Secrets of the Solar Powered SunAirPlus2 Controller – Application Notes
Want to Solar Power your project?
. What we are talking about here are three ways of using the SunAirPlus2 that aren’t completely documented in the specification. Buy it here!
The three secrets are documented below the description of SunAirPlus2. What the four secrets are:
- – Stepper Motor Controller / SunTracker
- – Turn off A USB Power Control with SunAirPlus2
- – Directly Charge an iPhone / Android Phone from SunAirPlus2 (secret coming next posting)
What is SunAirPlus2?
Ever wanted to build your own Solar Powered Raspberry Pi or Arduino system? SunAirPlus2 is a 4th Generation Solar Charging and Sun Tracking Board designed specifically for Arduino and Raspberry Pi systems. This project was funded (150%) by a successful Kickstarter.
It uses both Grove and Pin Headers.
The SunAirPlus2 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 (address 0x41) on the SunAirPlus2 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. SunAirPlus2 contains an INA3221 voltage /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 Interface for Servo motor or Stepper motor
- Built-in Interface for Limit Switches
Below is the block diagram of the SunAirPlus2 board.
The Secrets
Stepper Motor Controller / SunTracker
SunAirPlus2 contains a empty space for a stepper motor driver utilizing the L293D Dual H-Bridge Motor Driver. There is an excellent tutorial on Instructables: https://www.instructables.com/id/Control-your-motors-with-L293D-and-Arduino/. The L293D can be used for servomotors, stepper motors or DC motors.
JP20, JP19, JP17, JP21 and IC1 are all involved with the control and powering of the stepper motor. See the specification for SunAirPlus2 for details.
Why is this cool?
One of the things you can do to improve the performance of your solar power panels (up to ~30%!) is to track the sun as it moves across the sky. You can calculate where the sun should be if you know your latitude/longitude/time of day.
Below is a video showing Suntracking at work with a stepper motor.
Turn off A USB PowerControl with SunAirPlus2
SunAirPlu2s has a special device that will turn off if the power goes below 4.65V (nominal 5V from the boosted LiPo voltage). You
can wire this up to the LIPOBAT input of the USB PowerControl to turn off your Arduino when the solar power system is starting to brown out. Just connect a wire from JP3 (WatchDog Power) to the control input (LIPOBAT) on USB PowerControl and you can turn off USB devices based on the voltage input! Makes sure your Arduino won’t run on low power conditions. Note, that while it is possible to turn off a vRaspberry Pi computer using the same technique. It is not good to do so because shutting down a Raspberry Pi as you can destroy your SD card by not doing a software shutdown on the Raspberry Pi.
