Here is the Photon code and hardware details to build a solar powered environment monitor. It uses a combo module of 3 separate sensors that are read via I2C protocol to periodically measure and record:
- Temperature
- Humidity
- Light level
- Air pressure
- Battery charge
The 3 sensors are:
- HTU21D - Temperature and humidity sensor.
- Bosch BMP180 - Digital barometric pressure and temperature sensor.
- Rohm BH1750FVI - Ambient light sensor.
After the measurements are taken the values are sent to Dweet. The Photon then measure its own battery level and will deep sleep for a variable amount of time between measurements in order to conserve battery life. The sleep time will be longer when the battery gets low.
The following libraries are used:
- https://github.com/amcewen/HttpClient
- https://github.com/sparkfun/Photon_Battery_Shield
- https://github.com/adafruit/Adafruit-BMP085-Library
- https://github.com/sparkfun/SparkFun_HTU21D_Breakout_Arduino_Library/
- Particle Photon.
- SparkFun Photon Battery Shield: Used to charge the battery from the solar panel and read the battery charge level.
- 5V 500mA 2.5W 140x140mm Solar panel: Purchased from eBay.
- HTU21D/BMP180/BH1750FVI combo sensor: Purchased from AliExpress. Some examples here.
- Polymer Lithium Ion Battery 400mAh.
The pin connections are very simple as there is only one way to connect the battery, solar panel and sensor (just uses standard I2C pins).
