2 Replies Latest reply on May 5, 2014 9:58 AM by MediaPlayerFan

    Making Nook HD / HD+ Work with ANY USB Power Source

    MediaPlayerFan

      The Nook HD+ needs a specific voltage (or range of voltages) on the two USB data pins.  These are different voltages than the standard 500ma, 1000ma, or Apple settings.  With the correct voltage on the data pins, a wide range of charging voltage will work.  I tried 4.2V to 5.2V succesfully.

       

      When charging with the stock charger, the voltage on Pin 2 (D-, adjacent to V+) is 0.37V and Pin 3 (D+, adjacent to ground) is the same 0.37V.  I created two resistor voltage dividers to simulate this.  Each divider is:

       

      47K to V+

      3.7K to ground

      The connection between resistors goes to Pin 2 (often the white USB cable wire) and Pin 3 (often the green USB cable wire).

       

      The least destructive way to implement this is with a USB extension cable (one male and one female end).  Cut the cable and connect the resistor dividers to V+, ground, and the data pins going to the Nook HD+.  The data pins to the charger are not connected to anything.

       

      This system worked perfectly with a Power Bank battery and the 2.1A USB output.  I  found it was not necessary with my laptop using the "always on" USB port (Lenovo T410).

       

      Using these dividers, the voltage on data pin 2 is 0.34V and the voltage on data pin 3 is 2.85V.  Data pin 3 is a little surprising and must be driven by the Nook itself.  Regardless, it works and I left well enough alone.

       

      "Works" means the amber light is on indicating charging.  Using the Power Bank battery, the Nook charges up 4% in one hour with the screen and wifi off.  One last comment: There is the possibilty that the Nook HD+ sends a signal to shut off the charger when the battery is fully charged.  If so, using this resistor divider scheme, the power source will not be told to turn off.  On the other hand, my Power Bank battery turns off by itself when the load current approaches zero.

       

        • Re: Making Nook HD / HD+ Work with ANY USB Power Source
          DeanGibson

          MediaPlayerFan wrote:

          The Nook HD+ needs a specific voltage (or range of voltages) on the two USB data pins.  These are different voltages than the standard 500ma, 1000ma, or Apple settings.  .

           

          ...

           


          Once you described "500ma, 1000ma, or Apple settings" as voltages, I stopped reading for serious content.

           

          Students of advanced physics will be interested in the last item as a new unit of voltage (or was it current?)

           

          To everyone else:  All USB devices take the same voltage (5 vDC), with some amount of variation allowed.  This has nothing to do with the current required by the device, which can vary greatly.

           

          As someone who spends a significant amount of time designing consumer power distribution circuits, I can say that using a resistor network to control voltage is, in most cases, a fool's errand.  Devices may work temporarily in such situations, and then fail in other situations.

           

          And for what?  There is absolutely no need for the "modification" in the original message.

            • Re: Making Nook HD / HD+ Work with ANY USB Power Source
              MediaPlayerFan

              There are several posts around the web reagarding the voltages to put on the data pins to support charging Apple devices.  This is typical: 

               

              "Nowadays the iPhone expects a certain voltage on those two pins to decide how much current to absorb from the charger. Putting a 2.0 V voltage on both the pins the iPhone will absorb about 500 mA, while with 2.8 V on D- and 2.0 V on D+ it will absorb about 1000 mA"  There are also schematics for the resistor dividers used.  http://www.instructables.com/id/Modify-a-cheap-USB-charger-to-feed-an-iPod-iPhone/

               

              I don't appreciate the obtuse analysis that somehow implies the voltages on the data pins needed to support certain current supplies on the power pins is somehow mixing the units of current and voltage.  This is not helpful and seems intended to discredit a technically detailed, complete, and working solution.

               

              I did for the Nook HD+ what many before me have done for the Apple devices by providing a soluton customized for the Nook HD / HD+.