CC 277: Simulate and Design a Switched Capacitor Filter

Here is Lacoste’s experimental mockup. It’s not pretty, but it’s functional. The clock is at the top. The filter is below.

Circuit Cellar columnist Robert Lacoste doesn’t like to throw away his old magazines—at least the ones that have electronics projects.

And often it’s the lack of microcontrollers in such projects that he finds intriguing. The designs required “clever solutions to implement even simple features, which is always a good source of inspiration,” he says.

Lacoste was recently inspired by a 1981 Elektor magazine article on switched-capacitor filters (part of the old magazine collection in his basement). So, he decided to revisit the topic in his column appearing in Circuit Cellar’s August issue.

“I figured, why not refresh it for a Circuit Cellar Darker Side article, as mastering switched-capacitor filters is now mandatory for plenty of mixed-signal designs?”

Lacoste’s column shows you how to modify a basic low-pass filter into a switched-capacitor filter.

He explains why such a modification can be a good one:

“The most basic form of a low-pass filter is the simple one-pole RC filter… Why can’t we be happy with such simple RC filters? There are two reasons. First, it is often convenient to have a filter with an adjustable cutoff frequency. With a RC filter, you would need to change either the resistor’s or the capacitor’s value. This it is not easy to do if you want to design an inexpensive electronic system. The other reason is more linked to IC technology and CMOS in particular.

“Assume you want to design a filtering chip with a cutoff frequency of about 10 kHz. If you want to use a small and inexpensive capacitor—perhaps no more than 1 nF—you will need a high-value resistor… The problem is that designing a high-value resistor on a silicon chip is complicated (i.e., expensive). Moreover, unlike capacitors, on-chip resistors are difficult to manufacture with tight specifications.”

Lacoste found the solution by looking through few back issues of his magazine collection and a few past decades.

“In the late 1970s, IC designers looked for a way to replace high-value resistors with inexpensive and easy-to-integrate parts (e.g., small capacitor),” he says.

The idea of replacing a resistor with a switched capacitor produced the switched-capacitor architecture Lacoste presents in his August column. As a bonus, his design offers an easy way to adjust switching frequencies.

“Of course, no one is actually designing a switched-capacitor circuit from scratch, as I did for this article,” Lacoste says. “It was only for demonstration purposes. There are plenty of ready-made switched-capacitor chips on the market. Just read their datasheets and use them in your design, more or less as a black box.”

Still, Lacoste says, “the best way to learn is to never be afraid of any technology. Knowing the internals helps you avoid usage mistakes.”

Intrigued? Check out Lacoste’s column in the August issue for more details.

LED Characterization: An Arduino-Based Curve Tracer

Circuit Cellar columnist Ed Nisley doesn’t want to rely solely on datasheets to understand the values of LEDs in his collection. So he built a curve tracer to measure his LEDs’ specific characteristics.

Why was he so exacting?

“Most of the time, we take small light-emitting diodes for granted: connect one in series with a suitable resistor and voltage source, it lights up, then we expect it to work forever,” he says in his July column in Circuit Cellar. “A recent project prompted me to take a closer look at commodity 5-mm LEDs, because I intended to connect them in series for better efficiency from a fixed DC supply and in parallel to simplify the switching. Rather than depend on the values found in datasheets, I built a simple Arduino-based LED Curve Tracer to measure the actual characteristics of the LEDs I intended to use.”

The Arduino Pro Micro clone in this hand-wired LED Curve Tracer controls the LED current and measures the resulting voltage.

Ed decided to share the curve tracer with his Circuit Cellar readers.

“Even though this isn’t a research-grade instrument, it can provide useful data that helps demonstrate LED operation and shows why you must pay more attention to their needs,” he says.

Ed says that although he thinks of his circuit as an “LED Curve Tracer,” it doesn’t display its data.

“Instead, I create the graphs with data files captured from the Arduino serial port and processed through Gnuplot,” he says. “One advantage of that process is that I can tailor the graphs to suit the data, rather than depend on a single graphic format. One disadvantage is that I must run a program to visualize the measurements. Feel free to add a graphics display to your LED Curve Tracer and write the code to support it!”

He adds that “any circuit attached to an Arduino should provide its own power to avoid overloading the Arduino’s on-board regulator.”

“I used a regulated 7.5 VDC wall wart for both the Arduino Pro Mini board and the LED under test, because the relatively low voltage minimized the power dissipation in the Arduino regulator,” he says. “You could use a 9 VDC or 12 VDC supply.”

To read more about Ed’s curve tracer, check out Circuit Cellar’s July issue.


CC 276: MCU-Based Prosthetic Arm with Kinect

In its July issue, Circuit Cellar presents a project that combines the technology behind Microsoft’s Kinect gaming device with a prototype prosthetic arm.

The project team and  authors of the article include Jung Soo Kim, an undergraduate student in Biomedical Engineering at Ryerson University in Toronto, Canada, Nika Zolfaghari, a master’s student at Ryerson, and Dr. James Andrew Smith, who specializes in Biomedical Engineering at Ryerson.

“We designed an inexpensive, adaptable platform for prototype prosthetics and their testing systems,” the team says. “These systems use Microsoft’s Kinect for Xbox, a motion sensing device, to track a healthy human arm’s instantaneous movement, replicate the exact movement, and test a prosthetic prototype’s response.”

“Kelvin James was one of the first to embed a microprocessor in a prosthetic limb in the mid-1980s…,” they add. “With the maker movement and advances in embedded electronics, mechanical T-slot systems, and consumer-grade sensor systems, these applications now have more intuitive designs. Integrating Xbox provides a platform to test prosthetic devices’ control algorithms. Xbox also enables prosthetic arm end users to naturally train their arms.”

They elaborate on their choices in building the four main hardware components of their design, which include actuators, electronics, sensors, and mechanical support:

“Robotis Dynamixel motors combine power-dense neodymium motors from Maxon Motors with local angle sensing and high gear ratio transmission, all in a compact case. Atmel’s on-board 8-bit ATmega8 microcontroller, which is similar to the standard Arduino, has high (17-to-50-ms) latency. Instead, we used a 16-bit Freescale Semiconductor MC9S12 microcontroller on an Arduino-form-factor board. It was bulkier, but it was ideal for prototyping. The Xbox system provided high-level sensing. Finally, we used Twintec’s MicroRAX 10-mm profile T-slot aluminum to speed the mechanical prototyping.”

The team’s goal was to design a  prosthetic arm that is markedly different from others currently available. “We began by building a working prototype of a smooth-moving prosthetic arm,” they say in their article.

“We developed four quadrant-capable H-bridge-driven motors and proportional-derivative (PD) controllers at the prosthetic’s joints to run on a MC9S12 microcontroller. Monitoring the prosthetic’s angular position provided us with an analytic comparison of the programmed and outputted results.”

A Technological Arts Esduino microcontroller board is at the heart of the prosthetic arm design.

The team concludes that its project illustrates how to combine off-the-shelf Arduino-compatible parts, aluminum T-slots, servomotors, and a Kinect into an adaptable prosthetic arm.

But more broadly, they say, it’s a project that supports the argument that  “more natural ways of training and tuning prostheses” can be achieved because the Kinect “enables potential end users to manipulate their prostheses without requiring complicated scripting or programming methods.”

For more on this interesting idea, check out the July issue of Circuit Cellar. And for a video from an earlier Circuit Cellar post about this project, click here.


CC275: Build a Signal Frequency Counter

In the June issue of Circuit Cellar, George Adamidis, a physicist and electronics engineer from Greece, shares his design for a 1.5-GHz frequency counter.

His design is based on an 8-bit microcontroller, but his modifications enable using the device as a 28-bit counter.

Here is a picture of the complete project.

“This design began as a Microchip Technology 8-bit PIC learning project. But it became more than that,” Adamidis says in his article. “Although I used an 8-bit PIC, I actually created a 28-bit counter.”

“The device measures signal frequencies from 0.1 Hz to 1.5 GHz and displays them on a 2 × 16 character LCD,” Adamidis continues. “It offers a frequency resolution up to 0.1 Hz for frequencies in the 0.1-Hz-to-100-MHz range and up to 4 Hz for 100-MHz-to-1.5-GHz frequencies. (The display resolution generally differs from the measurement accuracy.) Minimum and maximum hold functions, selection of frequency units, and gate time adjustment are also supported. “

Adamidis says it is “remarkable” that his frequency counter is actually a 28-bit counter.

“It uses a Microchip Technology PIC18F2620 microcontroller, which has only 16-bit internal counters. I used the PIC18F2620’s internal 16-bit Timer0 module (configured as a 16-bit counter), an additional 4-bit NXP Semiconductors 74F161 binary counter, and the PIC18F2620’s internal prescaler (in 1:256 prescale mode) in series to achieve a total of 28 bits.”

This is the 1.5-GHz frequency counter’s block diagram.


To read more about  the theory of operation, hardware, and software behind Adamidis’s design, check out this month’s issue of Circuit Cellar.

DIY Single-Board Computers

Countless technological innovations have certainly made the earliest personal  computers long obsolete. As Circuit Cellar contributors Oscar Vermeulen and Andrew Lynch note:  “Today there is no sensible use for an 8-bit, 64-KB computer with less processing power than a mobile phone. “

Nonetheless, there exists a “retrocomputing”  subculture that resurrects older computer hardware and software in DIY projects. It may be sentimental, but it can also be instructive.

In their two-part series beginning in July in Circuit Cellar, Vermeulen and Lynch focus on that strain of retrocomputing that involves designing and building your own computer system from a “bag of chips” and a circuit board.

Part 1 describes a simple single-board CP/M design that uses just one high-capacity RAM chip and is compatible with a serial or PC terminal.

Here is a homebrew N8VEM system with a single-board computer (SBC) and disk/IDE card plugged into the ECB backplane.

“It is easy to create a functional computer on a little circuit board—considering all the information now available on the Internet,” Vermeulen and Lynch say in Part 1.  “These retro machines may not have much practical use, but the learning experience can be tremendously valuable.”

Some “homebrewed” computer creations  can be “stunningly exotic,” according to Vermeulen and Lynch, but most people build simple machines.

“They use a CPU and add RAM, ROM, a serial port, and maybe an IDE interface for mass storage. And most hobbyists run either BASIC (e.g., the 1980s home computers) or use a “vintage” OS such as CP/M.

“Running CP/M, in fact, is a nice target to work toward. A lot of good software ensures your homebrew computer can do something interesting once it is built. As the predecessor of MS-DOS, CP/M also provides a familiar command-line interface. And it is simple. A few days of study are enough to port it to your circuit board.”

But some Circuit Cellar readers may want more from a retrocomputing experience than a one-off project.  In that case, there are online resources that can help, according to the authors.

“Working on your own, it can become progressively more difficult to take the next steps (i.e., building graphics subsystems or using exotic processors) or to add state-of-the-art microcontrollers to create ‘Frankenstein’ systems (i.e., blends of old and new technology that can do something useful, such as automate your home).”

Part 1 of their article introduces a solid online resource for taking retrocomputing to the next level–the N8VEM Google group, which provides a single-board CP/M design meant to engage others.

This is the N8VEM in its $20 stand-alone incarnation.

“N8VEM is not about soldering kits. It is about joining in, trying new things, and picking up skills along the way. These skills range from reading schematics to debugging a computer card that does not operate as intended. The learning curve may be steep at times, but, because the N8VEM mail group is very active, expert help is available if or when you get stuck….

“As the novelty of designing a simple single-board computer (SBC) wears off, you may prefer to focus your energy on exploring graphics systems or ways to hook up 8-bit machines on the Internet. Or, you may want to jump into systems software development and share your experiences with a few hundred others.

“Retrocomputing is not always backward-facing. Making  ‘Frankenstein’ systems by adding modern Parallax Propeller chips or FPGAs to old hardware is a nice way to gain experience in modern digital electronics, too.”

For more, check out the July issue of Circuit Cellar for Part 1 of their series. In Part 2, scheduled for publication in August,  the authors provide a technical look at the N8VEM’s logic design. It also provides a starting point for anyone interested in exploring the N8VEM’s system software and expansion hardware, according to Vermeulen and Lynch.



CC275: Shape The Future

In January, Circuit Cellar introduced a new section, Tech the Future, which dedicates page 80 of our magazine to the insights of innovators in groundbreaking technologies.

We’ve reached out to a number of graduate students, professors, researchers, engineers, designers, and entrepreneurs, asking them to write short essays on their fields of expertise, with an emphasis on future trends.

Their topics have included high-speed data acquisition, Linux home automation, research into new materials to replace traditional silicon-based CMOS for circuitry design, control system theory for electronic device DIYers, and how open-source hardware will make world economies more democratic and efficient.

Our contributors have been diverse in more than just their topics. They have been talented

Tech the Future essayist Fergus Dixon designed this DNA sequencer, the subject of an article in the May 2013 issue of Circuit Cellar.

young researchers and seasoned professionals. Male and female. American, Portuguese, Italian, Indian, and Australian.

The one thing they have in common? They keep a close eye on the ever-changing landscape of technological change. And their essays have helped our readers focus on what to watch. We compensate authors for the essays we choose to publish, and we are eager to hear your suggestions on subjects for Tech the Future.

If you are an innovator interested in writing an essay for Tech the Future, e-mail me ( with the topic you’d like to address and some information about yourself. If you are a reader who wants to hear from someone in particular through Tech the Future or has a suggestion for an essay topic, please contact me.

The work of those we’ve featured so far can be found online at Here are just a few of the innovators you will find there:

Maurizio Di Paolo Emilio, a designer of data acquisition software for physics-related experiments and industrial applications, discussing the future of data acquisition technology.

Saptarshi Das, a nano materials researcher who holds a PhD in Electrical Engineering from Purdue University, focusing on the urgent need for alternatives to silicon-based CMOS. These alternative materials, now the subject of extensive scientific research, will be game changers for the microelectronics and nanoelectronics industries, he says.

Fergus Dixon, an Australian entrepreneur and designer of the popular software program “Simulator for Arduino,” explaining why open-source hardware is a valuable tool in the development of new medical devices. Design opportunities for such devices are countless. Hot technologies developed for 3-D printing and unmanned aerial vehicles (UAVs) have direct medical applications, including 3-D-printed prosthetic ears and nanorobots that utilize UAV technology.

Enjoy these articles and others online. In the meantime, I’ll be checking my e-mail for what you would like to see featured in Tech the Future.

Electrical Engineer Crossword (Issue 275)

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


2.    UNIFIEDMODELING—Language that standardizes software specifications
3.    KELVINBRIDGE—Compares low resistance values [two words]
6.    THINCLIENT—A codependent program [two words]
10.    BANANAPLUG—Makes electrical connections [two words]
11.    CONDENSER—aka capacitor
13.    ASTABLE—A multivibrator circuit
15.    FLIPFLOP—A fundamental building block [two words]
18.    AMMETER—Used to calibrate current
19.    CLOCKGATING—Method of lowering dynamic power dissipation [two words]
20.    THERMIONICVALVE—Uses a vacuum to control electric current [two words]


1.    VISITORPATTERN—Keeps an algorithm away from an object structure
4.    RUNTIME—Multi-lingual computer system
5.    FIELDEFFECT—This type is unipolar [two words]
7.    LISSAJOUSCURVE—An oscilloscope trace [two words]
8.    NONMASKABLE—Cannot be ignored
9.    CASCODECIRCUIT—Provides amplification [two words]
12.    CRON—Keeps things on schedule
14.    ROENTGEN—Radiation measurement
16.    RETFIE—Instruction that enables new interrupts to occur
17.    SELSYN—aka mag-slip

New Products: June 2013

C-Programmable Autonomous Mobile Robot System

The RP6v2 is a C-programmable autonomous mobile robot system designed for hobbyists and educators at universities, trade schools, and high schools. The system includes a CD with software, an extensive manual, plenty of example programs, and a large C function library. All library and example programs are open-source GNU general public license (GPL).

The autonomous mobile robot system has a large payload capacity and expansion boards, which may be stacked as needed. It receives infrared (IR) codes in RC5 format and includes integrated light, collision, speed, and IR-obstacle sensors. Its powerful tank drive train can drive up steep ramps and over obstacles.

The RP6v2’s features include an Atmel ATmega32 8-bit RISC microcontroller, AVR-GCC and RobotLoader open-source software for use with Windows and Linux, six PCB expansion areas, two 7.2-VDC motors, an I2C bus expansion system, and a USB interface for easy programming and communication.
The fully assembled RP6v2 robotic system costs $199.

Global Specialties

Smart Panels with Powerful CPU and Multiple OS Support

The SP-7W61 and the SP-1061 smart panels are based on the Texas Instruments 1-GHz Sitara AM3715 Cortex-A8 processor and an Imagination Technologies integrated PowerVR SGX graphics accelerator. The products support multiple OSes—including Linux 2.6.37, Android 2.3.4, and Windows Compact 7—making them well suited for communications, medical and industrial control, human-machine interface (HMI), and transportation applications.

The SP-7W61 (7” and 16:9) and the SP-1061 (10” and 4:3) have a low-power, slim, fanless mechanical design and a high-value cost/performance (C/P) panel PC module that uses powerful and efficient components. Compared with other x86 HMI or open-frame products, the SP-7W61 and the SP-1061 successfully keep power consumption to less than 5.9 W, which is half the typical rate. The smart panels feature multiple display sizes and low power consumption options. They can be implemented into slim and thin chassis types (e.g., for HMI, control panels, or wall-mount controllers).

ADLINK provides full support on software customization based on different platforms. A virtual machine or software development kit (SDK) is provided with related documentation for different platforms, so users can easily set up the software environment.
Contact ADLINK for pricing.

ADLINK Technology, Inc.

Fast-Switching 0.65-TO-20-GHz Synthesizer

The APSYN420B is a 0.65-to-20-GHz frequency synthesizer with a 0.001-Hz resolution and 0.1° phase resolution. The synthesizer provides a nominal output power of 13 dBm into 50 ?. The module features a high-stability internal reference that can be phase-locked to a user-configurable external reference or used in a master-slave configuration for high phase coherence.

The APSYN420B’s key features include low phase noise, fast switching (settling time is typically 20 µs with a 20-µs frequency update), and an internal OCXO reference that can be configured for high phase coherence between multiple sources. The synthesizer offers USB and LAN interfaces and consumes less than 10 W when powered from an external 6-VDC supply.

The APSYN420B’s modulation capabilities include angle, pulse, pulse trains, and pulsed chirps. Linear, logarithmic, or random-frequency sweeps can be performed with combined modulation running. Frequency chirps (linear ramp, up/down) can also be accomplished. The device can accept external reference signals from 1 to 250 MHz.

Applications for the APSYN420B include automatic test equipment, satellite, and other telecommunications needs. The APSYN420B is designed for a 0°C-to-45°C operating temperature range and weighs less than 2 lb in a compact 2.4” × 4.2” × 8.3” enclosure.
Contact Saelig for pricing.

Saelig Co., Inc.

SoC for Next-Generation Multimedia and Navigation Systems

The R-Car H2 is the latest member of Renesas’s R-Car series of automotive system-on-a-chip (SoC) offerings. The SoC delivers more than 25,000 Dhrystone million instructions per second (DMIPS) and provides high-performance and state-of-the-art 3-D graphics capabilities for high-end multimedia and automotive navigation systems.
The R-Car H2 is powered by the ARM Cortex A-15 quad-core configuration running an additional ARM Cortex A-7 quad core. The SoC also features Imagination Technologies’s PowerVR Series6 G6400 graphics processing unit (GPU). The GPU supports open technologies (e.g., OpenGL ES 2.0) and the OpenGL ES 3.0 and OpenCL standards.
The R-Car H2’s bus architecture includes dedicated CPU and IP caches, which reduce the double data rate type three (DDR3) memory bandwidth consumption. To ensure adequate memory bandwidth, the R-Car H2 is equipped with two independent DDR3-1600 32-bit interfaces.

The R-Car H2 integrates advanced automotive interfaces including Ethernet audio video bridging (AVB), MOST150, and CAN and mass storage interfaces such as serial advanced technology attachment (SATA), USB 3.0/2.0, secure digital (SD) card, and PCI Express for system expansion. As a device option, the GPS baseband engine handles all modern navigation standards. The R-Car H2’s additional features include 24-bit digital signal processing (DSP) for codec, high-quality audio processing with hardware sample rate converters, and audio mixing. Its multi-core architecture enables you to implement real-time features (e.g., quick-boot, backup camera support, and media processing) parallel to the execution of advanced OSes, such as QNX Neutrino RTOS, Windows Embedded Automotive, or Linux.

The SoC’s media hardware accelerators enable features such as 4× HD 1080p video encoding/decoding including Blu-ray support at 60 frames per second, image/voice recognition, and high-resolution 3-D graphics with almost no CPU load. These implemented hardware modules also execute the display content improvements needed for HMI/navigation data similar to movie/DVD handling.
Contact Renesas for pricing.

Renesas Electronics Corp.

KNX Device Control

The KNX Gateway enables HAI by Leviton’s Omni and Lumina Ethernet-based controllers to communicate with and control KNX devices through KNX’s standardized network communications bus protocol. You can use an HAI by Leviton interface or automated controller programming to control KNX devices (e.g., lighting devices, temperature and energy management, motors for window coverings, shades, and shutters) in homes and businesses.

The KNX Gateway maps specific data points of each KNX device to a unit or thermostat number on the HAI by Leviton controller. The interface between the KNX Gateway and the HAI by Leviton controller utilizes a RS-485 serial connection.

Compatible controllers include HAI’s OmniPro II home-control system, Omni IIe, Omni LTe, Lumina Pro, and Lumina. The KNX Gateway is powered by either a power over Ethernet (PoE) connection or a 12-to-24-V AC/DC converter.
Contact Leviton for pricing.

Leviton Manufacturing Co., Inc.

DC/DC Controller Uses Only a Single Inductor

The LTC3863 is a high-voltage inverting DC/DC controller that uses a single inductor to produce a negative voltage from a positive-input voltage. All of the controller’s interface signals are positive ground referenced. None of the LTC3863’s pins are connected to a negative voltage, enabling the output voltage to be limited by only the external components selection.

Operating over a 3.5-to-60-V input supply range, the LTC3863 protects against high-voltage transients, operates continuously during automotive cold crank, and covers a broad range of input sources and battery chemistries. The controller helps increase the runtime in battery-powered applications.

It has a low 70-µA quiescent current in Standby mode with the output enabled in Burst Mode operation. The LTC3863’s output voltage can be set from –0.4 to 150 V or lower at up to 3 A typical, making it well suited for 12-or-24-V automotive, heavy equipment, industrial control, telecommunications, and robotic applications.

The LTC3863 drives an external P-channel MOSFET, operates with a selectable fixed frequency between 50 and 850 kHz, and is synchronizable to an external clock from 75 to 750 kHz. Its current-mode architecture provides easy loop compensation, fast transient response, cycle-by-cycle overcurrent protection, and excellent line regulation. Output current sensing is accomplished by measuring the voltage drop across a sense resistor.
The LTC3863’s additional features include programmable soft start or tracking, overvoltage protection, short-circuit protection, and failure mode and effects analysis (FMEA) verification for adjacent pin opens and shorts.

The LTC3863 is offered in 12-pin thermally enhanced MSOP and 3-mm × 4-mm QFN packages. The controllers cost $2.06 in 1,000-unit quantities.

Linear Technology Corp.

Enhanced Web-Based Monitoring Software

HOBOlink is a web-enabled software platform that provides 24/7 data access and remote management for Onset Computer’s web-based HOBO U30 data logging systems. The software’s enhanced version enables users to schedule automatic delivery of exported data files in CSV or XLSX format, via e-mail or FTP.

HOBOlink can configure exported data export in a customized manner. For example, a user with four HOBO U30 systems measuring multiple parameters may configure HOBOlink to automatically export temperature data only. The time range may also be specified.

HOBOlink also enables users to easily access current and historical data, set alarm notifications and relay activations, and manage and control HOBO U30 systems without going into the field. An application programming interface (API) is available to organizations that want to integrate energy and environmental data from HOBOlink web servers with custom software applications.
Contact Onset for pricing.

Onset Computer Corp.

Digitally Tunable Capacitors for LTE Smartphones

Peregrine Semiconductor expanded its DuNE digitally tunable capacitor (DTC) product line with six second-generation devices for antenna tuning in 4G long-term evolution (LTE) smartphones. The PE623060, PE623070, PE623080, and PE623090 (PE6230x0) DTCs have a 0.6-to-7.7-pF capacitance range and support main antenna power handling of up to 34 dBm. The PE621010 and the PE621020 (PE6210x0) DTCs have a 1.38-to-14-pF capacitance range and are optimized for power handling up to 26 dBm, making them well suited for diversity antennas. The highly versatile devices support a variety of tuning circuit topologies, particularly impedance-matching and aperture-tuning applications.
The PE6230x0 DTCs are optimized for key cellular frequency bands from 700 to 2,700 MHz, featuring direct battery voltage operation with consistent performance enabled by on-chip voltage regulation.

The 5-bit, 32-state PE623060/70/80 DTCs have a 0.9-to-4.6-pF capacitance range. The 4-bit, 16-state PE623090 DTC has a 0.6-to-2.35-pF capacitance range. The PE623090 DTC’s lower minimum capacitance solves a critical problem in high-frequency tuning. The 5-bit, 32-state PE6210x0 DTCs support the 100-to-3,000-MHz frequency range. These DTCs extend the range of diversity antennas and improve data rates by optimizing the antenna performance at the operating frequency. The PE621010 DTC has a 1.38-to-5.90-pF capacitance range.

The PE6230x0 and PE6210x0 product families enable designers to develop smaller, higher-performing antennas. The product’s antenna-tuning functions—including bias generation, integrated radio frequency (RF) filtering and bypassing, control interface, and electrostatic discharge (ESD) protection of 2-kV human body model (HBM)—are incorporated into a slim, 0.55-mm × 2-mm × 2-mm package. All decoding and biasing are integrated on-chip, and no external bypassing or filtering components are required.
Contact Peregrine for pricing.

Peregrine Semiconductor Corp.

A Real-Time Fuel Consumption Monitor

Jeff Bachiochi’s real-time fuel consumption monitor for his Jeep.

Circuit Cellar columnist Jeff Bachiochi has enjoyed driving his wife’s Prius, in part because of the real-time feedback it gives him on the miles per gallon he is getting. It made him aware of how he could save gas with simple and immediate adjustments to his driving style.

With that in mind, he thought it would be a good idea to build an effective and affordable monitoring device that would give him the same real-time mpg for his Jeep.  After all, he can’t always borrow his wife’s car.

In the June issue, he shares what he came up with for an onboard diagnostics display. He explains below how he tapped into his own experience, as well as that of another Circuit Cellar author, to build the device for Jeep

“In the summer of 2011, I presented a three-part series about the on-board diagnostic system (OBD-II) built into every automobile produced since 1996 (Circuit Cellar 251–253)….”

“In 2005, Bruce D. Lightner wrote an article about his winning entry in the 2004 Atmel AVR design contest (“AVR-Based Fuel Consumption Gauge,” Circuit Cellar 183, 2005). Lightner’s project altered an analog tachometer gauge as a display for miles per gallon. I wanted to show a little more information, so my project uses a Parallax Propeller microcontroller to interrogate the OBD interpreter and drive a composite LCD.

“You can get a composite color display from Parallax or an online source. While I had a small 2.5” display to work with, I was looking for something a bit bigger. For less than $50, I found a 7” LCD, which happened to be combined with a camera (for mounting on a vehicle’s rear license plate frame)…

“I dug out my Propeller Proto Board and blew off the dust…. The Propeller microcontroller design includes eight 32-bit parallel processors (i.e., cogs) and peripheral support, including access to the 32 I/O pins, two counters, and a video generator per cog.  It is the video generator support that makes this project possible with a minimal component count…. only three resistors are required to develop a composite video output.“

To read more about Bachiochi’s OBD device, check out his article in the June issue.


New CC Columnist to Focus on Programmable Logic

We’d like to introduce you to Colin O’Flynn, who will begin writing a bimonthly column titled “Programmable Logic In Practice” for Circuit Cellar beginning with our October issue.

Colin at his workbench

You may have already “met.” Since 2002, Circuit Cellar has published five articles from this Canadian electrical engineer, who is also a lecturer at Dalhousie University in Halifax, Nova Scotia, and a product developer.

Colin has been fascinated with embedded electronics since he was a child and his father gave him a few small “learn to solder” kits. Since then, he has constructed many projects, earned his master’s in applied science from Dalhousie, pursued graduate studies in cryptographic systems, and become an engineering consultant. Over the years, he has developed broad skills ranging from electronic assembly (including SMDs), to FPGA design in Verilog and VHDL, to high-speed PCB design.

And he likes to share what he knows, which makes him a good choice for Circuit Cellar.

Binary Explorer

One of his most recent  projects was a Binary Explorer Board, which he developed for use  in teaching a digital logic course at Dalhousie. It fulfilled his (and his students’) need for a simple programmable logic board with an integrated programmer, several switches and LEDs, and an integrated breadboard. He is working to develop the effective and affordable board into a product.

In the meantime, he is also planning some interesting column topics for Circuit Cellar.

He is interested in a range of possible topics, including circuit board layout for high-speed FPGAs; different methods of configuring an FPGA; design of memory into FPGA circuits;

Colin’s LabJack-based battery tester

use of tools such as Altera’s OpenCV libraries to design programmable logic using C code; use of vendor-provided and open-source soft-core microcontrollers; design of a PCI-Express interface for your FPGA; and addition of a USB 3.0 interface to your FPGA.

That’s just a short list reflecting his interest in programmable logic technologies, which have become increasingly popular with engineers and designers.

To learn more about Colin’s interests, check out our February interview with him, his YouTube channel of technical videos, and, of course, his upcoming columns in Circuit Cellar.



DIY Surface-Mount Circuit Boards

James Lyman, an engineer with degrees in Aerospace, Electrical Engineering, and Systems Design, has more than 35 years of design experience but says he was “dragged” over the past decade into using surface-mount devices (SMD) in his prototypes. He had a preference for using through-hole technology whenever possible.

“The reasons are simple,” he says in an article appearing in the June issue of Circuit Cellar magazine. “It’s much easier to use traditional components for building and reworking prototype circuits than it is to use wire to make the connections. Plus, the devices are large and easy to handle. But time and technology don’t leave anyone at peace, so my projects have gradually drifted toward surface-mount design.”

In his article, Lyman shares the techniques he developed for designing prototypes using SMD components. He thought sharing what he learned would make the transition less daunting for other designers.

This accompanying photo shows one of his completed circuit board designs.

Lyman’s techniques developed out of trial and error. One trial involved keeping small components in place during the building of his prototype.

“When I built my first few surface-mount boards, I did what so many amateurs and technicians do. I carefully placed each minute component on the circuit board in its correct position, and then spent several minutes playing ‘SMD hockey,’ ” Lyman says. “With nothing holding the component in place, I’d take my soldering iron and heat the pad component while touching the solder to the junction. Just as the solder was about to melt, that little component would turn into a ‘puck’ and scoot away. Using the soldering iron’s tip as a ‘hockey stick,’ I’d chase the little puck back to its pads and try again, which was maddening. Finally, I’d get a drop of solder holding one end of the puck in place, usually with the other end sticking away from its pad. Then I could reheat the solder joint while holding the puck and position it correctly. I would have to start over with the next component, all the while yearning for that wonderful old through-hole technology.

“It slowly occurred to me that I needed something to hold each part in place while soldering—something that would glue them in place. Commercial houses glue the components down on the boards and then use a wave soldering machine, which does all the soldering at once. That’s exactly what I started doing. I use J-B Weld, a common off-the-shelf epoxy.”

Using an easy-to-get epoxy is just one of the tips in Lyman’s article. For the rest, check out his full article in the June issue of Circuit Cellar.


Electrical Engineer Crossword (Issue 274)

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

1.            MOSIPROTOCOL—Adds a state indicating ownership [two words]

3.            SPECTROMETER—Measures wavelengths

8.            SHELL—Protects an operating system’s kernel

10.          CHARGE—Q

12.          ASSIGN—A FORTRAN control statement

13.          HALL—American physicist (1855–1938) who had an “effect” [two words]

15.          FIELDPROGRAMMABLE—Configurable after purchase [two words]

17.          MOUNTPOINT—In a Linux system, create this first to access the queue [two words]

19.          CORDIC—Calculate digit by digit

20.          MEISSNEREFFECT—Flux jumping [two words]



2.            INTERPROCESSCOMMUNICATION—Data exchanging method [two words]

4.            SQUIRRELCAGE—Commonly used in asynchronous motors [two words]

5.            DEGLITCHER—Type of delay circuit, serves as a pulse generator

6.            MERCURYARC—Emits  bright bluish-green light [two words]

7.            BALLGRIDARRAY—Packages ICs [three words]

9.            THREADEDCODE—A compiler technique [two words]

11.          DARAF—Unit of elastance

14.          AMPEREHOUR—3,600 coulombs [two words]

16.          RIPPLE—Unwanted undulation

18.          NIXIE—Used for numeric display


Q&A: Scott Potter (Engineering a Way To Clean Solar Mirrors)

Designer and technology executive Scott Potter won first prize in the 2012 RL78 Green Energy Challenge, presented by Renesas Electronics in partnership with Circuit Cellar and Elektor magazines. The global contest called on participants to develop green energy designs utilizing Renesas’s RL78 microcontrollers. Scott won with his solar-powered electrostatic cleaning robot, which removes dust and debris from the tracking mirrors of large-scale concentrating solar power plants.—Mary Wilson, Managing Editor

Scott Potter

MARY: Where do you live and what is your current occupation?

SCOTT: I live in Los Gatos, CA, and I’m a senior director at Jasper Wireless, a company providing machine-to-machine (M2M) data communications services. I have been with Jasper since the beginning in 2005 when the company started with four people and a plan. Now Jasper is approaching 150 employees and we are a global company. I have served many roles at Jasper, working on location technology, device middleware, back-end reporting, and front-end software.

My other job is as an inventor at Taft Instruments. We are just now forming around the technology I developed for the RL78 design challenge. We are finding there is a big need for this solution in the solar industry, which is poised for tremendous growth in the next few years.

MARY: How did you first become interested in embedded electrical design? What is your educational background?

SCOTT: I started working for my father at his startup in the basement of our home in Long Island when I was a teenager (child labor laws were more lax back then). We were doing embedded electronics design along with mechanical modeling and prototyping. I learned from the best and it has stuck with me all these years. I went on to get a BSEE from Tufts University and I toyed with the idea of business school, but it never gripped me like engineering.

MARY: Why did you enter the 2012 Renesas RL78 Green Energy Challenge? What about its focus appealed to you?

SCOTT: The green energy design challenge came along at the perfect time. I had been working on the cleaning robot for a few months when I saw the challenge. The microcontroller I had originally picked was turning out to be not a great choice, and the challenge made me take a look at the RL78. The part was perfect, and the challenge gave me a goal to work toward.

MARY: How did the idea of designing a robot to clean solar-tracking mirrors (i.e., heliostats) for solar power plants come to you?

SCOTT: I can’t say it came to me all at once. I have participated in solar technology development sporadically throughout my career, and I have always tried to stay abreast of the latest developments. After the lessons learned from the parabolic trough concentrators, the move to high-concentration concentrating solar power (CSP) plants, which more efficiently convert solar power to electrical power, struck me as the right thing to do.

The high-concentration CSP plant utilizes hundreds of thousands of mirrors spread over many acres. The mirrors reflect sunlight onto a centrally located tower, which creates intense heat that drives a steam turbine generator.

The efficiency gains from the higher temperatures will make this the dominant technology for utility scale power generation. But there is a high maintenance cost associated with all of those mirror surfaces, especially in environments where water is scarce. A number of people have realized this and proposed various solutions to keeping the surfaces clean. Unfortunately, none of the proposed solutions will work well at the scale of a large utility plant.

I experimented with quite a few waterless cleaning techniques before coming back to electrostatics. It was my wife, Dia, who reminded me that NASA had been cleaning dust off panels on space missions for years using electrostatic principles. She convinced me to stop working with the forced-air concept I was doing at the time and switch to electrostatics. It was definitely the right choice.

MARY: What does the system do? What problems does it solve for power plants? How is the device different from what is already available for the task of cleaning heliostats?

SCOTT: Our patent-pending device is unique in many ways. It is completely autonomous, requiring no external power or water. The installation time is less than 10 s per heliostat, after which the device will remain attached and operating maintenance free for the life of the plant. We borrowed a marketing term from the military for this: “Set it and forget it.”

Most of the competing products have a long installation time and require some external wiring and maintenance. These can be logistical problems in a field of hundreds of thousands of mirrors.

Our device is also unique in that it cleans continuously. This prevents accumulation of organic materials on the surface, which can mix with dew and make a bio-film on the surface. That film bakes on and requires vigorous scrubbing to remove. We also have a feature to handle the dew, or frost, if it’s present.

MARY: What were some of your design challenges along the way and how did you address them?

SCOTT: They were numerous. The first challenge was the power source. It is important that this device be entirely self-powered to avoid having to install any wiring. I had to find a solar-panel configuration that provided enough power at the right voltage levels. I started with lower voltages and had a lot of trouble with the boost converters.

I also couldn’t use any battery storage because of the life requirement. This means that everything has to operate intermittently, gracefully shutting down when the sun fades and then coming up where it left off when the sun returns.

The next challenge was the mechanical drive. This had to grip the mirror tightly enough to resist a stream of water from a cleaning hose (infrequent cleaning with water will probably still be performed). And it had to do this with no power applied.

Another big challenge was the high-voltage electronics. It turns out there is little off-the-shelf technology available for the kind of high-voltage circuitry I needed. Large line output power transformers (LOPTs) for old cathode ray tubes (CRTs) are too large and expensive.

Some of the resonant high-voltage circuits used for cold cathode fluorescent lighting (CCFL) can be used as building blocks, but I had to come up with quite a few innovations to be able to control this voltage to perform the cleaning task. I had more than a few scorched breadboards before arriving at the current design, which is very small, light, and powerful.

MARY: You recently formed Taft Instruments (click here for Taft website). Who are the players in the company and what services does it provide?

SCOTT: We formed Taft instruments to commercialize this cleaning technology. We have been very fortunate to attract a very talented team that has made tremendous progress promoting the company in industry and attracting investment.

We have Steve Gluck and Gary Valinoti, both highly respected Wall Street executives who have galvanized the company and provided opportunities I could never have imagined. They are now recruiting the rest of the team and we are talking to some extremely qualified people. And of course my wife, Dia, is making numerous contributions that she will probably never get credit for.

MARY: How’s business? How would you describe the market for your product and the potential for growth and reach (both domestically and globally)?

SCOTT: We are not at the commercial deployment stage just yet. Our immediate focus is on the field trials we are starting with a number of industry players and the US Department of Energy National Laboratories. We fully expect the trials to be successful and for our large-scale rollouts to begin in about a year.

The market potential for this is tremendous. I’m not sure anyone fully realizes yet the global transformation that is about to take place. Now that the “grid parity” point is near (the point where the cost of solar power is competitive with fossil fuels), solar will become one of the fastest-growing markets we have seen in a century.

Entire national energy pictures will change from single-digit percentages to being dominated by solar. It is a very exciting time in the solar industry, and we are very happy to be part of it.

MARY: Are you individually—or is your company—developing any new designs? If so, can you tell us something about them?

SCOTT: Yes. I can’t say much, but we are working on some very interesting new technologies that will improve on the electrostatic cleaning principles. This technology will vastly expand the base that we can work with.

MARY: You describe yourself as a “serial entrepreneur” with a strong technical background in electronics, software, hardware, and systems design. That combination of skills comes in handy when establishing a new business. But it also helped you land your day job eight years ago as Director of Location Technology at Jasper Wireless. What do you see as future key trends in M2M communications?

SCOTT: M2M has really taken off since we began in 2005. Back then, there were only a few applications people had envisioned taking wireless. That list has exploded, and some analysts are predicting volumes of M2M endpoints that exceed the human population by tenfold!

We have seen large growth in a number of different verticals over the years, the most apparent one right now being automotive, with all the car companies providing connected services. Jasper is uniquely positioned to offer a global solution to these companies through our carrier partners.

MARY: Over the years, you have gained expertise in areas ranging from embedded electronics and wireless, to applications of the global positioning and geographic information systems (GPS and GIS). What do you enjoy most and what are some career highlights? Is one your involvement in the development of a GPS for the New York fire department’s recovery operations after the collapse of the World Trade Center?

SCOTT: What I enjoy most is working with motivated teams to create compelling products and services. One of my proudest moments was when our team at Links Point rose to the 9/11 challenge. At the time, I was a founder and the chief technology officer of Links Point, which provided GPS and location mapping.

When the request came from the New York fire department for a solution to locating remains at the recovery site, the team dedicated themselves to providing a solution no first responder had ever had access to previously. And we did that in record time. We had to come up with a proposal in a half-day and implement it within three days. You have to realize that GPS and PDAs were very new at the time and there were a lot of technical challenges. We also had to compete with some other companies that were proposing more accurate surveying equipment, such as laser ranging.

Our product, a PDA with a GPS attachment, won out in the end. The advantages of our handheld devices were that they were rugged and that firefighters could easily carry them into Ground Zero. We got the opportunity and honor of serving the  FDNY because of the extreme talent, dedication, and professionalism of my team. I would like to mention them: Jerry Kochman, Bill Campbell, Murray Levine, Dave Mooney, and Lucas Hjelle.

MARY: What is the most important piece of advice you would give to someone trying to make a marketable product of his or her design for an electrical device?

SCOTT: Whatever the device, make sure you are passionate about it and committed to seeing it come through. There is a quote that Dia framed for me hanging in my lab—this is attributed to Goethe, but there is some question about that. Anyway, the quote is very inspirational:

“Until one is committed, there is hesitancy, the chance to draw back. Concerning all acts of initiative (and creation), there is one elementary truth that ignorance of which kills countless ideas and splendid plans: that the moment one definitely commits oneself, then Providence moves too. All sorts of things occur to help one that would never otherwise have occurred. A whole stream of events issues from the decision, raising in one’s favor all manner of unforeseen incidents and meetings and material assistance, which no man could have dreamed would have come his way. Whatever you can do, or dream you can do, begin it. Boldness has genius, power, and magic in it. Begin it now.” I

Editor’s note: For more details, schematics, and a video of Scott Potter’s solar-powered electrostatic cleaning robot, click here.

Wi-Fi-Connected Home Energy Monitor

The Kunzig brothers of Pennsylvania use the word “retired” loosely.

Donald and Robert are both retired—each from long careers in the telecommunications industry. And after retirement, each took on a new job (Donald developing software to track and manage clinical trials managed by BioClinica, Inc., and Robert at a large data center).

So while other semi-retirees might prefer relaxing in poolside chairs or on the couch, what do these two do? They eagerly take on some technologies they haven’t worked with before and build a Wi-Fi-connected device to monitor a home’s power usage. And after two years of trial, error, and, finally, success, they develop an e-commerce website to sell it.

“Robert’s son, Jay, a design engineer working in San Jose, CA, suggested the project,” the two brothers say in article they wrote for the May 2013 edition of Circuit Cellar. “The main purpose was to design a Wi-Fi-connected monitor that would be able to measure usage from both a utility and an alternate source of power such as solar or wind.”

Their article describes how they designed a usable device that offers programmability and function. They used a Microchip MRF24WB0MB 802.11 transceiver for Wi-Fi access and a Microchip Technology PIC24FJ256GB108 microprocessor in their design. They eventually wrote the article about the ups and downs of the process (which included five prototypes) because they felt elements of their work would help readers developing their own embedded electronics devices.

“All this effort has been rewarding, perhaps not financially (yet), but certainly intellectually,” the brothers say. “After almost two years of effort, we have produced a product with an excellent hardware design, coupled with software that is better than average. The platform can be used for just about any implementation.”

“We wanted to produce an energy monitor that was fully wireless, very accurate, extremely easy to use, and based on hardware and software that is very stable. We think we were successful on all counts.”

Check out the May issue of Circuit Cellar for their article. And for more information, visit their e-commerce website at

G-Code CNC Router Controller

Brian Millier constructed a microcontroller-based, G-code controller for a CNC router. So, we gave the retired instrumentation engineer space to publish a two-part series about his project.

In Part 1 (Millier-CC-2013-04-Issue 273), Millier explains the basics of G-code and how it is converted into three-axis motion, via the router’s three stepper motors. In Part 2, he describes his design of the router’s axis controller (powered by three small microcontrollers) and the host controller (powered by a more powerful microcontroller).

He calls the project one of the most challenging he has ever tackled.

So why bother? Especially when the combination of a PC and ArtSoft’s Mach3 software is a common and affordable approach to running a CNC router? Well, like most DIYers, Millier couldn’t resist an opportunity to learn.

“I want to be upfront and say that this is probably not the most practical project I have ever done,” Millier says in Part 1. “You can usually pick up a used PC for free, and the Mach3 software is professional-grade and handles much more complex G-code programs than my DIY controller will. However, it did provide me with a challenging programming task, and I learned a lot about designing a program with many concurrent tasks, all of which are quite time critical. Even if you are not interested in building such a controller, you may find interesting some of the techniques and tricks I used to provide the multi-axis stepper-motor motion.”

Millier’s two articles focus on the two main tasks of his project.

“The first was to understand the G-code language used to program CNC machines well enough to be able to write the firmware that would parse the G-code commands into something that a microcontroller could use to control the stepper motors used for each of the three axes,” he says. “The second task was to design the hardware/firmware that would actually control the three stepper motors, all of which had to move synchronously at accurate, ramped speeds.”

Millier wraps up his project by saying: “This was probably the most challenging project I’ve tackled, outside of work projects, in many years. In particular, the Basic program code for both of the controllers ran beyond 3,500 lines.”

You can Millier-CC-2013-04-Issue 273. The second article is available via Circuit Cellar’s webshop.