power problem?

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  • My pico board works fine from the USB, but if i put 9v on BAT_IN and ground GND i get nothing (tested running a simple flash LED1 routine).

    voltage on the 3.3 pin is only 0.06v when powering from BAT_IN.

    Am i doing something wrong or do i have a poorly pico?

  • @user80719,

    I'll start with the obvious,

    1) You are certain the battery terminals are connected appropriately; [plus - BAT_IN] [minus - GND]
    2) The battery is fully charged and has been tested on a separate circuit under load.
    3) The USB cable has been removed from the Pico.
    4) What is the measured volatage at the positive terminal/BAT_IN of the 9v after it is connected?

    "It is the answers, not the questions, that are embarrassing." Helen Suzman

    5) Is 'save()' being typed before dis-connecting the USB cable and applying the 9v battery?
    6) If the battery is removed and USB cable re-applied does Pico execute the LED1 routine as expected?
    7) Are the battery wires soldered in place or using a breadboard?

    Posting an image of your connections/layout would assist greatly.

  • thanks for the reply,

    1) connected correctly
    2) its a 9v psu and works fine for other applications
    3) usb cable is out
    4) solid 9v
    5) saved correctly, no errors
    6)LED1 flashes then my LED2 flash test program runs
    7) breadboard, just the pico and the power connector attached

    • and - pads for the battery connector test fine with continuity connector to the BAT_IN and GND pins.
  • Mon 2017.08.28


    Using this diagram http://www.espruino.com/Pico#otherpins

    and plugging in the USB cable:

    1) What is the voltage between pin 1 GND and pin 2 VBAT
    2) What is the voltage between pin 1 GND and pin 3 3.3

    Remove the USB cable:

    Place your 9v power in on pin 18 BAT_IN and perform the same test as above:

    3) pin 1 GND and pin 2 VBAT
    4) pin 1 GND and pin 3 3.3

    Schematic at:

  • Hi,

    It sounds like what you're doing is fine - as @Robin says it'd be great if you could measure the voltage across GND and 3.3v (and also VBAT, just to make sure).

    Do you get anything from the Pico at all when you apply the 9v? Like a flash of the red LED?

    Did you solder the pins on the Pico yourself? so is it possible there might be a short on the board somewhere from doing that (or possibly a bad connection)?

  • Hi, thanks for your replies.
    Unfortunately i plugged the Pico into the USB and that doesn't work either anymore. No LED flash & not recognised by the WEB IDE. Terminal.
    I'll send it back to where i bought it for replacement.

  • Where did you buy from, and which country are you in? It seems like you're UK-based so it's probably easier to return it direct to me.

  • Just checking - is it possible you were using a 9v AC power supply, rather than DC?

    The last thing I'd want is to ship you a new board and have that blow up as well.

    Obviously while I'm happy to replace any boards that were shipped to you defective, if it turns out that a board was shipped to you perfectly ok and was then broken by something you did I'd want to charge you some discounted rate for a replacement so that I don't lose out.

  • Hi Gordon, definitely 9v DC
    Im in the UK, bought from Makersify.
    Let me know your address and I'll pop it in the post tomorrow.

    Cheers, Jon

  • Ok, email sent!

  • Right, a new one is in the post back to you now, and it's been tested running off the VBat pin.

    On the rev 1v3 Picos it's worth making sure you don't short out or draw too much power (over about 300mA) from the 5v output pin. It seems something like that killed the diode taking power from USB which caused the board not to work off USB power any more.

    When you do power the board from an external power supply I'd either make sure:

    • It's not powered or grounded from any other source
    • You connect the ground pin first

    Depending on the power supply you use, connecting the + volts before ground could cause upwards of 100v to go through the Pico's input pins - which obviously there's no way it can be designed to take.

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power problem?

Posted by Avatar for user80719 @user80719