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Fall 2014

Evaluating the Texas Instruments eZ430-RF2500-SEH Development Platform for Neighbor Discovery Research

By Earvin Caceres and Supanath Juthacharoenwong

Summer 2014

Agostino: An EnHANTs Prototype using COTS Components

By Marco Daldoss

In an effort to build next the next-generation EnHANTs prototype board, I developed, built, and tested the “Agostino Board", an energy harvesting hardware framework for Wireless Sensor Networks. This board has been realized with the best commercial off the shelf (COTS) components available at the time of the design.

The system is capable of acquiring information from sensors placed on a daughter board (boosterpack compatible) and is able to perform simple elaboration and communicate data to the network. The communication is achieved through a sub-GHz ISM radio channel, allowing an open-air range of 2-3 km. Agostino includes an energy harvesting circuit which allows the system to be supplied with indoor light energy. Moreover the board is capable of adapting its transmission rate depending on the available energy at the single node. In this way the node can intelligently alter the energy spent to obtain a Wireless Sensor Node able to work without any battery replacement. The Agostino Board demonstrates the feasibility of the energy harvesting-based Internet of Things using commercially available components.

Spring 2014

FPGA Development on the UWB-IR RF Transceiver Board

By Earvin Caceres

The work I did this semester built upon the integration efforts from the Fall 2013 semester with the new UWB-IR RF hardware. Specifically, the focus was on improving and developing the VHDL code for the FPGA which interfaces the MICA2 mote control board and the UWB-IR RF transceiver chipset. This semester, significant testing and debugging was performed on the hardware to address communication issues that were identified from last semester’s integration efforts. With these bugs addressed and communication proven to be stable, I was able to further develop our test software allowing us to more accurately measure various network parameters such as throughput and error rate to characterize the hardware. Future enhancements can be added to the test software as development with the new hardware progresses. Furthermore, efforts were made to refactor the VHDL code on the FPGA to improve extensibility as well as maintainability. This is key for future MAC/PHY cross-layer development planned for the EnHANTs hardware.

Fall 2013

Integration of new Ultra-Wide-Band Impulse-Radio (UWB-IR) RF Hardware into the EnHANTs Testbed

By Earvin Caceres

The goal of my project this semester was to further integrate the new version of the UWB-IR RF hardware into the EnHANTs testbed. There were two main aspects to the integration work. The first involved testing the communication between EnHANTs tags using the new UWB-IR RF hardware. A test application was written in TinyOS that passed network messages between two nodes in a simple point-to-point network. The messages contained data that emulated the typical payloads exchanged between tags communicating in the EnHANTs testbed. This simplified setup allowed us to quickly and easily exercise the hardware under real-world conditions, as well as track and fix bugs that were identified in both the hardware and software.

I also worked on updating the TinyOS based EnHANTs software framework to support the new UWB-IR RF hardware. The radio layer of the EnHANTs software framework provides the upper software layers an interface to the wireless communication hardware. A new physical layer driver was written to support the UWB-IR RF hardware which needed to be integrated into the radio layer. The layered architecture of the software framework allowed us to modify the radio layer to support the new hardware without requiring any changes to the upper software layers.

                 Test setup with new UWB-IR RF Hardware                    Software framework with updated Radio layer

Next-generation UWB Transceiver Integration

By Mengxi Lin, Earvin Caceres and Jianxun Zhu

In this project, we worked on building UWB wireless communication transceivers and integrating them with the MICA2 mote-based EnHANTs prototype. In total, 6 UWB transceivers were soldered, integrated and tested. After careful tuning, the wireless communication between two UWB transceivers can reach as far as 2 feet.

We also developed a test application to confirm the wireless functionalities. In the test, a PC generates packets, which are sent through the EnHANTs prototype software stack and onto the UWB transceiver. On the transmitter end, the packets are forwarded from the MICA2 mote to the FPGA through an SPI interface. The FPGA performs MAC layer functionalities including adding the preamble, length and CRC to the packet. Then, the modulated signal is sent out by RF circuitry of the transceiver. On the receiver side, the RF circuitry demodulates the signal, converting it into digital base band. The packet is then sent in up the protocol stack in the same manner as the sender. The tests confirm that the original packet reached the receiver module in the PC.

This overall test proves the capability of the next-generation UWB platform to provide the wireless support to the EnHANTs project. 

Implementation of MSP430-Compatible Softcore on an FPGA Platform

By Zhenyu Zhu

The goal of this project is to develop a softcore that is compatible to TI’s MPS430 microcontroller on an FPGA platform. In order to confirm the compatibility, we aim to load TinyOS onto the softcore. Based on the latest version of the open-source Verilog-HDL code for the softcore, we have made several modifications to ensure the compatibility of the softcore, particularly in the TimerA and the GPIO. The sample C code for testing those blocks is also modified accordingly to reflect hardware change. The functionality of both blocks are verified when implemented on the FPGA platform.

MSP430 Implementation

By Mina Cong 

The old version of the EnHANTs prototype utilized an MIB600 programming board and legacy MICA2 mote. The goal of this project was to replace this older Control Module (CM) with a Kmote that integrates properly with other modules on the prototype. The Energy Harvesting Module (EHM) is able to properly transmit data to the Kmote using the 1-Wire Protocol from Dalla Semiconductor. The Ultra-Wide Band Impulse Radio (UWB-IR) transceiver is able to properly transmit data to the Kmote using the Serial Peripheral Interface (SPI). To allow multiple devices to communicate with one another, Raspberry Pis (Rpis) are used as a gateway between the PC and devices. The project involved adjusting hardware connections and old software drivers to properly implement the new Kmote device. The last step that needs to be performed is to properly accept the transmitted data on the receiving end of the prototype (UWB-IB).

Development of the EnHANTs Software Framework 

By Richard Chiou

The existing EnHANTs multihop network utilized Fennec Fox, a platform consisting of a four-layer network protocol stack that supports network reconfiguration mechanisms. However, Fennec Fox has numerous limitations; for instance, the platform does not support global variables. Thus, a decision was made to recode the existing demo using a new framework with the functionality of Fennec Fox but without its restrictions. During the Fall 2013 semester, work began on developing the new interfaces for the different layers of the prototype. By the end of the semester, significant progress had been made on the radio and network layers. Work will continue on those layers this semester, along with the application and MAC layers. We hope to be able to test and link up our new interface to the existing demo soon.

Summer 2013

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. 

Spring 2013

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.

Fall 2012

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.

Summer 2012

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.

Spring 2012 

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.

Fall 2011

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.

Summer 2011

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.

Spring 2011

Design, Test and Integration of UWB (Ultra Wideband) Transceiver Board for EnHANTs Testbed

by Jianxun Zhu

UWB-IR board.

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.

Fall 2010

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.

Summer 2010

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.

 
Monitoring applicaiton screenshot examples.

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