• Summer 2013 • Spring 2013 • Fall 2012 •
• Summer 2012 • Spring 2012 • Fall 2011 • Summer 2011 • Spring 2011 •
• Fall 2010 • Summer 2010 • Spring 2010 • Fall 2009 • Summer 2009 •
New Version Ultra-Wide-Band Impulse Radio (UWB-IR) Design
by Mengxi Lin, Zoga Borova, and Jianxun Zhu
In this project, we integrated a new version of the UWB-IR RF board, controlled by an FPGA, with the MICA2 mote using an adapting board. The RF board and FPGA provide the physical and MAC layer for prototype.
For transceiver performance evaluation, a TinyOS application (written in nesC) was developed to verify the sending and receiving of messages are received by the mote. The FPGA, programmed using VHDL, provides FIFO packet buffering, S-OOK modulation, MAC layer packet creation, CRC calculation, and CRC verification. The RF board performs the physical layer transmission. The adapting board was developed to connect the mote, FPGA, and RF board together and provide a debugging interface.
Test results shows that new iteration of the UWB-IR transceiver demonstrates the improved sending and receiving capabilities. The data rate achieved is 500Kbps. Compared with the previous version of the UWB-IR transceiver, the PCB area is smaller and the FPGA offers many more logic elements which provide more complex functionalities, debug interfaces, and can be made flexibly.
Next Generation Energy Harvesting Module (EHM) and System Architecture for EnHANTs
by Zoga Borova
In the summer of 2013 I worked on improving the monitoring circuitry of the latest Energy Harvesting Module (EHM). The EHM uses a boost converter in order to guarantee charge operation from voltages as low as 0.75V. It also contains a battery protection feature to keep the battery from overcharging and being damaged. While this functioned well, there was an issue with the current sense amplifier not being able to properly read the energy levels from the photovoltaic cell. To improve the readings the amplifier was replaced with a low side current sense amplifier that can detect smaller common mode voltages. Future work for the EHM involves a transition to solid state batteries and more efficient energy conversion.
I also designed an adapting board which is an intermediate board in the EnHANTs prototype that will allow us to switch between first and second generation system modules. It can be used for debugging, assigning pin configurations to the Kmote sensor, and testing that the newer modules all work together. The board has connections to the MIB600CA Programming board, Mica2 mote, Kmote, EHM, and the De0-Nano FPGA board.
MSP430 Microcontroller-based New EnHANTs Prototype
by Tingjun Chen and Kanghwan Kim
Prior to this project, the Control Module (CM) of the EnHANTs prototype was based on an MIB600 programming board and a legacy MICA2 mote that runs the TinyOS applications. In the next generation of the EnHANTs prototype, the CM will be replaced by a KMote, which is a wireless sensor module on the TelosB platform with a MSP430F1611 microcontroller. The MSP430 microcontroller family from Texas Instruments is specifically designed for ultra-low power applications which can adapt to the new low-power feature and peripherals of the EnHANTs prototype.
With the KMote adapting boards, we tested the behaviors and communications between the Kmote and the other modules of the prototype including the Energy Harvesting Module (EHM) and the Ultra-Wide Band Impulse Radio (UWB-IR) transceiver. For the EHM, we developed external sensor module and interface to read the dynamic solar value from the photovoltaic, we also implemented the data transmission between the DS2740 coulomb counter and the KMote using the 1-Wire Protocol from Dallas Semiconductor. For the UWB-IR transceiver, we developed physical drivers for data transmission between the KMote and the DE0-nano FPGA using the Serial Peripheral Interface (SPI).
To communicate with multiple tags simultaneously and efficiently, the Raspberry Pi (RPi) is used as the gateway between the PC and the prototypes. We developed the serial data forwarding method using the netcat command to transmit the data across network connections using the TCP. We built up new testbed to demonstrate the serial data forwarding flows and used the Java-based Graphical User Interface (GUI) to show the data and packets transmitted.
Imlementation of MSP430 Softcore on FPGA
by Junlin Liu
In this project, we continue to implement the MSP430 softcore on a FPGA development platform. Several technical issues were resolved, which include (1) replacing EEPROM with SDRAM for storing program binary, (2) changing the size of data and program memory to match the architecture of TI's MSP430F1611, (3) enabling reprogramming (loading new program binary) through the serial debug interface.
Design, Development, and Fabrication of an Energy Harvesting Module (EHM) for Advanced EnHANTs Prototype
by Youngwan Kim
The purpose of my project is to develop fully fledged Energy Harvesting Module (EHM) with flexible thin-film ion battery and solar cell for advanced small EnHANTs prototype. I have designed and fabricated EHM, sized 3.5cmx3.5cm, to realize not only monitoring of the energy harvesting rate and the battery state, but also the protection of battery from over-discharging, overcharging, and overcurrent. The key operation among these functions is the protection part. As a result, EHM v6.0 can use lithium-ion (polymer) battery providing best energy densities, rare memory effect, and less self-discharging without any damage to battery life. Additionally, the stability of charging operation, in spite of low source voltage as low as 0.75V typically, is guaranteed by boost converter. Moreover, selectable output voltages such as 3.3V, 2.3V, or 1.8V are supported by using programmable linear regulator for each target application. Based on this configuration, the development of next generation EHM with the help of diverse potential improvements, such as higher efficiency of energy harvesting by fine adjustment and much smaller size through custom integrated circuit, is also expected.
Design and Implementation of New EnHANTs Control and Monitoring System
by Kanghwan Kim
For the academic year Fall 2012 and Spring 2013, I developed a microprocessor-based control module (CM) for future EnHANT prototypes and a real-time prototype control and monitoring system (CMS) compatible with the newly developed control modules. The new CM is a TinyOS compatible microprocessor board that has an MSP30F2617 microcontroller unit (MCU), connectors for external connections with other EnHANT prototype modules and the CMS, and several passive circuit components on a printed circuit board (PCB).
The new EnHANT CMS utilizes the combination of a Raspberry Pi, a credit-card-sized single-board ARM-based computer, and an FCD-PRG01 bootstrap loader (BSL) programmer as a gateway that provides the connection the control and monitoring PC and the new EnHANT CMs. While having same physical dimensions as an MICA2 mote, ATmega128L MCU based TinyOS compatible mote that the current EnHANT prototypes use, the new CM has more RAM, spends much less power, and is less than half the price of the MICA2 motes.
Integration of Thin-film Batteries and Flexible Solar Cells
by Ishaan Sayal, Matthew Cowan, and Willis Kim
EnHANTs run energy harvesting-adaptive algorithms which require precise knowledge of the incoming light energy and stored battery levels. In this project, we worked to integrate and carefully tune the newly incorporated thin-film batteries and flexible solar cells with the microcontroller interface.
The flexible solar cells, made by PowerFilm Solar, are 3.65x6.4cm and produce 22mA at 3V under solar illumination. The thin-film batteries , made by Infinite Power Solutions, are 2.5x5.8cm and operate at 4.1V with a 2.2mAh capacity.
We first developed battery charging calibration mechanism used to test the battery capacity. Following this, we calibrated the energy spending circuitry by developing a battery discharging calibration mechanism.
To calibrate the energy harvested by the solar cell, we first developed a joint hardware/software solution to eliminate noise due to variations in light modulation (alternating current or pulse-width modulation). Following this, we tuned the circuit gain to achieve a trade-off between measurement granularity and range of operation. We experimentally characterized the circuit inefficiencies to map the incoming light-energy to energy harvested (stored in the battery).
Softcore MSP430-Compatible Processor on an FPGA Platform
by Christopher Hong and Kyung Min Lee
The goal of our project is to develop an "softcore" MSP430 processor on an FPGA platform for next-generation EnHANTs prototypes. We investigated the open source openMSP430 processor and adapted the code to function on an Altera DE0-Nano development board. We then edited the code to allow users to program C code onto the softcore. A simple blinking LED code was written to test the basic functionality of the softcore. With this development, the stage is set for future code, like TinyOS, to be programmed onto the softcore. Eventually this will be adapted to a customized ASIC chip for EnHANTs.
Implementation and Optimization of a Multihop Network System
by Matt Cowan and Luis E. Peña
Prior to this project, the EnHANTs testbed contained a well-tested and working single hop implementation as well as a not fully operation implementation of a multihop system. The goal of this project was to optimize the EnHANTs system to handle the heavily increased computational load of a multihop system. To accomplish this, we carefully debugged and eliminated all bugs across three different networking stack layers. The micro-controller contains 4k of RAM which needed to be frugally managed.
Specifically, the memory of the runtime stack is crucial to various timers and events within the system, as well as stacked method calls. After optimization of both the network and application layers to remove all unnecessary variables, imports, and timers we were able to reduce the compiled memory footprint from 3616 bytes to 2640 bytes. This large reduction as well as a reduction in the packet size provided the overhead needed for the system stack to run efficiently and without memory issues. Additionally, we were able to modify the graphical user interface to allow all packets to be tracked and colored by the source node.
Finally, we implemented and tested multihop network algorithms which adapted packet rates, routing, and coordinator selection based on energy availability. The 4-node setup was demonstrated at the IEEE INFOCOM’13 conference in Turin, Italy.
This optimized multihop system will provide a great foundation on which more complex, many node, applications can be built.
New Version Ultra Wideband (UWB) Module Design
by Mengxi Lin and Jianxun Zhu
In this semester, we improved the schematic and the PCB design of the second generation of UWB transceivers. When used as a transmitter, this module receives the signal from Mote, encodes it and sends it out into the air. As a receiver, this module receives the signal from antenna, decodes it, and then sends a packet to Mote.
In this latest iteration of the design, we decreased the dimensions of the board and added a debugging interface. Additionally, in this module, the RF board hooks up with an FPGA board (DE0-nano) to implement some of the real-time driver functionality. The connection to the FPGA board reduces the area and provides a reliable interface.
Our test results show that the module could perform the desired function and is ready to be integrated with higher level system.
Compact Programmable Light Control System for the EnHANTs Testbed
by Kanghwan Kim
This fall semester, I continued to work on the Compact Programmable Light Control System that I designed and developed last summer to make the system more reliable and robust. I made several changes to the system. First, the layout of Java GUI was changed for better visibility. Second, the frequencies of the pulse width modulated signals (PWM) generated from the low-power LED driver / PWM generator was increased from 100Hz to 1kHz to reduce fluctuation in light generated from LEDs. Wires connecting modules were also replaced with twisted wire pairs to reduce noise. Each LED bulb was calibrated with a photodetector.
I am developing a Java-based command-line light control program and integrating light control program into the Java program of the testbed's control and monitoring system as an ongoing project.
Energy Availability Studies
by Kanghwan Kim and Mina Cong
This fall semester, we have finalized the studies of kinetic energy availability, expanded the studies of light energy availability, and begun the joint kinetic-and-light energy availability studies.
We wrapped up the kinetic energy availability studies by gathering more day-long kinetic energy measurement, creating a larger, and thus more reliable, pool of data. Conclusions from the studies were double-checked for accuracy.
For light energy availability studies, we continued to work with the Portable Light Energy Measurement Units developed last summer, studying the characteristics of indoor, outdoor, and mixed environment energy availabilities. Each measurement unit was set up so we could compare the data obtained from the unit directly to the data from the LabJack-based Light Measurement Collection System. We have conducted a number of long-term, short-term, mobile and stationary experiments while studying their characteristics, such as spatial and temporal variations in energy availability. We have studied the effects of location by exposing the units to several different light sources. We have also studied the variations in light energy availability on different human body placements by taking measurements on subjects under fluorescent ceiling lights. Lastly, we have studied typical day-long energy availability and its patterns by taking several day-long traces on average weekdays.
We have begun the joint kinetic-and-light energy availability study by taking simultaneous acceleration and irradiance measurements using ADXL345 acceleration measurement boards and the light energy measurement units. One of our experiments involved measuring and comparing the amount of energy each board collected while they were sitting in a grocery store basket.
We are currently working on collecting and analyzing more long-term mobile light traces as well as devising an algorithm for the sleeker comparison of motion and light energy availability data. For the latter, we are generating a MATLAB code that will allow faster and more reliable automatic comparison in replacement of the current manual, side-by-side graph comparisons.
Integration of UWB Radio Boards
by Luis Peña, Hao Wang, and Meng Wang
We integrated the new version of our ultra-wideband transceivers to the current EnHANTs setup. This integration involved the creation of a driver that interacts with the radio (physical) layer of the network stack. To add the radio driver, we had to create new TinyOS modules and debug existing ones. To test the results, we set up different test scenarios on the software and checked the signals coming out of the radio with an oscilloscope. For the second phase testing, we transmitted packets between two boards, and displayed them in our graphical interface. We sent packets with the wrong address or the wrong CRC checksum, but the new FPGA correctly filtered out these packets.
Design and Development of a Compact Programmable Light Control System for the EnHANTs testbed,
by Kanghwan Kim
In this project, we developed a new Programmable Light Control System which will replace the previous Software-based Light Control Setup for the EnHANTs testbed. The previous system, at the cost of precise irradiance control, consists of two heavy and expensive laboratory power supplies to power four LED units. The new system, instead, uses one small wall wart for each LED unit. The system consists of one 16-channel lower-power LED driver / pulse width modulated signal generator and multiples of high-power LED driver and LED bulb pairs. This new setup can control up to 16 LED's individual irradiances in 1024 levels. A newly developed Java-based control GUI lets the user simulate lighting conditions using either digital control, analog control, or repeatable irradiance trace based control with ease.
LED Driver Setup (left) and a controller GUI interface (right).
Energy Harvesting Active Networked Tags Testbed: Ultra-Wide Band Radio (IR-UWB) Enabled Testbed,
by Meng Wang, Hao Wang, and Felipe Duque
Based on the current generation chip-set of our custom IR-UWB radio with SOOK (Synchronous On-Off Keying) modulation, we have built a new prototype system to increase the maximum communication range and the data rate. The new UWB IR board is integrated with a new programmable logic (FPGA) so that the interface between the UWB IR board and the mote can be modified and improved. The FPGA performs CRC generation and verification, dummy MAC address generation and detection, preamble detection, byte synchronization and data buffering. With so many features implemented by FPGA on the UWB board, the microcontroller can deal with much more tasks from upper layer. The maximum data rate between mote and UWB board has been increased to 250kb/s, which is more than 10x faster than last version. By tuning RF front-end, the data rate over the air is more than 100x faster than before. Two off-chip pre-amplifiers are also integrated so that both of the transmitter output signal power and the sensitivity of receiver are improved.
Organic Solar Cell Fabrication for the EnHANTs
by Willie Pirc
My work over the summer of 2012 focused on the fabrication of organic solar cells that would be used to power the Energy Harvesting Active Network Tags. The fabrication of these solar cells is a slow and meticulous process, typically taking 2-3 days in order to make a batch of four cells. The process involves spinning multiple layers of chemicals onto the substrates that have already been etched with ITO. First, PEDOT:PSS is spun and baked onto the substrate to form the Hole Transport Layer. The photoactive layer, composed of a blend of PCBM and P3HT dissolved in 1,2 dichlorobenzene, is then spun on and baked. The evaporator is then used to evaporate a very thin layer of lithium fluoride, before evaporating a thick layer of aluminum on to form the cathode. The encapsulation process proved to be the most difficult part of the fabrication process, as the cells cannot be exposed to air. I made some adjustments to the encapsulation process that produced much better results. I used copper tape on the anode and cathode to wrap around to the non-active side of the substrate. OP-29 gel epoxy was then used to encapsulate the active cell with a plain glass substrate. To form contacts with wires, a copper paste was used to connect the wires to the copper tape. Due to the fact that the copper paste proved to be an unreliable adhesive, the wires were enclosed in the paste with a dab of OP-29 gel, to ensure that the contact would be sturdy.
Thin Film Encapsulation of Solar Cells
by Dov Fields
Design and Development of Portable Light Energy Measurement Units with Light Source Detector and Available Energy Calculator
by Kanghwan Kim
In this project, we designed a portable light energy measurement unit which will replace the previous Light Measurement Collection System. The previous system simply measured irradiance, not considering the spectral distribution of the light energy it is measuring. Moreover, because a computer always had to accompany each LabJack based sensor board, the system was not optimal for dynamic measurements. The new portable light energy measurement unit uses an additional RGB sensor for source detection, a combination of an on-board microprocessor and an on-board external memory for easier data collection. The unit consist of a commercial microprocessor board with a microSD card slot, a newly designed PCB for sensors, and a protective housing for the two-board system. With help of a MATLAB script which analyzes RGB sensor data and visible/infra red light intensity sensor data, the light measurement collected from the unit can be reprocessed and converted into either irradiance trace or theoretical harvest energy trace for specific solar cells.
Portable Light Energy Measurement Unit.
Accelerometer-based Motion Energy Availability Study
by Mina Cong
This summer I continued to work with ADXL_345 boards by collecting and analyzing human and object motion samples. I compared different motions, board placements, subjects, as well as test environments. Some old data was reevaluated, but most of the time was spent gathering new samples. I wrote codes to improve data processing efficiency and accuracy, as well as troubleshoot dysfunctional physical boards. I coordinated a multi-person experiment that involved gathering day-long samples to gauge the possibility of using everyday movement as a power source. Samples were recorded by the board with the logging of x, y, and z directional movements. The raw data was translated into more useful numbers relating to the maximum attainable power, critical frequency, duration, and more using MATLAB.
Analysis and Characterization of Acceleration-based Motion Energy Traces
by Craig Gutter
My research in the summer 2012 focused on determining the amount of energy that can be obtained by harvesters placed on people during their daily activities. Free living motion traces of acceleration data were obtained by people wearing accelerometers. This data was then analyzed to create a signal processing algorithm that determines when people are walking. Some of the challenges in this project included developing an algorithm that worked for different people, and adapting the algorithm for the fact that people do not walk continuously for a length of time. The acceleration data was then translated into energy data so that we could determine the amount of energy people gain through different daily activities. This data could be used to determine the type of energy harvesting network applications that could be developed from human motion.
Energy Harvesting Active Networked Tags Testbed: Characterization and Algorithm Implementation
by Albert E. Maldonado Sanchez
Our work in the summer of 2012 focused on testing and characterizations of the current EnHANTs testbed. This included testing the range of the antennas with the purpose of analyzing the testbed performance and documenting its behavior. It also included modifying the GUI, to separate groups of nodes in different windows. This summer we also focused on implementing and testing certain algorithms to see how they help EnHANTs adapt to the different levels of energy harvesting in various scenarios such as a single node case, a linked node case and a scenario with low energy levels. Algorithms were also implemented to determine the spending rate and forwarding node in a 4 node multihop case.
Designing and Developing a Software-based Light Control Setup for the EnHANTs prototype testbed
by Paul Miller and John Sarik
In this project we have designed and developed a software-based light control setup for the EnHANTs testbed. We have built individual dark box enclosures for the indoor solar cells that EnHANTs prototypes use for energy harvesting. Each dark box enclosure contains a component LED; the amount of light generated by the LEDs is controlled via software. Our setup can generate more than 5000 different irradiance levels. It allows exposing the EnHANTs prototypes to repeatable lighting conditions, including conditions that are based on the irradiance traces we have collected.
Software-based light control setup.
Building Adaptive Multihop Networks using UWB-IR Enabled EnHANTs
by Dillen Roggensinger and Elliot Katz
Envisioned EnHANT tags will form multihop networks and adapt the network topology to the energy availability. In this project, we first implemented a network layer protocol, compatible with the Fennec Fox platform, that handled the routing and forwarding of messages. The network layer was tested using two physical layer technologies. First, we demonstrated the network functionality using the reliable transceiver of the MICA2 motes. After successful demonstration using the known physical layer of the motes, we demonstrated a multihop network using the UWB-IR transceiver, which to our knowledge is the first of its kind. After basic network functionality was implemented and tested, energy adaptive algorithms were implemented, which adapted packet routing paths to the environmental energy availability. Finally, we improved the graphical user interface to easily show multihop parameters (such as routing tables) during demonstration and testing.
Adaptive mulltihop network topology where node 4 routes through nodes 2 or 3 based on energy availability.
EnHANT Testbed Calibration and Characterization
by Gerald Stanje and Haodan Huang
In this project we focus on calibrating, testing, verifying, and extensively characterizing energy-related and communications-related parameters of the EnHANTs prototypes in a complete testbed network under fully controlled light conditions, with different types of solar cells used as energy harvesters. As part of this project, we calibrated and extensively characterized the EHM's controlled energy spending functionality. We also calibrated and extensively characterized the MAC-layer behavior of the EnHANTs' UWB-IR transceivers in different configurations. Finally, we verified, and extensively tested and characterized a large set of energy harvesting adaptive EnHANTs algorithms and protocols.
Experimental validation of the EHM's controlled energy spending functionality.
Organic Solar Cells Fabrication Process Improvements
by Gregg Burrow
In this project we modified the fabrication process for the organic solar cells to improve the performance of the solar cells and increase yield. We designed and ordered pre-patterned ITO substrates. Using these substrates reduces fabrication time by 50%. Small process tweaks, such as using metal shadow masks during the cathode deposition, increased yield by 100%. We also investigated new encapsulation techniques to increase device lifetime.
Developing a new UWB IR communications board for the EnHANTs Prototypes
by Meng Wang and Wang Hao
In this project we have been developing a new version of UWB IR board. The new UWB IR board is integrated with a new programmable logic so that the interface between the UWB IR board and the mote can be modified and improved. This is expected to improve the maximum data rate by ten times. This reduces packet duration, and in turn improve the network throughput. With more logic resources, some routines can be implemented more efficiently with hardware, such as CRC check. An off-chip pre-amplifier is also integrated so that the maximum communication range will be increased to more than 10 meters.
Characterization of Energy Harvesting Applications
by Sonal Shetkar and Mina Cong
In this involved and innovative project we are investigating the integration of various energy-harvesting devices into a single board. We are working with custom-designed boards and writing and testing scripts to analyze and characterize the data collected by them. Various devices comprising the board have been developed in isolation for different purposes, and have never been jointly used before. Thus, as part of this project, we are integrating the sensor codes to ensure they work together. This project's insights should help us in characterizing energy harvesting designs and applications.
We also monitored several long-term light setups in various indoor light environments. This has provided us with valuable insights to further extend our knowledge on energy harvesting applications and their potential.
Advancing Energy Harvesting Capabilities of the EnHANT Testbed, by Paul Miller, Miao Meng, and Ying Teng
In order to improve the EnHANTs testbed, a new energy harvesting module is being developed to measure solar cell energy and consumed energy with greater precision. This involves a current sense amplifier better suited to the range of currents expected from the organic solar cells fabricated in-house (100 µA to 1 mA), as well as increased resolution for measuring the current into the battery. Although the NiMH battery operates in approximately 70% of its capacity with less than 10% deviation from its nominal voltage, using a measured voltage rather than the nominal voltage for power calculations adds precision. To complement a new EHM design, computer-controlled lighting will be implemented, enabling simulation of changing lighting conditions over time. This will require a calibration procedure in order to ensure a reproducible test.
Energy Measurement Board for EnHANT Energy Characterization
by Michael Zapas
In this project I am designing, developing, and testing an energy measurement board (EMB) that will allow simultaneously recording energy measurements corresponding to different types of ambient energy (e.g., sunlight, indoor light, and RF). Sensors for measuring different environmental energy sources are combined into one hand-held board. The goal of this project is to characterize, compare, and contrast availabilities of different types of energy in different environments to determine the most suitable energy type for different devices and application scenarios.
Designing and Developing Group Communication and Energy Adaptation Protocols for EnHANT Prototypes
by Gerald Stanje
My project focuses on designing and implementing EnHANT functionality required to support group communications and clustering in EnHANT prototypes. I designed and implemented a new medium access control (MAC) module for Ultra-Wideband (UWB) Impulse-Radio-based EnHANT prototypes. To support various communication and networking scenarios, this ALOHA-based MAC incorporates channel sensing and unicast and broadcast addressing. I have also designed and implemented a clustering protocol for EnHANTs prototypes that takes energy harvesting into account. I have designed and implemented an environmental-energy-based clusterhead selection procedure, and a procedure for joint device data rate adaptation in the presence of varying environmental energy. Finally, I have also modified the EnHANT testbed GUI to support visualization of group communications and networking.
Over 10 undegraduate, Masters, and PhD students from four different research groups completed various EnHANTs projects over this Summer semester. The achievements of Summer 2011 students were showcased in a mini-workshop held on August 29, 2011.
Design, Test and Integration of UWB (Ultra Wideband) Transceiver Board for EnHANTs Testbed
by Jianxun Zhu
In this project I have designed, tested the transceiver board for the EnHANTs platform and successfully interconnected it with the EnHANTs prototype testbed. The board integrates a custom-designed IR-UWB transmitter and receiver chipset onto a single PCB to enable half-duplex communication. The UWB chipset uses SOOK (Synchronous On-Off Key) modulation and works from 3GHz to 4GHz. A CPLD (Complex Programmable Logic Device) is used to serve as glue logic between the UWB chipset and the microcontroller. The CPLD performs data serialization and deserialization, clock recovery, preamble detection and byte synchronization. To interface the board with the current system, I have also developed the physical layer driver under TinyOS, which was later integrated into the protocol stack. The board has enabled us to fully characterize the UWB chipset and many important measurements are performed, such as transmit power spectrum density, receiver sensitivity, power consumption, narrow band interference rejection, multipath effect rejection etc. The board also serves as the wireless infrastructure of the EnHANTs testbed, and supports verification of proposed protocol stack, especially the MAC layer and the energy adaptive algorithm for application layer. Various potentials of improvement, such as system architecture, cross-layer energy optimization and next generation UWB radio development, are also discovered during the testing phase of this project.
Designing and Developing an EnHANT prototype Energy Harvesting Module
by Paul Miller
Update Energy Harvesing Module (left) and an EnHANT prototype integrated with the updated EHM (right).
In this project I designed and developed a new version of the EnHANTs Energy Harvesting Module (EHM). The fifth version of the EHM made improvements to the previous board by adding flexibility for testing and demonstration. A solar cell intended for indoor use, the Sanyo AM-1815 was chosen in conjunction with a 2.4V Varta NiMH battery with a capacity of 150 mAh. The NiMH battery is able to be charged by a number of methods, including trickle charging and fast charging. This allows for a number of different solar cells delivering a range of currents to be used. Simplicity was the motive behind some of the improvements; a resistor replaced the LED dummy load so that the discharged current is predictable and, by changing the resistor, adjustable. The batteries are now attached to their own daughterboards, which socket into the EHM so that batteries can be changed quickly without risking damage through soldering and desoldering.
Designing, Developing and Evaluating an EnHANTs testbed
by Gerald Stanje
A testbed of UWB-enabled EnHANT prototypes.
In this project I am designing, developing, and evaluating an experimental testbed of EnHANT prototypes. I integrated a custom-designed Ultra Wideband (UWB) Impulse Radio (IR) transceiver board with the existing testbed. I developed and implemented a MAC protocol for the UWB-enabled EnHANT prototypes. As part of the MAC protocol I developed functionalities for bit synchronization, error detection, and collision avoidance. I also integrated a novel energy harvesting module (EHM) with the EnHANT prototype, and extended the Java-based graphical user interface for the upcoming demo and experiments. I experimented and adapted the energy adaptive algorithms running on the application layer of the motes. This algorithms control the data rate depending on the harvested energy. I also evaluated the effectiveness of the proposed algorithms by running a set of experiments on the EnHANTs testbed.
Organic Solar Cells for Indoor Light Energy Harvesting
by Alex Smith
We use organic solar cells for our energy harvesting. Organic solar cells are better suited for our purposes than conventional crystalline silicon solar cells because of their superior response to indoor lighting, solution processability, and potential for inexpensive roll-to-roll manufacturing on flexible substrates. The current generation of devices is fabricated on a glass substrate with a photolithographically-patterned ITO layer that functions as a transparent anode. A hole transport layer is spin-coated on top of the ITO, followed by a spin-coated photoactive layer and a thermally-evaporated aluminum cathode. Our photoactive material is PV2000, a proprietary polymer:fullerine blend manufactured by Plextronics that boasts excellent performance under indoor lighting. Our design consists of 10 series-connected cells per substrate in order to produce an open-circuit voltage of ~4.6V.
Because of the air-sensitivity of organic electronics, we encapsulate our devices with a UV-curable epoxy and a glass slide, which improves the device lifetime substantially. Future devices manufactured on flexible substrates will require a more sophisticated polymer encapsulation layer in order to maintain device flexibility.
Prototyping EnHANTs: Enriching the EnHANT Prototype Testbed
by Hao Wang
In this project I have implemented several updates to the EnHANTs testbed GUI. To make the GUI more functional, I added to it the data rate panel which can show the curves of the data rate of each mote and the set parameter panel which can be used to change the max battery level, receiving energy consumption and transmitting energy consumption of all the motes. Also, for the purpose of implementing the group communication, I changed the code of the GUI to make it able to respond to the change of coordinator, show the coordinator and its dependent nodes in the demo graph and display the messages about those group communications in the text chart. In addition, I have contributed to the implementation of energy-harvesting adaptive behavior in prototype devices, where I have implemented a group communication protocol. Finally, together with Zainab Noorbhaiwala, I have enhanced the logging functionality of the testbed.
Statistical Analysis and Energy Spending Policy for EnHANTs
by Ran Schwartz
In this project I first looked into the statistical behavior of the EnHANTs devices that had been setup in various indoor locations. Those statistical measurements such as the mean, and the correlation both within one set of data points and between sets of data for different locations. These were meant to show how well light is absorbed in each setup. Those statistical measurements were broken down into specific values for weekday and weekends as well as between each weekday. Then using those statistics, energy-spending policies were developed in order to gain an understanding of what is the most efficient and productive way for a device to spend the energy it gets. This was first done one setup at a time, and culminated in testing the available data rate two devices can send to one another, and how much energy each will use.
Prototyping EnHANTs with Mica2 Motes: Phase II
by Zainab Noorbhaiwala, Michael Zapas, and John Sarik
In this project we enhanced the phase I prototypes that test communication protocols and verify overall functioning of a network of EnHANTs nodes. We ported the system to the Fennec Fox framework which improves maintainability and modularity of the code. Phase II prototypes are integrated with an energy harvesting module that contain a thin film solar cell, a small battery, and an LED. The solar cells charge the small battery which is discharged by flashing an LED when the prototype’s transceiver generates and sends out a wireless message. Through the energy harvesting module, the EnHANT prototypes determine the level of energy being harvested, as well as the battery energy storage level. We have also designed Custom sensor boards that allow using energy-related hardware components with the prototypes in this configuration. When communicating, the prototypes exchange their identifiers and their energy harvesting-related parameters, and determine the communication rates in accordance to their energy states, demonstrating energy harvesting adaptive communications.
A testbed of Phase II EnHANT prototypes.
Testbed Control and Monitoring Application
by Abe Skolnik
The goal of this project was to create an easily expendable robust graphical system for monitoring and controlling the testbed of EnHANT prototype devices. The project involved designing and developing the monitoring system functionality, as well as the necessary data structures and constant definitions that enable the communication between the motes and the managing computer. The centralized monitoring "MoteManager" program was developed in such a way that most of its functionality is accessible from a purely text-based interface (e.g., for access via SSH), and yet when run in graphical mode (via a simple command-line option), the program not only provides a GUI with a log window, but also a `visual demo' that shows the activity of the motes in a very easy-to-understand way, with graphical battery levels, `sun' icons for energy harvesting levels, and automatically-scaled-and-rotated arrows for mote message transmission. This visual demo also scales to different window sizes dynamically so as to accommodate different screen sizes and desired layouts.
Light Measurement Collection System
by Michael Zapas
The energy-harvesting network tags collect energy from light. Different locations have different light characteristics. We had four computers set up in four different locations each facing a different direction (North, South, East, West). These setups contained a PC that received the light data from a light sensor connected to a Labjack. The Labjack being a USB device that allows for automated measurements. These light measurements are running 24/7 as to create a comprehensive database of light characteristics, both indoor and outdoor. In addition to the stationary light measurement devices I carried out several mobile measurements. These included acquiring data while driving for extended periods of time, walking around Times Square, and other routine activities.
Optimizing the Synchronization of EnHANT Devices
by Michael Lin
Ultra-wideband Radio for Wirelss Sensor Networks
by Jiasi Chen
The goal of this project is to integrate a custom ultra-wide transmitter and receiver with an existing sensor network. This will allow us to test new networking algorithms that take advantage of the energy savings of UWB communication. A prototype was developed that is capable of sending and receiving bits between Mica2 motes at up to 25 kbps. The next step of this project is the increase the bit rate and develop higher level communication protocols for the UWB motes. Slides with a schematic diagram and a photo.
Prototyping EnHANTs with Mica2 Motes
by Tarun Sharma and Enlin Xu
In this project we have developed a prototyping system to test communication protocols and verify overall functioning of a network of EnHANTs nodes. For the purpose of prototyping we have used a testbed of Mica2 motes with custom made sensor boards, light-to-frequency converters, and silicon solar cells.
The aim of the project is to develop and test protocols that govern communication pattern and sleep-wake cycle of the mote that is aware of harvesting rate and current battery levels of not only itself but also neighboring node. A virtual battery emulates the flexible rechargeable batteries that will be connected to EnHANTs at a later stage. To provide maximum flexibility and room for future changes, the initial battery levels and energy consumption during sleep, ideal awake, transmission, receiving etc are configurable through GUI. However the harvested energy is the actual energy that solar cell could harvest based on the light falling on it.
To easily configure the prototypes’ parameters and to track their behavior, we have designed and developed a custom monitoring and control system with a Java-based GUI. This monitoring system includes a set of ‘live’ graphs that are used to demonstrate the changes in nodes’ communication patterns and energy states. The monitoring system is separate from the network functioning and does not influence the network. The system running on a computer can obtain relevant information from motes placed on Ethernet programming boards connected to an Ethernet switch. A wired monitoring system ensures that the monitoring system does not disrupt functioning of wireless network.
Emulating a Library Collection System
by Shilpa Srinivasan
The objective of this project is to use twenty wireless motes to emulate an automatic library shelving system. Using scripts in NES-C and a built-in CTP (Collection Tree Protocol) algorithm, the network is able to identify missing, misplaced, and found books. Each Mica2 mote uses pre-recorded energy values to determine its transmission rate. A special installation script was created to configure each mote with a unique set of energy values. This allows the motes to transmit at different rates at any given time. When implemented, the librarian is able to identify the misplaced books, the nearest-hop neighbor (via Collection Tree), the number of hops, and the routing path of the Collection Tree packet.
The achievements of Summer 2009 students were showcased in a mini-workshop in September 2009.
Thin Film Printable Batteries
by Ariel Schwartz
The goal of the battery was to be able to both store the energy that the solar cell collects, and to power the chip. In order to keep the battery as thin as possible, we developed a thin film printable battery, using a silver substrate, zinc and manganese oxide electrodes, and a potassium hydroxide electrolyte.
In order to be able to print these materials, we had to make our electrodes into inks, or 'slurries' that would be able to be printed. We also needed to make our electrolyte into a gel so it could be printed as well.
Organic Semiconductor Solar Cells
by Daniel Bendavid
This project focused on the development of a renewable power source for the EnHANT devices. We chose to work with organic photovoltaics because of the cheap cost of manufacturing, the ability to build them on flexible substrates, and their wide absorption spectrum. The PV stack consisted first of indium tin oxide anodes etched with photolithography and PEDOT spun on top. Then, the CuPc/C60 junction was thermally evaporated. The cathode, composed of aluminum, was then created also through thermal evaporation. Testing of the devices demonstrated that they could be used as ample power sources for the EnHANTs.
Custom Sensor Boards
by Deep Shrestha
In this project, we developed custom sensor boards and software to implement an automatic monitoring system to track and log the power provided by a solar cell as well as the light conditions. Mica2 (MPR400) motes can be programmed using NES-C in a Tinyos environment. The software written for this project enables the user to monitor and log the power supplied by a solar cell for various load resistors. The resistor values are obtained by programming the digital potentiometer (MAX5454). This is done by providing the potentiometer with clock pulses from the microcontroller (ATmega128). Each clock pulse, depending on the values of the U/D pin of the potentiometer, either increases (U/D High) or decreases the resistor values. The value of the voltage across the resistors are then read off with the help of the ADC in the microcontroller and stored in memory.
The amount of light falling on the solar cell is measured with the TSL230RD light-to-frequency converter chip. The developed software module measures the frequency coming out of TLS230RD which is then converted to the amount of light falling in µW/cm2 using a manufacturer provided factor. As the motes have limited memory, the system is capable of storing about two hours worth of data which is about 600 data entries in the log. After storing the data in the memory, they can be read off using another software built for this purpose.
Energy-aware Communication Protocols -
Implementation and Evaluation Using Sensor Motes
by Dongzhen (Park) Piao
In the EnHANTs project, we are building a network of energy-harvesting tags to exchange ID and location information. In this network, energy consumption is the key issue to consider, and several energy-aware communication protocols are implemented. For example, when the battery level is low or the lighting condition is bad, the tags will communicate with each other less frequently than when conditions are good. Protocols are implemented such that this algorithm can be run in a stand-alone or pairwise manner.
To run and test these protocols, we built a network platform of sensor motes in order to implement various protocols, run them, collect data, and verify their applicability. The platform consists of two parts: the mote side and the PC side. On the mote side, we use TinyOS programming structure to implement control logic and develop the protocols. On the PC side, we use Java programming language to implement the controlling mechanism. Using both methods, we can test various parameters in different protocols, and query and analyze data from the motes during runtime.
EnHANTS in a Sensor Network: Emulating a Library Shelving System
by Ellen Shlossberg & Imin (Aimee) Paung
The objective of this project is to use smart sensors in a wireless network to emulate an automatic library shelving system. We used Mica2 mote sensors with TinyOS software, a component-based operating system written in the Network Embedded System C (NES-C) language. By incorporating a one-hop neighbor-discovery protocol and the built-in Collection Tree Protocol (CTP) in the networking algorithm, we established a working system on a large scale test bed. When implemented with EnHANTS hardware, the algorithm will enable the tracking of missing and out of place books.
by Devendra Laulkar
The objective of this project is to simulate the workings of the enhanced active networked tags on the Android Mobile phone. The EnNANTs project aims to develop energy harvesting microchips that can network together to be used in various applications like disaster recovery. This project is emulating the same concept, using existing mobile devices. In this project, we have reconfigured the wifi chip on the Android G1 phone to be used in adhoc mode. We have developed a set of energy efficient protocols to exchange information among nodes. We have also developed a simulator to test out different protocols.