He’s using an everyday LED as a detector diode and an internal pull-up resistor in the ATtiny13 for the bias voltage. The antenna runs off the LED’s anode.

Light emitting diode (LED) lighting is becoming more and more popular, as incandescent lamps are being phased out globally. LEDs have several advantages over incandescent lamps, including energy ...

The research team led by Professor Hele Savin has developed a new light detector that can capture more than 96 percent of the photons covering visible, ultraviolet and infrared wavelengths.