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Re: [DVRPTR_V1] Re: power supply

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  • Jim Thisdale
    This method works well, doesn t bypass/defeat the Pi fuse either. Note a good hub won t back-feed power from it s upstream port and the Pi s microUSB
    Message 1 of 14 , Apr 15, 2013
      This method works well, doesn't bypass/defeat the Pi fuse either.
      Note a good hub won't 'back-feed' power from it's 'upstream' port and the Pi's microUSB connector
      doesn't have any data connections, it is strictly power only.

      ---------+ +------------------------
      upstream|<----<|A,USB Raspberry Pi
      | |B,USB
      USB A|>---->|microUSB power only
      HUB B| +------------------------
      C|
      D|>---->[USB, DVRPTR modem, power]<--- 12vdc
      |
      +5|<-- good 5 volt source, 2 or more amps.
      ---------+

      The fuse on the Pi is rated 1A, the Pi itself uses approx .7 amps. So even with a hefty power
      supply, the Pi can theoretically only supply about .25 A total to the USB ports, that is only about
      1/2 of what 1 port should be able to use, so best off to plug any significant load devices into the
      powered hub.
      This layout above works very well.
      -Jim- N1JMM, KB1YPL_B
      Visit my Pi running ircddb, dvrptr, Apache & many other things:
      http://n1jmm.no-ip.org

      On 4/15/13 5:04 AM, Howard Small wrote:
      >
      >
      > Jan
      >
      > Does this mean that if I use a 5V 2A powered usb hub with no devices connected directly to the
      > dvrptr board (all external devices connected to the dvrptr board via the hub), a usb A to usb B
      > cable providing the data link to the board then that would be OK For powering the board? Or is that
      > still not recommended?
      >
      > Howard
      > VK4BS
      >
      > On 15/04/2013, at 17:23, "do1fjn" <dvrptr@... <mailto:dvrptr@...>> wrote:
      >
      >> Hi Pierre,
      >>
      >> --- In DVRPTR_V1@yahoogroups.com <mailto:DVRPTR_V1%40yahoogroups.com>, Pierre Martel
      >> <petem001@...> wrote:
      >> > I know that mine from the german team is running on usb. There was a place
      >> > to jump on yhose board to make it run on usb. But that was just if you
      >> > wanted to run a hotspot with out the ambe board. Like in a repeater or
      >> > such...
      >>
      >> USB powering is not recommended for repeater / unmanned operation. If you use the board as Hotspot
      >> w/o Addons then you can use 5V USB.
      >>
      >> The weak point of my design is the 78L033 linear voltage regulator - it's a 'normal' part (no
      >> low-drop), so for a stable 3.3V it need a good 5V source. USB-Power is sometimes (Hubs) a bit
      >> lower: In this case, it's possible that the DV-RPTR do a reset by a small source voltage drop.
      >>
      >> I tested USB powering with some real HW (Notebooks, PCs) w/o any problems. Using "emulated" poor
      >> USB voltage (4.7-4.8V, 100mA) I can force a reset (by ST706T).
      >>
      >> For PC software (using my open source firmware) it's possible to detect a reset and restore
      >> configuration in this case. But I think this feature isn't used in Jonathans or Kurt's software.
      >>
      >> 73,
      >> Jan, DO1FJN
      >>
      >
      >
      >
    • do1fjn
      Hi, I think the RaspPI is more critical - a good / stable 5V source is needed ( 700mA). If the raspPI works, the 5V source is good enough to feed the DV-RPTR
      Message 2 of 14 , Apr 16, 2013
        Hi,

        I think the RaspPI is more critical - a good / stable 5V source is needed (>700mA).
        If the raspPI works, the 5V source is good enough to feed the DV-RPTR (30mA) too.

        The DV-RPTR can't handle 'longer' "brown-outs" (voltage < 4.7V) very well. There is no problem with the (low) current consumption.
        Another point are the USB-connectors: The USB-miniAB connector is not so stable like the USM-miniB...

        73,
        Jan
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