Solar Power – SunAirPlus Solar Power Controller for Arduino / Raspberry Pi
Ever wanted to build your own Solar Powered Raspberry Pi or Arduino system? SunAirPlus is a 3rd Generation Solar Charging and Sun Tracking Board designed specifically for Arduino and Raspberry Pi systems. The SunAirPlus board arrived from our manufacturer last week and works perfectly! This design was funded (150%) by a successful Kickstarter. We have a new Kickstarter running right now for Really Useful Breakout Boards (87%).
The SunAirPlus board takes Solar Power from 6V Solar Cells, charges a 3.7V LiPo Battery Pack and
supplies 5V power via a USB plug to the Raspberry Pi and Arduino. It supplies up to 5W (1000mA @ 5V) of good clean power to your USB connector. You can even charge your phone! The board has solar panel charge control system, a voltage booster, two A/D converters and an INA3221 on the SunAirPlus Board.
It has the charge control systems and GPIO interface circuitry systems for voltage level shifting and for servo motors as well as aiding in stepper motor control. SunAirPlus contains more robust ADS1015 A/D converters, INA3221 voltage and current sensing circuitry and an optional stepper motor controller.
It has the following other interfaces built into the board:
- Built-in I2C data gathering chips for system currents /voltages
- Built-in I2C Interface for Solar Tracking Photoresistor devices
- Built-in Interface for Servo motor or Stepper motor
- Built-in Interface for Limit Switches
Below is the block diagram of the SunAirPlus board.
Maximum Power Transfer Tracking
SunAirPlus does an approximation of the MPPT (Maximum Power Transfer Tracking).
It is the purpose of the MPPT system to sample the output of the cells and apply the proper resistance (load) to obtain maximum power for any given battery and temperature conditions. Although the fully charged battery pack voltage may be close to the solar cell maximum power point voltage, this is unlikely to be true at sunrise when the battery has been partially discharged. Charging may begin at a voltage considerably below the solar panel maximum power point voltage.
When the batteries are fully charged and the solar power production exceeds the load of the computer, SunAirPlus can no longer operate the panel at its maximum power point as the excess power has no load to absorb it. SunAirPlus must then shift the solar power operating point away from the peak power point until production exactly matches demand.
The CN3065 is set in SunAirPlus to deliver a maximum of 1000mA instantaneously to the connected LiPo batteries. Now note, that doesn’t mean you can’t use more than 6W of solar panels. The 6W solar panels won’t be delivering 1000mA most of the time.
RasPiConnect / ArduinoConnect Control Panel
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 (in April 2015). Those current owners of RasPiConnect / ArduinoConnect can download the configuration files from github.com/switchdoclabs in late March, 2015.
