ZigBee Wireless Soil Moisture Sensor Design for Vineyard ...

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Manufacturer Product ROM (KB) Atmel Meshnetics Chipcon Ram Transmit Power 23 Receiver Sensitivity TX Current RX Current Sleep Current AT86RF230 NA NA 3dBm -101dBm 16.5mA 15.5mA 20nA ATmega128 RZAV MNZB-24- A2 MNZB- A24-UFL 128 8KB 3dBm -101dBm 26.5mA 25.5mA 1.02uA 128 8K 3dBm -101dBm 18mA 19mA 6uA 128 8K 20dBm -104dBm 50mA 23mA 6uA CC2430 128 8K 0dBm -95dBm 26.9mA 26.7mA 0.5uA CC2420 NA NA 0dBm -95dBm 17.4mA 18.8mA 20nA Microchip MRF24J40 NA NA 0dBm -95dBm 23mA 19mA 2uA Table 2: Current ZigBee Transceivers The Chipcon CC2430 ZigBee microcontroller transceiver was selected for this research. The main reason are for this selection was that the CC2430 has a built-in microcontroller, so the final design does not require a separate microcontroller and ZigBee transceiver. The CC2430 microcontrollers are also cheaper than most other ZigBee solution devices. The CC2430 comes with a free full ZigBee stack and 802.15.4 MAC layer software stack with source code. Finally it has reasonable RF performance and acceptable power consumption. 2.3 Soil Moisture Monitoring Techniques There are several methods currently used to measure soil moisture content. Some methods are more precise than the others. Similarly some techniques are more expensive and complicated than others. In order to achieve a suitable compromise of complexity, price and accuracy, it is important to analyse the advantages and disadvantages of each technique. The other important factor is the suitability of the selection for a specific application and environment. 2.3.1 Gravimetric Technique (Oven dry and weigh) This is the simplest and most accurate technique for any soil sample. The basic principle is to dry a soil sample in an oven at 105 ۫◌C for 24 hours to
determine the soil moisture content. The soil moisture content equals to the initial field soil weight less the oven dry weight. The main advantages are it is relatively inexpensive, really simple, does not require specialised equipment and is highly accurate. The disadvantages are it is time consuming and labour intensive. The accuracy of the experiment depends on the accuracy of the scale. Moreover this technique is not suitable for measuring larger areas with larger sample sets, like a vineyard. 2.3.2 Dielectric Constant Soil Moisture Probe and Meter There are two techniques used to measure the soil dielectric constant, Time Domain Reflectometer (TDR) and Frequency Domain Reflectometer (FDR). Both techniques measure the capacitance of a non conductor (in this case soil) using high frequency electromagnetic waves or pulses. The result can be related to soil moisture content. The difference between these techniques is the TDR measures the time taken for an electromagnetic wave to travel through the soil between the probe pins, whereas FDR uses a radio frequency wave to measure the soil capacitance. The advantages of these types of soil measuring techniques are that they are relatively accurate (±1-2%) and can provide a direct read out of volumetric soil moisture percentage or continuous readings if required by a data logger or sensor network. These systems are relatively unaffected by soil mineralogy [11]. The TDR technique is more accurate and less affected by soil minerals [11], while FDR can detect bound water in fine soil particles. In general TDR instruments are considerably more expensive than FDR. Also the electronics for TDR is more complicated than for the FDR technique. Generally the FDR technique is preferable due to its reasonable accuracy, affordability and ease of use [11]. The disadvantages are these instruments are more expensive than most other techniques, reading error occur if good contact is not made with soil, and probes can be damaged in rocky soils. 24
Page 1 and 2: ZigBee Wireless Soil Moisture Senso
Page 3 and 4: Statement of Originality ‘I hereb
Page 5 and 6: Abstract The soil moisture level is
Page 7 and 8: 6.4.2 PCB Design Version Two ......
Page 9 and 10: Figure 46: Low Pass Filter and Comp
Page 11 and 12: 1 Introduction Wireless Sensor Netw
Page 13 and 14: 2 Literature Review 2.1 Wireless Se
Page 15 and 16: IEEE 802.15.4 networks can be separ
Page 17 and 18: The cluster tree topology is a spec
Page 19 and 20: Figure 6: Standard Technology Map [
Page 21 and 22: 2.2 Currently Available ZigBee Devi
Page 23: the supplied ZigBee stack is that m
Page 27 and 28: 2.3.4 Tensionmeter A tensiometer is
Page 29 and 30: 3 Vineyard Monitoring and Managemen
Page 31 and 32: Web Server Database Server Server L
Page 33 and 34: EW . e . T T For the temper
Page 35 and 36: Heaters: This is the only method, w
Page 37 and 38: Sprinklers: Relatively warm water g
Page 39 and 40: Figure 23: Bud-break Out to Bloom S
Page 41 and 42: 4 Objective and Methodology The mai
Page 43 and 44: and heat pulse readings for calibra
Page 45 and 46: etter stability with respect to sup
Page 47 and 48: 5 Wireless Sensor Network (ZigBee M
Page 49 and 50: 5.2 Hardware Design The hardware im
Page 51 and 52: simple differential interface to th
Page 53 and 54: Figure 31: CC2430 Microcontroller M
Page 55 and 56: sensor readings are obtained via th
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Page 59 and 60: functionality. This process allows
Page 61 and 62: 5.4 WSN Embedded Software Figure 38
Page 63 and 64: config.idleTimeout = 50; config.rx.
Page 65 and 66: frequency caused by introducing wat
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comparator reference clock circuit,
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6.5 Enclosure Design and Fabricatio
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Figure 53: Sensor Initial Calibrati
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Total Volume = 432 mL is constant.
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Once data was collected, a third co
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The main reason for the capacitance
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As the capacitance increases, the l
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Capacitance (pF) The moisture value
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In the final software calibration,
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8.2 Hardware and Software Improveme
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8.3 Second Generation Soil Moisture
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than over the whole vineyard. The s
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13. Henebry, G.M. and A.K. Knapp. S
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38. Wallace R., Antenna Selection G
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6V C18 1uF 1 3 1 5 0 0 2 1 2 1 3 1
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104 Sensor module schematics Vs 3 -
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106 Coordinator module schematics G
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108 Appendix B - Soil Moisture Sens
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Soil Moisture senor top/bottom laye
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Software Directory Soil Moisture Se
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