Connected Seeds' sensor unit

Nanda Khaorapapong

Description:

As part of a research into how Internet of Things and sensor technologies can benefit an urban food growing community in London, this sensor unit for Connected Seeds (CS) project is designed for outdoor monitoring weather and plant growing conditions. It measures 7 parameters hourly (i.e. luminosity, barometric pressure, air temperature and humidity, soil temperature and humidity and approximated voltage level of the power supply), all of which are averaged and stored in an SD card then uploaded hourly to a Cloud server Thingspeak channels via 3G communication.

Required hardware:

See component list

Required software:

• CS_sensorUnit (tested with Arduino 1.6.9)
• Arduino IDE
• Jack Christensen's DS3232RTC library
• Michael Margolis's Time
• Adafruit Sensor library
• Ardafruit TSL2591 library
• Adafruit BMP085 library
• Adafruit INA219 library
• Jonathan Oxer's SHT1x library

Circuit Building and Installation:

1. Prepare CS shields – download PCB design files (i.e. L2 and L4 and print each as a double-sided shield. See PCB design note for details.

2. Assemble – Solder components on both shields and assemble a 4-layer circuit. See Assemble note for details.
   A fully assembled CS sensor circuit:
   

3. Download and install all required libraries into Arduino/library folder

4. Download the zip folder of CS_sensorUnit software, unzip and open CS_sensorUnit.ino file in Arduino or other preferred C/C++ IDE

5. Create a channel on Thingspeak with 7 fields; copy the channel's API write key to replace the 16-digit key on line 153 in CS_sensorUnit.ino file

6. Upload software: set two slide switches on the top shield at 'usb' positions before uploading CS_sensorUnit software onto Arduino Mega board. Set both switches back at 'serial' positions once the uploading process is completed.

7. Switch on the circuit

8. Place all of the components in the enclosure and install it half way into the soil. Make sure the upper SHT10 sensor is exposed to air.
   
   A fully assembled CS sensor unit with two STH10 sensors on the side:
   

Usage:

• How it works – On start up, MCU is put into sleep mode and only wakes up by 2 alarms to perform series of events:
  • Alarm 1 wakes up MCU @ minute zero of every hour. This is to read, do a simple stat and store all data including alarm event in text files before entering sleep mode.
  • Alarm 2 wakes up MCU @ 23:10 every day to upload data to ThingSpeak and record alarm and 3G communication events in text files. After that, it checks 3G shield's power state and attempts to power it off (several times since the 3G shield is having issue with its power on/off feature of the original hardware). Before going into sleep mode, it sends out an sms notification to two phone numbers if the sensed voltage is lower than the mininum threshold.

Contributing:

The work is still under development. Though it is fully functional, several elements regarding both hardware and software can be improved. I will be very grateful if some parts or the entire system can be beneficial to your research or practice or play, and/or if you like to help improve. If so, please feedback using a contributing template or drop me a line at nanda.krpp@gmail.com

Credits:

• Connected Seeds project is sponsored by EPSRC and developed at Queen Mary University of London.
• Special thanks go to:
  • Research team i.e. Dr Nick Bryan-Kinns (PI), Dr Hamed Haddadi (Co-I) and Dr Sara Heitlinger (Researcher Co-I)
  • All seeds guardians i.e. Lutfun and Richard at Spitalfields City Farm, Lisa at Wilton Estate, Halema and Anwara at Selby Estate, Zimbabwean association and Nat at Cordwainern Garden
  • QMUL Electronics Lab
  • Production team Ireti, Meng, Matt and Yulia
  • Flim maker Donna Lipowitz
• Project partners

Licenses:

Copyright (c) 2018 Nanda Khaorapapong and Connected Seeds
GNU GPLv3 license