V3 ZigBee Features

SoilNet uses an hierarchical architecture that includes three types of wireless network units
1. Coordinator unit
2. Router unit
3. Sensor unit
based on the own hard and software development using JN5148 modules (Jennic Ltd, South Yorkshire, UK)

Wireless network protocol based on the IEEE 802.15.4™ specification
include tree routing, self-healing, listen-before-talk function using the JenNet Network stack (Jennic Ltd, South Yorkshire, UK)

The 2.4GHz radio transmission frequency used for SoilNet determines to a large extend the transmission range between transmitter and receiver. The maximum distance between a sensor unit and at least one router is 1000 m (free sight conditions), whereas the maximum distance between two routers or between a router and a coordinator is 2000 m. In case of hybrid underground configuration with the sensor unit being buried 5 cm below the surface, the transmission range between a sensor unit and router decreases to max. 100 m (depending on soil water content; see also Bogena et al., 2009).

All devices are independent from external power supply, therefore it is possible to install SoilNet in remote ecosystems

Sensor unit:

• A SoilNet sensor network can consist of up to 300 sensor units.
• Each sensor unit can host up to 9 SDI-12 sensors (e.g. to measure soil moisture, matrix potential, pressure etc.), 4 sensors with analog output signal, and one reed switch sensor (e.g. rain gauge).
• 3.6 V lithium battery can support at least 60000 measurements.
• Data logging function & handshake mechanism for unbroken dataflow
• A real-time clock enables high precision measurement timing and synchronization.
• Measurement frequency of each sensor unit is individually configurable (from 3 minutes to 12 hours). The frequency can be changes remotely at any time.
• Up to 3.8 Mio measurements can be stored on the onboard SD-Card
• The offline modus enables measurements without the need of a radio network
• GSM Modus enables data transmission over mobile network (Email)

Router:

• A full automatic weather station (Viasala WXT520) and 2 digital temperature sensors can be connected.
• Solar panels are used for self-sustaining electrical power supply.
• A 12V battery buffer ensures electrical power supply for up to 3 months.

Coordinator:

• OpenVPN data link is used for transnational communication with a net control station.
• Solar panels are used for self-sustaining electrical power supply.
• 12V battery buffer ensures electrical power supply for up to 3 months

SoilNet software functions:

• Configuration of network parameter
• Visualization and processing of sensor data
• Data output routine for data analysis and data archiving
• Control of network connection quality
• Automatic messaging in case of critical value exceeding