SunAirPlus Solar Power – INA3221 Arduino Library Released

SunAirPlus and SunAir are solar power controllers / sun tracker / power supply system developed by SwitchDoc Labs to power Arduino and Raspberry Pi based systems.  Internally, it is not a simple system, but it is designed to be simple to use.  This project was funded by a successful Kickstarter.  The whole process of running a Kickstarter successfully for a technical product will be the subject of an upcoming SwitchDoc Labs post.  It was quite the experience.   SwitchDoc Labs fully funded their Kickstarter in a total of 16 out of 30 days.  Pretty good for our first try!

SunAirPlus has three current/voltage sensors and an additional four channels of high quality A/D.  SunAirPlus is in final debug and is still on track to be shipped in February 2015 as scheduled.

INA3221 – I2C Triple Channel Voltage/Current Monitor

SwitchDoc Labs developed this INA3221 Arduino library as part of the SunAirPlus product development for use by customers.

The INA3221 is Triple-Channel, High-SideMeasurement, Shunt and Bus Voltage Monitor with I2C Interface made by Texas Instruments.  Here is the specification for the INA3221.

It is similar to using three INA219 High Side Current Monitors, but not quite.  There are significant differences in the chip itself and especially in the software needed.  In SunAirPlus, we want to measure the current and voltage for all three major subsystems:  The LiPo Battery, Solar Panels and the Computer.  You can see the INA3221 in the block diagram below.

We chose to use the INA3221 as it was quite a bit less expensive in board space and price compared to 3 INA219 sensors as we used in Project Curacao.

The software is located on the SwitchDoc Labs github under SDL_Arduino_INA3221.

Here are some results from the SunAirPlus board using the onboard INA3221.  You can see that the battery is supplying current here, while the solar cell is turned off.  The Output voltage is 4.88V because we are fiddling with the board.  The Library works like a champ.

SDA_Arduino_INA3221_Test
Measuring voltage and current with ina3221 ...
shut resistor=0.10
address=64
------------------------------
LIPO_Battery Bus Voltage: 4.10 V
LIPO_Battery Shunt Voltage: -15.76 mV
LIPO_Battery Load Voltage: 4.08 V
LIPO_Battery Current 1: 157.20 mA

Solar Cell Bus Voltage 2: 0.02 V
Solar Cell Shunt Voltage 2: 0.00 mV
Solar Cell Load Voltage 2: 0.02 V
Solar Cell Current 2: 0.00 mA

Output Bus Voltage 3: 4.88 V
Output Shunt Voltage 3: 11.20 mV
Output Load Voltage 3: 4.89 V
Output Current 3: 112.00 mA

------------------------------

RasPiConnect / ArduinoConnect Control Panel for SunAirPlus

Here is a tutorial on how to build your own control panels for RasPiConnect.

The RasPiConnect/ArduinoConnect control panel for SunAirPlus is shown below. SwitchDoc Labs has completed a licensing agreement with MiloCreek to put a version of RasPiConnect and ArduinoConnect up on the Appstore for SunAirPlus customers for $2.00.