[Atomic14] bought some wireless LEDs that receive power from a base station. They were very neatly packaged, but — we like it — he took one apart and made his own versions. They may not look as polished, but they work and they are undeniably cool.
The LEDs work by receiving power from an induction coil. Once you have power, lighting up an LED is no big deal. Reverse engineering found the transmitter sends 217 kHz into a 2.2 mH inductor. A capacitor resonates the coil and drives the attached LED.
Some experiments found that the circuit could supply about 2 mA -3 mA of current. [Atomic14] used two LEDs to get work out of each half of the AC waveform. He also dissects the transmitter, so you could roll your own there, too.
What would you do with a wireless LED? Maybe lighting in a model display or a checkerboard? We wondered if you could use two or more power frequencies to signal (for example, 200 kHz lights a red LED but 250 kHz lights a green one)? The original transmitter was fixed frequency, but if you used a microcontroller, it would be easy to make it frequency agile. In the end, there is an economic analysis of building these versus buying them ready-made, but we all know that isn’t always a decision that is strictly based on dollars. The commercial versions did look a little nicer, but with surface mount components, even the DIY version could probably look a bit cleaner.
We’ve actually seen these before. We wondered if you could draw power from something that was transmitting anyway.