Friday, November 18, 2022

Welcome the Tempest Weather Station

Prime day

The most feared day of the year for my wife is Amazon Prime day, and last prime day was like none other. We (well I) ordered lots of very useful stuff and spend WAY too much time looking at lightning deals. With the current state of my weather station (mostly dead) I ran across a lighting deal for a WeatherFlow Tempest weather station. A small self contained external unit for $60 off, interesting.

Tempest

I looked into it quickly (it is a lightning deal after all) and found the Tempest had the major requirements covered: Temperature, wind direction, Humidity, solar powered, wireless, Rain sensor. So far so good, but I want to integrate this with my Home Assistant and some other side projects, so I need the data. Well the Tempest has integrations out of the box, including: WeatherUnderground, IFTTT, Google, Alexa, Seri, SmartThings (Late 2022), to name only a few! But having an integration does not mean I can get to the data myself, does it?

Data

Welcome the Weatherflow Tempest API & Developer platform. The API offers full REST and Websocket documentation that can all be accessed once you create an access token. Although the documentation recommends using the API, the Tempest does have a local UDP interface to your local network.

Integrations

The end goals are to integrate this into my Home Assistant house automation and to be able to have some remote weather displays. I am going to be looking into weatherflow2mqtt for interfacing with Home Assistant. I am going to be looking at using a Raspberry Pico to interface an LED Matrix for displaying weather information in the house. But those are for next time.

Monday, November 7, 2022

Part 3 - The end of DIY weather stations

A Weather Station Postmortem

In Part 1 I built a weather shield out of bowls and Part 2 filled it with all sorts of gadgets, powered it using a battery and a charged the battery using a solar panel. The station was remotely deployed in the back yard to avoid interference from blacktop and other structures.

Deployed

Deployed in 2017 the DIY weather station was solid for several years. It ran and logged data without any intervention. The battery never died and the solar charging worked flawlessly. The logging via the MQTT server and the integration into home assistant was fairly easy and provided years of data (that I have since lost while upgrading Home Assistant).

Issues

After 3 years things started to get glitchy, I would have to restart the Arduino by taking it apart and disconnecting the battery and solar connector. This would work and it would run for a few more weeks. Not sure if this was related to the solar panel which after a few years I had to start cleaning to remove the film left over the years.

Another issue was that the bowls used where very thin and cheap and have become very brittle; one stray baseball or soccer kick and you ended up looking like this.

End Result

It was a great project and lasted much longer given the less than great weather proofing I provided. In retrospect I should have used some higher quality bowls combined with some good silicone to plug the holes. I also would have added a power switch to the outside of the case and hooked up a small USB cable and left it in place to allow debugging without completely disassembling the unit.

Overall, for a first project of this scale, I think it was a great learning experience.

Sunday, November 6, 2022

Part 2 - DIY Home built weather station

In Part 1 I built a radiant heat shield out of plastic bowels. I shared the design but never did the follow up showing the final product (better late than never)?

For this post I will detail the design to it with all sorts of gadgets and powered it using a battery and a charged the battery using a solar panel. The station was remotely deployed in the back yard to avoid interference from blacktop and other structures. It sent its data using a nRF24l01 transmitter to a Raspberry pi running another nRF24 transmitter. I never really went into the details, so here are what I deployed 8 years ago. (Yes, there is much better hardware options available now!)

Weather Instruments

I wanted to collect remote temperatures that are not affected by the driveway, so I started with the DHT11, then moved to a DHT22 during testing. While browsing I found an AHT20, which is an outdoor version of the DHT22. This fits perfectly since it is already wired and can just hang inside the shield. To collect barometric pressure, I added the BMP085, which also includes a temperature sensor which can be used to keep the DHT22 in check. To keep track of sunlight I added a simple Photocell to track sunlight brightness.

Power & Charging

To power the Arduino I added the Adafruit USB / DC / Solar Lithium Ion/Polymer charger - v2 with a 1200mAh Lithium ion battery. Since the weather station would be outside in NJ and be subjected to occasional cold days I added a 10K Thermistor that would stop charging the battery when the temperatures are hot (50°C) or cold (0°C). This was powered during the day via a 165mm x 165mm 6v Solar panel mounted above the station.

Guts

Once all the instruments and power was setup I used an Arduino 3.3V Pro Micro to read the instruments. This would run and gather the results and transmit via a nRF24l01 transmitter to a Raspberry Pi which collected the results and posted them to a mosquito MQTT broker which displayed them on a Home Assistant (all outside the scope of this article).

Data

The data transmitted include the temperature from the DHT22 as well as from the BMP180. The humidity was also captured via the DHT22 which was then used to calculate the dewpoint. The photocell calculated the light level. Some additional metadata was included for tracking system performance including the voltage of the battery, if the battery was currently charging or done charging,

Packaging

To deploy I soldered the Arduino to a small double sided PCB board that would fit into a small metal Sucrets tin (this was before I owned a 3d printer). I cut holes in the tin to be able to hook a USB cable into the Arduino and update code (in retrospect I wish I would have left the cable attached). I also had to fish the wires out and leave a connection to the solar panel. In the end everything fit snug.

Code

Since this was running on a battery and on a solar panel I wanted to take advantage of the LowPower module to put it to sleep since I only need to read the temperatures every few min. I also take and grab the temperatures into an array and only send the average every min. The code also includes a simple python version for the Raspberry pi to read the data and decode the RF stream and print the struct out.

The code is located here on github.