The microclimate sensor are based on the Arduino MKR WAN 1310, which provides a practical low-power solution for processing sensor data and connecting to LoRaWAN.
More technical information about the coding of the MKR 1310 that Paul Schulz, our STEM volunteer, has developed is on his GitHub here: https://github.com/PaulSchulz/paeiot-sensor-one
The sensor we are using to measure CO2, Temperature and Humidity is the 3-in-1 Grove Sensor. Although we could use separate sensors at a similar cost, this 3-in-1 package covered what we needed, simplified wiring requirements, and seems to be widely available.
The Grove 3-in-1 Arduino-compatible sensor I²C can measure CO2, temperature, and humidity. The CO2 sensor is based on the Sensirion SCD30, which is a Non-Dispersive Infrared (NDIR) carbon dioxide sensor.
The Grove sensor is also designed to be suitable for weather stations. This is proffered as many similar sensors are only designed for indoor air quality applications. However, this still does not mean the sensor is waterproof or weatherproof, so will need to be enclosed within a Stevenson screen.
Further, the Arduino MKR WAN 1310 needs greater protection from the elements and so enclosed in a waterproofed enclosure that will protect from moisture, rain, sunlight and high temperatures. Also, it will need to be wall mountable and able to enclose other electronics that will allow the Arduino to operate from a solar/battery system and be maintained to allow servicing, software updates, reboots and even other electronics.
Voltage Dividers – Measuring Salar and Battery Status.
The open-circuit voltage of the solar panel is 22V. We also don’t want to waste power in the divider, so we’ll set R1 at 1M ohm, and we also want the input voltage to the MKR A0 to be the reference voltage of 1V, so R2 comes out at ~47K. Equally, when measuring the battery voltage, we don’t want to drain the battery, so we’ll also need to set R1 at 1M ohm, and as we want the input voltage to the MKR A0 not to exceed 1V reference, R2 comes out at ~150K ohms this comes out at about 5-6 uA and negligible drain on the battery. All this, fortunately, can finally be adjusted in the code to reflect the actual correct voltage equivalents in the data sent.
1 x Sensor Package – Part Number: 101020634
1 x Arduino MKR WAN 1310
1 x Arduino MKR Proto Shield Large
1 x 6.4V 4.5Ah Lithium Deep Cycle Battery
1 x 813514396145 MPPT Solar Controller 7.2V 1A
1 x 10W 12V Monocrystalline Solar Panel Altronics Part N0010F
1 x Enclosure ABS Polycarbonate UV resistant, waterproof hinged lid
1 x Pigtail 90° U.FL Plug to SMA Jack
1 x 915-928Mhz waterproof UV resistant antenna
1 x Stevenson Screen enclosure to suit Grove sensor
1 x Cable Gland for sensor cable
1 x 4 core shielded cable for sensor
2 x 1M Resistor 1/2w MF 1%
1 x 150k Resistor 1/2w MF 1%
1 x 47k Resistor 1/2w MF1%
1 x 1N4004 common available diode
1 x SPDT PCB Mount switch to isolate power when swapping out updated MKR board.
1 x P9482 2 Pin 5A Locking Female Line IP67 Waterproof Socket
1 x P9462A 2 Pin 5A Locking Male Chassis IP67 Waterproof Plug
1 x P9484 4 Pin 5A Locking Female Line IP67 Waterproof Socket
1 x P9464A 4 Pin 5A Locking Male Chassis IP67 Waterproof Plug
1 x Pryda Nail-On Connector Plate 75 x 380mm
3 x Antsig Antenna Mount U-bolt 6.3mm (1/4″)
Project Overview: https://stemlibrary.space/microclimates/
IoT overview: https://stemlibrary.space/iot-microclimate/
Live microclimate data: https://stemlibrary.space/microclimate-data/
Enfield Library test and calibration
Port Adelaide Library