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.
Jared Boone (http://www.sharebrained.com/) gave me advice about the hardware design at many steps along the way. Check out his Chronulator: http://www.sharebrained.com/chronulator/
Laen made several rounds of prototype printed circuit boards for me: http://dorkbotpdx.org/wiki/pcb_order