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  • 1 Post By hoangde
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  • 1 Post By geekpeter
  1.    #1  
    Following is the detail:

    Sleep mode:
    5.3 Vdc @ 200mA

    Active mode:
    5.3 Vdc @ 1.1A

    Off mode:
    5.3 Vdc @ 150mA

    Based on the above info, I built a car charger, computer charger, solar panel charger for my Touchpad. The Touchpad is charging (lightning bolt icon displays).

    You can buy any micro USB car charger (or micro USB cable) on eBay (as long as output is 5 VDC +- 5% and minimum 400ma), modified so data line is 2.6 Vdc.

    If your Touchpad at Off mode, you can use car charger or even PC USB port to charge Touchpad.

    I did charged on PC and car charger for a week without any issue. Also successfully with Solar panel (Output 5Vdc @ 800 mA).

    Again, fyi only if you want to build one for yourself. Beware that many ad. for TOUCHPAD car charger (only power to Touchpad but without charging battery). If you decide to buy one, ensure to ask for TouchPad battery charger, NOT TRICKLE Charging as advertise.
    Touchpad required 2.6 Vdc present at data line to switch to charging mode. Without switch to charging mode, any input power to power lines in TOUCHPAD just as a supplemental voltage.
    Better off to build one for you or wait for a while before resellers modify as schematic below. Do not waste money to buy something that will not work. Touchpad needs build in circuit below in usb cable/cigarette adapter to switch to charging mode.

    Notes:
    1st image is the schematic
    2nd image is charging with car charger (look for lightning bolt icon).
    3rd image is charging with homemade AC adaptor.
    4th image is connect with solar panel...under fluorescent light so not enough output to charge unit.
    Attached Images Attached Images
    Last edited by hoangde; 11/06/2011 at 05:21 PM.
    errhead likes this.
  2. #2  
    pictures?
  3. #3  
    So, same 'trickle charge' rate as was being worked around here?

    http://forums.precentral.net/hp-touc...ouchpad-8.html

    Good work.. (if it's sunny!).

    Last edited by Mutoidi; 11/04/2011 at 01:48 PM.
  4. #4  
    Quote Originally Posted by hoangde View Post
    Following is the detail:

    Sleep mode:
    5.3 Vdc @ 200mA

    Active mode:
    5.3 Vdc @ 1.1A

    Off mode:
    5.3 Vdc @ 150mA

    Based on the above info, I built a car charger, computer charger, solar panel charger for my Touchpad. The Touchpad is charging (lightning bolt icon displays).

    You can buy any micro USB car charger (or micro USB cable) on eBay (as long as output is 5 VDC +- 5% and minimum 400ma), modified so data line is 2.6 Vdc.

    If your Touchpad at Off mode, you can use car charger or even PC USB port to charge Touchpad.

    I did charged on PC and car charger for a week without any issue. Also successfully with Solar panel (Output 5Vdc @ 800 mA).

    Again, fyi only if you want to build one for yourself.
    You seriously should consider an engineering career for webOS. They could use someone like you.
    - Save webOS
    Last edited by fred1955; 11/08/2011 at 09:54 AM.
    ka1 likes this.
  5.    #5  
    Will post pictures in the weekend. I am at work right now
  6. #6  
    Quote Originally Posted by Mutoidi View Post
    So, same 'trickle charge' rate as was being worked around here?

    http://forums.precentral.net/hp-touc...ouchpad-8.html

    Good work.. (if it's sunny!).

    If you want to charge it while it is active (turned on), you'll need a 2.0 Amp charging device as is explained in that same thread. Based on the specs in this thread, it needs 1.1 Amps while active so a 1 Amp charger still won't do for charging while in use, only for trickle charging while turned off.

    Wheel_nut will build and sell 2.0 Amp car chargers for you including shipping for about $25 ea. See the thread above.
    ----------------------------------------------------------------------------------------------------
    I am an AT&T employee and the postings on this site are my own and donít necessarily represent AT&Tís positions, strategies or opinions.
  7. #7  
    Quote Originally Posted by hoangde View Post

    You can buy any micro USB car charger (or micro USB cable) on eBay (as long as output is 5 VDC +- 5% and minimum 400ma), modified so data line is 2.6 Vdc.
    This is NOT correct. Besides requiring the D+ & D- lines held at ~ 2.6V, the TouchPad is fussy about the impedance of the potential divider requiring ~ 300K Ohms. The Apple iPad spec units have separate potential dividers at ~ 50K Ohms on each of the Data lines but the Data Lines are NOT bridged. The other charger that I initially recommended in the other thread has the Data lines bridged but at lower impedance.

    The only verified way to charge the TouchPad at full pelt is to emulate the Barrel Power Supply by bridging the Data lines and applying a Potential of ~2.6V with 300K to +5V and 240K to Gnd.

    With thanks to Wilywyrm for breaking into his Barrel PSU to discover this.
    Last edited by Wheel_nut; 11/04/2011 at 06:45 PM.
  8.    #8  
    No need to get diff. value for voltage divider circuit.

    Based on the HP charger spec. unit, data lines bridged and required 136K at each power line to get 2.6Vdc. (I said: "modified so data line is 2.6 Vdc).

    So to get 300K or 240K is over the line and different voltage at ground and positive may cause voltage unstable.

    Again, this is specification from HP wall charger unit that I use. Diff. value may just do the job fine.

    If you need circuit diagram to build, just let me know.
    Last edited by hoangde; 11/04/2011 at 05:11 PM.
  9. #9  
    Quote Originally Posted by hoangde View Post
    No need to get diff. value for voltage divider circuit.

    Based on the HP charger spec. unit, data lines bridged and required 136K at each power line to get 2.6Vdc. (I said: "modified so data line is 2.6 Vdc).
    Could you attach a copy of this "HP charger spec" please
    So to get 300K or 240K is over the line and different voltage at ground and positive may cause voltage unstable.
    Please could you explain what you mean. The Resistor values were determined by opening the HP Barrel PSU and examining the circuit.
    Again, this is specification from HP wall charger unit that I use. Diff. value may just do the job fine.

    If you need circuit diagram to build, just let me know.
    Yes please.
  10.    #10  
    I will post circuit diagram tonight when I am home.

    For detail how to do:
    1./ Search in eBay for solar panel with 5v output. I do search: "brunton solar 5".
    2./ Get a micro usb cable. eBay search: "micro usb cable"
    3./ Modified micro usb cable.
    4./ Now with this modified usb cable, you can use with:
    solar panel
    5./ OR (search eBay for : "usb cigarette lighter") car charger to charge Touchpad (ensure cigarette lighter has more than 1.1 A).
    6./ OR USB port on your PC or Laptop (due to USB port at computer limited to 500 mA, ensure Touchpad at OFF mode).
    Last edited by hoangde; 11/04/2011 at 06:32 PM.
  11. #11  
    Quote Originally Posted by fred1955 View Post
    You seriously should consider an engineering effort for webOS. webOS needs more good engineers like yourself.
    - Save webOS
    Funny. You really think that HP/Palm do not have competent engineers who can figure this out? Don't forget there is business/money making business behind all these.

    If you are an iPhone user, you probably know that iPhone uses 5v chargers. However, when you use some of the generic 5v chargers/cables with your iPhone, apple will snug you with a message declaring that your charger sucks and disables the sound on your iPhone. Well, is it really so? Remember apple needs to sell its accessory product lines (often at a premium price).

    Making small things like charger etc incompatible with cheap products can be used as a business tactic to ensure the thriving of the eco system something like ***pad creates.

    Another thing to remember is that you WILL get far less than perfect products in their 1st generation. Businesses need product life cycle extension (don't confuse this with the life of the product you purchased) to ensure long term profitability. They WILL not give you all the goodies they have in their disposal in a single product.
  12.    #12  
    If you are not quite sure about this, feel free to contact me. I will lay out Build of material so you can do it.
  13. #13  
    Hoangde, Your measurement of 136K from the bridged Data lines to both +5V and Gnd of the Barrel PSU is correct. However, your conclusion drawn from these measurements is wrong.

    Inside the Barrel PSU are three resistors.
    1) 300k from D+- to Gnd
    2) 240K from D+- to +5V
    3) 1000 Ohms from +5V to Gnd. (this is a bleed resistor to prevent instablity under no load)

    If you consider that an Ohmmeter placed between D+- and Gnd will read 240K in parallel with 300k + 1000 Ohms = ~136K

    Similarly, an Ohmmeter placed between D+- and +5V will read 300K in parallel with 240K + 1000 Ohms = ~136K

    Whereas your assertion that 136K (which is NOT a preferred value) to both +5 and Gnd works, you will find that it doesn't charge the TouchPad at full rate although the display may show the lightening strike.

    I have already suggested that the resistors can be applied external to the PSU using a USB Male A to Female A adapter. Your schematic is OK.... it is the Resistor values that are wrong. THe values of 240K and 300K were posted by Wilywyrm who broke open his Barrel Power Supply to examine it and posted the findings in the other thread.
    Last edited by Wheel_nut; 11/07/2011 at 06:57 AM.
  14.    #14  
    Wheel_nut !

    Whatever is work, we will more than happy to use it. Resistors values here or there is not my concern. If we can get D line to the voltage level as HP required to switch unit to charging mode is what we wanted.

    Resistance value measured at no load nor any juice remaining, I am quite sure 136K for each line is dead on the target. Also 100 ohms between positive and ground is a killer. No one place that value between power line, it will burn out as fast as you can blink an eye (Is it a cap or must be a cap somewhere in series with it. Purpose of this cap and resistor just for noise control)
    With my schematic, I tested with mine or friends units, all working fine with same or faster charging time compared with HP barrel charger.

    Feel free to help people to build one to use, I just want people to aware that they can build one easily rather than get from eBay that never get TP switch to charging mode.
    Last edited by hoangde; 11/06/2011 at 08:46 PM.
  15. #15  
    I apologise for my error; It was 02:00 in the morning! The Bleed resistor is 1000 Ohms (Component is marked 102) but it doesn't materially affect my calculations.

    BTW, even at 100Ohms, the bleed resistor would only dissipate 0.25W so your (edited at 02:46 a.m.) dramatics are unjustified,
  16. #16  
    oooh if only there was a solar powered version of the HP Case/stand that gave at least some tiny trickle charge.

    add to that 1 day, maybe wed also get something similar to...

    Concept phone charges from your body heat (Wired UK)

    recharging via solar power + body heat recharge + our usual touchstone, ahhh that would be sweet dreams.
    ka1 likes this.

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