A light in the bottle to light up your cozy evenings
I tried to experiment with AA battery instead of 18650 Li-Ion. The design is slightly smaller and lighter, but I think it will be worse on the long run. 18650 can provide more power and it's easier to have step up and charger on the same board.
I recycle my 18650 cells from old Laptop batteries. Usually those batteries go bad just because of 1 or 2 cells only, while other cells are still usable.
Or you can always buy 18650 cells online if you don't feel like cracking up laptop battery or don't have one to spare.
My rough estimates are about 150mA while light bottle is on, so 18650 should be plenty for several hours of your night talks.
After I played with some parameters in the Ardiono sketch, I realize it may be a good idea to add Bluetooh capabilities to be able to adjust it remotely.
I'm thinking about adding something like HC-05/06 module to receive commands from your Smartphone.
I had Arduino sketch written before I implemented the bottle in hardware, and with some minor changes it worked out of the box.
It changes the light color. I made colors dull so they won't distract much.
I just put the code on GitHub (link attached to the project page).
Here is the bottle with a manual turn on lighting up on my table in the middle of the night.
I just completed with the initial concept in hardware using 4 WS2812B LEDs. I still need to figure out the easiest way to turn on and turn off the power. There are a few tricks I want to try -- controlling it with some mosfet and be able to turn on with a light tap, and other similar ideas.