CHAPTER-1:- INTRODUCTION
1.1 Introduction
The amount of energy available to harvest from a radio tower density PD is
dependent upon the power being emitted P from the RF source, the gain-directionality of
the antenna from the consists of two schottky diodes and two capacitors.
We know that maximum power is received when the receiver is in the main
beam. For cell site consisting of transmitting towers of RF band, signal strengths are calculated
in given Table at various distances according to Friis transmission equation.
Pr =PtGt Gr [λ/(4πR)]2
Where,
Pr = Received Power
Pt= Transmitted Power
Gt= Gain of the transmitted Antenna
Gr= Gain of the receiver Antenna
R= Distance between the transmitter and receiver antennas
A small, low-cost, wireless sensor node is important for ubiquitous sensing.
However, the need for frequently replacing its battery has always been a problem, which has
limited its use of WSNs. Energy harvesting is one of the key techniques used to solve this
problem. We focus on using an ambient RF field as an energy source to power wireless sensor
nodes. The use of this unutilized energy as a power source will not only reduce the battery
replacement cost, but also enable a long period operation in WSNs. The energy generated from
an energy harvester varies in time and space. Therefore the use of RF energy harvesters also
requires a change in both the hardware and the software of wireless sensor nodes. Since WSNs
can be applied to many types of applications such as environment and habitat monitoring,
healthcare applications, and industrial process monitoring and control. Placing a large number
of spatially distributed low-cost sensor nodes will increase the amount and reliability of the
sensor data.
Energy supply has always been a key limiting factor to the lifetime of the agricultural WSNs.
Current commercial WSN nodes are typically powered by onboard batteries, as shown in Figure
1.1, which have fixed energy rating and limited lifespan. To maintain the sensor operability,
these batteries need to be replaced in due time. The maintenance cost of WSN nodes can be
very high, especially if the network is deployed in hard-to-service locations. For example, a
buried wireless soil sensor node must be unearthed before the exhausted batteries could be
replaced. This would increase the labour cost. Depending on the deployment location, the cost
of changing batteries could range from $10 per node for easily accessible nodes up to $100 per
node [10]. This replacement cost would be even higher if the network consists of thousands of
nodes distributed across a large field. ON World, one of the leaders in wireless research,
predicted that the labour cost of changing batteries in the wireless sensors sector could be $1.1
billion over the next several years [11]. In addition, there are growing concerns over the disposal
of batteries. Most wireless sensor batteries contain heavy metals such as lead, cadmium and
mercury, which can pollute the environment if they are improperly disposed of. In the UK, it is
reported that more than 600 million household batteries are disposed to landfill sites every year
[12]. In May 2009, The Waste Batteries and Accumulators Regulations [13] were introduced in
the U.K. with the aim of reducing the amount of waste batteries going to landfill, as well as
increasing battery recycling rates. The motivation behind this research is to overcome the
drawbacks of limited battery life and subsequent replacement, by exploring possible alternatives
to conventional, disposable batteries in powering the agricultural wireless sensor nodes, thus
making the WSN indefinitely self-sustaining. One possible solution is to use energy harvesting,
in which ambient energy is captured, converted into electrical energy, and stored. Several
energy harvesting techniques using different ambient sources, such as light radiation,
temperature difference, electromagnetic field, human power and vibrations, have been reported
in the literature [14-16]. Depending on the intended application, selection of a feasible energy
harvesting scheme is mainly determined by two criteria; these are the environmental conditions
under which the sensors will operate, and their power requirements.
1.2 Sensor Node
As mentioned in generic class of wireless ground-level sensor networks deployed in
an outdoor setting. Although some of these agricultural WSN nodes [17, 18] are often amenable
to energy harvesting techniques based on photovoltaic (notably from sunlight) and kinetic
energy based generators (such as those utilizing wind), these techniques are not ubiquitously
applicable. There is a significant class of potential applications where individual sensor node
may be buried within a structure or soil, and not subject to daylight for all or appreciable lengths
of time. Such duties may include WSNs for sub-soil irrigation management and detection of pest
infestation.
In this research, we will focus on this particular type of application, where the
sensor nodes are distributed across an outdoor field within a vicinity of domestic, agricultural or
commercial buildings, as shown in Figure 1.2. A typical deployment consists of about 20 to 30
nodes. Each node is placed within a range up to 5 meters from the periphery of the buildings. All
nodes are static at all time and buried at a depth of soil (hence the given name of ‘wireless
ground-level sensor node’) with their transceiver slightly raised above the ground to enable
wireless communication between the nodes and the base station. Due to a wide dynamic range
of outdoor environments, these wireless ground-level sensor nodes could be located in an open
field, under the shade of trees, or surrounded by growing vegetation’s, such as shrubs and crop
canopies.
RF power harvesting is a process whereby Radio frequency energy emitted by sources
that
generate high electromagnetic fields such as TV signals, wireless radio networks and cell phone
towers, but through power generating circuit linked to a receiving antenna, captured and
converted into usable DC voltage. Most commonly used as an application for radio frequency
identification tags in which the sensing device wirelessly sends a radio frequency to a
harvesting
device which supplies just enough power to send back identification information specific to the
item of interest. The circuit systems which receive the detected radio frequency from the
antenna
are made on a fraction of a micrometer scale but can convert the propagated electromagnetic
waves to low voltage DC power at distances up to 100 meters. Depending on concentration
levels which can differ through the day, the power conversion circuit may be attached to a
capacitor which can disperse a constant required voltage for the sensor and circuit when there
isn’t a sufficient supply of incoming energy. Most circuits use a floating gate transistor as the
diode which converts the signal into generated power but in linked to the drain of the transistor
and a second floating gate transistor linked to a second capacitor can enable a higher output
voltage once the capacitors reach full potential .
Though the effectiveness of energy harvesting depends largely on the amount and
predictable
availability of energy source; whether from radio waves, thermal differentials, solar or light
sources, or even vibration sources. There are three categories for ambient energy availability:
intentional, anticipated, and unknown as shown in Figure 1 below Fig.1. Pictorial view of
intentional, anticipated, and unknown energy sources. Our research relies basically on the
intentional using the Powercast harvester.
1.3 Intentional Energy Harvesting:
The designs rely on an active component in the system,such as an RF transmitter
that can explicitly provide the desired type of energy into the environment when the device
needs it. Powercast support this approach with an energy source of 3W 915MHz RF
transmitters, the P1110 and P2110 also use along with it as receiver. The intentional energy
approach is also appropriate for other types of energy, such as placing an energy harvesting
on a piece of industrial equipment that vibrates when it is operating. Using an intentional
energy source allows designers to engineers a consistent energy solution. A quick look at
the basic operation of the Transmitter and receiving circuit is as discussed below.The
Powercast TX91501 is a radio frequency power transmitter specifically designed to provide
both power and data to end devices containing the Powercast P2110 or P1110 power
harvester receivers [30]. The transmitter is housed in a durable plastic case with mounting
holes. It is powered by a regulated 5V DC voltage mostly from a power source of 240V AC,
rectified and regulated to its accommodated voltage of 5V DC from its in-built internal
circuitry. The transmitter has a factory set, fixed power output and no user adjustable
settings. Also a beautiful and control feature of it is the status LED which provide a feedback
on functional state. It provides a maximum of 3Watts EIRP (Equivalent or Effective Isotropic
Radiated Power). A side view, real view and its transmission state are as shown below in
Fig a side view, and (b) a real view of a TX91501 Powercaster Transmitter in its\
transmission state The Powercast transmitter transmits power in the form of Direct
Sequence Spread Spectrum (DSSS) and Data in the Amplitude Shift Keying (ASK)
modulation and at a center frequency of 915MHz. The power output is 3 watts EIRP and
vertically polarizes for optimal transmission. For data communication, it has an 8-bit factory
set, TX91501 identification (ID) number broadcast with random intervals up to 10ms using
Amplitude Shift Keying (ASK) modulation. Its operating temperature is within the range of 20oC to 50oC at the power input from mains
CHAPTER-2:- REQUIREMENT STUDY
2.1 Procedure steps
Our project is divided into three phases
1) Develop hardware for RF to DC voltage generating and battery charging.
2) Develop a PCB according to prototype.
3) Do the programming and troubleshooting.
Fig 2.1 :- Simplified schematic of the RF energy harvesting node
2.2 Characteristics of RF Energy Harvesting
RF energy from TV broadcasts is 100 times weaker than solar power [11]. In addition, as
compared to solar energy that can only obtain power during daytimes in fine weather, RF
energy from TV broadcasts can obtain power all day except during the maintenance period. The
energy harvested from TV broadcasts could not be estimated properly because the RF power
attenuated because of the multipath effect reflection, shielding objects, etc. We conducted a 7
days measurement of the characteristics of TV broadcast RF energy harvesting. The objective
of this measurement is to clarify the characteristics
of RF energy harvesting and to verify that energy harvested from the ambient RF field is
sufficiently stable for WSNs. Unlike solar power[1], TV broadcast signals are artificially
generated; therefore they are not interfered by the weather. This measurement was performed
in the balcony of our laboratory, which is located 6.6km away from the Tokyo tower; this tower
broadcasts TV signals over the UHF band. Figure 7 shows the amount of power harvested over
7 days. A 1kΩ resistor was used as a load resistor; this resistor can extract maximum power
from the energy harvester.
Fig 2.2 The amount of power harvested over 7 days
Results show that the amount of harvested power decreases every day at
midnight, i.e. from around 1:00 a.m. to 6:00 a.m.; this decrease is caused by the daily and the
weekly maintenance in some broadcast stations. Except the power decrease at midnight, RF
energy is rather time constant as compared to solar power which can only provide energy
during the daytime and depends on the weather
Frequency selection is an important consideration in RF Energy Harvesting
(RFEH) systems and at the same time might be environment specific. As an example for an
indoor application wavelengths up into the low GHz would be a better choice, due to their ability
to propagate well in these environments, rather than lower VHF/UHF transmissions. These
might be more useful to outdoor or remote location harvesting applications. This project
considers and indoor built environment application, where the frequency selection reflects this.
Generally in the modern built environment GSM mobile phone signals are
prevalent, and propagate well both into and out of buildings, offering harvesting potential from
both the GSM base stations as well as the user’s handsets. With the general growth of mobile
phone usage additional bands have been brought into service to cope with the demand.
CHAPTER-3:- SYSTEM ANALYSIS
Renewable energy sources provide an alternative to conventional natural sources, of
which there are limited supplies. Renewable energy can be broadly defined as a kind of energy
that is generated from natural sources, which is not typically depleted, such as sunlight, wind,
rain, tidal motion, flowing water, biomass, geothermal heat, among others. According to the
International Energy Agency, renewable energy is derived from natural processes that are
replenished constantly [13]. Some additional features of renewable energy sources that make
them an attractive alternative to the classical natural sources are:
• Renewable energy sources are often accessible without geographical and national
barriers, though certain regions may be more conducive to their large-scale use (e.g., coastal
regions for tidal energy; countries situated around the equator for solar energy).
• Renewable energy sources generally do not result in harmful by-products of
generation,which adversely affect the environment. Hence, they are very clean and safe to use.
• These sources are inexhaustible in the near term, unlike fossil fuels, which are
gettingused up faster everyday. They are generally free to harness, though specialized
equipment may be needed for high conversion efficiency.
The efficiency of the energy harvesting devices has increased with recent
technical developments, especially while capturing energy from ambient sources.
Additionally, power consumption of engineered devices is reducing over time, with
advancements in microprocessor technology. In combination of the above two facts,
energy harvesting is becoming a viable way to drive many low-power applications,
potentially replacing current sources of power in the future.
Energy harvesting can be a maintenance-free alternative to battery technology,
which is costly and inconvenient to replace. Thus, lifetime of the appliance may be
unlimited if run with well-designed energy harvesting systems. If the source of the
energy is guaranteed to available, energy harvesting systems can be used more reliably
than battery and plug-based connections.
Figure 3.1: Energy harvesting systems, courtesy
• Energy harvesting can be used as backup generator in power systems, which
helps to improve the reliability and prevent power interruptions.
• Energy harvesting systems can provide mobility to devices, which are
dependent on the traditional plug-based electricity sources. Thus, some wired (cabledriven) applications 9 are transformed into wireless applications.Energy harvesting
systems can be classified according to the source which energy is harvested from. The
most commonly observed energy harvesting systems are based on the following;
• Mechanical Energy (piezoelectric vibrations, human body movement, etc.)
• Thermal Energy (using geo-thermal energy of the earth, difference in
temperatures of two points of a conductor etc.)
• Light Energy (primarily, solar energy)
• Electromagnetic Energy (mainly from radio frequency waves, magnetic
coupling)
CHAPTER-4:-SYSTEM DESIGN
This section, deals with the design of the following modules:
i.
an antenna for maximizing RF signal
ii.
a suitable matching network to match the complex load impedance to the
antenna impedance
iii.
optimization of voltage doubler stages in RF-DC conversion module.
4.1. Antenna Design
The proposed antenna was an E-shaped single patch from the conventional wide band
microstrip antennas. The topology of the antenna was designed on a FR4 substrate. It is a
grade designation assigned to glass-reinforced epoxy laminate sheets and printed circuit boards
(PCBs). This is one of the popular industry-wide standard substrate material format for
electronic circuit boards. The key property of FR4 relates to the °ame retardant qualities of the
material. The important speci¯cations chosen in simulation for this design are: the thickness of
substrate 1.6 mm, the thickness of copper 0.035 mm, the relative permittivity 3.9, and the loss
tangent 0.01. The antenna size is characterized by its length, width and height (L, W, h) and is
fed by pi matching network, feed line and is followed by a partial ground plane. The antenna is
designed and optimized to capture the energy from the ambient at downlink radio frequency
range of GSM- 900 band.
4.2 Antenna Module
The properties and performance of the proposed antenna have been predicted and
optimized through electromagnetic simulation software in Agilent ADS 2009 environment. The
method of moments (MOM) was used for analysis and the Green's vector function was chosen
as the basis function to demonstrate the performance of the wide band confguration. The
characteristics of the fabricated antenna have been measured using the Advantest R3767CG
network analyzer.
4.2.1. Performance Study with Various Dimensions of Antenna Geometry
A performance study was conducted with various dimensions of antenna geometry. This
study includes the rectangular patch plus the pi matching network to determine the best
structure and dimensions for the antenna. The investigations were focussed on the effect of
the ground plane towards the performance of the required parameters: Return loss better than
¡20 dB at resonance with an impedance match close to 50 -, impedance bandwidth (¡10 dB)
better than 150MHz and a good overall performance of antenna at the desired frequency
Figure 4.1. Confguration of E-shaped patch antenna with pi matching network and partial
ground plane.
In order to expand its bandwidth, two parallel slots are incorporated into this
patch. The pi matching network is designed and optimized to provide an impedance
matching for the antenna 377- impedance to the complex load 63-j117- impedance (input
of the RF- DC convertor). The feed line is appropriately positioned at the upper leg of the
E-shaped patch antenna as shown in Figure 1. The slot length, width, and position are
important parameters in controlling the achievable bandwidth. Traditionally, the property
of the patch antenna is suitable for narrow bandwidth applications. The challenge here is
to make the patch antenna for wideband energy harvesting environment. The antenna
design required to look into the permittivity or dielectric constant of the substrate, width,
length of the patch antenna and the ground plane. The permittivity of the substrate plays
a major role in the overall performance of the antenna. It affects the width, the
characteristic impedance, the length and therefore the resonant frequency that resulting
to reduce the transmission effciency.
Figure 4.2.2 . Screen capture of E-shaped patch antenna
.
Figure 4.2.3. Simulation results of
return loss.
Figure 4.2.4. Simulation results of
impedance on Smith chart
.
4.3. RF-DC Conversion Module
Modeling and simulation was carried out in Multisim software environment. The
simulation and practical implementation was done with ¯xed RF at 945MHz § 100 MHz, which is
close to the down link center radio frequency (947.5 MHz) of GSM-900 band. The voltage
obtained at the ¯nal node (VDC7) of the doubler circuit was recorded for various input power
levels from ¡40dBm to +5dBm with power level interval (spacing) of 5 dBm. The input
impedance 63-j117- of the voltage doubler is obtained using the network analyzer. This 63j117- was tested from 900MHz to 1000 MHz. as the antenna was designed for the down link
radio frequency range of GSM-900 band.
Figure 4.3.1. Photograph of assembled circuit board of 7-stage voltage doubler.
RF power harvesting is a process whereby Radio frequency energy emitted by sources
that generate high electromagnetic fields such as TV signals, wireless radio networks and cell
phone towers, but through power generating circuit linked to a receiving antenna, captured and
converted into usable DC voltage. Most commonly used as an application for radio frequency
identification tags in which the sensing device wirelessly sends a radio frequency to a
harvesting device which supplies just enough power to send back identification information
specific to the item of interest. The circuit systems which receive the detected radio frequency
from the antenna are made on a fraction of a micrometer scale but can convert the propagated
electromagnetic waves to low voltage DC power at distances up to 100 meters. Depending on
concentration levels which can differ through the day, the power conversion circuit may be
attached to a capacitor which can disperse a constant required voltage for the sensor and circuit
when there isn’t a sufficient supply of incoming energy. Most circuits use a floating gate
transistor as the diode which converts the signal into generated power but in linked to the drain
of the transistor and a second floating gate transistor linked to a second capacitor can enable a
higher output voltage once the capacitors reach full potential . Though the effectiveness of
energy harvesting depends largely on the amount and predictable availability of energy source;
whether from radio waves, thermal differentials, solar or light sources, or even vibration sources.
There are two categories for ambient energy availability intentional, anticipated.
Fig:- energy harvesting
WSN in environment, agriculture, and structures applications requires continuously
available power source with long lifetimes. Self-powering with energy harvesting.
CHAPTER-5:-SYSTEM ARCHITECTURE
CHAPTER-6:- SYSTEM COMPONENTS
6.1. CC3200 LaunchPad
•Wifi Development Board
•CC3200 Single Chip Wireless MCU
•40-pin BoosterPack Headers
•Micro USB connector for power and debug
•FTDI based JTAG emulation with serial port for Flash programming
•8mbit/1MB external serial flash
•Two buttons and three LEDs
•On-board accelerometer and temperature sensor
•On-board chip antenna and U.FL connector
6.1.1. CC3200 Single-Chip Wireless MCU
•Applications Microcontroller Subsystem
•ARM Cortex-M4 80Mhz Processor
•Wi-Fi Network Processor Subsystem
•Dedicated ARM MCU - Completely Offloads Wi-Fi and Internet Protocols from the
Application Microcontroller
•Power-Management Subsystem
•Integrated DC-DC Supports a Wide Range of Supply Voltage
.Advanced Low-Power Modes (2xAA Batteries for over a Year!)
•Clock Source
•40.0-MHz Crystal with Internal Oscillator
•32.768-kHz Crystal or External RTC Clock
•CC3200 Module (Available 3rd Quarter 2014)
•An FFC certified module that includes serial flash and crystal/RTC
6.1.2. Applications Microcontroller Subsystem
•256KB RAM
•32-Channel μDMA
•8-Bit Parallel Camera Interface
•1 McASP, 1 SD/MMC, 2 UART, 1 SPI, 1 I2C
•4 General-Purpose Timers with 16-Bit PWM Mode
•1 Watchdog Timer
•4-Channel 12-Bit ADCs
•Up to 27 Individually Programmable Muxed GPIOs
•Hardware Crypto Engine AES, DES, 3DES, SHA2, MD5 CRC and Checksum
6.1.3. Wi-Fi Network Processor Subsystem
•
802.11 b/g/n Radio, Baseband, MAC, Wi-Fi, Supplicant
•
Station, AP, and Wi-Fi Direct® Modes
•
Multiple provisioning methods including SmartConfig™, AP Mode and WPS
•
Embedded TCP/IP Stack including mDNS
•
Embedded BSD Sockets API
•
8 Simultaneous TCP or UDP Sockets
•
2 Simultaneous TLS and SSL Sockets
•
Onboard HTTP web server for configuration and custom applications
•
Powerful Crypto Engine with 256-Bit AES Encryption for TLS and SSL Connections
•
WEP, WPA, WPA2 Personal and Enterprise Security
6.1.4 How do you create products with the CC3200 LaunchPad
Product Development Ecosystem
• BoosterPacks
. Software Tools
•Hardware Design Resources
•Documentation
•E2E Community
BoosterPacks
•BoosterPacks make it simple to develop a diversity of products
•They plug directly into the 40 pin headers available on the CC3200 LaunchPad
•BoosterPacks are available from Texas Instruments, third party vendors and community
members
•BoosterPacks include displays, audio, storage, positioning, motor control, prototyping and
many more
Software Tools
•Integrated Development Environments (IDEs) & Compilers
–Code Composure Studio v6
–IAR Embedded Workbench and GCC
–Energia and EmbedXcode – Based on Wiring and Arduino Frameworks
•Operating Systems, SDK and Muxing Tool
–TI-RTOS and FreeRTOS
–CC3200 Software Development Kit (SDK)
–Pin Mux Utility for ARM Microprocessors
•Application and Firmware Flashing
– UniFlash for CC3100/CC3200
•Provisioning and Configuration
–SimpleLinkiOS and Android Apps
–Web based configuration
•Testing
–SimpleLink Wi-Fi Radio Testing Tool
•Trouble Shooting Tools
CC3200 SDK
•Each example has a ready compiled binary, which can be easily flashed to the CC3200, this
includes the original Out Of Box example that the CC3200 comes preinstalled with.
•FTDI drivers so you can connect and debug the CC3200 (Will also install from the Microsoft
online service automatically if you wish)
•Documentation includes getting started guides, programming guides, driver library information,
hardware assembly and schematics.
•Comprehensive doxygen browser based SimpleLink Host Driver API documentation, which
includes code samples
•Also includes the all important driver libraries and third party resources such as FreeRTOS and
fatfs
CC3200 SDK: SimpleLink API
Device
–Initializes the host
–Controls the communication with the Network Processor
•Wlan
–Connection to the access point
–Scan access points
–Add/Remove access point profiles
–WLAN Security
•Socket
–UDP/TCP Client Socket
–UDP/TCP Server Socket
–UDP/TCP Rx/Tx
•Netapp
–DNS Resolution
–Ping remote device
–Address Resolution Protocol
•Netcfg
–IP/MAC address configuration
•Fs
–File system Read/Write
UniFlash for CC3100/CC3200
•Format the serial flash as a secure or non-secure file system
•Program an application binary or newly added files to the flash
•Install CC3200 firmware service pack updates
•Retrieve bootloader and chipset versions
•Add, erase or update files, which can include HTLM, images, text, new MAC address, security
certificates etc. Console outputs information requesting input and debug information that can be
used to solve problems
UniFlash: Important Jumpers
•Sense On Power Jumpers
–SOP2: Serial Flash Programming
•On when programming serial flash with UniFlash or debugging with IDE
•Removed when running program that has been flashed to serial flash
–SOP1: 2 Wire SWD Programming
–SOP0: 4 Wire JTAG Programming
•Force AP Mode Jumper
–For the out of the box example
–Not required in custom applications, modes can be changed programmatically
•More Jumper Configurations Details
–CC3200 LaunchPad Hardware Users Guide
Web Based Configuration
•Manually Configure Network Setting
–Access point mode
–Station mode
–Manage station mode profiles
–Device name including name advertised through mDNS
–Connection Policies
•Device About Information
–Firmware and hardware version details
–MAC Address
–AP channel and SSID details
•Onboard HTTP Web Server
–Can be used for custom applications
AP mode supports Open, WEP and WPA. Station mode supports Open, WEP, WPA and WPA2
security. Stored Wi-Fi network profiles can be given different priority load orders
Trouble Shooting Tools
•Windows
–UDP Test Tool – Tool for sending and receiving UDP packets
–TCP Test Tool – Tool for sending and receiving TCP packets
–SMTP Test Tool – Tool for testing SMTP connectivity
–Cool Term – Easy to use serial port terminal (Windows, Mac and Linux)
–Network Monitor – Network packet sniffer
–Wireshark – Network packet sniffer (Windows, Mac and Linux)
•iOS
–Fing - Excellent utility to find out what is connected on your network
–UDP Tools – Tool for sending and receiving UDP packets
–Discovery - mDNS/Bonjour utility
–mDNS Watch - mDNS/Bonjour utility
•Android
–Fing - Excellent utility to find out what is connected on your network
–UDP Sender/Receiver – Tool for sending and receiving UDP packets
–Bonjour Browser - mDNS/Bonjour utility
–ZeroConf Browser - mDNS/Bonjour utility
Hardware Design Resources
•CC3200 LaunchPad Reference Design
–Used to check for consistency and accuracy of custom board designs
–Includes reference schematics, bills of materials, as well as Gerber files
•Hardware Design Review
–Ensures that custom board design follows the guidelines provided by TI
–Hardware Design Review Process checklist
–PCB Layout Guidelines
E2E Community
•The go to place for support and technical questions on the CC3200 LaunchPad
•Community members and TI engineers contribute to answering questions and solving problems
•Includes announcements about the latest updates and service packs
•Share knowledge, ideas and learn technical and trouble shooting skills
What kind of real world products can you develop with the CC3200 LaunchPad
Sensor and Control
.
Example: Out of Box
•Comes preloaded with the CC3200 LaunchPad
•The web application runs on top of the CC3200 onboard HTTP web server
•Source code can be found in the CC3200 SDK
•Application binary can also be found with the CC3200 SDK
•4 different sensor and input demos which can be view at a TI video on YouTube
•For details get the QuickStart Guide
Sensor Example:
Uses the accelerometer to display an alarm on the web page and flash LEDs
Control Example:
Uses the web page to control LEDs and web page graphic
Internet of Things Example: Exosite
•Cloud Based IoT
–Uses Cloud services to control the CC3200 from a remote location
–Uses Cloud services to collect sensor and location data from the CC3200 from a
remote location
•Installation and Configuration
–Will need to flash the CC3200 LaunchPad with the binary available on the Exosite site
–Alternatively the source code for the CC3200 LaunchPad application is available on
github
–You will need to visit the Exosite site and sign up, at which stage you can add a new
device
–The Exosite Cloud service uses the CC3200 MAC address as an identifier, you will
need to provide this when adding a new device Displays temperature data that has been
sent by the CC3200. Remote control an LED from the web page Displays the location of
the CC3200 LaunchPad based on IP information Displays accelerometer data that has
been sent to the Exosite Cloud service
Home Automation Example: LightServer
LightKitis an App that controls RGB Intelligent lighting via Wi-Fi. It uses SimpleLink to find
existing LightServers and to add new LightServers to a Wi-Fi Router network
LightServeris a hardware device that connects to RGB Intelligent lighting and has SimpleLink
Wi-Fi (including a web server that provides browser based control)
App automatically finds and lists all available LightServers. Control of lights can be selected
individually or grouped When a new LightServer needs to be added. This can be easily
achieved through the integrated Smart Config feature Lights can now be controlled in many
different ways, color wheel, candy cane, music, special events and more
Resources
•Documentation and Learning
–CC31XX/CC32XX Wiki
–CC3100/CC3200 Overview Training by Jon Beall (YouTube)
–CC3200 LaunchPad Hardware User Guide
–CC3200 Data Sheet
–CC3200 Technical Reference Manual
–CC3200 Single Chip Wireless MCU Programmers Guide
–CC3200 SimpleLink API Programmers Guide
–CC3200 Peripheral Driver Library User's Guide
–UniFlash Quick Start Guide
–UniFlash Full Documentation
•Product Example Links
–CC3200 LaunchPad Out of Box Experience (YouTube)
–Exosite Quick Start Guide
–Exosite Source Code (GitHub)
–LightServer and LightKit Demos (Vimeo)
Software
–Code Composure Studio v6
–UniFlash for CC3100/CC3200
–Energia
–EmbedXcode
–CC3200 Software Development Kit (SDK)
–Pin Mux Utility for ARM Microprocessors
–SimpleLink/SmartConfigiOS an Android Source Code
–SimpleLink/SmartConfigiOS iTunes Store
–SimpleLink/SmartConfig Google Play
–SimpleLink Wi-Fi Radio Testing Tool
•Hardware
–CC3200 LaunchPad Reference Design
–CC3200 Hardware Design Review Process sheet
–CC3100 and CC3200 PCB Layout Guidelines
•Marketing
–Meet the new Internet: Embedded Wifi for IoT (YouTube)
6.2. LM2765
6.2.1. FEATURES
166666• Doubles Input Supply Voltage
• SOT-23 6-Pin Package
• 20Ω Typical Output Impedance
• 90% Typical Conversion Efficiency at 20 mA
• 0.1μA Typical Shutdown Current
6.2.2 APPLICATIONS
• Cellular Phones
• Pagers
• PDAs
• Operational Amplifier Power Supplies
• Interface Power Supplies
• Handheld Instruments
6.2.3 DESCRIPTION
The LM2765 CMOS charge-pump voltage converter operates as a voltage
doubler for an input voltage in the range of +1.8V to +5.5V. Two low cost capacitors and a diode
are used in this circuit to provide up to 20 mA of output current. The LM2765 operates at 50 kHz
switching frequency to reduce output resistance and voltage ripple. With an operating current of
only 130 μA (operating efficiency greater than 90% with most loads) and 0.1μA typical shutdown
current, the LM2765 provides ideal performance for battery powered systems. The device is
manufactured in a SOT-23 6-pin package
Basic Application Circuits
Voltage Doubler
fig:- pin diagram of lm2765
6.2.4 Pin Description
Pin Name Function
1.
V+ Power supply positive voltage input.
2.
GND Power supply ground input.
3.
CAP− Connect this pin to the negative terminal of the charge-pump capacitor.
4.
SD Shutdown control pin, tie this pin to ground in normal operation.
5.
VOUT Positive voltage output.
6. CAP+ Connect this pin to the positive terminal of the charge-pump capacitor.
Fig 6.2.1: - electrical characteristics
Fig 6.2.2: - performance characteristics
6.2.5 CIRCUIT DESCRIPTION
The LM2765 contains four large CMOS switches which are switched in a sequence to double
the input supply voltage. Energy transfer and storage are provided by external capacitors. the
voltage conversion scheme. When S2 and S4 are closed, C1 charges to the supply voltage V+.
During this time interval, switches S1 and S3 are open. In the next time interval, S2 and S4 are
open; at the same time, S1 and S3 are closed, the sum of the input voltage V+ and the voltage
across C1 gives the 2V+ output voltage when there is no load. The output voltage drop when a
load is added is determined by the parasitic resistance (Rds(on) of the MOSFET switches and
the ESR of the capacitors) and the charge transfer loss between capacitors. Details will be
discussed in the following application information section.
Figure 6.2.3. Voltage Doubling Principle
POSITIVE VOLTAGE DOUBLER
The main application of the LM2765 is to double the input voltage. The range of
the input supply voltage is 1.8V to 5.5V.The output characteristics of this circuit can be
approximated by an ideal voltage source in series with aresistance. The voltage source equals
2V+. The output resistance Rout is a function of the ON resistance of the internal MOSFET
switches, the oscillator frequency, and the capacitance and ESR of C1 and C2. Since the
switching current charging and discharging C1 is approximately twice as the output current, the
effect of the ESR of the pumping capacitor C1 will be multiplied by four in the output resistance.
The output capacitor C2 is charging and discharging at a current approximately equal to the
output current, therefore, its ESR only counts once in the output resistance. A good
approximation of Rout where RSW is the sum of the ON resistance of the internal MOSFET
switches. RSW is typically 8Ω for the LM2765. The peak-to-peak output voltage ripple is
determined by the oscillator frequency as well as the capacitance and ESR of the output
capacitor C2. High capacitance, low ESR capacitors can reduce both the output resistance and
the voltage ripple. The Schottky diode D1 is only needed to protect the device from turning-on
its own parasitic diode and potentially latching-up. During start-up, D1 will also quickly charge
up the output capacitor to VIN minus the diode drop thereby decreasing the start-up time.
Therefore, the Schottky diode D1 should have enough current carrying capability to charge the
output capacitor at start-up, as well as a low forward voltage to prevent the internal parasitic
diode from turning-on. A Schottky diode like 1N5817 can be used for most applications. If the
input voltage ramp is less than 10V/ms, a smaller Schottky diode like MBR0520LT1 can be
used to reduce the circuit size.
SHUTDOWN MODE
A shutdown (SD) pin is available to disable the device and reduce the quiescent
current to 0.1 μA. In normal operating mode, the SD pin is connected to ground. The device can
be brought into the shutdown mode by applying to the SD pin a voltage greater than 40% of the
V+ pin voltage.
CAPACITOR SELECTION
As discussed in the Positive Voltage Doubler section, the output resistance and
ripple voltage are dependent on the capacitance and ESR values of the external capacitors. The
output voltage drop is the load current times the output resistance, and the power efficiency is
the quiescent power loss of the IC device, and Rout is the conversion loss associated with the
switch on-resistance, the two external capacitors and their ESRs. The selection of capacitors is
based on the specifications of the dropout voltage (which equals I out Rout), the output voltage
ripple, and the converter efficiency. Low ESR capacitors are recommended to maximize
efficiency, reduce the output voltage drop and voltage ripple.
Other Applications
PARALLELING DEVICES
Any number of LM2765s can be paralleled to reduce the output resistance. Each device
must have its own pumping capacitor C1, while only one output capacitor Cout is needed . The
composite output resistance is:
Figure 6.2.4. Lowering Output Resistance by Paralleling Devices
CASCADING DEVICES
Cascading the LM2765s is an easy way to produce a greater voltage (A two-stage cascade circuit
The effective output resistance is equal to the weighted sum of each individual device:Rout =
1.5Rout_1 + Rout_2 Note that increasing the number of cascading stages is pracitically limited
since it significantly reduces the efficiency, increases the output resistance and output voltage
ripple.
Figure 6.2.5. Increasing Output Voltage by Cascading Devices
REGULATING VOUT
It is possible to regulate the output of the LM2765 by use of a low dropout regulator
(such as LP2980-5.0). The whole converter is depicted .A different output voltage is possible by
use of LP2980-3.3, LP2980-3.0, or LP2980-adj. Note that the following conditions must be
satisfied simultaneously for worst case design
Figure 6.2.6. Generate a Regulated +5V from +3V Input Voltage
6.3.. Antenna
6.3.1 Introduction
Considering maximum effective aperture as the desired setpoint for our antenna
selection, the ideal candidate antenna for the medium wave AM broadcast band would 4 have
been without a doubt the longwave antenna. The longwave antenna, as its name indicates, is
called a “longwave” antenna because the wire defining its dimensions unwinds into a full
wavelength. This would not be a problem at higher frequencies like 2.4 GHz where the
wavelength is a scant .125 meters, but at medium frequencies like 500KHz, 700KHz, or
900KHz, it is not a simple task. A true longwave antenna for a radiated electromagnetic wave
varying in time at 700,000 cycles per second, for example, would need to be approximately 430
meters long. This certainly would give us a large physical aperture, and coupled with even
mediocre aperture efficiency, would easily give us the highest effective aperture for our desired
medium frequency bandwidth.
The parameters of this project defined a transducer (an antenna is a transducer since it
converts time varying electric currents to and from radiated electromagnetic waves) that
operated at 700,000Hz, was mobile enough to transport between the lab and field, affordable
within the confines of a senior design project, and provided the best effective antenna aperture.
Electrical aperture (W/m2) is the amount of power that can be captured from the power density
of a plane wave, and delivered to a load between the antenna’s terminals. The longwave
antenna was a clear winner in the antenna aperture department, but considering we were not
even 100% certain that our RF Harvesting approach was valid, a 430 meter antenna was clearly
not within our limitations. Despite our desire to have the greatest effective antenna aperture
imaginable, the space and cost implications of the longwave antenna lead us to our next best
transducer option, the spiral wound air loop antenna.
Cost, size, and immobility are some of the major disadvantages of a true longwave
antenna. The spiral loop antenna, though sizeable in its own right, does not need to be a full
wavelength long. The spiral loop air core antenna can operate as a relatively high aperture
antenna at approximately 1/10th of a wavelength or less. This instantly reduced the proposed
footprint of our project to 1/10th the size of the longwave antenna, and also provided us a
situation where we could test our project in the lab as well as the field. Although the construction
still called for more than 40 meters of wire, the spiral shape made the antenna compact enough
for our needs. The loop antenna could have been constructed using an edge wound design.
Whereas the loops on a spiral wound antenna get progressively smaller, the loops of an
edgewise antenna are all the same size. The major advantage of the edge wound antenna
would have been the fact that most of the equations available are built around this type of
antenna. These equations are at best only approximations of reality, but they are still very
helpful to have during the design process. The UMR-EMC Lab Formula is an example of this.
We tried to port the desire parameters of the spiral wound antenna into the confines of the
UMR-EMC formula, but did not get dependable results. In retrospect, the availability of these
types of equations should have tipped the balance in favor of an edge wound antenna. Thus is
the power of retrospect.
The spiral loop antenna is considered a highly directional antenna. This high directivity
means that the antenna reception is much more focused than an isotropic antenna. An example
of a low directivity antenna would be a cell phone antenna because a signal from any direction
can be received. The spiral loop does not work like this, and must be positioned carefully to take
advantage of the antenna’s areas of maximum gain. For the spiral wound antenna, the signals
received at the antenna’s sides are received, while signals coming in off the sides are greatly 5
Volt Peaks we Observed at our Antenna Terminals attenuated. I will attempt to explain this
better later, but for now knowledge that the spiral antenna has high directivity will suffice. The
longwire antenna is also a high directivity antenna, but the compact size of the spiral loop allows
for it to be repositioned easily to manipulate the nodes and nulls. With this in mind, early in the
design process we knew that the antenna would need to be mounted to a stand that had full alt
azimuth rotational ability in order to maximize its reception pattern.
One of the main advantages of the spiral loop antenna (using the longwave antenna as
our reference frame) is that it can comfortably fit inside the trunk of a normal sized car. Our
primary goal was to prove the concept of RF Harvesting, so we knew that we would be required
to spend many hours tied to the University laboratory room operating under controlled
conditions. We could not deny, no matter how hard we tried, that we wanted to get the harvester
working in the field. From day one of the project it was clear to us that we wanted to design our
antenna so that we could perform field tests. The ability to transport the antenna from the lab to
field, from the lab to each of our homes, enabled the prospect of field testing. This was made
feasible by the spiral loop antenna.
6.3.2 . Early calculations
The designer of the antenna must determine the size of the loop. The amount of gain
you can get from a loop antenna is dependent on the size of the loop. A larger area translates
into larger (directional) gain. At over 40 meters, our spiral antenna design would still be
considered a small loop antenna because it is less than 1/10th of a wavelength. Smaller loops
can be built but most certainly would require an amplifier at the antenna terminals in order to be
effective. An amplifier would have nulled the purpose of harvesting RF energy, so all of the
smallest loop options were removed from the table. An equation that we used early in the
design process, , relates the effect of the antenna’s area to the voltage produced at the
terminals of the antenna. This equation was intended for an edge wound air loop antenna, but it
is still effective for explaining the principles involved with a spiral wound loop. A is the area of
the loop, N is the number of turns of wire in the loop, is the strength of the signal in volts per
meter (V/m), is the angle of arrival of the signal, Q is the loaded Q of the antenna when the air
capacitor is added to the circuit, and is, of course, the wavelength of the electromagnetic wave.
Since area is in the numerator of this equation, we wanted to get it as close to 1m as possible
(of course 2,3,or 4 meters would have been better but would have reduced the portability
factor). However, increasing the area of the loop has a tradeoff in the numerator. N, the number
of 6 turns, is reduced as the area of loop expands. We estimated that a 1 meter loop would
require approximately 20 loops of wire. An electric field strength of 2V/m, with an antenna Q of
90, and an angle of 0 to the transmitting antenna would give us approximately 50 volts at the
output of our loop. Knowing that this was at best an approximation of reality, we were still
encouraged by the calculations. Theoretically we could build an antenna at 700KHz that would
produce more than enough voltage at its output terminals to charge a supercapacitor to a
working voltage.
6.3.3 . Construction of receiving antenna
The spiral loop air core antenna (again using the longwave antenna as our reference
frame) can be relatively easily and cheaply constructed for medium frequency applications. The
tools list was modest and consisted of a drill, a saw, approximately 50 meters of 18 to 24 gauge
wire (AWS), some wood glue, and an alt azimuth capable stand. We wanted to make a quick
and dirty prototype of our antenna. The short materials list was a definite plus since the addition
of the prototype would cause us to construct the antenna at least 2 times.
The first spiral loop antenna we built was made with 18 gauge stranded bare copper
wire. Early research revealed that performance did not depend on whether the antenna was
wound with single strand or multiple strand wire, insulated or bare, 18 gauge or 22 gauge. We
felt strongly that any combination of these characteristics would not have a noticeable impact on
the effective aperture of our antenna. Researching one characteristic of the wire did reveal a
performance dependent material component. The only copper wire that we found to be readily
available was stranded copper wire. We knew that stranded wire would not affect our design,
but we thought a single strand of wire would be easier to work with, as well as make our overall
design look better. We considered replacing the stranded copper wire with single stranded
aluminum wire. Our local hardware store carried the length of single stranded bare wire that we
desired, but in aluminum and not copper. Our early research indicated that this would not be a
problem, but as we dug deeper into this question we uncovered claims and data that indicated
substituting aluminum wire would cost our antenna nearly 3dB of signal strength. This was
clearly not acceptable for our transducer, so we decided to use the stranded bare copper wire
since it was readily available in the 43 meter lengths we required. Our later research would lead
us to an altogether different type of wire to use for our final presentation antenna, Litz wire. I will
discuss Litz wire later. At this early stage, it is important to note, we were completely unaware
that Litz wire even existed.
The choice of frame material came down to wood versus PVC pipe. To be honest, the
PVC pipe would have probably been the best choice because it is a light, cheap, and sturdy
material. PVC pipe would have given us more flexibility for design changes, and would have
been more rugged overall. However, we had plenty of free wood available to us that was also
light, sturdy, and rugged enough. We had a specific design in mind, and since free costs less
than cheap, we decided use the free wood for our frame. With our antenna material in hand, it
was time to actually construct the prototype antenna. We cut one piece of wood slightly larger
than a meter, and then cut another two pieces of wood slightly larger than half a meter apiece.
We drilled 40 holes into our meter length wood, and then drilled 20 holes into each half meter
length. In all we drilled 80 holes into our frame with a hand power drill. The hand drill produced
somewhat crooked holes through our wood, so we decided that for the presentation antenna it
would be essential to use a drill press. Regardless, the crooked prototype holes would
eventually contain 19 loops of multi-stranded 18 gauge copper wire that we hoped would
respond effectively to the magnetic component of the radio wave.
The antenna schematic dictated that the wire was to be wound in a square pattern that
spiraled inwards at approximately 25mm’s per loop, and included a separate external loop
known as a pickup coil. The idea was to have the inner loop connect directly to the variable air
capacitor, and the then the pickup loop would connect directly to the input of our voltage
multiplier. The pickup loop is essentially a secondary winding that helps impedance match, and
therefore transfer, the captured signal to the intended load. In total, counting the inner loop and
the pickup coil, the amount of wire used for our prototype antenna was a little bit less than the
size of 1/10th of a wavelength of a radiated electromagnetic wave varying in time at 700,000
cycles per second, which is approximately 43 meters of wire.
I do not want to conclude the antenna construction section without first mentioning the
difficulties we faced while weaving the wire around the antenna frame. Although not a complete
comedy of errors, wiring the prototype antenna was certainly made more difficult because of the
stranded copper wire. We thought the logistics to snake 43 meters of stranded wire around 1
meter spiral loop was daunting enough. To make matters worse, If we weaved the stranded
copper wire too fast, the wire would kink so we would have to stop the process and fix the kink.
When a kink formed, the copper fibers began to separate. This forced us to carefully, and
slowly, pull the wire through nearly 80 separate holes.
Another problem with the stranded wire was that pulling at a pace slightly above “slow”
would cause the stranded wire to splinter apart at its end. When this splintering occurred, we
would have to stop and attempt to tighten the strands of wire. However, the wire would never
regain its original compactness after it became splintered, making it harder to feed the holes.
We thought that if we pulled the entire length of wire, all 43 meters of it through each individual
hole, then the kinking and splintering would abate. The problem with pulling the full length of
wire individually through each hole, though it would have been the easiest method, was that we
had no good place to store the 43 meters of wire each time it was pulled. If we let the wire pile
up into a mound, it would tangle up like a string of Christmas lights in a storage box.
Probably the best place to construct this spiral loop antenna would have been at a
football field!
In the end, to prevent tangling of the wire, we had to lay the wire all over the lab as we pulled it
through each hole. We wrapped the stranded copper wire around chairs, tables, and backpacks,
all in an effort to prevent the wires from tangling into an unworkable mass. As if to compromise
with the physics and mechanics of the wire, we chose to manually pull a few meters at a time in
an attempt to eliminate the negative effects inflicted on the structure of the wire.
After much perseverance, the prototype antenna was finally complete. Feeling that every
good prototype needs a name, we decided to call our initial prototype antenna the Silver Surfer.
We did not have our Ramsey 100mW rated transmitter working at this point in time, so we were
unable to test our prototype in a controlled laboratory. For this reason, after first attaching a
near-zero to 365pF variable air capacitor to the inner coil of the spiral loop antenna, and then
attaching the pickup coil of the Silver Surfer to an oscilloscope, we went directly to the field to
see if we could actually catch any radiated electromagnetic waves.
CHAPTER-7:- WORKING
RF energy harvesting is an idea whose time has come.”you can resist an invading army,
but you cannot resist an idea whose time has come”. Today there are over 5 billion cell phones,
44000 radio stations, thousands of tv stations, and countless home wi-fi system irradiating rf
energy into the atmosphere. RF energy harvesting converts RF waves into dc power using a
rectifying antenna, which is a combination of antenna and rectifying circuit. The amount of
harvestable power depends on the incident of the location, efficiency of power conversion and
size constraints of the energy collection device that is antenna. RF radiation source are
emitted by broad cast transmitters, cell phone towers or wireless local area networks. describes
the different technologies such as light energy harvesting, thermoelectric, vibration,
electromagnetic, fluid, motion, and other types like RF harvesting. The energy from the
surroundings it into usable energy for portable electronic devices this can be done without using
the batteries and power also stored into battry. Consumer electronics covers watch, mobile,
mp3 players, and other low power devices. The domestic market of the device has wide field.
A voltage doubler is designed using Dickson Multiplier topology. Silicon based Schottky
diode having threshold voltage of 230 mV and diode capacitance of 0.26 pF is chosen. At
microwave frequency, the non-linear capacitance of the diode give RMS the maximum power
transfer to the load and amplitude of the rectified output as input impedance of the rectifier
changes with frequency.Six-stage voltage doubler is implemented to measure the power
dependence of the rectifier for lower power level as the voltage measured at single stage is very
low. Single stage voltage doubler is used for Rectennameasurements inside the lab and near
the cell towers as the power level are higher at these places.
Input impedance of the diode
changes with the input power as the dc operating point of the I-V curve moves in a non- linear
fashion.A resistive impedance matching network is used to allow maximum power transfer.The
value of Rmatch depends on the input impedance of the antenna. This approach provides an
approximate and simple matching between the antenna and rectifier. The 6- stage rectifier is
tested for its performance by feeding it directly from a RF source Rectenna is a combination of
rectifier and antenna.
The LM2765 is used to doubling received voltage. For the variation of supply regulate
using the voltage regulator TPS79733 for the low power regulator. To store the received power
used the Li-Ion battery, for the charging of the battery with single cell and load sharing using the
BQ25505. Which is ultra low power operating and useful for the energy harvesting.
CHAPTER-8:- CONCLUSION
Most of the world’s energy in the future will be generated using power harvesting
technologies. It can be used in electronic device controlling, low power displays, audio /
headsets and keyboards and mice. RF energy harvesting system from presented cell towers,
RF transmitter. A high gain electromagnetically coupled antenna is developed. A silicon based
schottky diode single stage and 6 stage rectifier are also designed. A voltage of 2.78V is
measured at a distance of 10m from the cell tower. Due to the increase in the population
density, many people live within 10m from the cell tower. RF energy harvesting from cell towers
would therefore provide two fold benefits, provide an alternative source of energy and protect
people living in close vicinity of the tower from radiation health hazards.