A compact, cheap interface unit for NRG #40C 3-cup anemometers.
This project started because I found a great deal on some NRG anemometers on eBay. Two for $40 was hard to turn down, especially because each unit is calibrated from the factory and said calibration is freely available on NRG's website.
The heavy lifting of the circuit was already done for me - the technical whitepaper from NRG clearly illustrates an almost-complete schematic. The only real work to be done was selection of components, the MCU interfacing, and board design for a nice compact meter.
I went through a lot of initial brainstorming for the interface concept - battery powered, or DC? Integrated data logging, or keep it simple? How many buttons? Should it beep at you annoyingly?
In the end, a dead-simple interface showing current and maximum wind readings was decided on. Power is provivded via a micro-USB plug, which also creates a serial port for real-time data transfer to a PC. The display is your standard run-of-the-mill eBay 1.3" OLED display, driven by I2C, and available for a few dollars all over the place. Boards were designed in Kicad and manufactured by JLCPCB. Components were sourced from Digikey, and the whole thing took a couple days to get working.
