Reverse polarity power

iveyj1iveyj1
edited January 2018 in Installation, Antennas and Interference
So I managed to hook my KiwiSDR to reverse polarity power.  When I apply power now (correct polarity) it is basically a short to ground (0.25 V).  Something clearly bit the big one.  Is there any chance the RF board is still ok?

Thanks,
Jack

 

Comments

  • jksjks
    It's possible the Kiwi board is fine. It depends on how the PMIC on the BBG failed exactly. 5V power from the Kiwi board DC jack goes to the BBG first, through the power management IC (TPS65217C PMIC) then elsewhere on the BBG and back to the Kiwi board. So if you're lucky the BBG has acted as a US$44 fuse. The PMIC input as configured on the BBG will withstand -0.3 to +5.8 VDC relative to ground. So a polarity reversal at 5V is a problem.

  • iveyj1iveyj1
    Ok, thanks, that's what I figured.  I'm probably the only one dumb enough to let this happen, but it might be worth considering adding a hefty schottky reverse-biased diode across the input if you ever do another board turn.   No guarantee it will help, (it won't necessarily keep the PMIC in its absolute max range) but it might limit the damage.

    I'll order a new Beaglebone and try it out.  If it doesn't work I can always get another Kiwi board.

  • jksjks
    edited July 2017
    Yeah, I should have spent the time to add a low Rds(on) P-FET.
    I should have spent the time to do a lot of things, but then we'd still be waiting for the Kickstarter, lol..

    Best YT video about this topic is here:

     

    And the most humorous is here:



  • UR5VIBUR5VIB
    > Yeah, I should have spent the time to add a low Rds(on) P-FET.

    I incorporate IRLTS2242 in each device I'm designing since some of my previous ARDF transmitters were accidentially burned by applying the reverse polarity by club members while being course setting in the woods. LoL

    Thanks for videos, John.
  • iveyj1iveyj1
    No go, the new Beaglebone will boot by itself but doesn't even light up when the Kiwi is connected.  Time for a new one, oh well.

    Thanks,
    Jack
  • jksjks
    Are you using a power supply that has previously been known to work with a Kiwi?

    The case of "it works with the BBG alone, but not with the Kiwi added" is a well-known symptom of a power supply that can't handle the current requirement, or a cable from the power supply to the Kiwi with insufficient wire gauge causing excess voltage drop at the moment of BBG power-on (i.e. the PMIC on the BBG won't power up because it sees < 4.75 V).

  • iveyj1iveyj1
    Good point, but it is having the problem with a power supply I've been using for some time. 
  • jksjks
    edited July 2017
    Okay. Well, if you mail me the dead Kiwi board I'll send you a new one for free. I can justify that by getting a chance to analyze the failure and hopefully make future designs better. Please email me: support@kiwisdr.com

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