Cellphone Re-use to reduce E-WasteThree million tons of household electronics were thrown out in the United State in 2006. Many of items were cell phones that were discarded despite being functional and useful. These problem leads to the exposure toxic materials (e.g. batteries) to the environment and an increased carbon footprint. The goal of this research is to make reusing electronics as simple as reusing a glass jar. The repurposing of cell phone poses several engineering research challenges:
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| Researchers: Frank Maker, Ashkan Eghttesadi |
Circuit Design for Energy Harvesting Power SuppliesCurrent work focuses on developing flexible digital and analog circuits to operate on the AC power supplies provided dircectly from vibration-based energy scavengers. Uing AC power directly eliminates the energy waste associated with AC/DC conversion. Taking advantage of this energy savings requires ciruits and architectures that can operate and adapt to a varying supply voltage and varying available power. Self-timed circuits, energy aware algorithms, and robust memories are some of the techniques currently being researched and tested:
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| Researchers: Justin Wenck |
Energy Scalable Computational Array for Energy Harvesting SensorsHarvesting energy from environmental sources can extend wireless sensor network node lifetime beyond the limits of battery technology. However, the output power from an energy harvester is highly variable. Our research is to design and implement an energy efficient and energy scalable computational array which maximizes sensor performance by matching system power consumption to the available scavenged energy through power scalable approximate signal processing. The array consists of distributed arithmetic (DA) based functional units coupled with a reconfigurable interconnect structure. Each functional unit can be configured to perform a set of linear and nonlinear signal processing functions in an area efficient manner which also minimizes leakage power. The sensor DSP flowgraphs are realized on the array by assigning an appropriate function to each computational unit and configuring the interconnect structure. Currently, we are at the second iteration of the micro-architecture design of the functional unit and our circuit work is focused on evaluating several low-swing driver and receiver circuit combinations and coding techniques to address interconnect power. We are also exploring using energy recovery circuits to further reduce the array's power consumption. A custom integrated circuit will ultimately be implemented to validate our architecture, communication, and circuit concepts. |
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| Researchers: Liping Guo,
Mackenzie Scott |
Energy Scalable DC/DC ConversionWe are developing a novel approach to implement very low power DC/DC conversion for battery-operated and energy harvesting systems with applications in biomedical devices, portable electronics, and wireless sensor networking. The system consists of a buck converter with a mixed-signal sliding-mode controller. This approach shows promise in terms of decreasing power consumption and providing energy scalability: the ability to trade off power for output voltage quality. In this case, figures of merit for the output include voltage ripple, conversion efficiency, and settling time. |
| Researcher: Nate Guilar |
Integrated Solar Energy Harvesting and StorageTo explore integrated solar energy harvesting as a power source for low power systems, an array of energy scavenging photodiodes based on a passive-pixel architecture for CMOS imagers has been fabricated together with storage capacitors implemented using on-chip interconnect in a 0.35 micron CMOS logic process. Integrated vertical plate capacitors enable dense energy storage without limiting optical efficiency. Measurements show 225 microW/mm2 output power generated by a light intensity of 20k LUX. |
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| Researchers: Nate Guilar,
Travis Kleeburg, Albert Chen |
Mechanical Vibration Energy Harvesters: Models, Circuit Interfaces, and ControlEnergy harvesting and recovery schemes exploiting piezoelectric materials such as PZT can help address the growing gap between silicon performance and battery energy density by providing a complementary source of energy for system operation. The primary challenge is that the voltage and power output of a PZT scavenging device is variable, both in magnitude and frequency. To improve energy scavenging system design, we are developing equivalent circuit models for piezoelectric vibration-based energy harvesters and incorporating them into standard circuit simulators. We plan to extend this work by exploring low-power mixed-signal circuits which can monitor the energy harvester output and provide feedback to scale system power consumption with the available energy |
| Researchers: Andrew Chang, Nate Guilar |
Energy Scalable Distributed Arithmetic on FPGAsEnergy scalability is a system feature which allows the user to trade off energy consumption for some metric of performance, such as clock frequency or output signal-to-noise ratio. Previous work has focused on custom hardware for energy scalability. However, increasing design complexity and time-to-market pressures drive more and more digital designs to Field-Programmable Gate Array (FPGA) implementation. This research develops software and architectures for implementing energy scalable DSP on commercial FPGAs. |
| Researcher: Zulfi Ansari |
Nanoscale Sensor Circuit Interfaces and ArchitecturesNovel nanoscale materials such as carbon nanotubes and silicon nanowires are promising candidates for low power and highly sensitive gas sensors. Applications include environmental monitoring, industrial process control, and homeland security. Current projects underway with this focus include:
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| Researchers: Albert Chen,
Jeffrey Loo |
Computer Architecture ProjectsPast and current projects and collaborations in computer architecture. |
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