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Caution: Chinese Nano

Discussion in 'Arduino' started by MrAl, Mar 29, 2016.

  1. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello there,

    I just wanted to mention that a little extra caution is needed when using the Chinese Nano with a wall wart.

    As most here know, the Arduinos can be run from a wall wart if the power is applied to the Vin terminal of the board. That typically takes a 9vdc wall wart and powers the Arduino. Once programmed, that makes it a stand alone application without the need for a USB port.

    This post is about the Nano but i am not sure if any other boards apply too.

    The main thing is that the Nano original specification was that it would contain a 5v linear regulator chip that takes up to around 30vdc input. That chip would regulate the unregulated wall wart down to 5v to run the Nano properly. If the current draw was not too high (loaded pins or other loads on the 5v supply) the wall wart could be as high as 20v without a problem.

    What i found out was at least some of the Chinese Nano's use a 5v regulator that is only specified for a max of 15v input. 16v is too high. This means that an unregulated 12vdc wall wart would probably blow out the regulator chip and possibly damage other parts on the board. That's because a 12vdc wall wart can put out 16v or more because of the rectified peaks. A *regulated* wall wart however does work ok, as tested today. 12vdc regulated wall warts would be max 12.5v so any should work, although you may want to test the voltage first.

    So the bottom line is be careful what wall wart you use with the Chinese Nano's if it is over 9vdc.

    What else i dont know is if a lot of the Nano's are coming like this now. It may be more widespread than i know of at this time. So check the actual installed regulator part number on your Arudino board to make sure before you power it up for the first time with a wall wart. The part number for the ones i have is ASM1117-5.0 and that only takes a 15v max input voltage. There may be other part numbers being used too. The original regulator was a higher rated part like the 78M05 which took up to 35v input without blowing out, which could easily handle an unregulated 12vdc wall wart.

    Good luck with it :)
     
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  2. Wp100

    Wp100 Active Member

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    Well spotted ! and very true about the unregulated wall warts which the unwary will have no idea of the potential problem.

    Just checked my boards, the original genuine Uno is fitted with an ON 117 -5, which seems to be Arduinos specification of 20v max.

    All my other clone boards Uno, Mega, Nano fitted with that AMS1117-5.

    Interestingly the Mega was supplied from Hobby Components (uk) , their "own" board and they specify it as 20v input max.
     
  3. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Wow that's amazing too. I would think they would know their own parts :)
    If someone applies 20v it could blow the regulator and who knows what else.

    The upside to the AMS1117 is better regulation over temperature i think. The 78yxx line of regulators are pretty poor on that.
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    The Yun requires a regulated 5V.
     
  6. fezder

    fezder Well-Known Member

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    Thanks for heads-up, in fact, I've ruined two of mine pro mini's, both ones regulators blew up, but what is interesting, both worked about half month or even month, not sure before blowing up.
     
  7. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Not sure if i will use one of those, but that's good to know just in case.
     
  8. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,

    Wow, sorry to hear that. So the problem is not limited to just Nano's. I'll have to check some of my other boards too now.
    i cant even remember what made me check the regulator in the first place, but glad i did because i almost powered one up with a 12v non regulated wall wart which probably would blow the chip.
     

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