-June 2009-

Walk, Don’t Crawl

By Sean Donnelly

While at the recent Sensors Expo in Rosemont, IL, I was introduced to The Samraksh Company, which was showing off its low-cost Pulsed Doppler Radar sensor board called BumbleBee. The BumbleBee offers numerous sensor network applications including crowd estimation, people activity monitoring, and intrusion detection based on phase, amplitude, spectrum and velocity-based motion detection. But I must say that I smiled as Chief Technology Officer Anish Arora, Ph.D. discussed the possibility of a particular application—identification based upon a person’s unique gait characteristics. If the BumbleBee had been readily available 17 years ago, I wonder if the following, now infamous conversation would have ever transpired.

An excerpt from Steve Ciarcia’s “The Circuit Cellar Home Control System II.”

“Don’t talk. Just bark!”

“Bark?” Merrill looked at me and shook his head.

“Bark,” I said. “Like this, Arf! Arf! Arf!”

Soon we were both barking and woofing up a storm. My two Scotties would’ve been proud of us. We kept it up for about 25 seconds, until the lights and the ferocious dogs stopped as miraculously as they had started.

Speaking very softly and not waiting for questions, I said, “Hey, you can stop barking. There’s a laser perimeter intrusion detector in this comer of the yard. It sensed our presence below the three-foot level. It turned on the floodlights and the recorded sounds of barking dogs to see what it was or try to scare it off.

“Now, here’s what the computer is great for. After all that was triggered, the computer turned on a microphone to listen out here at the same time. When it heard us barking the same as any real dog would do upon hearing the recording, it shut off the alarm sequence. You see, Merrill, the computer thinks we are just a dog that wandered through the yard and not an intruder. A real burglar, smart enough to see the different sensors and trying to crawl as we have been doing, wouldn’t know enough to bark back at the computer. Neat, huh? Now we can finish crawling to the house. It won’t bother us again.”

Download the original 1992 article:

http://www.circuitcellar.com/library/print/hcs-pdf/25-Ciarcia.pdf

For more about the BumbleBee: http://www.samraksh.com

The Critter Chronicles

A July 2009 Steve Ciarcia Priority Interrupt Photo Preview

“There I was in the plumbing aisle cutting 8” pieces of plastic pipe fitted with closed-end caps and piling them in the cart as three staffers walked down the aisle toward me. One of them cautiously asked, ‘Sir, are you planning on filling those pipes with something flammable?’”

Catch the full story in the July issue of Circuit Cellar.

Virtual Expo

A trip to the annual Sensors Expo once meant meeting and greeting the makers of unruly devices often found bolted to the insides of industrial smoke stacks or cemented into launch pads at the Kennedy Space Center. It’s a different Expo today—one that’s much more interesting to the embedded developer.

This year, the folks at Sensors helped bring together a pavilion dedicated to energy harvesting and power management technology. The following companies have been gaining much attention as the design community continues to look for creative power solutions.

Infinite Power Solutions: Solid-state, rechargeable thin-film micro-energy storage devices for a variety of micro-electronic applications. www.InfinitePowerSolutions.com

Powercast Corporation: Transmitting common radio waves to wirelessly power devices with embedded Powerharvester modules. www.powercastco.com

Mide Technology Corporation: Piezoelectric transducers for sensing, actuating, and energy harvesting. www.mide.com

AdaptivEnergy: Piezo-based energy harvesting DC power supplies to enable self-sustaining microelectronics. www.AdaptivEnergy.com

KCF Technologies: Self-powered wireless sensors; thermal power harvester. www.kcftech.com

Cymbet Corporation: Thin film battery technology and energy harvesting power management solutions. www.cymbet.com

Micropelt: World’s first fully self-powered wireless sensor system; Thermal energy harvesting and perpetual power supplies for self sustained electronic devices. www.micropelt.com

Advanced Cerametrics: Vibration energy harvesting to power sensors, wireless networks and low power circuits. www.advancedcerametrics.com

EQ Interactive

Contributed by David Tweed

Problem—The figure shows one way of generating a gated clock signal. What’s wrong with this approach? How can this be fixed?

Think You Have a Great EQ Challenge of Your Own?
E-mail your best EQ question and answer to eq@circuitcellar.com for a chance to be recognized by Circuit Cellar as an EQ guru.

Solution—The circuit is almost guaranteed to produce glitches, especially if the gate’s propagation delay (A) is slightly less than the clock-to-output delay of the flip-flop (B), as shown in the following timing diagram. For simplicity, assume equal t_PLH and t_PHL throughout.

Note how the first rising edge of the clock is delayed through both the flip-flop and the gate, shortening the output pulse width (X) relative to that of the input (W). Also, the second rising edge of the clock forces the output high before the falling edge of the flip-flop can cut it off, creating a glitch that may or may not activate the subsequent logic.

It is better to arrange the logic so that both edges of the output pulse are controlled by the clock edges, effectively hiding the propagation delay of the flip-flop. One way to accomplish this is shown here:

As the timing diagram below shows, now the output pulse width is the same as the input pulse width, and the glitch is gone. The active (rising) edge of the output pulse is now one clock period later than in the original design, but it should always be possible to rearrange state machines to accommodate this.

The best solution of all, of course, is to avoid gated clocks altogether and use flip-flops that have “enable” inputs instead. In FPGA design, making a design fully synchronous often allows special global clock networks to be used, bypassing the usual limitations on fanout, skew, and routability.

ESC Boston - September 21-24, 2009 - Hynes Convention Center - Boston, MA

LEARN TODAY. DESIGN TOMORROW. If you are an engineer involved in designing and developing embedded systems, you can’t afford not to attend ESC. The conference is your chance to learn about design techniques and best practices from the leading experts in the industry.

Congratulations!

Circuit Cellar recognizes Joe Mueck as an EQ guru. Joe’s “Test Your EQ” submission is being published in the July 2009 Internet & Connectivity issue. In addition to a Circuit Cellar certificate of appreciation, Joe is receiving an Esensors EM01B Websensor—an environmental monitoring sensor that provides accurate measurement of temperature, relative humidity, and light. http://www.eesensors.com

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