Issue 263: H2M & M2M Communication

Posted on 2012/05/22 by C. J. Abate

Before I introduce this issue, I’d like to bring your attention to our recently redesigned website, CircuitCellar.com. It enables engineers and programmers around the world to communicate and share ideas via project articles, videos, and social media. The site’s features range from project posts (how-to articles, videos, and photos) to daily updates about products and industry news. We also run short write-ups on actual circuit cellars and workbenches in the well-received “Workspaces” section of the site. I encourage you to submit photos and info about your workspaces. Share your space with the design community!

Now let’s focus on this issue, which has articles on both human-to-machine (H2M) and machine-to-machine (M2M) communication. Topics as diverse as smart switch management and human motion-sensing systems are covered.

Kevin Gorga kicks off the issue with his “AC Tester” project (p. 14). It is an isolated variable voltage power source that includes an electronic circuit breaker for testing and debugging equipment. An mbed controller displays voltage and current, and it controls the breaker’s trip point and response time.

Circuit Cellar published 15 of Aubrey Kagan’s articles from 2000 to 2010. In an interview on page 24, Aubrey shares some of his engineering experiences from designing controllers for mines in Africa to helping create specs for the remote control arm on the International Space Station.

On page 28, Fergus Dixon presents a ’Net-connected controller for up to 50 smart switches for lighting systems. The controller’s RTC pulses a 24-V AC line once or twice to turn off the smart switches at the end of the day.

Final PCB with a surface-mount Microchip Technology ENC28J60 Ethernet chip (Source: F. Dixon, CC263)

Turn to page 36 if you’re interested in computer vision technology. Miguel Sánchez introduces depth camera technology, and describes how he used Microsoft’s Kinect in an interactive art project.

On page 44, columnist Bob Japenga starts an articles series on the subject of concurrency in embedded systems. In this article, he defines concurrency and covers some concurrency-related pitfalls.

Last month columnist George Novacek examined the topic of product testing and simulation. In this issue, he tackles a different yet equally important topic: diode ORing (p. 48).

On page 52, columnist Ed Nisley carefully explains MOSFET channel resistance. He describes power MOSFET operation and explores the challenges of using a MOSFET’s drain-to-source resistance as a current-sensing resistor.

A serious RF designer should have a sound understanding of frequency mixers. On page 58, columnist Robert Lacoste summarizes the basics of RF mixers and presents real-life applications.

A simple single-diode unbalanced mixer and its simulation done with Labcenter's Proteus. The RF and LO frequencies are 340 MHz and 300 MHz respectively. You can see on the output spectrum that these two frequencies are still visible, but as well as the difference 40 MHz and sum 640 MHz, among others. (Source: R. Lacoste, CC263)

Jeff Bachiochi wraps up the issue with an article about a DIY, MCU-based blood pressure cuff project (p. 68). He converted a manual blood pressure cuff into an automatic cuff by adding an air pump, a solenoid release valve, and a pressure sensor.

Circuit Cellar Issue 263 (June 2012) is now available on newsstands.

Issue 262: Advances in Measurement & Sensor Tech

Posted on 2012/04/24 by C. J. Abate

As I walked the convention center floor at the 2012 Design West conference in San Jose, CA, it quickly became clear that measurement and sensor technologies are at the forefront of embedded innovation. For instance, at the Terasic Technologies booth, I spoke with Allen Houng, Terasic’s Strategic Marketing Manager, about the VisualSonic Studio project developed by students from National Taiwan University. The innovative design—which included an Altera DE2-115 FPGA development kit and a Terasic 5-megapixel CMOS sensor (D5M)—used interactive tokens to control computer-generated music. Sensor technology figured prominently in the design. It was just one of many exciting projects on display.

In this issue, we feature articles on a variety of measurement-and sensor-related embedded design projects. I encourage you to try similar projects and share your results with our editors.

Starting on page 14, Petre Tzvetanov Petrov describes a multilevel audible logical probe design. Petrov states that when working with digital systems “it is good to have a logical probe with at least four levels in order to more rapidly find the node in the circuit where things are going wrong.” His low-cost audible logical probe indicates four input levels, and there’s an audible tone for each input level.

Matt Oppenheim explains how to use touch sensors to trigger audio tags on electronic devices (p. 20). His design is intended to help visually impaired users. But you can use a few capacitive-touch sensors with an Android device to create the application of your choice.

The portable touch-sensor assembly. The touch-sensor boards are mounted on the back of a digital radio, connected to a IOIO board and a Nexus One smartphone. The Android interface is displayed on the phone. (Source: M. Oppenheim)

Two daisy-chained Microchip Technology mTouch boards with a battery board providing the power and LED boards showing the channel status. (Source: M. Oppenheim)

Read the interview with Lawrence Foltzer on page 30 for a little inspiration. Interestingly, one of his first MCU-based projects was a sonar sensor.

The impetus for Kyle Gilpin’s “menU” design was a microprocessor-based sensor system he installed in his car to display and control a variety of different sensors (p. 34).

The design used to test the menU system on the mbed processor was intentionally as simple as possible. Four buttons drive the menu system and an alphanumeric LCD is used to display the menu. Alternatively, one can use the mbed’s USB-to-serial port to connect with a terminal emulator running on a PC to both display and control the menu system. (Source: K. Gilpin)

The current menU system enables Gilpin to navigate through a hierarchical set of menu items while both observing and modifying the parameters of an embedded design.

The menU system is generic enough to be compiled for most desktop PCs running Windows, OSX, or Linux using the Qt development framework. This screenshot demonstrates the GUI for the menU system. The menu itself is displayed in a separate terminal window. The GUI has four simulated LEDs and one simulated photocell all of which correspond to the hardware available on the mbed processor development platform. (Source: K. Gilpin)

The final measurement-and-sensor-related article in this issue is columnist Richard Wotiz’s “Camera Image Stabilization” (p. 46). Wotiz details various IS techniques.

Our other columnists cover accelerated testing (George Novacek, p. 60), energy harvesting (George Martin, p. 64), and SNAP engine versatility (Jeff Bachiochi, p. 68).

Lastly, I’m excited to announce that we have a new columnist, Patrick Schaumont, whose article “One-Time Passwords from Your Watch” starts on page 52.

The Texas Instruments eZ430 Chronos watch displays a unique code that enables logging into Google’s Gmail. The code is derived from the current time and a secret value embedded in the watch. (Source: P. Schaumont)

Schaumont is an Associate Professor in the Bradley Department of Electrical and Computer Engineering at Virginia Tech. His interests include embedded security, covering hardware, firmware, and software. Welcome, Patrick!

Circuit Cellar 262 (May 2012) is now available.

Issue 261: Cap-Touch Amp Design, RL78 Intro, Embedded Linux, & More

Posted on 2012/03/23 by C. J. Abate

The April issue is now available. As usual, it comprises a wide variety of content: a capacitive-touch amplifier design, an intro to using the Renesas RL78 for low-power apps, info on sigma-delta modulators, Linux software development tools, mesh networking tips, an interview with Dave Jones (of The Amp Hour and EEVblog) and more.

One of Dave Jones's old projects from the '80s. It's a Veroboard construction with items from his junk bin (Source: D. Jones, CC261)

A portion of the PIC-based PodAmp schematic (Source: C. Denninger & J. Lichtenfeld, CC261)

You’ll also notice some changes this month to Circuit Cellar magazine and our website. They’re all for the better.

The magazine has an updated layout. We haven’t changed fonts or style, but we did add the imprint you can see on pages 6–7. Its purpose is to show you that we are an ever-growing international company dedicated to bringing you essential information on a variety of important advanced electronics topics.

I added our editorial calendar, as well as a brief summary of the content we have in queue, to page 2. The idea is to give you a clear idea of what we will cover and when you can expect it. Members frequently ask for this information, so it makes sense to make it easily accessible for everyone.

As for CircuitCellar.com, well, you’ve likely watched it change slowly over the past few months. We did this purposely. We developed the site in stages so readers wouldn’t be burdened with dead links and redirects. So, what’s new about the site?

The layout is a bit different. A few things are quickly apparent. One, the site is markedly brighter and easy on the eyes. Two, we created three distinct columns that provide you with easy access to handy articles, digital downloads, and more (see below). Three, we’re tagging and categorizing all the content on our site. Thus, you’ll find targeting specific information to be uncomplicated and immediately gratifying.

What sorts of content can you expect? The old site was fairly static. We’d make several changes each month and we’d run a few viewable articles. Now we’re constantly posting relevant content of all sorts. This means you can rely on CircuitCellar.com for all of your electronics engineering needs: DIY articles, engineering tips, industry news, product reviews, vendor information, issue previews, links to source code, and even job openings in electronics engineering and embedded design.

If you are constantly plugged in, you’ll find our website makes accessing your digital membership a cinch: just point and click to log in and download each issue! Plus, you can add our site to your RSS reader and read our content at your convenience (www.circuitcellar.com/feed/rss).

We are not finished building CircuitCellar.com. In the coming weeks and months, we’ll enable more social interaction, post more videos, and broaden our areas of coverage. I suggest you visit our site each day to get your fix of embedded technology news and info. And please recommend the site to colleagues, friends, and others who have a passion for microcontrollers, programming, and everything else that’s “inside the box.”

Issue 260: Creativity in Design

Posted on 2012/02/28 by C. J. Abate

The seed for the interview with Hanno Sander on page 16 (Circuit Cellar March 2012) was sown at the 2008 Embedded Systems Conference in San Jose, CA. Hanno was at the Parallax booth demonstrating his “Dancebot,” which is a Propeller-based, two-wheeled balancing robot he wrote about in Circuit Cellar 224 (March 2009).

Balancing robot design (Source: Hanno Sander CC260)

Since Circuit Cellar is scheduled to publish Hanno’s book Advanced Control Robotics later this year, it made sense to interview him for our annual Robotics issue. As you’ll learn, Hanno is an enthusiastic designer whose intellect and passion for engineering have enabled him to travel the world and make electronics innovation his life’s work. His story should be an inspiration to everyone who reads this magazine.

After you finish the interview, check out the two robotics-related articles featured in this issue.

Square playing field (Source: Larry Foltzer CC260)

First, on page 20, Larry Foltzer tackles the topic of robot navigation with a fascinating article about position determination and acoustic delay triangulation. Next, turn to the back of the issue for Jeff Bachiochi’s article, “Wheel-Free Mobile Robots” (p. 64). Jeff takes you inside a Freescale FSLBOT mechatronics robot. Study the concepts he covers to prepare yourself for your next mobile robot design.

The rest of the issue includes a variety of articles on creative designs and essential engineering topics. I’m sure you’ll agree that the following articles are just as inspirational as they are informative.

Engineer and video game enthusiast Chris Cantrell explains how he built a Propeller-based TV gaming platform (p. 28). He describes how he hacked a joystick and got the classic Space Invaders video game up and running.

Propeller-based gaming platform (Source: Chris Cantrell CC260)

On page 36, Charles Edmondson presents his Rainbow Color Reader. The compact design can identify and announce colors for visually impaired users.

In the February issue, Alexander Pozhitkov introduced the NakedCPU project. This month he wraps up the article series by describing actual experiments and sets the foundation for future research (p. 42).

On page 50, George Novacek helps you prepare for the inevitable: microelectronic component obsolescence. You’ll find his tips invaluable as you move on to new projects.

Interested in the topic of thermal detection? Want to know how IR thermal sensing works? Turn to Richard Wotiz’s article on page 54.

On page 60, columnist George Martin provides his next engineering lesson learned from a real-world project. This month he covers the topic of working with—or without?—printer port connections.

I’d like to wrap up with a note to our staff and long-time readers. This is the 260th issue of Circuit Cellar. That’s quite an achievement! Thank you, colleagues, friends, and readers!

Circuit Cellar Issue 260 March 2012

Issue 259: Innovation in Wireless Technology

Posted on 2012/02/06 by C. J. Abate

Clayton Gumbrell's mbed-based QRSS-Rx

The topic of wireless communication is more relevant than ever. The technology is used everywhere from vehicles to hospitals to consumer electronics to military systems. Therefore, electronics engineers around the world are devoting their careers to innovating technologies to meet the ever-growing demand for wireless devices.

Since its inception in 1988, this magazine has been publishing articles on wireless technology. Examples include Ed Nisley’s “Digitizing Infrared Signals” (Circuit Cellar 2), Maurizio Ferrari’s “Secrets of Using the DS1209 in an RF Transponder” (Circuit Cellar 41), and Steve Ciarcia’s “Wireless Remote Control of the AVMux” (Circuit Cellar 46). This month we continue the tradition.

On page 14, Clayton Gumbrell describes his QRSS-Rx design. The mbed-based receiver can digitize a small bandwidth of RF signals and send them to a server for processing.
Turn to page 30 to learn how Steve Lubbers built his “KartTracker,” which is a standalone GPS-based timing system used to time racing activities. An LCD operates as a user interface, an integrated accelerometer records G forces, a serial port provides connections to a GPS receiver and a wireless transmitter, and removable flash memory stores data.

Ed Nisley tackles the topics of capacitor self-resonance, GPS technology, RF energy, and data transmission in the first part of his series titled “RFI Bypassing” (p. 38). He presents a radio project featuring SMD capacitors for suppressing RF energy, and he describes test-fixture measurements on isolated capacitors.

As usual, this issue is not devoted solely to its theme. CPUs, power supplies, ADCs, Linux, and protocols are also covered.

On page 24, Alexander Pozhitkov begins a two-part series about the NakedCPU platform. It is designed to provide full access to hardware and a CPU without any OS restrictions while working in the protected mode.

In the first part of his series on building a robust power supply, George Novacek described how to make a power supply operate properly when the primary power distribution bus voltage is lower than nominal. This month he explains what happens when it encounters an abnormal surge voltage (p. 44).

On page 52, Robert Lacoste details how to work with high-speed ADCs. The article is intended to demystify the process of using high-speed converters effectively.
Another topic that needs demystification is embedded Linux, which is why Bob Japenga has been covering the subject in his ongoing series “Getting Started with Embedded Linux.” This month he addresses various licensing issues you’ll face as you work with Linux (p. 60).

Columnist Jeff Bachiochi wraps up this issue with the article “Multi-Serial Protocol Tool” (p. 64). As you’ll see, it’s fairly easy to build a multi-serial protocol tool designed to connect from a USB host an I2C, SPI, RS-232/422/485, or Dallas 1-Wire format.