When designing a power management system for a wireless remote sensor, it is important to choose a primary battery that last for decades under extreme operating conditions. Lithium thionyl chloride chemistry is the preferred choice due to its proven ability to deliver 25-plus years of service life.

Optimizing battery life and long-term reliability involves numerous variables, including the chemistry, the cell design, the quality of mechanical components, the purity of raw materials and the manufacturing processes employed. Shortcuts in quality can negatively impact service life.

The total amount of active chemical ingredients and the ratio of each ingredient determine the cell’s nominal capacity. Predicting expected operating life solely on the cell’s nominal capacity can be misleading however, as the cell’s capacity is affected by the active components, the internal self-discharge, the application power profile and environmental factors. Since the volume of active ingredients is limited by the size of the cell, nominal capacity values often do not vary substantially. So the key differentiator often involves the inner structure of the cell and the ratio of active ingredients. For this reason, design engineers should evaluate the battery’s Equivalent Operating Capacity (EOC) to properly calculate its expected operating life, taking into account the cell’s self-discharge rate, application current profile and environmental conditions.

More info here.

From the NYT:

Several years ago, I watched Vint Cerf, who helped draft the architecture of the Internet and is now chief Internet evangelist at Google, give a talk about the future of the Internet.

During his presentation, he discussed the early days of the Internet, when he was developing the protocol called TCP/IP with the United States Department of Defense. He talked about some of the strange early networking experiments his team did, but he also talked about his socks. He explained that one day everything would be connected to the Internet, including his socks, and if one should fall behind the washing machine while he was doing laundry, it would be able to notify the other sock of its whereabouts.

The basis for this concept is called “the Internet of things.”

The day when we have communicative socks might not be too far off, according to a report released Monday by McKinsey & Company. The paper highlights some of the major changes that will result from the growing ubiquity from sensors and objects connected to the Internet, including “sensor-driven decision analytics” and “complex autonomous systems.”

The complete article is available here.

Link reliability is an important metric for WSN but the nature of RF propagation and the congestion of ISM bands makes link stability a hard guess. However, the flexibility and economy that low-power wireless networks promise are bringing increasing efforts in the community and the industry to better grasp the effects of path loss and the interference situation in the wireless link.

In challenging environments, the required link budget necessary to maintain a given Packet Error Rate (PER) can be quite significant, which is not compatible with the constrains introduced by inexpensive radio architectures and low-power requirements which define WSNs.

RadiaLE, recently presented at EWSN 2010, is an open benchmarking testbed that allows performance evaluation of Link Quality Estimators (LQEs), it aims for experimentation with existing and future LQE implementations.

More info here

A panel of experts has been drawn together to discuss the future of wireless sensor networks at the Embedded Systems Conference, which take place April 26 to 29 at the McEnery Convention Center in San Jose, California.

Collections of autonomous smart wireless sensors that could connect together to form ad hoc networks were not practical until recently. But in the late 1990s it became clear that Moore’s Law would eventually take performance up and power consumption and form factor down, to the point where they would be possible.

And the juxtaposition of sensors (and potentially actuators), conversion circuits, digital logic, power and power management and wireless transceivers is a potent combination because it is, in essence, the superset template for a vast swathe of electronic systems. So not only were wireless sensor networks becoming possible, they were set to be revolutionary.

And that is where the fun begins because myriad questions quickly follow. What are the right applications for wireless sensor networks? What is the right architecture for the right application? What about the trade-offs of performance against range against power consumption against cost? Is energy harvesting viable to avoid battery costs? What is the right radio protocol? What legacy hardware, software and protocol stacks can be reused? What are the right standards to ensure interoperability?

More info here.

New Scientist magazine has written an article titled “Unplugged: Goodbye cables, hello energy beams” which discusses several technologies and companies in the wireless power market, including Powercast.

As it relates to wireless sensors, RF energy is the only controllable, practical technology to provide power over distance to multiple sensors simultaneously.  Other technologies are either too directional for one-to-many powering (i.e. IR LEDs), or have severe range limitations (i.e. induction, MR).  There are the critics that say RF power is not efficient and most of the energy is wasted.  However, using RF to power sensors at long range (e.g. energy management and building automation) is not about the efficiency of the charging mechanism, it’s about enabling applications and achieving greater system-wide efficiency.  Having a transmitter than consumes a few watts but provides power to sensors which feedback data to control thousands (or tens of thousands) of watts or BTUs provides a significant “energy ROI”.

Ever since the very first Sun SPOTs were delivered to Sun Labs we have relied on shared code resources and building on the work of others rather than re-inventing the wheel every time around. The more complex the Sun SPOT platform gets, the more difficult it can be to remember how to access a specific sensor, network protocol, etc. while writing an application. Understanding this, we decided to make code sharing amongst our community members an integral part of our software experience and encourage our developer community to share freely with one another. To that end there is a new feature in the latest version of the Sun SPOT Manager tool (used for installing and maintaining the Sun SPOT SDK) to make the sharing of code ’snippets’ (short pieces of Java Code used in Sun SPOT applications) easy and convenient. Download the latest version of Sun SPOT Manager here and start developing Sun SPOT Wireless Sensor Network (WSN) applications quickly and easily!

More info here.

Imagine a job that involved sitting in front of a refrigerator 24 hours a day and checking its temperature every five minutes. It is doubtful many people would apply. Plus, what organization would want to spend the money on that person’s salary? It might be nice to be sure the temperature in the refrigerator remained constant, but is  it really worth it in the scheme of things? How much would the owner be out if just one refrigerator breaks?

Try $80,000. That’s how much a research pharmacy lost when one of its refrigerators failed over one week-end. The unit contained $80,000 worth of research pharmaceuticals, which all had to be thrown out. That’s quite a loss for one weekend.

The complete article is available here.

The Sixth Workshop on Hot Topics in Embedded Networked Sensors (HotEmNets 2010) brings together wireless sensor network researchers from academic and industrial backgrounds to present groundbreaking results that will shed light on present and future research challenges.

Due to numerous request, the paper deadline has been extended.
New deadline: 1 March 2010.

For more information go to the workshop website