I ordered my PCB through OSH Park.

The board came out very nicely, but I did notice one error I made. Several of the footprints were custom made, including the supercapacitors. For these components I only considered the pad dimensions, but not the full package size (which is wider than the pads).

I was still able to fit two of the capacitors on the board, and further added to this by stacking another two on the first ones.

The first tests seemed to work as intended, but after being removed from the charging coil, the LEDs would go dark, and a few seconds later turn on again for only dozens of seconds. I had not considered in designing that the charging circuit would be back-fed by the capacitors and waste the energy that was just stored. I added a diode in series with the 5V coil output to stop any current flowing back to the charging module. This solved the issue and allowed for much longer operation time.

I designed the schematic and did the PCB layout with KiCad.

The visual representation has some parts missing as a lot of the footprints were custom made.

The idea is to have an LED coaster powered from super capacitors and wirelessly charged. As capacitors don't have the storage capabilities of batteries, it is important to design this to have as low of power draw as possible. For that reason I won't be using a microcontroller, or having more than one LED on at a time.

Main working parts:

Wireless charging coil:

-5V in, 5V out

Super capacitors:

-15F devices, rated for 2.8V

Voltage regulator:

-brings in 5V from the charging coil, regulates to 2.75V

555 Timer:

-set a frequency for a 4-bit binary counter

4-bit binary counter:

-count from 0-15. Feeds 4-16 bit decoder.

4-16 bit decoder:

-a counter feeding into this allows to pulse one LED at a time (16 total LEDs)

LEDs:

16 LEDs along the edge of the coaster. The effect of one on at a time will create a spinning effect.