Senior Design Project: Bluetooth Low Energy Mesh Agricultural Sensor Network

Project Description

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.

Engineering Design Requirements

Functionality

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

Reliability

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

Power

The system shall draw 0W from an external grid source

The system shall successfully transmit its data payload to a central database.

Usability

The software interface shall provide a data export function to a CSV file

The software interface shall display temperature data

Safety and Cost

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

Long Wires

Dependent Mesh

Independent Mesh

Long Wires

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

Dependent Mesh

Wires are used to

communicate with the

hub or gateway instead directly instead of using individual row hubs

Independent Mesh

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

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.

Proposed System Block Diagram

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