Electrical Engineer Crossword (Issue 273)

The answers to Circuit Cellar’s April electronics engineering crossword puzzle are now available.


1.         BITDENSITY—Bits per inch of magnetic tape, for example [two words]

3.         KALMANFILTER—aka LQE [two words]

5.         EMBEDDEDSECURITY—Circuit Cellar columnist Patrick Schaumont covers this topic with articles about authentication, encryption, and electronic signatures [two words]

7.         HAMMING—Error-correcting code

8.         SPURIOUS—Unintentional

11.       LAND—Electronics and Computer Engineering professor at Cornell University and Circuit Cellar frequent contributor (many of his students contribute to Circuit Cellar as well)

13.       CLAPP—American inventor who developed an oscillator frequency standard

14.       ELECTRODE—Able to interact with nonmetallic circuit parts

16.       RINGOSCILLATOR—A feedback structure with an odd number of digital inverters [two words]

17.       PLESIOCHRONOUS—A system that’s not quite in synch

18.       OSCILLOGRAPH—Takes electric current measurements

19.       REFLECTEDBINARYCODE—Created by Bell Labs physicist and researcher Frank Gray [three words]



2.         DEADBAND—Potentiometer’s part shortened by a tap [two words]

4.         BECHTOLSHEIM—Electronics engineer and co-founder of the company that created Java

6.         CHIPBIOMETRICS—Digital fingerprints [two words]

9.         INCANDESCENT—Illuminating

10.       ALOHANET—Computer networking system from the 1970s

12.       EEVBLOG—Where to find electronics engineer David L. Jones’s off-the-cuff online videos

15.       EULERMETHOD—Solves equations [two words]

17.       POPOV—Helped make electromagnetic radio waves more useful

Build a Simple Dedicated Tester

Whether you’re planning a small controller for your own use or an electronic device for mass production, you need to keep “testability” in mind. So, it’s a good idea to make a dedicated tester for your product part of its initial design.

Such a tester can ensure your device is functioning smoothly in your workshop—before it ships to a customer.

A dedicated tester (with the white panel) simulates inputs and loads for an embedded controller. A breakout box (with the red terminals on the panel) allows access to every interface line.

In the upcoming May issue of Circuit Cellar, columnist and engineer George Novacek discusses how to build a simple and inexpensive dedicated tester for a product.

“According to old engineering wisdom, every new project should begin with test design,” Novacek says in his column. “If you don’t follow this advice, your product may have features that are too awkward, too time-consuming, or impossible to test. You always need to keep testability in mind. Ultimately, it improves reliability, reduces manufacturing cost, minimizes field returns, speeds up production, and reduces the cost of repairs.”

Engineers certainly have access to a broad range of general testing equipment, from oscilloscopes to signal generators and analyzers.

“While these instruments are sufficient for testing, working with them solely may be slow and cumbersome,” Novacek says. “Imagine an embedded controller with a number of input and output devices, all of which need to be monitored while different signals are injected for the test. That’s where the dedicated tester comes in. Companies with deep pockets can purchase various types of automatic test equipment (ATE), but this may be too expensive for a small operation. Or, it may not be practical because of the complex setup for a low-volume production. Building a dedicated, inexpensive tester can solve the problem by ensuring an efficient and repeatable test.”

Check out the May issue of Circuit Cellar for more of Novacek’s guidance on why and how you should build a dedicated tester.

Novacek plans to continue examining product testability in upcoming issues, addressing topics that include the design of hardware and software that enables a product to be efficiently tested.

CC273: Necessity and Invention

Tom Cantrell wanted to stop fiddling with his sprinklers as he tried to balance conserving water in California and keeping his lawn green. So he asked himself if he could craft a weather-savvy sprinkler controller.

In the April issue of Circuit Cellar, he describes how to weatherize an embedded app. He uses a Texas Instruments MSP430 microcontroller and a WIZnet W5200 smart Ethernet chip to access National Weather Service forecasts and data (p. 36).

Engineer and entrepreneur Michael Hamilton also has found that necessity breeds invention—which in turn can start a new business. “While working for Ashland Chemical in clean room environments, I realized there was a need for an accurate humidity controller,” he says. “This led me to design my own temperature and humidity controller and form my first company, A&D Technologies.”

In our interview, he talks about what he has done since, including founding another company and becoming an award-winning designer in the RL78 Green Energy Challenge (p. 44).

A shift in the timing signal—or jitter—of a digital transmission can adversely affect your high-speed designs. It’s been an issue for at least 40 years, with the advent of the first all-digital telecommunications networks such as PDH. But you may not have dealt with it in your designs. In the April magazine, Robert Lacoste explains how to diagnose a case of the jitters (p. 54).

Jeff Bachiochi isn’t a musician. But he didn’t need to be one to work with the musical instrument digital interface (MIDI), which relays instructions on how to play a piece directly to an instrument (bypassing the musician). In the April issue, he describes the circuitry needed to connect to MIDI communication and display messages between devices (p. 60).

Atmel’s ATmega88 and ATmega1284 microcontrollers are at the heart of the CNC controller.

Also, Brian Millier describes how he built a microcontroller-based G-code controller for a CNC router. Even if you are not interested in building such a controller, you can learn from the techniques he used to provide the multi-axis stepper-motor motion (p. 30).

You also might find Scott Weber’s experience instructive. After placing microcontroller-based devices throughout his home, he found he needed a control panel to enable him to update the devices and check on their operation. He shares his panel’s basic structure and its software design. Its display shows him all the information he needs (p. 22).

While wear and tear affect the reliability of hardware, software reliability is different. Whatever causes software to fail is built-in, through errors ranging from poor coding to typos to omissions. On page 51, George Novacek shares some methods of calculating the probability of faults in your firmware.

Also in the April issue, Bob Japenga continues looking at concurrency in embedded systems. In the sixth article of his series, he discusses two Linux mechanisms for creating embedded systems—POSIX FIFOs and message queues (p. 48).

Finally, “From the Archives” features a 2003 article by Mark Balch about Verilog HDL. He discusses how to use it in your custom logic designs for digital systems (p. 68).

Open-Source Hardware for the Efficient Economy

In the open-source hardware development and distribution model, designs are created collaboratively and published openly. This enables anyone to study, modify, improve, and produce the design—for one’s own use or for sale. Open-source hardware gives users full control over the products they use while unleashing innovation—compared to the limits of proprietary research and development.

This practice is transforming passive consumers of “black box” technologies into a new breed of user-producers. For consumers, open-source hardware translates into better products at a lower cost, while providing more relevant, directly applicable solutions compared to a one-size-fits-all approach. For producers, it means lower barriers to entry and a consequent democratization of production. The bottom line is a more efficient economy—one that bypasses the artificial scarcity created by exclusive rights—and instead focuses on better and faster development of appropriate technologies.

Open-source hardware is less than a decade old. It started as an informal practice in the early 2000s with fragmented cells of developers sharing instructions for producing physical objects in the spirit of open-source software. It has now become a movement with a recognized definition, specific licenses, an annual conference, and several organizations to support open practices. The expansion of open-source hardware is also visible in a proliferation of open-source plans for making just about anything, from 3-D printers, microcontrollers, and scientific equipment, to industrial machines, cars, tractors, and solar-power generators.

As the movement takes shape, the next major milestone is the development of standards for efficient development and quality documentation. The aim here is to deliver on the potential of open-source products to meet or exceed industry standards—at a much lower cost—while scaling the impact of collaborative development practices.

The Internet brought about the information revolution, but an accompanying revolution in open-source product development has yet to happen. The major blocks are the absence of uniform standards for design, documentation, and development process; accessible collaborative design platforms (CAD); and a unifying set of interface standards for module-based design—such that electronics, mechanical devices, controllers, power units, and many other types of modules could easily interface with one another.

Can unleashed collaboration catapult open-source hardware from its current multimillion dollar scale to the next trillion dollar economy?

One of the most promising scenarios for the future of open source hardware is a global supply chain made up of thousands of interlinked organizations in which collaboration and complementarity are the norm. In this scenario, producers at all levels—from hobbyists to commercial manufacturers—have access to transparent fabrication tools, and digital plans circulate freely, enabling them to build on each other quickly and efficiently.

The true game changers are the fabrication machines that transform designs into objects. While equipment such as laser cutters, CNC machine tools, and 3-D printers has been around for decades, the breakthrough comes from the drastically reduced cost and increased access to these tools. For example, online factories enable anyone to upload a design and receive the material object in the mail a few days later. A proliferation of open-source digital fabrication tools, hackerspaces, membership-based shops, fab labs, micro factories, and other collaborative production facilities are drastically increasing access and reducing the cost of production. It has become commonplace for a novice to gain ready access to state-of-art productive power.

On the design side, it’s now possible for 70 engineers to work in parallel with a collaborative CAD package to design the airplane wing for a Boeing 767 in 1 hour. This is a real-world proof of concept of taking development to warp speed—though achieved with proprietary tools and highly paid engineers. With a widely available, open-source collaborative CAD package and digital libraries of design for customization, it would be possible for even a novice to create advanced machines—and for a large group of novices to create advanced machines at warp speed. Complex devices, such as cars, can be modeled with an inviting set of Lego-like building blocks in a module-based CAD package. Thereafter, CNC equipment can be used to produce these designs from off-the-shelf parts and locally available materials. Efficient industrial production could soon be at anyone’s fingertips.

Sharing instructions for making things is not a novel idea. However, the formal establishment of an open-source approach to the development and production of critical technologies is a disruptive force. The potential lies in the emergence of many significant and scalable enterprises built on top of this model. If such entities collaborate openly, it becomes possible to unleash the efficiency of global development based on free information flows. This implies a shift from “business as usual” to an efficient economy in which environmental and social justice are part of the equation.


Catarina Mota is a New York City-based Portuguese maker and open-source advocate who cofounded the openMaterials (openMaterials.org) research project, which is focused on open-source and DIY experimentation with smart materials. She is both a PhD candidate at FCSHUNL and a visiting scholar at NYU, and she has taught workshops on topics such as hi-tech materials and simple circuitry. Catarina is a fellow of the National Science and Technology Foundation of Portugal, co-chair of the Open Hardware Summit, a TEDGlobal 2012 fellow, and member of NYC Resistor.

Marcin Jakubowski graduated from Princeton and earned a PhD Fusion Physics from the University of Wisconsin. In 2003 Marcin founded the Open Source Ecology (OpenSourceEcology.org) network of engineers, farmers, and supporters. The group is working on the Global Village Construction Set (GVCS), which is an open-source, DIY toolset of 50 different industrial machines intended for the construction of a modern civilization (http://vimeo.com/16106427).

This essay appears in Circuit Cellar 271, February 2013.

Electrical Engineer Crossword (Issue 272)

The answers to Circuit Cellar’s March electronics engineering crossword puzzle are now available.


1.     JACOBSLADDER—Climbing arc [two words]

5.     WOZNIAK—Apple I

8.     SPARKCOIL—Uses a low-voltage DC supply to create high-voltage pulses

10.   JITTER—Creates an imperfect timing signal

11.   ERG—Energy measurement

13.   ACOUSTICOHM—Equivalent to µbar s/cm3 [two words]

15.   BUFFER—Provides electrical isolation

16.   WIFI—Provides movement to smartphones, PCs, and tablets

17.   POSIX—An IEEE operating system compatibility standard

18.   PEAKTOPEAK—Alterations between high and low values

19.   MUTEX—Capable of ensuring atomic access to any shared resource

20.   NAKAMURA—University of California, Santa Barbara professor credited with inventing the blue LED



2.     OSCILLATOR—American physicist George W. Pierce (1872–1956); piezoelectric

3.     EIGENTONE—A pitch capable of resonance

4.     FRETSONFIRE—Open-source gameplay for music lovers [three words]

6.     NEGATIVEFEEDBACK—Type of amplifier invented in 1927 by Harold Black [two words]

7.     BAFFLE—Sound wave obstruction

9.     MORSECODE—A pre-texting means of communication [two words]

12.   COMBFILTER—Capable of causing delay [two words]

14.   CHIPSET—Intel created the first family of these