the host, and 100mA is still too little to charge properly. 500mA is the maximum allowed by the USB spec, but devices must negotiate it (there may be too many devices on the bus for negotiation to succeed).
Before there was a spec for "dumb" USB chargers, Apple used the resistors as a sentinel to avoid drawing too much current from undersized chargers in order to avoid damaging the host. This is a hack, but it works, and honestly, we're smart enough to figure out a couple resistors on the data lines. It's not like they're using crypto auth on the charger. They have a perfectly valid reason to do this. Devices which charge from "dumb" chargers aren't following the spec, though this is a common industry practice.
As it turns out, the USB-IF came up with a USB Battery Charging spec [usb.org]. The spec is long and boring, but it boils down to: short together the data lines (no resistors required) and you indicate that you're a dumb charger that can supply anywhere from 0.5A to 1.5A.
Guess what happens when you short the data lines of an iPhone 3G and supply 5V [marcansoft.com]. Did Apple just follow a standard? Incredible!
(Yes, I'm not following the USB spec there by in turn using a USB cable to supply the 5V and not negotiating over its data lines. I didn't feel like grabbing a dedicated 5V PSU for the shot, so sue me.)"""
http://marcansoft.com/transf/iphonechg.jpg
ok ??? no need for resistors, only 5.3V MAX and d+ and d- shorted
Thnx for the tip gonna try this later on my sanyo eneloop power booster tried it yesterday without this mod and it doesn't charge so gonna look for a AF to AF converter and modify it to gound the D+ and D-
@adolfotregosa
I tried again shorting d-d+, with iphone it works but with GT it's not working.
I use BatteryWatch and it is saying Not Charging. It's detecting the connection like usb port but is not. I use some device build by myself with 1 amp capabilities. D- and D+ r free of any connection and i can do with them what i want.
I dont say you r wrong but it's not working with GT.
Sent from my GT-P1000 using XDA App
but smt is wrong on your custom setup, voltage ??
EDIT: i just measure the original charger and it has no resistance between the data and power pins.
I think i know what could be wrong, when you plug in the Tab and it says not charging, how many volts have you got at that time ?
The original charger is very good because when it not charging the tab it has 5.3x volts but when you plug it in it lowers to 4.8x V Max and that is very good ! most chargers tend to lower much more (bad quality or just not powerful enough) and that is what causes the not charging messages on the tab or other devices.
Well i rest my case on this.
My device with no load it have 5.21v and with load 5.03v so it's not from him and i have another supply 5v/12 amp and it's doing the same (not charging, only with data shorted).
When u r trying to measure the original ps u can read ~7k between gnd and data but from 5v to data u cant because it have some capacitors.
Maybe samsund did something else, i have to try, maybe data pins drawing some current (mA) and that's why it's not working with only shorting them.
For the moment it's the only (working) solution i've found and i'm happy with it .
P.S. If i'm not finding anything else the last resort will be to open the original ps
Sent from my GT-P1000 using XDA App
USB Charger
This is what worked for me.
Items Needed:
USB Extension Cable
33k-Ohm Resistor (Shack Part No. 271-1129)
10k-Ohm Resistor (Shack Part No. 271-006)
Steps:
1. Cut USB Extension Cable in half, lets name the 2 halves, the half you will plug into the power suppy will be called "Cable A" and the half that you plug into the Galaxy Tab Data Cable will be called "Cable B"
2. On 'Cable A" strip outer plastic to expose all wires within, eliminate Green and White on this cable only as it will not be needed, leaving you with only the Red and the Black Cables
3. On "Cable B" strip outer plastic to expose all wires within, this should leave you exposing all 4 wires
4. On "Cable B" strip both the Green and White wires and join thes 2 wires with the 2 resistor ends (you should be using the resistor ends that have the red band with these wires), these can be joined by either soldering or just twisting together.
5. Strip Red wire from both cables and join together with the 33k-Ohm Resister (this will be the larger of the 2 resistors and should also be the end with the Gold Band) and as well join these together with solder or just twisting together.
6. Repeat the above process with the Black wires and 10K-Ohm Resistor.
7. No finally use Electrical Tape or Shrink Tubing to cover all your work.
This worked using it on a Champtek 5v 2.1a USB Car Charger and Home Charger. Also worked with iPhone charger. Also works with Original Galaxy Tab.
Hope this helps out.
May I just ask some clarifying questions?
rick75204 said:
This is what worked for me.
...
4. On "Cable B" strip both the Green and White wires and join thes 2 wires with the 2 resistor ends (you should be using the resistor ends that have the red band with these wires), these can be joined by either soldering or just twisting together.
Click to expand...
Click to collapse
Does it matter WHICH resistor you join to which of these two wires?
rick75204 said:
5. Strip Red wire from both cables and join together with the 33k-Ohm Resister (this will be the larger of the 2 resistors and should also be the end with the Gold Band) and as well join these together with solder or just twisting together.
Click to expand...
Click to collapse
So that you have effectively bridged the red wire with 30K-Ohms to one of either green or white running to the TAB?
rick75204 said:
6. Repeat the above process with the Black wires and 10K-Ohm Resistor.
Click to expand...
Click to collapse
And bridged the black wire with 10K-Ohms to the other of either green or white running to the TAB?
Would this be an accurate picture, with the 33K Ohm Resistor on the left, and the 10K Ohm Resistor on the right?
I think the intention was that you short the green and white wires together: so you are connecting both wires to both resistors.
That way the two data lines are both held at a fixed voltage of about 1.2V
Thanks, that clarified it.
I noticed today that if I connect my Tab to my keyboard (standard Apple USB KB with keypad, connected to a circa 2006 iMac), the device started charging according to battery stats. When it was plugged in it was at 48% and it ended up at around 60% after a few hours. Am I being deceived or something? I was under the impression that it would only charge if connected to the mains charger. Well I guess I'll see how long it runs now it's off the leash and see if it lasts till the morning (left my charging cable at work - D'oh!).
No, it definitely does charge even when it says it isn't - just slowly. I've got a 2A non-official USB charger that charges it up pretty quick, but still says it isn't charging. If the screen is off, it will even charge off one of those tiny Kindle chargers that must be delivering less than 500mA, but *really* slowly.
Clarify
Sorry guys, only a clarification.
As far as i understood:
the GT DOES charge with *any* charger (or connection to PC);
if you use the original charger (2Amp), it charges showing the charging-icon;
if you use a non-original charger, it charges in any case but NOT showing the charging-icon and depending on the charger power (even 1Amp charges, or 500mAmp, *VERY-REALLY* slowly);
if you use a non-original charger with the two resistors (33k + 10k) it charges showing the icon (even with a 1Amp).
Can anybody confirm if i understood well?
Thanks!!
eiem said:
Sorry guys, only a clarification.
As far as i understood:
the GT DOES charge with *any* charger (or connection to PC); Yes but slower than the original charger
if you use the original charger (2Amp), it charges showing the charging-icon; Yes, exactly
if you use a non-original charger, it charges in any case but NOT showing the charging-icon and depending on the charger power (even 1Amp charges, or 500mAmp, *VERY-REALLY* slowly); Yes.
if you use a non-original charger with the two resistors (33k + 10k) it charges showing the icon (even with a 1Amp). Depends, i get various results even though i am using the mod since day 1.
Can anybody confirm if i understood well?
Thanks!!
Click to expand...
Click to collapse
Thats it for now.
It seems that the Tab could recognize the status of the usb connection by measuring the usb data rx/tx wire level. If it is not shorted, the "pluged in but not in charging" status will appear, as the mismatch voltage of the usb connection is made.
Sent from my XT701 using XDA App
I have been closely watching these threads and found some mixed results.
http://forum.xda-developers.com/showthread.php?t=1791717
http://forum.xda-developers.com/showthread.php?t=1780211
http://forum.xda-developers.com/showthread.php?t=1793059
http://forum.xda-developers.com/showthread.php?t=1781680
http://forum.xda-developers.com/showthread.php?t=1784322
http://forum.xda-developers.com/showthread.php?t=1785976
So, I conducted some experiments and the results are below. For those of you that don't care for the data, you can scroll down to the CONCLUSION.
Some of the information presented here are derived directly from the above threads and from the Internet. All values are approximate and measured using a digital multimeter. Some of you may already know but for the sake of other readers, I will be using the following terminology and acronyms.
AWG = American Wire Gauge. The thickness or the diameter of an electrical conductor(s) within a single wire. Most flexible wires contain multi-stranded conductors instead of a single solid conductor. The important thing is, as the AWG number DECREASES, the thickness of the conductor INCREASE. Thicker wires can carry more current
OEM = Original Equipment Manufacturer
Connector Pigtail = A connector with its individual wires exposed and part of the wire's insulation removed as a means to perform electrical measurements.
(XX / YY) = "XX" represents the AWG of the data wires (D+ / D-). "YY" represents the AWG of the power / ground wires (+5v / GRN). Some USB cables will be imprinted with its rating on the cable itself such as "28AWG/1P 26AWG/2C". I will be referring to this cable as (28/26) meaning the data cables are 28AWG and the power / ground wires are 26AWG
USB data wires = The White wire (D-) and the Green wire (D+) contained within the USB cable.
Testing Jig:
1. 12 inch USB A male to USB A female extension cable (28/28) cut in half to produce 1-USB A Male pigtail and 1-USB A Female pigtail.
2. 12 inch MicroUSB B male to MicroUSB B female extension cable (28/26) cut in half to produce 1-MicroUSB B Male pigtail and 1-MicroUSB B Female pigtail. http://www.ebay.com/itm/Micro-USB-B..._USB_Cables_Hubs_Adapters&hash=item3f1497b3e1
3. 18 inch test leads (18 AWG). http://www.harborfreight.com/18-inch-low-voltage-multi-colored-test-leads-66717.html
I used 3 different MicroUSB cables and 1 USB A extension cable:
OEM = 3 feet, unknown AWG (not imprinted on the cable), impedance of power/ground wires = 0.2 ohms, length of MicroUSB male end = 6 mm, resistance / continuity check reveals nothing special. It is a standard MicroUSB cable.
Monoprice = 6 feet, (28/24), impedance of power/ground wires = 0.2 ohms, length of MicroUSB male end = 5.5 mm, resistance/continuity check reveals nothing special. I purchased 2 of this cable. The MicroUSB male end on the other cable measured 6 mm. http://www.monoprice.com/products/p...=10303&cs_id=1030307&p_id=5458&seq=1&format=2
Amazon = 6 feet, unknown AWG (not imprinted on the cable), impedance of power/ground wires = 0.5 ohms, length of MicroUSB male end = 5.5 mm on both, resistance/continuity check reveals nothing special. http://www.amazon.com/Case-Star-Bla...id=1344416273&sr=8-70&keywords=microusb+cable
Generic extension cable = USB A male to USB A female, 6 feet, (28/24), impedance of power/ground wires = 0.2 ohms.
I used 4 different chargers:
OEM = Rated at 2 A, resistance between data pins = 0.5 ohms (shorted).
iPhone 4 OEM charger = rated at 1 A, resistance between data pins = 53100 ohms.
Belkin = 2 port, each port rated at 500 mA, resistance between data pins = 58000 ohms. http://www.amazon.com/Belkin-Mini-Surge-Protector-Charger/dp/B0015DYMVO
AT&T Car charger = An iPhone charger with an auxiliary USB charging port, unknown rating, resistance between data pins = not connected (infinity).
Amperage readings measured at the cable using connector pigtails with test leads and with a completely drained Nexus 7 (Surprising Results!!!):
OEM charger + OEM cable = Charges at 821mA AND displays AC charging.
OEM charger + OEM cable with the data wires disconnected (open)= Charges at 821mA BUT displays Discharging.
OEM charger + OEM cable + Generic extension cable = Charges at 631 mA AND displays AC charging.
OEM charger + OEM cable with the data wires disconnected (open) + Generic extension cable = Charges at 631 mA BUT displays Discharging.
OEM charger + Monoprice cable = charges at 823 mA BUT displays Discharging.
OEM charger + Monoprice cable with data wires shorted = charges at 823 mA AND displays AC charging.
OEM charger + Monoprice cable + Generic extension cable = charges at 635 mA BUT displays Discharging.
OEM charger + Monoprice cable with data wires shorted + Generic extension cable = charges at 635 mA AND displays AC charging.
OEM charger + Amazon cable = charges at 451 mA BUT displays Discharging.
OEM charger + Amazon cable with data wires shorted = charges at 451 mA AND displays AC charging.
OEM charger + Amazon cable + Generic extension cable= charges at 258 mA BUT displays Discharging.
OEM charger + Amazon cable with data wires shorted + Generic extension cable= charges at 258 mA AND displays AC charging.
iPhone 4 OEM charger + all above cable combination = charges at a maximum rate of 635 mA BUT displays Discharging. Increasing the length of the cable decreased the charging rate.
iPhone 4 OEM charger + all above cable combination + data wires shorted = charges at a maximum rate of 635 mA AND displays AC charging. Increasing the length of the cable decreased the charging rate.
Belkin charger + all above cable combination = charges at 259 mA BUT displays discharging. Increasing the length of the cable did not change charging rate.
Belkin charger + all above cable combination + data wires shorted = charges at 259 mA AND displays AC charging. Increasing the length of the cable did not change charging rate.
AT&T car charger + all above cable combination = maximum charging rate of 830 mA BUT displays discharging. Increasing the length of the cable decreased the charging rate.
AT&T car charger + all above cable combination + data wires shorted = maximum charging rate of 830 mA AND displays AC charging. Increasing the length of the cable decreased the charging rate.
NOTE: With the Nexus 7 powered off, all combinations of above chargers and cables, regardless of whether the data wires were shorted or not displayed the charging indicator.
CONCLUSION:
1. Nexus 7 OEM charger is nothing special, just the data pins are shorted.
2. Nexus 7 OEM MicroUSB cable is nothing special. It is a standard MicroUSB cable.
3. Any USB car/wall charger should charge the Nexus 7.
4. Nexus 7 will charge regardless of whether it displays "AC Charging" or not.
5. The charging rate is dependent on the capacity of the charger and the total charging circuit impedance (lower the impedance the better).
6. Increasing the length of the cable increases the charging circuit impedance and decreases the charging rate.
SOLUTION:
1. Use a high quality, high amperage USB charger.
2. Use a cable with an AWG of (28/24) or lower.
3. Cables longer than 6 feet is not suggested regardless of lower AWG as the connectors itself (especially at the MicroUSB end) will be the bulk of the impedance for that cable.
4. If you desire to have "AC Charging" be displayed on your Nexus 7, short the data wires/pins. Remember, this has no effect on the charging rate.
5. If you plan to modify the charger, take a resistance measurement of the data pins first (unplugged), any readings other than 0 ohms or infinity (open or not connected), you will need to isolate the data pins from the charging circuit prior to shorting. If you do not, you risk damaging the charger and/or your precious Nexus 7.
6. If you plan to modify the cable, short the data wires at the MicroUSB end and leave the data wires open or not connected at the charger end. Use heat shrink to insulate the exposed conductor of the data wires.
7. Make sure the MicroUSB connector end is about 6.0 mm in length.
Thanks for this great post.
I have been switching back and forth all morning between the oem cable/charger and a blackberry charger with removable usb cable. This post solves the riddle of why the oem charger with the longer blackberry usb cable was charging demonstrably slower than the oem combo (at least according to my battery widget).
Thank you for the detailed information. This was driving me nuts.
I am surprised with the charging rate of 821mA ...
OEM charger + OEM cable = Charges at 821mA AND displays AC charging.
Click to expand...
Click to collapse
So, basically, we don't really need 2A charger?
Will charging my phone (HTC Desire S) with the Nexus 7 charger have any damage on my phone?
generationgav said:
Will charging my phone (HTC Desire S) with the Nexus 7 charger have any damage on my phone?
Click to expand...
Click to collapse
No, there's current limiters that keep it at a safe level.
Sent from my LG-P999 using xda app-developers app
Thanks for all the info, that was what we really needed.
Now.. what's our best source for a quality cable with long enough connector for a reasonable price?
Edit: I think I'll short some data pins and trim some hoods back with a knife tonight.
Awesome. Perhaps I don't need to replace my car setup. I've shorted out the DATA pins IN the charger. My Galaxy Nexus reads it as AC charging now but the N7 doesn't even detect it. I'll throw it on the charger on my way home from work and see if it does in fact charge it.
This is exactly the way my Samsung Galaxy Tab behaves. It was dead when I got it (used) and none of my chargers would work (display charging). I found that even if it didn't say charging, it was, in fact, charging.
So technically the unit is sucking down the juice but telling us it isn't. Perhaps some devs can figure out how to force it to display charging any time it grabs juice. Just seems like a software bug. There is no reason my Galaxy Nexus see's my car charger as AC (1A) but nothing on the N7.
Glad you did this test. It proves very helpful.
gogol said:
I am surprised with the charging rate of 821mA ...
So, basically, we don't really need 2A charger?
Click to expand...
Click to collapse
You do need a 2A charger. All testing was done when the N7 was completely dead. I suspect when the battery is at like 50%, the charging rate will peak to 1300-1500mA and start decreasing when the battery nears its capacity.
I didn't make measurements at the various charge stages as this experiment was just about whether it charges with the various chargers and cable combinations.
janedoesmith: When you said that the Nexus 7 was completely drained, does that mean that it was turned off? If it was off, then would you mind performing the stock charger test with it turned on (and maybe something like 50% charge)? I'm just curious to see if it draws more current when turned on. Would you also mind testing charging from your computer's USB port? Since your testing has shown that the Nexus 7 tries to draw greater than 500mA even when the data pins are open, then it means that it doesn't follow USB charging specs (with open data pins, a device should never try to draw more than 500mA).
AZImmortal said:
janedoesmith: When you said that the Nexus 7 was completely drained, does that mean that it was turned off? If it was off, then would you mind performing the stock charger test with it turned on (and maybe something like 50% charge)? I'm just curious to see if it draws more current when turned on. Would you also mind testing charging from your computer's USB port? Since your testing has shown that the Nexus 7 tries to draw greater than 500mA even when the data pins are open, then it means that it doesn't follow USB charging specs (with open data pins, a device should never try to draw more than 500mA).
Click to expand...
Click to collapse
The tests were performed with the N7 powered on and powered off. The current draw was the same for both conditions.
My N7 is currently fully charged. I will make one additional amperage measurement when it discharges to 50%.
Basically, a charging circuit cannot draw no more than what the charger can supply. When my N7 discharges to 50%. I'll make some measurements from the computer's USB port.
I understand about not being able to provide more than the charger can supply. I brought up the USB charging specs issue because some computers will shut down if the connected device tries to draw more than 500mA, which is why there's supposed to be a difference between having the data pins bridged or not. Open is supposed to make the device think that it's connected to a computer's USB port, meaning it shouldn't try to draw over 500mA. Bridged is supposed to signal that it's ok to draw up to 1A because it's supposedly connected to a dedicated charging port.
AZImmortal said:
I understand about not being able to provide more than the charger can supply. I brought up the USB charging specs issue because some computers will shut down if the connected device tries to draw more than 500mA, which is why there's supposed to be a difference between having the data pins bridged or not. Open is supposed to make the device think that it's connected to a computer's USB port, meaning it shouldn't try to draw over 500mA. Bridged is supposed to signal that it's ok to draw up to 1A because it's supposedly connected to a dedicated charging port.
Click to expand...
Click to collapse
I'm no expert when it comes USB specifications but this is what I suspect:
When a device connects to a host via USB, the data lines are no longer open and it becomes and active data circuit. Once a handshake takes place, the device and the host knows what its roles are and the N7 displays " USB charging". Due to this active data circuit, I will not be disconnecting nor shorting the data lines when I perform the additional tests when my N7 discharges to 50%. I will be just measuring amperage with various cables and lengths.
I picked up one of these: http://www.monoprice.com/products/p...=10303&cs_id=1030307&p_id=5458&seq=1&format=2
Has worked without a concern of charging or not and seems to feed sufficient current to charge the device in a timely manner. I know this isn't scientific, but wanted to provide the cable that I am using without issue.
Mustang7302 said:
I picked up one of these: http://www.monoprice.com/products/p...=10303&cs_id=1030307&p_id=5458&seq=1&format=2
Has worked without a concern of charging or not and seems to feed sufficient current to charge the device in a timely manner. I know this isn't scientific, but wanted to provide the cable that I am using without issue.
Click to expand...
Click to collapse
Thank you. That cable was used in the experiment. Any 6 foot cable with a AWG of (28/24) will work flawlessly.
janedoesmith said:
Thank you. That cable was used in the experiment. Any 6 foot cable with a AWG of (28/24) will work flawlessly.
Click to expand...
Click to collapse
Not necessarily - it seems that a lot of MicroUSB cables have male connectors that are excessively short. These interfere with the N7's case.
However, those Monoprice 24/28AWG "premium with ferrite" cables work flawlessly for me. I have a whole pile of them.
I have had the following chargers work properly with my N7 and cables like the Monoprice ones:
Samsung Tab 10.1 charger - Shorts D+ and D- and additionally floats them at 1.8 with a weak voltage divider (the latter is not necessary for N7, but it happens to be a method that is compatible with standards-compliant devices like the N7 and all of my phones)
Scosche iPad car charger modified so that it behaves just like the Samsung Tab charger (Shorted D+ and D-, removed one of the pullup resistors in the voltage divider)
Galaxy Note charger (shorts D+ and D-)
Old HTC charger (shorts D+ and D-)
Using CurrentWidget (my kernel is patched so it works - see http://review.cyanogenmod.com/#/c/20891/), I see the following:
Tab 10.1 charger seems to charge faster than stock. This doesn't make sense as when unloaded, the 10.1 is dead-on at 5.0 volts, and the stock charger is 5.1 volts. However the stock charger may behave differently under load. This may just be test variance - CurrentWidget is reporting current into the battery, so this will vary depending on CPU/screen power usage. I'm still looking to see if there is a separate current measurement device somewhere that will report USB input current.
The Galaxy Note charger reports significantly lower charging current than the stock charger or Tab 10.1 charger - not surprised, it's only rated 1.0A
Entropy512 said:
janedoesmith said:
Thank you. That cable was used in the experiment. Any 6 foot cable with a AWG of (28/24) will work flawlessly.
Click to expand...
Click to collapse
Not necessarily - it seems that a lot of MicroUSB cables have male connectors that are excessively short. These interfere with the N7's case.
Click to expand...
Click to collapse
The length of the MicroUSB connector was covered in the first post.
Interesting results, what did you use to measure the mA rate? Is it possible from a battery app? I have a kill-a-watt plug lying around though, will see tomorrow if it can display mA but I doubt it.
Salty Wagyu said:
Interesting results, what did you use to measure the mA rate? Is it possible from a battery app? I have a kill-a-watt plug lying around though, will see tomorrow if it can display mA but I doubt it.
Click to expand...
Click to collapse
I used a digital multimeter and measured it at the cable.
Great topic! Thank you!
Has anyone torn down a car charger to direct wire the car charger into a vehicle?
Why not just use an inverter and plug it into that?
Car Charger
partin_us_99 said:
Has anyone torn down a car charger to direct wire the car charger into a vehicle?
Click to expand...
Click to collapse
Why tear one down. You would have to completely redesign and rebuild it. The plug and wire is about all you would be able to use.
This is kinda pricey but I think this is what you want:
powerstream. com/ADC-p006. htm PST-YD100W
There is a couple of things to consider.
1. A car electrical system typically runs from about 9 volts on the low side to about 15 volts on the high side taking in consideration noise spikes maybe more in very short spikes.
2. your tablet is designed to run very close to 12 volts probably + or - 5% or 11.4 to 12.6 volts it may work okay up to + & - 10% or may not.
3. the adapter must be able to supply 12 volts @ at least 1.5 amps - you can find this value on your AC Adapter that came with your tablet.
So while the car may still run down to ~10 volts the tablet would likely have problems. Regulators normally take the input voltage and use a couple of volts to regulate. So if the input is 12 volts the output is going to be around 10 volts - to low for the tablet to work reliably. In most cases the car regulator when charging outputs around 14.4 volts. That on the other hand would work. One solution and the one I believe is used by the device from the power stream website is to use a voltage multiplier or DC to DC converter that amplifies the voltage then regulates it down to what is needed.
By the way it also comes with a bunch of plug adapters to match the jack on the tablet.
Regards,
- Phil
Found an article on hard wiring it with an add a circuit so I'm gonna do that. This isn't my first car wiring rodeo so it'll work. Thanks for all the replies I'll keep y'all updated
Sent from my GT-N7005 using xda app-developers app
I used an old Nokia 636 plug that I had that has the 3X1mm tip needed and spliced it into a mini usb car adapter, that was for my Tilt2 at the time, right after the fuse so I could power my phone and A500 simultaneously. It's been working fine for over a year and a half, I still use the Tilt2 as my dash cam. The Tilt2 plug also has an extra full usb port and friends and family will occasionally use that to charge their phones on trips so that one plug powers 3 devices and works fine.
So go for it, you will be fine.