WIP: My first PCB: Arduino Pro Mini + RFM69 small node (feedback wanted)

  • Hi,

    To increase the WAF of my door/window sensors I created this small PCB. It connects a RFM69 to an Arduino Pro Mini with the lowest footprint I could come up with. There is additional space for a booster and a voltage divider though the voltage divider is optional (Just cut it if you don't need it).

    Criticism/Feedback and everything in between is very much welcome since I literally have no idea what I am doing and I hope somebody can point out issues before I order my first batch. So: so far this is untested, please don't order it until I got my hands on the first batch.

    I was also hoping that somebody could tell me how to set up the project so that mysensors gets a few dollars for every ordered batch, I've seen other projects do that and I want to give back to the community too.

    If, unexpectedly, there are no issues with the PCB the next step in the project will be to create a 3D-printable enclosure (I am leaning towards tinkercad, but again, I have no idea what I am doing and I am open to suggestions).

    Small pro mini rfm69 shield



  • @kiesel Looks like you are well on your way.
    If you post a schematic, you'll likely get more feedback.
    If you are using one of those Chinese step up converters to 3.3V, I found I had to add a 1 uF cap on Vin to get good performance at no load.9ffc2873-7429-4314-a592-74958b0342b1-image.png

    Most designs I've seen also have a 0.1 uF decoupling cap at the power connections to the radio.

    I can't tell where you are connecting the door switch, directly to an unused pins on the pro mini?

    One limitation to the pro mini is that you only have 2 interrupts and 1 is used for the radio, leaving you 1 for your project, which is probably fine for your application.
    If you used a pro micro (32U4) instead, you would have 5 interrupts, leaving 4 for your project. And I don't think I've ever seen an rfm69 board for the pro micro, so it would be a first. Just a thought.

  • @KevinT

    Thank you for your feedback!

    I have (or at least I think) a decoupling cap on the pcb (C2). And you are right, I should have added the schematics from the start.

    I tried doing it on openhardware.io but now the pics of the pcb itself show an older version (the schematics are fine though, I'll add them here too).

    I added pins for a HDC1080 temperature/humidity sensor, because that's what I'll probably end up adding anway.

    1 interrupt should be all that I need, but if I need more I'll probably use this workaround. But thank you for letting me know about the micro, didn't even know that existed 🙂

  • @kiesel Thanks for the schematic.
    For the decoupling cap, it should be as close to the 3.3V & Gnd pins of the radio as possible.
    Keep us posted, thanks.

  • @KevinT

    hmmm, that's really not the case atm. I just ordered the first batch and will report back once I assembled the first sensor. If it's an issue I'll rearrange the footprints. Thanks for the info! 🙂

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