I have a HC-05 module which works absolutely fine with an Arduino Uno. Because I need to reduce the size of it, I tried using an Arduino Nano.

After correctly wiring it up to the Nano, sometimes the LED doesn`t turn on, or sometimes it does not appear in the devices listing of my smartphone. It also resets randomly the Arduino. I have tested it and it fully works without any problems with the Uno.

I think it is a power issue, but not from my computer or any other computer because I tried on all my computers.

  • Are you powering it from 3.3V or 5V?
    – Majenko
    Aug 23, 2018 at 13:35
  • 1
    the regulator on the nano may not be able to supply enough current for the HC-05. See if you can find a part number on the regulator and look up its specs.
    – Chad G
    Aug 23, 2018 at 15:35
  • @ChadG If it's running from the 3.3v pin then it may even be using the internal 3.3v regulator of the CH340G, in which case you'd be lucky to get a few tens of mA from it...
    – Majenko
    Aug 23, 2018 at 16:28
  • 1
    Please provide a schematic and the type of HC-05 module you have. The HC-05 itself runs in 3.3V, but most modules, that you can buy, add an extra voltage regulator for 5V, so that you can power it directly from the Arduino.
    – chrisl
    Aug 23, 2018 at 21:39


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