Grape varieties grown in the vineyard at the Lake Erie Regional Grape Research and Extension Center (LERGREC) have different sensitivities to cold temperature.
High value grapes of the vinifera class are the most sensitive to cold.
Establishing a vineyard is expensive and production is not achieved for at least three years after planting, which makes placement of high value varieties critical for success.
The goal of this projects is to set up an array of sensors, at ground levels and at 1 meter, to log temperature levels over a season. This information is valuables in establishing locations in the vineyard that would be more suitable to the high value grape varieties.
The system shall record temperature data from each sensor
Each sensor node shall support at least two distinct temperature inputs
The system shall store and transmit temperature data
The sensor node shall record a temperature reading at a configurable interval
The sensor ode enclosure shall have a mechanical impact protection of IK08
The sensor node and all external connectors shall have an ingress protection rating of IP69K
The sensor node enclosure and all metallic hardware shall be rated to NEMA 4X or equivalent
The system shall have a design life of 2 years
The system shall draw 0W from an external grid source
The system shall successfully transmit its data payload to a central database.
The software interface shall provide a data export function to a CSV file
The software interface shall display temperature data
The battery shall be fully sealed in a non-corrosive, leak-proof case
The sensor enclosure, sealants, and any external components shall be fabricated only from materials recognized by the FDA as Food Contact Substances
All electronic components shall be RoHS-compliant, specifically using lead-free solder and components free of leachable RCRA 8 heavy metals
Design Choices and Alternative Options
Possible System Architectures
Temperature sensing
wires are run along the
rows and then report to
sensor hubs for each
row before passing the
data through a wired
connection to the
central hub or gateway
Wires are used to
communicate with the
hub or gateway instead directly instead of using individual row hubs
An array of sensors
communicates
wirelessly with a
central hub or gateway
The group has settled on building an independent mesh network of sensors due to the cost saved on wires. However, this choice opens the system up to other difficulties surrounding power and reliability.
Basic System Model
https://www.nordicsemi.com/Products/Wireless/Bluetooth-Mesh/What-is-Bluetooth-Mesh-and-NLC?lang=en#infotabs
Bluetooth Low Energy Mesh (BLE Mesh) is a technology that utilizes Bluetooth low energy to form the backbone of a wireless mesh network. A BLE Mesh network is made up of many nodes fulfilling different purposes to maintain the integrity of the network. BLE Mesh is a many to many communication protocol which means that packets are flooded across the network until they arrive at their destination.
Many sensors along with a Wi-Fi enabled transmitter make up a BLE Mesh network where data is gathered and packaged for storage. This data is then stored in a hard drive which when paired with a data analysis system enables the generation of easy to understand graphics and other analysis tools.
Necessary Component Selection
The group elected to use a Nora 206B by uBlox for it's following features:
Integrated BLE antenna
Built on Nordic nRF54L15 Microcontroller
Low active current < 25mA
Large amount of non-volatile memory
Existing BLE Mesh stack
Extensive developer tools provided by manufacturer
Other Microcontroller devices considered:
Espressif ESP32 - high active current
Arduino Nano R4 - Lacks Bluetooth capabilities.
Nordic nRF52840 - Lacks equired memory for long term storage.
SiLabs EFR32HG22 - Lacks the required memory to support a large BLE Mesh network
The group elected to use a DS18B20 for it's following features:
±0.5°C accuracy
1-Wire protocol easy for multi-sensor setups
Built in ADC
Built in CRC check-sums automatically detect
and discard corrupted packets
Convenient Pre-packaged configurations available
Popular temperature sensor device with many manufacturers
Other temperature sensing devices considered:
TMP1827NNGRR - Less accurate with no convenient package available
Thermistor - Requires calibration due to non-linear temperature response
STS40-CD1B-R3 - Lacks a pre-packaged, ruggedized solution
The group elected to use a Lithium Thionyl Chloride (Li-SOCL2) battery technology for it's following features:
Ability to operate reliability down to -55°C (-67°F)
Elimination of external charging complications
Cost effective $14.50 per unit
Large size: 19000 mAh
Nominal voltage (3.6V)
Other battery technologies considered:
Lithium Iron Phosphate (LiFePO4) - Inefficient power usage, would require a heater.
Lithium Titanate Oxide (LTO) - Low nominal voltage (2.4V) would require complex power management solutions.
Early Testing and Estimations
Road Map Moving Forward