My weather station hasn't been working right for awhile. I've got a handful of ESP8266 boards sitting here, so I've decided to repurpose the housing and sensors to build my own direct-to-wifi WX station. Most of the sensors are straightforward: a moving piece with a magnet attached triggers a reed switch to count the movements as pulses (wind speed, rainfall). The temp and humidity sensor is a very common I2C chip (SHT21). The wind direction indicator, however, is fascinating. The wind position indicator is the black circle with four concentric grooves cut in it. An LED slides in near the outside edge and illuminates a reflector/diffuser under the groves. Four more LEDs mounted on the PCB lined up over the groves. Since LEDs produce a small voltage in the presence of light, those four LEDs detect which grooves are exposed, producing four-bit indication of the wind angle. To reuse the wind indicator, I'll need to build a new PCB with holes for the sensor LEDs in just the right spots. Measuring small things is hard...