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Powering Raspberry Pi and Arduino Mega from a 9.6v battery pack

Discussion in 'Power Electronics' started by liomry, Sep 25, 2012.

  1. liomry

    liomry

    16
    0
    May 7, 2012
    Hi all,

    I've come up with the attached circuit to power my Pi / Arduino combo. I'm wondering if this will work or if it will blow one or the other due to some silly mistake?

    I'm not great at electronics or circuits, just beginning so in words -

    9.6v battery positive branches to a 5v BEC and a barrel jack. 5v BEC feeds a usb port which returns ground to BEC. Ground runs from BEC to negative of battery, joining ground running back from arduino barrel jack.

    I have a feeling that sharing the ground here could cause huge problems without protection but that's why I'm asking you guys

    Thanks in advance
     

    Attached Files:

  2. liomry

    liomry

    16
    0
    May 7, 2012
    Maybe it would help if I generalised instead of focusing on the pi and arduino

    My main concern is - is it safe to have a 5v step-down device sharing ground with an unregulated 9.6v line? Should I have some device stopping the flow of current back "up" the ground wire to the 5v device?
     
  3. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    The Arduino and Pi both have on board regulators, in some instances you might have some ground loop noise that will have to be addressed but generally no problem running them off one power source...
     
  4. liomry

    liomry

    16
    0
    May 7, 2012
    Thanks a million for the reply.

    What's ground loop noise? Is that the issue I was worried about with the higher voltage travelling back along ground? How would I prevent that from happening?
     
  5. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    The basics here http://en.wikipedia.org/wiki/Ground_loop_(electricity)

    That is the million dollar question... The answer is don't create one in the first place, but when you start mixing and matching individually designed circuits (that you have no control over) you sometimes can't help but create one if they share the same power source... Then you are onto the long and complicated 'filter' or 'reduce' the effect diagnosis that is honestly a field unto itself in many respects...
     
    Last edited: Sep 26, 2012
  6. liomry

    liomry

    16
    0
    May 7, 2012
    Thanks again,

    Quick related question - would connecting the Raspberry Pi ground to the main ground with a 220 ohm resistor have any positive effect?
     
  7. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    No that would likely increase the effect and force the Pi to ground through the other device...

    IF you have issues you can install a low pass filter on the supply lines of the devices, this is a simple resistor/inductor and capacitor... But, I wouldn't bother unless you have issues to start with...

    [​IMG]
     
  8. liomry

    liomry

    16
    0
    May 7, 2012
    It seems to be working ok for now but I haven't yet started running a serial connection between the devices or powering sensors. I'll report back if that throws up any issues

    Thanks a million for all the help
     
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