Firefly cap has no battery and is meant for indoor light harvesting

[Michael Ossman] wrote in to show off his newest project. He calls it the Firefly cap, which we think is something of a play on words. You can see that it serves as the cap of a Mason jar, but it also uses a supercap instead of a rechargeable battery.

Posts about firelfly jars go way back. And [Michael] mentions that a similar firefly project was his first embedded project. The concept uses LEDs suspended in a jar. When a light detector senses the target level of darkness, the lights inside begin to twinkle like their insect namesakes.

We like this design for two reasons. It’s aimed at collecting light in an indoor environment so you don’t have to worry about placing it in the sun. And it uses a super capacitor instead of a battery so this should truly keep going and going without wearing out the energy storage components. We also like the fact that although this is a Kickstarter project, everything you need to build your own is already available at the Github repository.


  1. Jay says:

    The first link is wrong.

  2. metrazol says:

    Link in the first graph is broken, goes to that awesome telemetry post from earlier.

  3. eldorel says:

    A $65,000 kickstarter for a firefly jar pcb?


    Sometimes I think these people are just looking for a reason NOT to follow through with projects like this….

  4. Dr. James says:

    When compared to other KickStarters I’ve supported, this is amazingly pricy for what it delivers. I’ll pass this one up.

  5. Bob dole says:

    The capacitor seems like a gimmick. I doubt even a several-farad capacitor can power a LED for very long.

    The description says “several minutes” which doesn’t seem very entertaining… Once per day, you have a chance to watch a blinking light for “several minutes” if you catch it at exactly the right time.

    At $35 each and a minimum of $2^16 of preorders, I don’t think this will get off the ground.

    • tomas says:

      I personally have been wanting to build one for a long time. quick calc – a 25F,2.7V cap (maxwell) is 4.1$ (mouser) and stores 91 joules of energy. a 3V, 30ma (bright) LED can stay constantly on for 17 minutes on this charge. if you run it with some kind of flickering so its on only 25% of the time, it will run for about an hour (a little overhead for chip doing the flickering). So that’s about 4$ per LED per hour. if you use his design, for 35$ of parts (minus PCB) you can get impressive results.

      • tomas says:

        forgot to say – I HATE seeing these cheap solar “garden lights” , that are so environmentally friendly except they use a cheap ni-cad battery for storing energy , which dies after 6 months and then usually the thing goes in the trash.

  6. David s says:

    Considering you can make the one on instructables for less than 10 dollars, but it doesn’t have a solar cell or super cap…. Doesn’t really seem worth it.

  7. blauehavik says:

    While Bob noticed the goal was 2^16, it appears the significance of 2^16 was lost.

    I honestly LOL’d when I saw the goal. I expected more of a sense of humor from this crew. :)

    I must say I am surprised he’s already raised $1,338 as of this post. Maybe you guys do have more of a sense of humor than I’m crediting…. :)

  8. Alvie says:
  9. torwag says:

    $65.000 dollar ?!

    This is a nice crafted PCB but even the idea isn’t new

    They made hundreds of them and shipped them to the Earthquake region. Definitely sure they never collected $65.000 in advance to make it happen.

  10. Destate9 says:

    Yay Laen

  11. Cyril says:

    If it looks like a scam and smells like a scam there’s probably no need to taste it… right?

    • tomas says:

      hold on – selling an overpriced product is not a scam. it’s just business. even more so when the source is open and you can see the cost of manufacturing! he looks like an honest person, maybe not the sharpest businessman. but you learn from mistakes. he’s one of ours and throwing this kind of dirt should be frowned upon.

      • Cyril says:

        Ummmm….YES! yes it is…. How many dishonourable things get dismissed wit (deliberate typo: sounds like Mit) the glib: “it’s just business”
        Kinda like “it’s just paedophilia, you do understand they really do LOVE the children”

        From the infallible wikiP:
        “When accomplices are employed, they are known as shills.”

        there’s a $65,536 question you conveniently forgot to answer.

      • Tony says:

        Scam is a bit harsh.

        You know what your getting, the odds are you will get it, and if you’re happy to pay $35, well, where’s the scam?

        It’s over-priced for what it is (no jar!), but hardly falls into the Mythic or ZionEyez category.

  12. Pscyh0 says:

    This upsets me, because Michael Ossmann is a really good guy. He should have stuck to software or bluetooth. This is a little steep, but so is the ubertooth, so I could see it coming.

  13. Robot says:

    How is this a scam?

    $10 for a PCB seems like a good deal to me. $35 for an assembled unit also seems fair; consider that it’s not being mass produced in China and labor is expensive.

    I think a less expensive kit option would be nice. Still, I’ll get some PCBs.

    – Robot

    • Robot says:

      Well, maybe it is being assembled in China? I’ve worked with a couple of assembly houses in the US and they aren’t cheap! In any case the project doesn’t seem worthy of the hate.

  14. Drone says:

    It didn’t take long for Kickstarter to be affected by Charlatanism. I bet you could do a Kickstarter for fifty dollar Chia Pets and get away with it.

    Thanks HaD for dropping the ball on the link.

  15. Colibri says:

    I’d definitely like to see more “energy harvesting” projects. Energy being from any source available : light, temperature, vibration, wind and so forth.

    Basically, if I want to leave some autonomous device in the outside world, how much energy can I imagine harvesting, and how can I do that reliably ?

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