WeatherPi Solar Power Weather Station – Monitoring the Sun

April 3, 2015 Matplotlib Graphs, Products, Project Curacao, Projects, Python Raspberry Pi Software, Raspberry Pi, Solar Power, SunAirPlus, SwitchDoc Products, Weather, WeatherPiArduino, WeatherRack

WeatherPi Solar Power Weather Station – Monitoring the Sun

We have now wired up the SunAirPlus Solar Power Controller to the battery and to the Raspberry Pi.  The SunAirPlus has an embedded INA3221 3 channel Current/Voltage monitoring chip so we can see all of the currents and voltages flowing through the system.

SunAirPlus on RasPiConnect
SunAirPlus on RasPiConnect (Click to Enlarge)

We can see:

– Battery:  Voltage, Current In/Out

– Load (Meaning the Raspberry Pi):  Voltage, Current Out (obviously, we get no current in from the Pi)

– Solar Panels:  Voltage, Current Out (we get no current IN to the panels, just out – there is a protective diode on the SunAirPlus board)

This reading shows the Solar Panels (actually a variable power supply at the moment) at 5.3V, the battery fully charged (by the meter and the fact that no current is flowing into the battery at the moment) and the Pi Model A is currently taking 193mA.  When we switch to the Raspberry Pi Model A+ next week, this will drop significantly.  We also are generating power graphs to be shown on RasPiConnect using MatPlotLib.

Solar Power
WeatherPi in the Box Ready for Final Wireup

We are using RasPiConnect to display the power system and show all the environmental weather data graphs.  More on that, including software, next week.

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SunAirPlus Solar Power Controller (with INA3221 embedded)

We are using the SwitchDoc Labs INA3221 Python Library to talk to SunAirPlus.

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WeatherRack Weather Wind and Rain Sensors

The WeatherPi software is basically done, with the exception of the issues with the AM2315.  The WeatherPiArduino is talking to the WeatherRack Wind and Rain Sensors perfectly.

4 Channel I2C Mux

We now have a 4 channel I2C Mux to change the AM2315 to 5V to see if that makes a difference.  The 4 Channel I2C Mux is a new SwitchDoc Labs product funded by a kickstarter here.

On April 2nd, we got the 4 Channel I2C Mux Breakout Board production prototypes, tested them and released it to

4 Channel I2C Mux Breakout Board
4 Channel I2C Mux Breakout Board

production.  It will be available in about 3 weeks.  This board allows you to connect mix 4 separate I2C busses into one I2C bus under computer control.  It allows any combination of 3.3V and 5.0V I2C buses to be used and removes the problems of having I2C address conflicts.  Immediately, we had a use for the board.

We are using the prototype I2C Mux Breakout Board now in the WeatherPi Box to allow us access to both the Inside Humidity and the SunAirPlus INA3221 3 Channel ADC (which share I2C address 0x40 and can’t be changed).

We are now working on the 3D Printed parts to mount the Voltaic Systems Solar Panels on the outside of the box (with a sliding bracket that will allow us to change the angle of the panels depending on latitude and the location of the box).  We will post those files in the next couple of days.

Next up on design testing is running the battery all way down reading all the data to figure out where to set the thresholds for shutting down the Raspberry Pi and then using the USB Power Control to reboot the machine when the battery voltage reaches 3.9V.  Don’t like those brownouts!  Brownouts kill Raspberry Pi SD Cards!

Updated Parts List (April 1, 2015)

Block Diagram

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