DIY Onion-Mini-Dock

  • Hey guys, so I just got my Onion2+ but of course I forgot to buy the dock...
    Because I am living in Germany, I think it will be faster and cooler if I develop my own open-hardware onion-dock.

    Looking on the schematics of the dock from I wonder how important is the component Q1 as I am thinking in having it always on while the micro-usb is connected.

    Second questions, could anyone suggest a component for items D12, D13 and D14?

    I will use this thread to show the progress.

    Cheers :)

  • Looks like those diodes are "transient-voltage-suppression diodes", and are used to clamp down on electrostatic discharge from frying the rest of the circuit.

    As for the transistor, you could probably do without it (though I don't claim to be any sort of expert) and just have the regulator connected directly to the power bus through a switch.

    I'm going to be doing something similar, but I just got a cheap CP2102 breakout board on amazon (they generally come with 3V3 output, so no need even to connect through the regulator) to save myself the hassle.

    quidquid latine dictum sit, altum sonatur


  • Thanks, but I believe that the AO3401 is also not really necessary, right?

    I am almost done with the project, then I will share it here for you to take a look.

  • @Daniel-Andrade I would agree that I don't think the A03401 is really needed.

    You might also like to consider the use of a TSR 1-2433 in place of the BL1117-3.3
    The TSR 1-2433 will give you a regualated 3.3v from any input supply in the range 4.75 – 36 VDC
    But I would highly recommend that you still use suitable capacitors across the input and output. See sample circuits in the datasheet for the TSR-1 series which can be found at

  • Hey, right now the project looks like this:

    alt text

    Schematics and extra docs here:

    For 3v3 regulator, I am using a TLV1117LV33DCYR from Texas.
    Don't really need so much power from the Traco.

    Any extra tips and ideas?


  • @Daniel-Andrade It's an excellent idea to have the Omega pins available for customized use, and on standard headers to boot. :thumbsup:

  • @fossette Yes, I want it to be Breadboard friendly!

  • @Daniel-Andrade Cool. So basically a form of Mini dock with all the pins exposed for breadboarding/external connections. Great :-)

  • This is great! I thought of doing something like this myself, but yours is much more capable. I want one!

  • Just sent the first board to production.
    Going to CES and taking some holidays. I will be back in mid-january.

    If everything works I will post here and I can send them to anyone with production + shipping cost :)

  • @Daniel-Andrade Please do. I'd be interested!

  • @Daniel-Andrade any news on your boards?

    Home and Business Automation


  • @Costas-Costas @Daniel-Andrade I too would be most interested in any updates on availability of this. Thanks

  • @Daniel-Andrade hope it will be available in Brazil too ...

  • Ist the micro usb acts as USB host or client? I think you should add USB host connector...

  • @Victor-Tagayun The schematics show the microUSB-port is simply connected to a CP2102 USB-TTL-adapter. It's not connected to the Omega2 itself.

  • I've never made a single PCB before, let alone used Kicad, but after tussling with it for a day I managed to do my own take on a mini-dock. I skipped on the USB-TTL, because I am going to be using an external one anyways, if needed, nor do I need those reset-buttons, but I did decide to include ESD-protection on the USB-port's data-lines. I also added a header with a couple of extra power-pins, either for powering the device from, or to power any external modules I may want to connect to it.


  • @WereCatf Nice to have another dock option! So, the Omega mounts over the header socket?

  • @Ken-Conrad No, I figured it'd just about fit under the Omega2, when I solder the female 2.0mm headers, but then I just simply forgot to actually measure it.

  • @WereCatf Worth a measure... I'll advise using at least 805 or 12xx SMT resistors and caps as the smaller stuff is the pits to solder!!