About this project
The Firefly Cap is a fun kit you can use to build an electronic jar of fireflies powered by light. Place the jar indoors in a location with moderate to bright lighting and let it charge throughout the day. After dark, the simulated fireflies twinkle for a little while.
Unlike many solar powered kits, the Firefly Cap is optimized for indoor light and does not require bright light or direct sunlight. It collects more power and runs longer if you place it in a brighter location, but it puts on a show for at least a few minutes even if placed in a location with only moderate indoor light throughout the day.
The Firefly Cap stores energy in a supercapacitor, so there are no batteries to replace. The circuit board fits on top of a standard Mason jar, replacing the jar lid. You provide the jar and solder the LEDs; everything else is assembled for you.
Instead of building a jar of fireflies, you can use the Firefly Cap as a power source for your own low-power electronics project. Just connect your 2.7 V device to the Firefly Cap's output and draw current sparingly. You can even connect a serial interface to the Firefly Cap's MSP430 microcontroller and use it as a power supervisor, monitoring the supercapacitor voltage and ambient light level. Alternatively you can write your own firmware for the Firefly Cap's microcontroller.
The Firefly Cap is open source hardware. All hardware design files and firmware source code are released under the GPL v2 license. It's a great way to get started with electronics!
Project home: http://greatscottgadgets.com/fireflycap/
A jar of fireflies is a popular microcontroller project. There are too many prior works to list, but I personally took inspiration from Kyle Anderson (https://xkyle.com/my-jar-of-fireflies/) and Xander Hudson (http://www.instructables.com/id/Jar-of-Fireflies/).
Thanks to my nephews, Archer and Caleb, for running down the battery of my first jar of fireflies so many times that I started thinking about how to make one without batteries.
Dan Gottesman (http://dangottesman.com/) edited my Kickstarter video, this time with more than a day's notice. He is an excellent photographer and producer of all things audio/visual.
Laen made several rounds of prototype printed circuit boards for me: http://dorkbotpdx.org/wiki/pcb_order
The diameter is 68 mm (2.68 inches). It is designed to fit jars with a 60 mm (2 3/8 inch) mouth diameter.
Shipping to anywhere on Earth is included with each reward! In my experience, the only way to ship from the US to other countries with reliable delivery times is to use an express service for $80 or more. Otherwise, you are just as likely to experience multi-week delays with a $20+ service as you are with USPS First Class International for under $10. To keep things simple, I've set the pledge levels for the rewards so that I can afford to do the latter.
I handled international shipping in the same way for Ubertooth One (and delivered about 30% of the rewards to other countries). It worked out pretty well with most international backers receiving their rewards in two to four weeks.
There is a reason I haven't made specific claims about the running time; it is because the design is not 100% final yet. I don't want to say that it will run for 20 minutes under certain conditions and then deliver something that ony runs for 10. However, I can tell you my estimates based on the prototypes I have tested so far: In moderate indoor lighting conditions, I've seen running times of around 10 minutes, and, in bright indoor lighting conditions, I have seen them last for 30 to 60 minutes. At maximum charge it can run for an hour or more.
The running time is highly dependent on the amount of light that reaches the photovoltaic panel throughout the charging period. Relative light levels are hard for humans to discern because our pupils so often change size without us noticing. You might move a Firefly Cap from one place in a room to another place in the same room that doesn't seem much brighter and find that it doubles the running time!
Fireflies in nature illuminate actively for only a short time each evening. I read somewhere that one species is active for precisely 27 minutes. You should be able to find locations with natural or artificial lighting where you can place a Firefly Cap that will result in running times of tens of minutes, a fairly accurate simulation of the insects.
Yes. Although the Firefly Cap is optimized for indoor lighting conditions, it will charge even faster in full sunlight and will reach maximum charge in much less than a full day.
Note that the Firefly Cap is not suitable for use in wet conditions. If you want to use it outdoors, you'll have to devise your own weather-proofing.
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