Product review: wireless LEDs
I came across a discount for wireless LED kit on Aliexpress and decided to give it a try. (The discount was probably due to seller’s mistake as the emitter+LEDs set was cheaper than the LEDs only. In fact the price was the same as only LEDs at other sellers. Now they’ve seem to have corrected the mistake)
Couple days later, I received a coil with emitter PCB and 10 LEDs. Emitter is equipped with a USB Type-C socket, but when I tried to power the thing with a Type-C charger, it didn’t work.
As it turned out, the PCB lacked necessary resistors for Type-C identification, so a compliant Type-C charger did not detect it (at least none that I have at home worked). After that realization, I took Type-A to Type-C cable and a Type-A charger, and everything worked well from then on.
Best brightness is achieved when the LEDs are near coil wires, not when they are in the center. The brightness falls off with distance very quickly, they are barely noticeable at around 5cm from coil plane.
"LEDs" are SMD LEDs, an SMD capacitor and most of the volume of the item is taken by an inductor with core.
Interestingly, a Qi-compliant charger for a smartphone is able to power the LEDs as well. 2 of the Qi chargers I have cause the LEDs to blink, because a Qi charger does not emit power when no phone is around, so it looks for a phone every couple seconds. However, one chinese Qi charger powers the LEDs constantly, and the brightness is very good, even better than when powered with original coil. This is also surprising because, as far as I’ve know, Qi uses different frequency from 100 to 200 KHz. Maybe my particular wireless charger is emitting at different frequency.
Techy details
The PCB has 2 ICs, a SOIC-8 marked WPT306ME (google doesn’t know it) and SOT23-6 marked XKT001.
The first is most probably a MOSFET while the second is an integrated wireless power IC. I couldn’t find its datahseet in English, here ity is in Chinese:
The PCB runs off 5V (as expected from USB device) and consumes 220mA maximum. It seems to switch between different modes and different power levels, another stable mode I saw was around ~80mA.
Connecting oscilloscope to the coil showed the following.
The frequency if the wave is around 224KHz with 17V peak-to-peak. It’s not a simple sinewave, it’s chopped at bottom.
The oscilloscope was connected between GND and one of the coil wires. As far as I noticed, another coil wire sit at around 7V from GND.
Placing or removing LEDs from the coil does not seem to affect the waveform.
If you want more info about how it works, check out links below.