Backyard Weather Station

Evergreen, San Jose, CA

Live data:

  • Temperature: 82.7F
  • Pressure: 100775Pa
  • Humidity: 52%
  • Battery voltage: 4.19V

WeatherImp checked in at  2022-08-10 13:19:48

The inspiration

About three months into the pandemic, I was cleaning out a box of random electronic parts and came across a pair of Electric Imps.

 

These came out in 2014 but were still supported by the company and I decided to build a weather station.  These devices are very low power and have some great features:

  • Software configurable I2C, SPI or UART lines
  • Built-in low power WiFi
  • A very unique optical activation system
  • 3.3V operation supports 3.7V LiPo batteries

The breakout board is small enough to use as-is in your projects!

The Prototype

A breadboard prototype was very useful in determining the sizing of the battery and solar panel to power this weather station for at least a week to handle overcast days.

The BrainThe brain is of course the ElectricImp 001 housed in an April Breakout Board.

The SensorThe weather sensor is a DHT22 that measures temperature and humidty.  It uses a proprietary 1-wire protocol and I found a nice library for the imp so it was straightforward.

The ChargerAdafruit has a compact LiPo charger compatible with USB chargers and 6V solar panels.

The BatteryIt was easy to find 3.7V LiPo batteries.  I calculated a 2500mAH battery would last several days if the Imp sampled the weather once very minute.

The Better SensorThe DHT22 lacks pressure sensing, and the Bosch BME280 not only does all three but uses a standard I2C bus.

The Power SourceThe Adafruit 6V/2W solar panel is perfect for this project.

The Housing

The Stevenson screen is the most popular outdoor instrument housing.   You can find designs on thingiverse but I designed and printed my own.  The design is composed of five sections and mid-section is replicated 4-5 times for the desired height.

The Electronics

Side A of electronics assembly with the Electric Imp and sensor board.

Side B of electronics assemby with the charger and battery.

Electronics assembly inserted into housing.

The Software

Both the device code and the cloud-based backend ("agent") code are developed and managed within Electric Imp's cloud-based IDE, impCentral.  The environment is now supported by Twilio after their acquisition of Electric Imp.

 

My source code is freely available under the MIT License.

Analytics

The agent's REST API returns weather and battery information as JSON, and I use InfuxDB and Telegraf to pull data every minute for graphing.

© Venky Raju, All Rights Reserved.