Iowa State University
Ridgeline
Meteorological
Sensor Network
Final Report
Stephen Copeland, Xau Moua, Joseph Lane, Robert Akerson
12/9/2010
Table of Contents
List of Figures ................................................................................................................................................ 4
List of Tables ................................................................................................................................................. 4
List of Definitions .......................................................................................................................................... 5
1. Project Overview ....................................................................................................................................... 6
1.1
Executive Summary ............................................................................................................... 6
1.2
Acknowledgements............................................................................................................... 6
1.3
Problem Statement ............................................................................................................... 6
1.4
Problem Solution................................................................................................................... 7
1.5
Operating Environment ........................................................................................................ 8
1.6
Limitations............................................................................................................................. 8
1.7
Expected End Product and Other Deliverables ..................................................................... 9
2. Design Requirements .............................................................................................................................. 10
2.1
Design Objectives ................................................................................................................ 10
2.2
Functional Requirements .................................................................................................... 10
2.3
Non-Functional Requirements ............................................................................................ 10
2.4
Design Constraints .............................................................................................................. 11
2.5
Technology Requirements .................................................................................................. 11
2.6
Technical Approach Considerations.................................................................................... 11
2.7
Testing Approach Considerations ....................................................................................... 11
3. Detailed Design ....................................................................................................................................... 12
3.1
Wireless Mesh Network Protocol Technology .................................................................... 12
3.2
UHF Wireless Transceiver/Communication Module........................................................... 14
3.3
Serial Interface Modes ........................................................................................................ 17
3.4
UHF Antenna ....................................................................................................................... 17
3.5
Power Supply ...................................................................................................................... 21
3.6
Microcontroller ................................................................................................................... 21
3.7
Casing .................................................................................................................................. 22
4. System and Unit Level Testing Cases ...................................................................................................... 23
4.1
UHF Transceiver/Communication Module Unit Level Testing Cases .................................. 23
4.2
UHF Antenna Module Unit Level Testing Cases .................................................................. 24
4.3
Microcontroller Unit Level Testing Cases ........................................................................... 24
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4.4
Casing Unit Level Test Cases ............................................................................................... 25
5. Implementation ...................................................................................................................................... 26
5.1
Hardware............................................................................................................................. 26
5.2
Software .............................................................................................................................. 30
6. System and Unit Level Test Case Results ................................................................................................ 31
6.1
UHF Transceiver/Communication Module Unit Level Testing Results ............................... 31
6.2
UHF Antenna Module Unit Level Testing Case Results ....................................................... 33
6.3
Wind Sensors Testing Case Results ..................................................................................... 34
6.4
PCB Signal Converter Circuit Testing Case Results .............................................................. 35
6.5
Microcontroller Unit Level Testing Case Results ................................................................ 36
6.6
Casing Unit Level Test Cases ............................................................................................... 37
7. Recommendations for Project Continuation .......................................................................................... 38
7.1
Technology Continuations .................................................................................................. 38
8. Estimated Resources and Schedule ........................................................................................................ 39
8.1
Estimated Resources ........................................................................................................... 39
8.2
Schedule .............................................................................................................................. 41
8.3
Task Breakdown .................................................................................................................. 42
9. Closure Material ...................................................................................................................................... 43
9.1
Project Team Information ................................................................................................... 43
9.2
Closing Summary ................................................................................................................. 44
References .................................................................................................................................................. 45
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List of Figures
Figure 1: Mesh Network Solution ................................................................................................................. 7
Figure 2: Scout Tower System Block Diagram............................................................................................... 8
Figure 3: Building Blocks for Mesh Network Solution ................................................................................ 10
Figure 4: Micro-controller to transceiver interface connections................................................................ 15
Figure 5: Horizontal and Vertical Radiation Map of Dipole 1/2-Wave Antenna ........................................ 18
Figure 6: Horizontal and Vertical Radiation Map of Dipole 1/4-Wave Antenna ........................................ 19
Figure 7: Horizontal and Vertical Radiation Map of Yagi Antenna ............................................................. 20
Figure 8: Printed Circuit Board .................................................................................................................... 26
Figure 9: Signal Converter PCB.................................................................................................................... 27
Figure 10: Transceiver ................................................................................................................................. 27
Figure 11: Arduino Microcontroller ............................................................................................................ 28
Figure 12: Full system device ...................................................................................................................... 28
Figure 13: Wind Vane and Anemometer .................................................................................................... 29
Figure 14: Wind Sensor Mount ................................................................................................................... 29
Figure 15: Latency Testing Case .................................................................................................................. 32
Figure 16: Latency Testing Results .............................................................................................................. 33
Figure 17: Antenna S11 Parameters ........................................................................................................... 33
Figure 18: Anemometer Testing Results ..................................................................................................... 34
Figure 19: Wind Vane Testing Results......................................................................................................... 35
Figure 20: Signal Converter Circuit Test Results ......................................................................................... 35
Figure 21: Data Communication Aggregated .............................................................................................. 36
Figure 22: Data Communication Results ..................................................................................................... 37
Figure 23: Project Schedule ........................................................................................................................ 41
Figure 24: Task Breakdown ......................................................................................................................... 42
List of Tables
Table 1: Estimated Cost for a Single Unit .................................................................................................... 39
Table 2: Estimated Development Labor Cost.............................................................................................. 39
Table 3: Estimated Project Cost .................................................................................................................. 40
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List of Definitions
CFD
Data Logger
Ethernet
Mesh Network
Met Tower
NEMA4 Enclosure
RF
SCADA
Scalable System
Self Healing Network
Wireless Transceiver
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Computational Fluid Dynamics; a numerical computer model that
calculates wind (mass) flow given a digital model of the terrain and
the expected wind dynamics
A device which obtains data from various sensors and stores the
gathered information in a form of memory for future reference
A type of connection used for data transfer between the data
logger and the transceiver
A network type where each node may act as a router, relaying
information for other nodes.
Meteorological tower; central collection station tower
Enclosure standard set by NEMA, which type 4 enclosure is
constructed for indoor or outdoor to provide a degree of protection
to personnel access, the equipment inside against foreign objects,
harmful effects such as water, rain, sleet, snow, and external
formation of ice on enclosure
Radio Frequency
Supervisory control and data acquisition refers to a monitoring and
controls system for industrial processes
The ability to add and expand more to the system which will
increase performance of the system
A network that is able to re-route the path by which data is
transferred in case of the loss of a node in the network
A device which is capable of receiving and transmitting signals
wirelessly
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1. Project Overview
1.1
Executive Summary
There has been a push for renewable energy in the 21st century and wind energy is among
the main sources. Mountain ridgelines are a common topology for wind energy projects.
The ridgeline is valuable to capture high elevation wind potential, but due to the complex
terrain, collecting meteorological data is difficult.
The current solution of retrieving meteorological data involves dispatching people to
download the data from data loggers. The data collected from the ridgeline is difficult to
retrieve by dispatch and is expensive to transmit through cell phone and satellite MET
towers.
The need for the project is to develop a mesh network system of remote sensors to
transmit the meteorological data to a single source, home, without having to worry about
retrieving the data, as well as to collect much more data at a lower cost than before. With
more data collected, a more accurate representation of the area can be achieved leading
to increased productivity. The mesh network system would solve the problem of
transmitting through complex terrain, and there will be no need to dispatch anybody to
retrieve the data. The mesh network is a reliable solution because of its self healing ability
to revert to alternative paths if connection is lost or a device failure occurs.
The end product will be a mesh network system that is stable through its self healing
network, have a one to two kilometer range between each node, capable of withstanding
rough weather and easy to configure. The building blocks of the mesh network are the
wireless transceivers, antenna, and microcontroller.
1.2
Acknowledgements
The team would like to thank Doug Taylor from John Deere Renewables out of Des Moines,
Iowa for his guidance and support on this project. The team would also like to give thanks
to, Benazir Fateh, Iowa State University PhD student, on Energy-aware Resource
Management in Networked Embedded Systems research focus, for providing help with
transceiver technology considerations and for demonstrating a sensor network.
1.3
Problem Statement
Meteorological data must be collected for analysis of complex terrain wind projects placed
on a mountain ridgeline to assess the potential of wind power. The benefit of placing wind
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turbines on a mountain ridgeline is the ability to capture high-elevation winds in locations
that do not have adequate wind power in the valley floor. It is difficult to capture
accurately the assessment of potential wind power in the complex terrain due to the harsh
conditions. The more data that is able to be acquired, the more accurate the assessment
will be. Currently the method of collecting data is done with a small number of large MET
towers that have three levels of sensors. These towers are expensive and not easily
transported. What is needed is a solution that can acquire more data at a cheaper cost.
1.4
Problem Solution
The proposed solution is to incorporate a large number of smaller scout towers that will be
capable of wirelessly transmitting their measurements to the large MET towers. Wireless
communication will be accomplished via radio transceivers located on each scout tower
and MET tower. The transceiver will have a built-in mesh networking protocol that will
enable towers to be added and removed from the network on demand, as well as self
healing. Figure 1 below shows a complete mesh network solution with four scout towers
on a mountain ridgeline. The mesh network will be in sync with real-time while collecting
the meteorological data.
Figure 1: Mesh Network Solution
The scout tower will consist of four measurement sensor devices, a temperature sensor, a
barometric sensor, an anemometer to measure wind speed, and a wind vane to measure
wind direction. The measurements will be logged into the data logger with one to three
second resolution. A microcontroller will control the data measurements from the
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interface of the data logger and tell the data to be transmitted through the transceiver.
The transceiver will transmit the data measurements through the antenna, which will
communicate with the other scout towers. Figure 2 below shows a complete system of a
scout tower that will be deployed.
Figure 2: Scout Tower System Block Diagram
1.5
Operating Environment
The unit will be exposed to a harsh outdoor environment. The device must be operable in
temperatures ranging from -30 to 100 °F. The transceiver is required to have a NEMA Type
4 enclosure, which must protect against rain, sleet, snow, splashing water, and hose
directed water. The antenna shall be able to communicate with the transceiver under high
elevation winds.
1.6
Limitations
The limitation on this project is the lack of knowledge and access of the area. We are
limited to the knowledge of the terrain and topography. We will not have the ability to test
our equipment in a similar environment with harsh weather and complex terrain. Our
testing will heavily rely on our estimation and research to determine the best transceiver.
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1.7
Expected End Product and Other Deliverables
At the end of the project, our client expects three to four transceivers to be ready to
deploy in the field to be field test. The transceivers must be capable of minimally
transmitting over a one to two kilometer area range of subsidence, compatible with the
data logger, withstand harsh weather conditions and have plug-in play.
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2. Design Requirements
2.1 Design Objectives
2.1.1 Obtain a working proof-of-concept of the wireless mesh network system
consisting of the basic building blocks shown on figure 3.
2.1.2 Develop a microcontroller to communicate between the data logger interface
and the transceiver
Figure 3: Building Blocks for Mesh Network Solution
2.2 Functional Requirements
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.2.7
2.2.8
The minimum range of the transceiver must be 1-2km
Network shall utilize a mesh network protocol
Data shall be sent home a minimum of once a day
Data shall be logged onto the towers own memory device
Components shall be enclosed in a NEMA4 type enclosure
Low power consumption and efficient (optional)
Network will be synchronized with real-time
Data will be collected in 1-3 second resolution
2.3 Non-Functional Requirements
2.3.1
2.3.2
2.3.3
2.3.4
Network shall be self healing in that a broken path shall be re-routed
Wireless signal shall be able to penetrate rough terrain
Wireless signal shall be able to penetrate precipitation
Network shall be plug-and-play in that little configuration shall be needed to
increase or decrease network size
2.3.5 The data acquired from the logger shall be buffered at the scout towers before
being transmitted
2.3.6 The network shall be a scalable system
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2.4 Design Constraints
2.4.1 Terrain can attenuate wireless signal
2.4.2 Topography could create unforeseen bottlenecks in mesh routing
2.4.3 Climate could stress operability of components
2.5 Technology Requirements
The chosen wireless technology must have the ability to penetrate dense forestry. The
electrical components must be able to handle extreme environment at a temperature
range of -30 to 100 °F.
2.6 Technical Approach Considerations
During the design phase of the project, we will conduct




research on mesh network capability in the transceivers
research on out to overcome the range issue
site testing at small-scale lab setting to overcome obstacle issues
research solutions relating with RF network issues
2.7 Testing Approach Considerations
Testing will be done in a two step process. First we will use an indoor small scale laboratory
setting to test the wireless communication to ensure that the system is working, followed
by outdoor field testing. Tests conducted will include, range transmit tests, interference,
reception, and power tests. Testing will need to be done at both low and high areas. Initial
outdoor testing will be done at a park that contains dense forestry in Ames, Iowa. Some
places to consider testing high elevated areas are the roofs of Iowa State University
buildings, which will also be good for testing the range of the wireless devices. Once initial
testing is done, further testing will be done on the field.
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3. Detailed Design
3.1 Wireless Mesh Network Protocol Technology
A wireless mesh network is needed to transmit and receive data. The current design uses
cellular wireless technology to transmit data, which is not a mesh network. Different
wireless technology protocols were considered and evaluated according to the design
function requirements to implement a wireless mesh network.
3.1.1 Cellular



Advantages
Very long transmission range
Very fast data rate and reliable
Security


Disadvantages
Very high cost
Very high power consumption


Disadvantages
High cost
High power consumption
3.1.2 802.11/Wi-Fi



Advantages
Respectable transmission range
Fast data rate and reliable
Security
3.1.3 Point-to-Multipoint



Advantages
Statically configured
Good data movement
Low cost

Disadvantages
Not scalable
Single points of failure (no way to
route around changing conditions)
Need coordinator to start


Disadvantages
Routers must always be powered
Need coordinator to start


3.1.4 802.15.4/ZigBee




Advantages
Very low power
Very scalable
Security
Low cost
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3.1.5 DigiMesh






Advantages
Reliable (time synchronized)
Peer-to-peer network; self healing
Very low power
Low cost
Security
Scalable

Disadvantages
Latency (router sleeping)
3.1.6 Detailed Design
Through evaluation, the Zigbee and DigiMesh protocols were the best options for the
wireless mesh network mainly because of cost and low power. Cellular was the
current form of data transmission and its costs were too high, which applies to Wi-Fi
also. Though Zigbee and DigiMesh protocols have lower data rates, they are reliable,
low cost, secure, and scalable. Through evaluation, the DigiMesh protocol is the most
attractive method.
The DigiMesh protocol is a homogenous network. There is only one node type and the
nodes are interchangeable. The network setup is simple, reliable and flexible to
expand. The DigiMesh protocol also has a built-in feature called the Sleep Mode,
which would allow the network to be power efficient.
Sleep mode allows the RF module to enter a low power state. The XBee-PRO DigiMesh
900 module support a network synchronized sleep to conserve power when it is not
being used.
One node in a sleeping network acts as the sleep coordinator. During normal
operations, at the beginning of a wake cycle the sleep coordinator will send a sync
message as a broadcast to all nodes in the network. This message contains
synchronization information and the wake and sleep times for the current cycle. All
cyclic sleep nodes receiving a sync message will remain awake for the wake time and
then sleep for the sleep period specified. The sleep coordinator will send one sync
message at the beginning of every cycle with the currently configured network wake
and sleep times. All router nodes which receive this sync message will relay the
message to the rest of the network. If the sleep coordinator does not hear a rebroadcast of the sync message by one of its immediate neighbors then it will re-send
the message one additional time. A sleeping router network is robust enough that an
individual node can go several cycles without receiving a sync message (due to RF
interference, for example). As a node misses sync messages the time available for
transmitting messages in the wake time is reduced to maintain synchronization
accuracy. By default a module will also reduce its active sleep time progressively as
sync messages are missed.
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3.2 UHF Wireless Transceiver/Communication Module
The following section describes each transceiver technology that was considered. Different
technology approaches were evaluated in detail according to their advantages and
disadvantages.
3.2.1 XBee-PRO DigiMesh 900 extended range module





Advantages
Built-in DigiMesh protocol

Scalable and interoperable with
devices from different vendors
Module is manufactured and readily
made by Digi
UHF can penetrate dense forestry
Self-healing and discovery for network
stability
Disadvantages
No knowledge on cases on range
tests
3.2.2 DigiMesh 9XTend OEM RF module




Advantages
Built-in DigiMesh protocol
Longest LOS range capability up to 40
mile range according to specification
Very High Frequency can easily
penetrate dense forestry
Module is manufactured and readily
made by Digi

Disadvantages
The transmission of the 9Xtend
was only tested to reach
approximately 2.5 miles with line
of sight
3.2.3 Analog Devices 7021


Advantages
Cost effective
Feature rich
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


Disadvantages
No built in mesh protocol
Build from scratch
more external parts are required
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3.2.4 Detailed Design
XBee-PRO DigiMesh 900 was the chosen solution to test and prove the concept of
wireless mesh networking system. This solution was chosen because of its benefits
from both XBee and DigiMesh protocols, whereas the 9Xtend module only consists of
the DigiMesh protocol.
3.2.4.1 Network Protocol
The data logger is designed to be part of an ad hoc wireless mesh network
protocol. One of the main advantages of choosing the XBee-PRO DigiMesh 900 is
because of its built-in DigiMesh protocol, which allows a very simple set-up.
3.2.4.2 Pin Connections
The only required pin connections are VCC, GND, DOUT and DIN. Where VCC and
GND are the power supply connections, and DOUT and DIN are the input and
output USART connections. However we will also be using the CTS and RTS pins.
CTS and RTS are the flow control pins. When CTS is switched it tells the microcontroller not to send any more data to the transceiver so that the transceiver
has time to transmit the data in the nearly full buffer, as well as vice versa for the
RTS pin. An illustration of these connections is shown in figure 4.
Figure 4: Micro-controller to transceiver interface connections
Other pins that we will be using are the Associate LED pin (pin 15), and the
commissioning button pin (pin 20). The Associate LED pin is used to indicate the
status of the transceivers association with the network. The commissioning
button pin will be connected to a push button. The function of the push button
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will be to set various functions in the field without the need to send commands to
the transceiver. These features can be implemented as shown in figure 5.
Figure 5: Pin Configuration of XBee-PRO DigiMesh 900
3.2.4.3 Channel hopping
Channel hopping is a method of transmitting wireless signals by rapidly switching
the operating channel. The largest advantage this serves in our project is to
greater security. The transmitter and the receiver only know a pseudo-random
channel switching sequence. For an eavesdropper to intercept the message they
must know the switching sequence.
3.2.4.4 Encryption
The chosen transceivers are capable of built in AES encryption. AES is among the
very best in publicly available block cipher encryption schemes. AES is a
symmetric key based scheme where only one key is used for encryption and
decryption. Every node in the networks transceiver will be programmed with the
same encryption key. Our chosen transceiver makes use of a fixed 128-bit key for
the AES encryption.
Since the confidentiality of this key is paramount it will be wise to not let a
human chose the key since computers are far better at choosing random
elements. To choose a key the use of the openssl encryption suite will be used to
generate our random key. The below command will output a random sequence
encoded in hexadecimal of 16-bytes for our 128-bit key.
$ openssl rand -hex 16
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3.3 Serial Interface Modes
There are two modes of serial operation in the transceiver that effect how data is
communication is handled by our microcontroller application.
3.3.1 Transparent Mode
In transparent mode, the module simply queues up data received by the application
and sends it out over the DOUT pin. Configuration commands are handled by entering
a command mode.


Advantages
Easy to implement
Less debugging



Disadvantages
Must enter command mode to
send to multiple nodes
Source node information not
available to receiver
Remote configuration not possible
3.3.2 API Mode
Frame-based API extends the level to which a host application can interact with the
networking capabilities of the module. When in API mode, all data entering and
leaving the module's UART is contained in frames that define operations or events
within the module.



Advantages
Easy to send data to multiple
destinations
Received data indicates
senders address
Remote configuration of nodes


Disadvantages
Complicates design
Most features not needed
Sleep Mode
3.4 UHF Antenna
An antenna is needed in order for the signals to be transmitted for the wireless mesh
network system. It is important to have an antenna that is capable of withstanding
extreme environment and range. The antenna must be able to fit and work with the XBeePro DigiMesh 900.
3.4.1 Conductive Sleeve Dipole Half-Wave Antenna
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At a defined frequency of 900 MHz, the longer the length of the antenna and the
higher antenna gain, the longer the range of the antenna.




Advantages
Easy to implement
Inexpensive
Higher antenna gain than 1/4
Omni-directional

Disadvantages
Range may be limited due to
omni-directional aspect
The radiation pattern maps are shown vertically, horizontally and in 3-Dimensional in
figures 5 below. The ½ wave dipole antenna has a respectable gain and is omnidirectional, which is necessary to communicate with multiple nodes.
Figure 5: Horizontal and Vertical Radiation Map of Dipole 1/2-Wave Antenna
Figure 5a: 3-Dimensional Radiation Map of Dipole 1/2-Wave Antenna
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3.4.2 Conductive Sleeve Dipole Quarter-Wave Antenna
The ¼ wave dipole antenna is similar to the ½ wave dipole antenna except the fact
that the wavelengths are smaller by half.




Advantages
Easy to implement
Inexpensive
Less antenna gain than 1/2
Omni-directional

Disadvantages
Range may be limited due to
omni-directional aspect
Although the ¼ wave dipole antenna have the same radiation patterns, the ¼
wavelengths produce less gain than the ½ wave lengths, thus will have less range than
the ½ wave dipole antenna.
Figure 6: Horizontal and Vertical Radiation Map of Dipole 1/4-Wave Antenna
3.4.3 Yagi Antenna
The Yagi antenna is an antenna made up of an array of simple dipole antennas. It can
vary in gain based on the length of the elements and the number of elements. If more
antenna elements are implemented, the gain will increase, but the directivity will not
be as good.
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



Advantages
Easy to implement
Inexpensive
High gain antenna
High range

Disadvantages
Directed line of sight, not omnidirectional
Figure 7: Horizontal and Vertical Radiation Map of Yagi Antenna
Although the range of the Yagi antenna may fit well for the design situation, the
antenna can only focus in a direct line of sight range. To allow the function of a selfhealing mesh network, the antennas must be able to transmit to multiple nodes. The
trade offs for using the Yagi antenna may not benefit the mesh network solution
design because it does not allow more than one node in its sight.
Figure 7a: 3-Dimensional Radiation Map of Yagi Antenna
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3.4.4 Detailed Designs
The need for the antenna is to help obtain a range greater than 2 km. Since the
specifications refer to line of sight ranges, the conductive sleeve dipole antenna is the
best option. The antenna is inexpensive and will be shielded properly to filter
unwanted frequency and from extreme weather.
3.5 Power Supply
Poor power supply can lead to poor radio performance especially if the supply voltage is
not kept within tolerance or is excessively noisy. To help reduce noise, a 1.0 µF and 8.2 pF
capacitor are recommended to be placed as near to pin1 on the PCB as possible. Other
problems can arise with the use of a switching power supply but in our case the switching
power supply is unlikely so details will not be given.
3.6 Microcontroller
A microcontroller is needed in order for the wireless communication module to
communicate with the data logger. The microcontroller will take the data from the data
logger and tell the transceiver module to send the specified data to the end point.
3.6.1 Development platform for LPC2148





Advantages
Powerful processor
Feature rich
Lots of memory
Socket for storage
Built in accelerometer


Disadvantages
Highest price
Less support base

Disadvantages
Not as easy to code as others
3.6.2 Development board for PIC18F4550




Advantages
USB programmable
Feature rich
Multiple coding languages
Abundant support
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3.6.3 Arduino




Advantages
Lowest cost
Massive base of supporters
Very simple coding
Very modular


Disadvantages
Least feature rich
Slowest processor
3.6.4 Detailed design
The chosen microcontroller is the Arduino. The Arduino is the lowest cost and easiest to
use solution. For our application we only need the microcontroller to act as a proxy to
the transceiver and data logger. In the future if more features are needed, for example
an Ethernet or Storage device, the Arduino has many commercially available drop-in
modules to add functionality.
3.7 Casing
An enclosure that has the ability to protect the unit is important because this unit will be
operating in extreme weather conditions.
3.7.1 Industrial Casing
The industrial casings are made of polycarbonate to house electrical components and
meet industry standards. These casings are customizable for all shape and sizes.
3.7.2 Detailed Design
The industrial casing fulfills the requirements of industrial standards meeting the
National Electrical Manufacturers Association (NEMA) standards. The enclosure
standard type NEMA 4 is required to meet the operating environment.
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4. System and Unit Level Testing Cases
4.1
UHF Transceiver/Communication Module Unit Level Testing Cases
Preliminary tests will be tested in the laboratory to ensure transceiver to transceiver
communication with each transceiver. Using Digi’s firmware, data will be sent from one
transceiver to another to ensure that communication has been made between each unit.
The ad hoc mesh network protocol will be tested when communication has been
established between each transceiver. Data will be sent from each transceiver to test and
verify the mesh network protocol.
4.1.1 Range Testing
The communication module was tested under different ranges. Computer notebooks
were used as monitors of the data being transmitted as well as temporary power
sources which aided the testing of the range between each transceiver. Range testing
was first done indoors from transceiver to transceiver within the lab. Data was then
sent from one transceiver to another from low to high distances between each node.
Testing was done under outdoor conditions including the following:




Flat terrain, such as the intramural fields
High elevated areas, such as various points on rooftops of Coover Hall
Dense forestry areas, such as Ames local parks
Areas with congestion, such as Iowa State Campus grounds
4.1.2 Power Consumption Testing
The overall power consumption of our design will be determined using National
Instrument’s LabView software in conjunction with digital multi-meters to measure
the current and voltage both during the active and inactive modes of data
transmission. Probes used to measure voltages will be placed at the VCC and GND pins
of the XBee module as well as the Vin and GND nodes of the development board.
Current readings will be made by connecting the ammeter in series with a spliced USB
cable which connects the Arduino to a computer being used as a power source. After
measurements are collected, the equation P(watts)=I(amps)*V(volts) will be used to
find the total power consumed by our product. This will produce a better
understanding of which functions, carried out by the device, consume the most
power. Based on our findings, we will then decide which source or combination of
sources will be adequate for long term operation of our final design.
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4.1.3 Self-healing Testing
The self-healing feature of the mesh protocol will be tested using various methods
such as turning off or unplugging one transceiver. Data will be sent continuously to
test the self-healing network. Multiple transceivers will also be turned off or
unplugged to test the self-healing network capability.
4.1.4 Security Testing

Channel hopping
To test channel hopping capability we will send data between two transceivers
and analyze the frequency spectrum with a spectrum analyzer to verify that the
message is not transmitted on a single channel and that hopping is indeed
occurring.

Encryption
As specified by the client further testing of encryption other than verification of
transceiver configuration is beyond the scope of the project.
4.1.5 Latency Testing
A way to test for latency is to send and receive different data packages and analyze
the sending and receiving rate versus data size. To achieve this we will use a computer
to act as the data logger, which will be running a simulation program. The program will
simulate various data sizes and append a time stamp that will be analyzed later to
determine latency. The computers running the simulation program will be time
synchronized prior to testing.
4.2
UHF Antenna Module Unit Level Testing Cases
The transceiver/communication module will be tested under ideal conditions and then
under its operating environment. The university’s antenna laboratory equipment will be
used to measure the radiation pattern for the antenna.
4.3
Microcontroller Unit Level Testing Cases
4.3.1 Basic data communication
We shall verify that communication from the simulation program and other devices is
successful.
4.3.2 Message integrity
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We will send large amounts of data with the simulation program and verify that the
message received is uncorrupted.
4.3.3 Throughput
Our simulation program will calculate throughput by sending a set amount of data e.g.
100,000 bytes, and timing how long it takes to receive the message. The following
formula will be used to calculate throughput.
Throughput 
Message length
Transmition time
4.3.3 Power
 Consumption
Power Consumption of the micro controller will be measured using both the voltmeter
and ammeter functions of multi-meters. Voltage readings will be taken by placing
probes at VCC and GND pins. Current values will be measured by placing probes in
series with the VCC pin of the microcontroller. LabView will be used to determine the
microcontroller’s power consumption over time. This will provide information about
which functions of the microcontroller require the most power.
4.4
Casing Unit Level Test Cases
To test the durability and resistivity to meet the operating environment, these tests will be
performed:



Realistic and measurable force impact on the enclosure at operating environment
temperatures
Shock and vibration tests with a test circuit within the case. The test circuit will be
tested after the shock and vibration tests to check the functionality of the circuit.
Contact in a variety of materials such as water, ice, and snow.
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5. Implementation
5.1
Hardware
The assembly and implementation of the hardware is described in this section. We have
both a physical mount and an electrical hardware that is implemented for the project. We
have four transceivers with shields plugged into an Arduino. The hardware will be
populated to match the number of transceivers. The electronic hardware includes a
printed circuit board layout, antenna, transceiver, Arduino microcontroller with shield, 4
AA battery pack, and wire cables. The physical mount includes PVC piping, hose clamps and
brass pipes.
5.1.1 Printed Circuit Board Layout
The PCB layout was done using Eagle. The main function of this PCB is to convert the
sinusoidal-wave signal from the anemometer into a square-wave signal. From the
square-wave signal, we can measure the time between each period of the squarewave and calculate the wind speed. The PCB layout was simple; therefore each
component on our board contained an associated footprint. Due to time constraint,
our team did not order a printed circuit board based off our layout, but assembled the
electronic components and the layout onto the PCB by hand.
Figure 8: Printed Circuit Board
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Figure 9: Signal Converter PCB
5.1.2 Transceiver Configuration
The transceiver contains two modes as described in the previous sections. The
transceiver is configured to be in transparent mode to ensure which node is the
transmitter and which is the receiver.
Figure 10: Transceiver
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5.1.3 Arduino Microcontroller
Due to the versatility of the Arduino Microcontroller, we implemented code to the
Arduino to function similar to a data logger for our system. The program can be
configured to average, collect, log, and transmit both wind speed and wind direction
at the user’s desired timeframe.
Figure 11: Arduino Microcontroller
Figure 12: Full system device
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5.1.4 Wind Sensors and Mounting
The wind vane and anemometer provided by John Deere were implemented and
attached to a mount for testing.
Figure 13: Wind Vane and Anemometer
In order to interface with Iowa State University’s EE491 senior design wind turbine
project, we need to collect real-time data from the rooftops of Coover Hall. The
strategy to design and implement the mounting is to place the anemometer and the
wind vane together using PVC pipes and clamping the PVC pipe with hose clamps onto
piping located on the rooftops of Coover Hall.
It should be noted that we did not have visual of what the rooftop looked like; we only
had some specifications concerning the pipes and ledge height with the advice from
the Coover Hall building manager. After assembling the mount, we realized that we
had to trim the mounting in order to minimize wind interference by putting all the
hardware components more compact together.
Figure 14: Wind Sensor Mount
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5.2
Software
5.2.1
Arduino microcontroller
Our microcontroller software was written and compiled with the Arduino
microcontroller IDE (Integrated development environment). The software’s job on the
microcontroller was to take measurements from the sensor devices connected to the
microcontroller input ports and convert the raw data into the appropriate unit of
measurement. After measurements are taken the software averages the readings
over a specified time period and averages the data. The averaged data is then sent out
to the transceiver via an onboard serial connection.
5.2.2
Data aggregation and display
At the receiving node the microcontroller is connected to a computer via a serial
connection where a program running on the computer takes incoming data from
multiple nodes and averages over a specified time. After the data is averaged it is
written to a file for logging. The log file read by a graphing program in real time to
graphically display changes in wind speed over the individual nodes, as well as an
aggregate average.
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6. System and Unit Level Test Case Results
6.1
UHF Transceiver/Communication Module Unit Level Testing Results
Preliminary tests were tested in the laboratory to ensure transceiver to transceiver
communication with each transceiver. Using Digi’s firmware, data was sent from one
transceiver to another to ensure that communication was made between each unit.
The ad hoc mesh network protocol was tested after communication was been established
between each transceiver. Data was sent from each transceiver to test and verify the built
in mesh network protocol.
6.1.1 Range Testing Results
The range testing for our transceivers provided us with some issues initially. We tried
simply holding each of the nodes at a height of about 4 feet off the ground for our first
set of tests. After discovering that our range was much lower than anticipated we
decided to raise the transceivers to a greater height. This allowed the Fresnel zone
between the antennas to be relatively free of obstacles that could impede the signal
being transmitted. The maximum distance that we were able to reach for transmission
of data between two nodes was approximately 1.75 kilometers over unobstructed
terrain. Our next step was to find the maximum transmission distance over rough
terrain. For these tests, trees and other solid objects were placed within the Fresnel
zone between nodes. The distance that we were able to achieve during these tests
came out to be approximately 0.8 kilometers.
6.1.2 Power Consumption Testing Results
The Use of Ohms law allowed us to calculate the power used by our product. Based on
our findings, we were able to determine that the required current and voltage was
103mA and 4.89V respectively with the sensors connected. When we disconnected
the sensors we found that the current was reduced to 90mA while the voltage
remained at 4.89V. This brought us to the conclusion that our scout tower devices
would require 0.504W while our central node would only require 0.4401W. With this
information we determined that our current battery pack configuration of 4 AA (1.5
Volt) batteries could power each of our modules for approximately two and a half
days.
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6.1.3 Self Healing Results
We were able to prove the existence of the mesh network protocol by place three of
the nodes in series with a distance between the first and first node that would prevent
direct communication from the first to last node without the existence of a middle
transceiver. By removing the middle node we found that the signal was no longer able
to reach its destination at the final node. Upon replace the middle node,
communication was restored. We then added a fourth node to the system at
approximately the same distance that the middle node was between the first and last
node. This gave us the opportunity to prove the mesh network protocol by removing
one of the middle nodes while still maintaining a line of communication between the
three remaining nodes due to the built in rerouting capabilities of the transceiver.
6.1.4 Security Results
The transceiver was configured to enable encryption by setting the AES keys in the
transceiver configuration. As per our requirements, the fact that communication
occurred between two nodes with encryption enabled, and did not on a node with
encryption disabled was sufficient proof of concept.
6.1.5 Latency Testing Results
Through our latency testing we were able to identify at which points we experience
latency, and also how latency scales with the increase of nodes on the network.
Latency was found at three main points: From computer to microcontroller,
microcontroller to transceiver, and transceiver to other transceivers. We also
observed that the latency followed a linear pattern as the number of nodes a message
goes through is increased as shown in the graph below.
Figure 15: Latency Testing Case
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Figure 16: Latency Testing Results
6.2
UHF Antenna Module Unit Level Testing Case Results
To test the performance of the quarter-wave dipole antenna we used a network analyzer
to test the reflection S-parameters. The antenna had frequencies that were accepted, but
for the 900Mhz frequency range, most of the frequency was reflected according to the SParameter test.
Figure 17: Antenna S11 Parameters
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The antenna was very sensitive when testing with the network analyzer. We made sure the
antenna was positioned the way that the antenna was going to be positioned when
implemented into the system.
6.3
Wind Sensors Testing Case Results
6.3.1 Anemometer Testing Case Results
The anemometer was tested directly using an oscilloscope in the lab to ensure that it
is functioning appropriately. Below is the output signal of the anemometer. The
anemometer acts as a generator.
Figure 18: Anemometer Testing Results
6.3.2 Wind Vane Testing Case Results
The wind vane was tested connected to a 5 volts power supply directly using an
oscilloscope in the lab to ensure that it is functioning appropriately. Below is the
output signal of the wind vane. The wind vane acts as a potentiometer, which is why
we connected the wind vane to a power supply. The voltage varies as wind vane
changes direction from 0 to 360 degrees. The wind vane will be connected directly to
the Arduino microcontroller.
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Figure 19: Wind Vane Testing Results
6.4
PCB Signal Converter Circuit Testing Case Results
The signal converter circuit’s purpose is to convert the anemometer’s sinusoidal-wave
signal into a square-wave signal. Once the signal is converted into a square-wave, a
frequency relative to the sinusoidal-wave will be produced with a pulse, allowing the
microprocessor to calculate the wind speed.
Figure 20: Signal Converter Circuit Test Results
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6.5
Microcontroller Unit Level Testing Case Results
6.5.1 Basic data communication
Using two nodes each connected to a computer via the serial port, we were able to
test basic data communication by typing messages to each computer. The flow of data
starts from the computer via a terminal program, goes through the computers serial
port to the microcontroller, then the microcontroller sends that data though another
serial connection to the transceiver were the process is reversed at the destinations
transceiver.
Figure 21: Data Communication Aggregated
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Figure 22: Data Communication Results
6.5.2 Throughput & Integrity Testing Results
Due to our scope change and time constraints, we were unable to perform throughput
or integrity testing and suggest that future continuations of our project perform this
testing if throughput is a concern.
6.6
Casing Unit Level Test Cases
Our NEMA-4 enclosure testing consisted of temperature range testing. We were able to
keep the enclosures outdoors in 6℉ temperature without any compromising of the
structure’s integrity. The other portions of our testing concluded that our enclosure could
maintain a watertight seal while being held under running water and that, once some
padding was applied to the inner walls, the enclosure could prevent the contents from
being damaged by dropping, shaking, or other possible vibrations that could take place if
this product were to be deployed.
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7. Recommendations for Project Continuation
7.1
Technology Continuations
In the case that this project is chosen in an upcoming semester, there are several ways in
which the new team could build upon what we have accomplished. Firstly the use of an
alternative energy source such as solar or even a small wind turbine could be implemented
as the power source for each of the scout towers. Once this is incorporated, the
completion of senior design team MAY11-01’s project will future teams to fully interface
with our project. This will allow the wind turbine, which is coupled to a motor, to be driven
using the text file containing our anemometers’ aggregated wind speed data. This joining
of projects would also allow for a more in depth look at the efficiencies of the turbine used
for MAY11-01’s project. Computational fluid dynamics calculations could be done to
determine the maximum theoretical output that the turbine should be generating. In order
to do these tests the addition of a few extra sensors would be needed. Connecting both a
barometer and a temperature sensor would provide the necessary data to undergo further
research with regard to the full capabilities of the given wind turbine in a specific location
on campus or otherwise.
The fact that this device can transmit data over rough terrain using mesh protocol allows
for many more uses aside from what we have established during the past two semesters.
There are countless ways in which these devices could be used. The two major ideas that
we have come up with include the use of our system to transmit data from transmission
lines wirelessly. This would provide a better early detection system for potential fault
conditions on transmission lines through the use of various sensors, which could alert
system operators when an issue arises within the grid.
The second potential use for these devices could be implemented with the addition of GPS
to our current design. The devices could then be mounted on vehicles operated by Cyride,
Iowa State University’s bus system. This would give the Cyride staff the capability of
locating exactly where individual buses are at any given time. Cyride could then not only
insure that bus drivers remain on their predetermined schedule, but they could also
provide passengers with a real-time update of the bus’ location in relation to the nearest
bus stop in case the conditions near the bus stop are less than favorable.
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8. Estimated Resources and Schedule
8.1
Estimated Resources
Based on the technology considerations, the estimated total cost of the technology on a
single scout tower is $4292.00 if we included the anemometer, wind vane, barometric
pressure sensor, temperature sensor and the data logger. The estimated total cost for the
scope of this project is $282.00.
Item
Estimate Cost ($)
Transceiver
Microcontroller
Enclosure
RF Antenna
Ethernet Interface
Total (Communication)
Anemometer
Wind Vane
Barometric pressure sensor
Temperature sensor
Data Logger
Total (Scout Tower Technology)
$82.00
$15.00
$50.00
$100.00
$35.00
$282.00
$285.00
$205.00
$325.00
$195.00
$3,000.00
$4292.00
Table 1: Estimated Cost for a Single Unit
The total development labor cost is estimated in table 3 with and hourly rate of $20 per
hour. The hours were based on each task, included individual work, team meetings, and
meetings with the client and advisors. The development labor cost will be donated.
Task
Estimated Hours (hrs)
Estimated Cost ($20/hrs)
Problem Definition
Technology Research/Selection
Product Design
Product Implementation
Product Testing
Presentation
Documentation
Total
70
60
150
150
300
40
100
910
$1400
$1200
$3000
$3000
$6000
$1600
$2000
$18,200
Table 2: Estimated Development Labor Cost
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The total estimated cost for the project is $20233, which includes development labor and
four total units for the communication aspect.
Description
Communication Unit
Development Labor Costs
Total
Estimated Unit Cost Estimated Quantity
$282/unit
4 units
$20.00/hour
910 hours
Extended Cost
$1128
$18,200
$19,328
Table 3: Estimated Project Cost
We would like to give our acknowledgements to John Deere. The funds for the technology
for this project including the towers, data loggers, and sensors will be provided by John
Deere.
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8.2
Schedule
Figure 23: Project Schedule
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8.3
Task Breakdown
Figure 24: Task Breakdown
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9. Closure Material
9.1
Project Team Information
9.1.1 Client Information
John Deere Renewables
Contact: Doug Taylor
Wind Assessment and SCADA Manger,
Email: TaylorWilliamD@JohnDeere.com
9.1.2 Advisor Information
Dr. Manimaran Govindarasu
3227 Coover Hall
Ames, IA 50011
Phone: 515-294-9175
Email: gmani@iastate.edu
Dr. Venkataramana Ajjarapu
1122 Coover Hall
Ames IA 50011-3060
Phone: 515-294-7687
Email: vajjarap@iastate.edu
9.1.3 Student Information
Stephen Copeland
2124 Fredericksen Ct.
Ames, IA 50010
Phone: 214-802-0813
Email: ohmantic@iastate.edu
Xau Moua
171 University Village Apt. H
Ames, IA 50010
Phone: 612-309-2068
Email: xmoua@iastate.edu
Joseph Lane
2520 NW Heritage Ave
Ankeny, IA 50023
Phone: 515-975-3444
Email: jrodericklane@iastate.edu
Robert Akerson
9107 Buchanan Hall
Ames, IA 50013
Phone: 563-826-2151
Email: rakerson@iastate.edu
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9.2
Closing Summary
Our former client, John Deere Renewables, presented us with the task of improving their
current meteorological communication system. We were charged with developing a
deployable wireless mesh network which could aid in the long range transmission of
valuable data. Despite the loss of our client, we were able to successfully complete our
project within the two semester time period provided. Despite minor setbacks along the
way the end result of this project has met our system requirements and the joining of our
project with that of senior design team MAY11-01’s will undoubtedly provide the electrical
and computer engineering department of Iowa State University with an adequate means of
obtaining meteorological data over long distances by means of a wireless mesh network.
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References
Balanis, Constantine A. Antenna Theory: Analysis and Design. Hoboken, NJ: John Wiley, 2005.
Digi. 15 Feb 2010 <http://www.digi.com/>.
"Mesh Network." Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc. 15 Feb 2010.
Web. 15 Feb 2010. <http://en.wikipedia.org/wiki/Mesh_network>.
"SCADA." Wikipedia: The Free Encyclopedia. Wikimedia Foundation, Inc. 2 Mar 2010. Web. 2
Mar 2010. <http://en.wikipedia.org/wiki/SCADA>.
Sparkfun. 15 Feb 2010 <http://www.sparkfun.com/commerce/categories.php>.
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