Protect your electronic device designs from thermal runaway and counterfeit batteries

Most electronic device designers are using or considering rechargeable batteries.  Cars, cellphones, laptops, media players, and even airplanes are increasingly reliant on lithium chemistry. As we’ve seen in some famous examples, if they are not engineered properly, thermal runaway in these batteries can make them very dangerous.  That’s a product performance problem you really don’t need!

Several design factors have been attributed to thermal runaway, but some result from counterfeit batteries and chargers that don’t include the requisite safety features. The engineers at Texas Instruments (TI) have looked into these causes to develop a battery platform and portable power management system to help prevent the batteries in your designs from catching fire.

Temperature Monitoring of Rechargeable Batteries

Many things can increase the chances that a battery will overheat. Some notable causes of overheating are: improper ventilation (like charging under a pillow), using the device while charging (or in extreme conditions), and using counterfeit batteries.  Thankfully, a simple thermistor can help detect when the battery is over-heating.

When a battery is being charged, a certain amount of voltage and current is being applied to the battery.  Too much current or too much voltage can create a very hot battery.  Many battery management systems will monitor only current or voltage, but TI’s bq24060 and bq24070 will monitor them both to ensure safe charging. This video shows that once the temperature reaches a safety margin, the power to the battery is shut off.

However, temperature monitoring is the last line of defense to ensure product and user safety. Designers must also ensure that authentic batteries are used and the charging is properly managed.

Authentication & Identification of Replacement Batteries

Not all consumers will listen to the warnings to use your custom made batteries and chargers.  Unfortunately, counterfeit batteries that aren’t specifically designed for a device may not supply the correct voltage and current levels while charging.

To prevent counterfeit battery use, TI has a portfolio of authentication devices that range from the basic to very complex. If the battery doesn’t pass authentication, then the device will either not start or it will send an error message during start-up.

The simplest of schemes use Identification-Based Authentication. It works somewhat like wireless authentication and identification.  A host (phone) sends a constant signal to the responder (battery) and a constant reply is sent back. The host can then read the data and verify that the battery was made for the product.  The bad news with this scheme is that the codes can be duplicated by counterfeiters, often within just weeks of production.

For added security, a challenge and response-based authentication scheme can help to confound the counterfeiters. This scheme changes the challenge and response each time the battery is inserted. The security is in a secret key that is shared between the device and the battery. When the battery is plugged in, the phone sends a set of numbers that are fed into the key. If the returned value matches the value calculated by the host, the device is powered up.

The challenge and response-based scheme also employs public authentication.  Public authentication platforms are effective because they can more thoroughly evaluate against attacks seeking to uncover the secret key.

For even more security, the SHA-1/HMAC-based (Secure Hash Algorithm-1/Hash Message Authentication Code) can be implemented. This method has been used for several years to secure internet transactions. It works similarly to the Challenge and Response scheme using a secret key.  However, this method uses a 160-bit challenge.  This creates 2160 or 1.46 x 1048 possibilities, which greatly increases security.  If you want to use this method, then TI’s bq26100 IC is right for your design.

Charging Management

As a safety feature, typical chargers place the battery and the system in parallel with each other. In this configuration, if a user is charging their battery while using the phone, less current is available to charge the battery. In some designs, if the system current is greater than the battery current, then the battery will actually start discharging. That’s why turning off GPS and Wi-Fi systems will charge your phone faster.

Other configurations manage battery charging differently. For example, the current flow Power Path Management (PPM) system uses a pair of transistors to control how much power is on the power bus and the amount of current that is applied to the battery.  This ensures a regulated amount of voltage and current are applied to the battery during the charging cycle.



Additionally, a Dynamic PPM (DPPM) will maximize the available power from the adapter by monitoring the power bus for input fluctuations. In this set up, if the battery and system current becomes greater than the current being supplied, then adjustments are made so that both receive a proper amount of current equal to what is available. Additionally, this configuration will allow your design to use a smaller power rating and a less expensive AC adapter. This DPPM set up is used in TI’s bq24070 IC.


Fuel Gauging

Has your battery gauge ever told you that you have 20 minutes of charge remaining, only to shut down 2 seconds later? Fuel gauging isn’t just for user satisfaction. It’s also important in measuring the proper battery charge.

Most devices employ either a voltage-based or the coulomb counting-based algorithm to determine the charge of your device’s battery. However, both of these algorithms have their limitations.

TI’s patented Impedance Track™ technology, however, uses both algorithms to help measure the charge and the resistance of the battery over time. Another algorithm is used to learn the behavior of the battery to better utilize the battery’s capacity.  The system then keeps a database of various characteristics of the battery. This method helps to predict the remaining battery capacity with up to 99% accuracy. TI’s bq27520-G4 uses Impedance Track technology to perform this function. The IC can also report:

battery capacity (mAh)
state-of-charge (%)
state-of-health (SOH%)
run-time to empty (min.)
voltage (mV)
temperature (°C)

Power management isn’t just for cell phones.  Whether you are dealing with power tools or eMotorcyles, portable medical monitoring devices or portable audio systems, TI’s power management system can increase the battery safety on your project. If you want to see how these design advances can impact your electronic device performance, TI has the documentation that can help get you started.

Professional Engineering (PE) Licenses Offer Access to a High Growth Market

Becoming a licensed PE is a privilege that must be earned by demonstrating competence and experience. To begin the process, each state requires aspiring professionals to pass a Fundamentals of Engineering (FE) exam. They also require that engineers work for a certain number of years practicing under a licensed Professional Engineer before they are eligible to apply for a professional license. This web site is a great resource for frequently asked questions about professional licensing.

Once you do become licensed, the benefits to you and the community you'll serve are plentiful. Considering what you have to gain, now may be the perfect time to start planning.

According to the U.S. Bureau of Labor and Statistics Employment Projections, between 2012 and 2022 , the anticipated retirement of thousands of baby boomers will provide significant opportunities for upcoming engineers. The two top engineering fields in terms of growth are Construction and Computer engineering, which are projected to grow at a rate of 21.4% and 18.0%, respectively.

Need more of an incentive to become an engineer and work toward your PE license? A recent college salary report by PayScale.com lists the top 10 majors with the best salary potential. Engineering majors make up 70% of that list.

The American Society of Mechanical Engineers and the American Society of Civil Engineers reported in their 2013 Salary Survey that the earning potential for engineers is dependent on four key factors: job experience, location, discipline, and skills. According to this report, “engineers with a PE license reported a median annual income of $104,132.”

The Path to a PE License

As engineers, we tend to overthink almost everything. We set a plan and analyze all aspects in hopes of anticipating and avoiding any roadblocks along the way.

The ideal path would be to:

•  graduate from an accredited engineering program

•  obtain the Engineer-in-Training (EIT) certificate by passing the FE exam

•  land a job practicing under a licensed PE

•  work for the minimum number of years of experience required by your state

•  pass your PE exam

But the truth is, when it comes to becoming a licensed PE there is no typical path. The National Society of Professional Engineers told the story of Allen Oertel, PE, who proved that even at age 48, there is no time like the present to become licensed. Mr. Oertel stated that without a PE license, “…I began to see that many of my advancement opportunities would eventually be limited.” So, he persevered through the hurdles of juggling family commitments with higher education to eventually become licensed. He now serves as an associate and group manager and supervises 13 fellow engineers and technical staff members.

Mr. Oertel estimates that he spent approximately “600-700 hours preparing for the F.E. and P.E. exams”. Was that time commitment worth it? According to Mr. Oertel, absolutely. “I am obviously an advocate for professional licensing and continuing education and believe I can serve as an example to my co-workers that one is never too old to accomplish life's goals, both professional and personal.”

A Certificate is not a Certification, and neither one is a License

Obtaining any professional credentials will certainly boost your value in your engineering field, but sometimes understanding the difference between certificates, certifications, and licenses can be confusing. The NSPE published a report that helps differentiate between them.

Certifications, such as the Engineer-in-Training certification, “…attest to an individual's capability to perform a defined task or related series of tasks…” and “…require a sufficient period of experience acceptable to the certifying body and successful completion of an examination.”

Certifications should not be confused with certificates, however. Certificates are simply acknowledgement given to individuals for attendance or completion of a particular course or study. For example, your employer may hire a third party to give specified training on a new computer software program that you will be implementing in the office. After you finish the course, you may be offered a certificate validating that you attended and completed the course.

Licenses go beyond certificates. When it comes to engineers serving the public, “licenses are employed by governments, usually states, to regulate the practice of certain professions to protect the public from incompetence and misconduct of practitioners…” and “… are required for a professional to offer those services to the public. Certifications are not required and do not grant authority to a professional to offer services to the public.”

Licenses and certifications work in conjunction with each other. In order to obtain a PE license, one must first obtain an accredited certification (i.e., an EIT certification) from the National Council of Examiners for Engineering and Surveying (NCEES).

The difference between a licensed PE or PS and an accredited EIT certification is important—particularly for your career path. While both distinguish you from other engineers without credentials, once you're a PE, you'll have more opportunities to grow your career and serve your community. For more information about engineering certification and licensure, or for review materials to help you pass your FE or PE exams, visit PPI's website, at

Great Lakes Commits $9M to Fight STEM Attrition

You don’t have to go far to hear about the STEM skills gap. According to the non-profit Great Lakes Higher Education Corporation & Affiliates (Great Lakes), the STEM job market will increase 1.7 times faster than other industries. Unfortunately, only 40% of students that enter into a STEM major will complete a STEM degree.

"STEM drives our nation’s innovation and competiveness, and we’re concerned that the United States is falling behind in producing college graduates with degrees in these essential disciplines,” said Richard D. George, CEO of Great Lakes. “That’s why Great Lakes is committing $9 million to three initiatives that will help more two- and four-year college students persevere in their pursuit of STEM degrees, preparing them for in-demand, well-paying jobs."

Another disturbing finding by Great Lakes is that attrition is specifically high for minorities and often marginalised groups. Female students, students of color, students from low-income families, or the students that are among the first of their family to attend a higher education institution appear to be hit the hardest. As such, Great Lakes is committing $1.875 million of the funds to low-income students. This comes to $2500 each for 750 students.

George said, "Now in the third year of our scholarship program, we have provided more than $5.6 million to STEM majors across the country … We’re fortunate to see the positive difference that higher education makes in lives every day, and we’re pleased to continue our scholarship commitment to help these ambitious students advance their careers."

Of the remaining donation, $3.2 million will go towards faculty training and cross-network sharing with the Center for the Integration of Research, Teaching and Learning (CIRTL). This will help to educate STEM faculty in new proven techniques to educate their students.

It is no secret that many faculty members have devoted their life to research, but find themselves forced to fill teaching positions in order to do so. The result can be a mind numbing experience for students. The CIRTL’s goal is to teach post-docs and grad students how to become excellent researchers and instructors. The network of 22 Universities spans 16 states. Their education training is comprised of mentoring and evidence-based teaching techniques such as active learning, real-world situation topics, inclusive learning environments, teamwork and continual improvement.

"CIRTL Network universities currently graduate about 20 percent of the nation’s new STEM faculty each year … Our intention through investments like this is to take ideas that work to scale. We hope the 80 remaining research universities will adopt the successful CIRTL model and truly shape the future of STEM education for thousands of future faculty, and an entire generation of undergraduate students," said George.

The final $4 million from Great Lakes will go towards further research and to inform policymakers of the financial burdens associated with a STEM degree. The labour intensive degrees often translate to more time in the lab and library with less time for part-time jobs. This can be a major contributing factor to the attrition of students from low-income families.

The $4 million will be broken up into grants for hundreds of students in 10 Wisconsin schools. Each student receives $1000/year for up to five years for taking part in this experimental study.

"Our grants will allow students at both two- and four-year colleges to focus on their studies instead of a salary, and we hope that will make it easier for them to complete their STEM majors," said George.

The actual research portion of the study will be funded by the National Science Foundation (NSF). The Wisconsin HOPE Lab will then determine if the funding has helped the students to complete their STEM degrees.

Dr. Sara Goldrick-Rab, founding director of the Wisconsin HOPE Lab said, "Policymakers and practitioners need to know how and why grant aid contributes to critical workforce needs, such as those in STEM fields … Thanks to the support from Great Lakes, the HOPE Lab has the opportunity to generate rigorous empirical evidence to provide that information while also supporting students across the state."

Engineers Reach New Heights with Pioneering ‘Flying Wing’ Project

Members of the AMRC Design and Prototyping GroupUAV team, left to right Sam Bull, Mark Cocking, Keith Colton, Daniel Tomlinson, John Mann and Garth Nicholson.

The team, from the Advanced Manufacturing Research Centre’s Design and Prototyping Group, gained worldwide publicity when they used their expertise to develop an Unmanned Aerial Vehicle (UAV).

Now, they have taken another step forward, developing their original glider to incorporate electric-powered, ducted fan engines.

Members of the team recently returned from Salt Lake City, after being invited to deliver a presentation on the UAV project to an aerospace manufacturing conference organised by SAE, the global association for aerospace, automotive and commercial vehicle industries engineers and technical experts.

The project is designed to showcase the Group’s skills and technological capabilities – particularly for helping small and medium-sized manufacturers to develop new products and move into new markets.

Making the glider involved developing new techniques that rapidly reduced the time, the amount of materials and the cost of manufacturing components using 3D printing technology.

Creating the latest version of the UAV has involved further advances in making functional parts using Rapid Manufacturing (RM) technology.

These include developing new manufacturing techniques for producing carbon fibre components and making component jigs, fixtures and moulds, as well as parts of the UAV’s airframe, by Fused Deposition Modelling (FDM).

The team succeeded in making the central body of the UAV, complete with the twin engine ducts and complex internal features, as a single, printed part, demonstrating how RM technologies can replace assemblies involving multiple components.

Designers also improved pitch control by creating a moveable “Duck Tail” that uses concepts similar to those recently used in Formula One racing to harness the air leaving the UAV’s engines for aerodynamic effect

Last, but not least, the team designed a launch catapult, using a number of RM parts.

The catapult is capable of propelling the UAV into the air with an acceleration up to three times that of gravity, achieving a launch speed of 12 metres a second or just under 30 miles an hour.

Having turned their 2kg glider into a 3.5kg powered UAV, capable of cruising at around 20 metres a second, or almost 45 miles an hour, the team members’ next challenge will be to replace the electric ducted fans with miniature gas turbine engines and seeking to double the UAV’s wingspan to three metres.

The team is also looking at using novel methods of controlling flight to replace conventional elevons, employing vapour polishing for finishing some printed components, including composite moulds, and developing structural batteries – batteries made from carbon composites that could act as part of the UAV’s structure.

Senior design engineer Dr Garth Nicholson said: “The project was a success on all levels, from team building, experience gained in structural and systems design and design for manufacture through to testing and validation of Computational Fluid Dynamics.

“The aircraft was developed using both an incremental design philosophy, as well as trialling experimental manufacturing techniques in carbon fibre production”.

Lead additive manufacturing engineer Mark Cocking said the UAV project pushed the limits of design for Rapid Manufacturing, making the transition from theory to reality.

Building a Time Machine for the Weather

Climate science has always been a tricky business. Though in the last half-century sophisticated computers, satellites and a world-wide-web of data collectors have made that job a bit easier. But

what if you wanted to look into the weather systems that ruled the globe a century ago? Would you be able to find an accurate and comprehensive record of global precipitation? Until recently the answer was "no".

Samuel Shen, a professor of mathematics at San Diego State University, recently unveiled an astonishing piece of software. Called the spectral optimal gridding of precipitation (SOGP), Shen's new tool is designed to help researchers accurately view weather patterns since 1900. With the ability to view weather anywhere between global and local-scale, SOGP can help researchers better understand weather patterns as they've developed over time.

“In the past, only a couple dozen scientists could do these reconstructions,” Shen said. “Now, anybody can play with this user-friendly software, use it to inform their research, and develop new models and hypotheses. This new tool brings historical precipitation reconstruction from a ‘rocket science’ to a ‘toy science.’”

Although Shen's new software is a revelation for those looking into the Earth's meteorological past, its powers aren't relegated to the rear-view. Scientists working at the forefront of meteorology can leverage data derived from SOGP to make more accurate inferences about their research and reveal more about the future of Earth's climate.

Magnetic Mirrors Enable New Technologies by Reflecting Light in Uncanny Ways

As in Alice’s journey through the looking-glass to Wonderland, mirrors in the real world can sometimes behave in surprising and unexpected ways, including a new class of mirror that works like no other.

As reported today scientists have demonstrated, for the first time, a new type of mirror that forgoes a familiar shiny metallic surface and instead reflects infrared light by using an unusual magnetic property of a non-metallic metamaterial.

By placing nanoscale antennas at or very near the surface of these so-called “magnetic mirrors,” scientists are able to capture and harness electromagnetic radiation in ways that have tantalizing potential in new classes of chemical sensors, solar cells, lasers, and other optoelectronic devices.

“We have achieved a new milestone in magnetic mirror technology by experimentally demonstrating this remarkable behavior of light at infrared wavelengths. Our breakthrough comes from using a specially engineered, non-metallic surface studded with nanoscale resonators,” said Michael Sinclair,  a scientist at Sandia National Laboratories in Albuquerque, New Mexico, USA who co-led a research team with fellow author and Sandia scientist Igal Brener.

These nanoscale cube-shaped resonators, based on the element tellurium, are each considerably smaller than the width of a human hair and even tinier than the wavelengths of infrared light, which is essential to achieve magnetic-mirror behavior at these incredibly short wavelengths.

“The size and shape of the resonators are critical,” explained Sinclair “as are their magnetic and electrical properties, all of which allow them to interact uniquely with light, scattering it across a specific range of wavelengths to produce a magnetic mirror effect.”  

Early Magnetic Mirror Designs

Conventional mirrors reflect light by interacting with the electrical component of electromagnetic radiation. Because of this, however, they do more than reverse the image; they also reverse light’s electrical field. Though this has no impact on the human eye, it does have major implications in physics, especially at the point of reflection where the opposite incoming and outgoing electrical fields produce a canceling effect. This temporary squelching of light’s electrical properties prevents components like nanoscale antennas and quantum dots from interacting with light at the mirror’s surface.

A magnetic mirror, in contrast, reflects light by interacting with its magnetic field, preserving its original electrical properties. “A magnetic mirror, therefore, produces a very strong electric field at the mirror surface, enabling maximum absorption of the electromagnetic wave energy and paving the way for exciting new applications,” said Brener.

Unlike silver and other metals, however, there is no natural material that reflects light magnetically. Magnetic fields can reflect and even bottle-up charged particles like electrons and protons. But photons, which have no charge, pass through freely.

“Nature simply doesn’t provide a way to magnetically reflect light,” explained Brener. Scientists, therefore, are developing metamaterials (materials not found in nature, engineered with specific properties) that are able to produce the magnetic-mirror effect.

Initially, this could only be achieved at long microwave frequencies, which would enable only a few applications, such as microwave antennas.
  
More recently, other researchers have achieved limited success at shorter wavelengths using “fish-scale” shaped metallic components. These designs, however, experienced considerable loss of signal, as well as an uneven response due to their particular shapes.

Mirrors Without Metals

To overcome these limitations, the team developed a specially engineered two-dimensional array of non-metallic dielectric resonators—nanoscale structures that strongly interact with the magnetic component of incoming light. These resonators have a number of important advantages over the earlier designs
.
First, the dielectric material they use, tellurium, has much lower signal loss than do metals, making the new design much more reflective at infrared wavelengths and creating a much stronger electrical field at the mirror’s surface. Second, the nanoscale resonators can be manufactured using standard deposition-lithography and etching processes, which are already widely used in industry.

The reflective properties of the resonators emerge because they behave, in some respects, like artificial atoms, absorbing and then reemitting photons. Atoms naturally do this by absorbing photons with their outer electrons and then reemitting the photons in random directions. This is how molecules in the atmosphere scatter specific wavelengths of light, causing the sky to appear blue during the day and red at sunrise and sunset.

The metamaterials in the resonators achieve a similar effect, but absorb and reemit photons without reversing their electric fields.
 
Proof of the Process

Confirming that the team’s design was actually behaving like a magnetic mirror required exquisite measurements of how the light waves overlap as they pass each other coming in and reflecting off of the mirror surface. Since normal mirrors reverse the phase of light upon reflection, evidence that the phase signature of the wave was not reversed would be the “smoking gun” that the sample was behaving as a true magnetic mirror.

To make this detection, the Sandia team used a technique called time-domain spectroscopy, which has been widely used to measure phase at longer terahertz wavelengths. According to the researchers, only a few groups in the world have demonstrated this technique at shorter wavelengths (less than 10 microns). The power of this technique is that it can map both the amplitude and phase information of light’s electric field.

“Our results clearly indicated that there was no phase reversal of the light,” remarked Sheng Liu, Sandia postdoctoral associate and lead author on the Optica paper. “This was the ultimate demonstration that this patterned surface behaves like an optical magnetic mirror.”

Next steps

Looking to the future, the researchers will investigate other materials to demonstrate magnetic mirror behavior at even shorter, optical wavelengths, where extremely broad applications can be found. “If efficient magnetic mirrors could be scaled to even shorter wavelengths, then they could enable smaller photodetectors, solar cells, and possibly lasers,” Liu concluded.

Great Birmingham Run entrants warned of rail engineering works

Thousands of people due to take part in the Bupa Great Birmingham Run are being warned about rail engineering work that may affect travel plans.

Train operator London Midland said there will be no services between Coventry and Birmingham, until 10:24 BST on Sunday.

About 21,000 runners are expected to take part in the 13.1-mile race, which starts just after 10:00.

London Midland said the work was "unavoidable".

A spokesman for the run said: "It's unfortunate that some people's travel plans have been affected by the engineering works but we hope this doesn't impact too significantly on their enjoyment of the day.

"We will continue to work with Birmingham City Council and public transport providers to provide access to the event, and with that in mind the 2015 date of 18th October has already been announced."