Planning PWS Hardware
It has been a dream of mine to create my own personal weather station (PWS). I've been working on this project for over 6 years now. Due to school and scope creep: I have not been able to complete this project. This time will be different. I have a plan. This plan has been split up into two parts: hardware and software. In previous iterations, I have developed hardware and software at the same time without a clear plan, which I believe is part of the reason why it has taken me so long.
With this semester is almost over, I have done a bit of planning so I can hit the ground running with this project. I want to have the hardware installed as soon as reasonably possible so that I can start work on the software remotely.
The general idea for this project is to have a weather station that hosts a web-app. This would allow you to view the current weather conditions from anywhere in the building.
In order to do this, I will have a raspberry pi to host the server and communicate with the station hardware. The station hardware will include a weather vane, rain meter, temperature, humidity, pressure, and possibly a uv-index sensor. This will all be directly controlled by a teensy.
The raspberry pi will sit on the roof in a shady spot. It will be connected to the internet via ethernet and get power over ethernet (PoE). The pi will interface with the teensy using CAN over an ethernet cable. It's possible that the pi could be placed indoors, but I want to attach a camera as a little bonus thing. The teensy will be directly connected with all the sensors over i2c. The weather vane and rain meter don't have any logic chips and so will need to be specially programmed.
The teensy will generally act as a bridge between the sensors and the pi. The weather vane and rain meter will need special logic which I will go into later. The teensy will respond to requests from the pi. The pi will run OctoWeather (PWS software that I am developing). I haven't made any plans yet of how this software will work, but I have general ideas of what it will do in my projects page.
The weather vane has two parts: wind direction and wind speed. Both of these use reed switches to detect what is happening. The wind speed closes the circuit on every rotation (maybe every 180º I can't quite remember which). The wind direction has eight reed switches each connected to a different resistance to detect which cardinal direction the wind is blowing in. The rain meter has one reed switch that triggers every time 0.01 inches has fallen. The wind speed and rain meter will need to have special software to asynchronously determine how much rain has fallen and how fast the wind is blowing. This should be relatively easy by using pin change interrupts. The wind direction can be connected to a voltage divider to measure resistance on an analog pin.
What I've done so far
I have been able to install an ethernet cable that goes from the basement to the roof. I have also collected all of the hardware that I plan to use for this project.