Secrets of the Solar Powered SunAirPlus Controller – Application Notes
Want to Solar Power your project? Secrets? What could be Secret about SunAirPlus?
OK, well not really secrets. What we are talking about here are four ways of using the SunAirPlus that aren’t completely documented in the specification. Buy it here!
The four secrets are documented below the description of SunAirPlus. What the four secrets are:
- – Stepper Motor Controller / SunTracker
- – Turn off A USB Power Control with SunAirPlus
- – Directly Charge an iPhone / Android Phone from SunAirPlus (secret coming next posting)
- – More More More Analog to Digital Inputs (secret coming next posting)
What is SunAirPlus?
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. This project was funded (150%) by a successful Kickstarter.
It uses both Grove and Pin Headers.
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.
The Secrets
Stepper Motor Controller / SunTracker
SunAirPlus 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 SunAirPlus 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. The way to do this is with a stepper motor with an optional set of photoresistors (to find the sun!). You don’t HAVE to have the photoresistors because you can calculate where the sun should be if you know your latitude/longitude/time of day. But it’s still cool to use photoresistors.
Below is a video showing Suntracking at work with a stepper motor.
Turn off A USB PowerControl with SunAirPlus
SunAirPlus 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.
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