OpenSprinkler Forums Hardware Questions OpenSprinkler Pi (OSPi) New Open Hardware project: OSPI HAT

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  • This topic has 3 replies, 3 voices, and was last updated 3 years ago by Ray.
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  • #51106

    thinkfat
    Participant

    Hi all,

    over the last year (or was it even longer?) I developed a little PCB, a Raspberry Pi “Hat” that is compatible with OpenSprinkler. It is the same basic circuit as the original OSPI, except that it is missing some hardware features that weren’t really necessary for my own purposes. Most notably, there’s no ADC converter on the board and also the terminals for the RF link are missing. There is a terminal for a rain (or other) sensor, though.

    I originally started the project because I got some leftover OpenSprinkler Pi PCBs from a friend and while soldering the components I found that there are some that really weren’t nice to handle with just a soldering iron. So I set out and redid the PCB from scratch, mainly for it to be smaller (and therefore cheaper) and mostly using components that are still handle-able with just a standard soldering tip and a set of tweezers. Apart from one transistor, no footprint is smaller than 0805.

    It is densely packed, though, to cram all of the required functionality and a DC/DC converter circuit onto a board roughly the size of a standard Raspberry Pi “hat” (64mmx66mm).

    It features 8 24V AC channels and there’s an expansion header that will at a point connect to a stackable extender board with another 8 channels. The extender board is currently under development.

    I did this project mainly for educating myself, with no commercial intentions. I’m also not planning to sell kits.

    One of the prototypes is currently busy keeping my lawn and the rest of the garden nice and fresh and I’m soon going to launch the very final PCB, which is currently receiving some final touch-ups before it goes to the PCB maker.

    So, if you’re in an experimental mood, head over to the following URLs:

    https://circuitmaker.com/Projects/Details/Matthias-Welwarsky/OSPI-HAT
    https://circuitmaker.com/Projects/Details/Matthias-Welwarsky/OSPI-HAT-Extender

    Regards,
    Matthias

    #52710

    sloth
    Participant

    Too bad you don’t have the intention to sell. Would love to use this instead of the OSPI, but I’m extremely bad at soldering 😉

    #52719

    thinkfat
    Participant

    The economics of selling hardware are unfortunately not in my favour. To make it halfway viable I’d have to at least buy or make a reflow oven and rig a setup to apply the solder paste by stencil, otherwise it takes way too long to assemble a board.

    I’ll have a closer look at assembly houses or full service providers like circuithub, but it seems that I’d need to have batches of at least 100 units at a time to drive down cost, which would be quite an investment.

    I could probably provide single units hand-made with some lead time, but that’d be more a “labour-of-love” thing (or quite expensive).

    Kits are an option. But, not many people would attempt hand assembly and the inevitable handling of returns for failed attempts would certainly kill the fun.

    BR,
    Matthias

    #52796

    Ray
    Keymaster

    “Kits are an option. But, not many people would attempt hand assembly and the inevitable handling of returns for failed attempts would certainly kill the fun.” — that’s the unfortunate truth, and is the main reason why we stopped selling OpenSprinkler DIY kit. We’ve come to a point where there were a number of customers who soldered poorly and the circuits didn’t work, and we didn’t want to see them disappointed so we ended up having to fix solder joints for them. It’s one of those things that it’s easy to say, on paper, that we are not responsible for soldering issues, but in practice, customers expect more. So we decided it’s not a sustainable product and discontinued the DIY stuff.

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OpenSprinkler Forums Hardware Questions OpenSprinkler Pi (OSPi) New Open Hardware project: OSPI HAT