About Mary Wilson

Mary Wilson is Circuit Cellar's Managing Editor. You can reach her at mwilson@circuitcellar.com and @mgeditor_cc.

Designing Wireless Data Gloves

Kevin Marinelli, IT manager for the Mathematics Department at the University of Connecticut, recently answered CC.Post’s newsletter invitation to readers to tell us about their wearable electronics projects. Kevin exhibited his project,  “Wireless Data Gloves,” at the World Maker Faire New York in September. He spoke with Circuit Cellar Managing Editor Mary Wilson about the gloves, which are based on an Adafruit ATmega32U4 breakout board, use XBee modules for wireless communication, and enable wearers to visually manipulate data and 3-D graphics.

MARY: Tell us a little bit about yourself and your educational and professional background.

KEVIN: I am originally from Sydney, Nova Scotia, in Canada. From an early age I have

Kevin Marinelli

Kevin Marinelli

always been interested in taking things apart and creating new things. My degrees are a Bachelor’s in Computer Science from Dalhousie University in Halifax, Nova Scotia, and a Master’s in Computer Science from the University of New Brunswick in Fredericton, New Brunswick. I am currently working on my PhD in Computer Science at the University of Connecticut (UConn).

My first full-time employment was with ITS (the computer center) at Dalhousie University. After eight years, I moved on to an IT management position the Ocean Mapping Group at the University of New Brunswick. I am currently the IT manager for the Mathematics Department at  UConn.

I am also an active member of MakeHartford, which is a local group of makers in Hartford, Connecticut.

MARY: Describe the wireless data gloves you recently exhibited at the World Maker Faire in New York. What inspired the idea?

KEVIN: The idea was initially inspired 20 years ago when using a Polhemus 6 Degree-of-Freedom sensor for manipulating computer graphics when I was at the University of New Brunswick. The device used magnetic fields to locate a sensor in three-dimensional space and detect its orientation. The combined location and orientation data provides data with six degrees of freedom. I have been interested in creating six degrees of freedom input devices ever since. With the Arduino and current sensor technologies, that is now possible.

Wireless data gloves on display at World Maker Faire New York. (Photo: Rohit Mehta)

Wireless data gloves on display at World Maker Faire New York. (Photo: Rohit Mehta)

MARY: What do the gloves do? What applications are there? Can you provide an example of who might use them and for what purpose?

KEVIN: The data gloves allow me to use my hands to wirelessly transmit telemetry data to a base station computer, which collects the data and provides it to any application programs that need it.

There are a number of potential applications, such as manipulating 3-D computer graphics, measurement of data for medical applications, remote control of vehicles, remote control of animatronics and puppetry.

MARY: Can you tell me about the data gloves’s design and the components used?

KEVIN: The basic design guidelines were to make the gloves self-contained, lightweight, easy to program, wireless, and rechargeable. The main electronic components are an Adafruit ATmega32U4 breakout board  (Arduino Leonardo software compatible), a SparkFun 9d0f sensor board, an XBee Pro packet radio, a LiPo battery charger circuit, and a LiPo battery. These are all open hardware projects or, in the case of the battery, are ordinary consumer products.

The choice of the ATMega32U4 for the processor was made to provide a USB port without any external components such as an FTDI chip to convert between serial and USB communications. This frees up the serial port on the processor for communicating with the XBee radio.

For the sensors, the SparkFun 9dof board was perfect because of its miniscule size and

Top of glove

Top of glove

because it only requires four connections: two connections for power and two connections for I2C. The board has components with readily available data sheets, and there is access to working example code for the sensor board. This reduced the design work greatly by using an off-the-shelf product instead of designing one myself.

The choice of an 800-mAh LiPo battery provides an excellent lightweight rechargeable power supply in a small form factor. The relatively small battery powers the project for more than 24 h of continuous use.

Palm of glove

Palm of glove

A simple white cotton glove acts as the structure to mount the electronics. For user-controlled input, the glove has conductive fabric fingertips and palm. Touching a finger to the thumb, or the pad on the palm, closes an electrical pathway, which allows the microcontroller to detect the input.

For user-selectable input, each fingertip and the palm of the hand has a conductive fabric pad connected to the Adafruit microcontroller. The thumb and palm act as a voltage source, while the fingertips act as inputs to the microcontroller. This way, the microcontroller can detect which fingers are touching the thumb and the palm pads. Insulated wires of 30 gauge phosphor bronze are sewn into the glove to connect the pads to the microcontroller.

MARY: Are the gloves finished? What were some of the design challenges? Do you plan any changes to the design?

KEVIN: The initial glove design and second version of the prototype have been completed. The major design challenges were finding a microcontroller board with sufficient capabilities to fit on the back of a hand, and configuring the XBee radios. The data glove design will continue to evolve over the next year as newer and more compact components become available.

Initially I was designing and building my own microcontroller circuit based on the ATmega32U4, but Adafruit came out with a nice, usable, designed board for my needs. So I changed the design to use their board.

SparkFun has a well-designed micro USB-based LiPo battery charger circuit. This would have been ideal for my project except that it does not have an On/Off switch and only has some through-hole solder points for powering an external project. I used their CadSoft EAGLE files to redesign the circuit to make it slightly more compact, added in a power switch and a JST connector for the power output for projects.

The XBee radios were an interesting challenge on their own. My initial design used the standard XBee, but that caused communication complications when using multiple data gloves simultaneously. In reading Robert Faludi’s book Building Wireless Sensor Networks: With ZigBee, XBee, Arduino, and Processing, I learned that the XBee Pro was more suited to my needs because it could be configured on a private area network (PAN) with end-nodes for the data gloves and a coordinator for the base station.

One planned future change is to switch to the surface-mount version of the XBee Pro. This will reduce both the size and weight of the electronics for the project.

The current significant design challenge I am working on is how to prevent metal fatigue in the phosphor bronze wires as they bend when the hand and fingers flex. The fatigue problem occurs because I use a small diamond file to remove the Kapton insulation on the wires. This process introduces small nicks or makes the wires too thin, which then promotes the metal fatigue.

A third version is in the design stage. The new design will replace the SparkFun 9dof board with a smaller single-chip sensor, which I hope can be mounted directly on the Adafruit ATmega32U4 board.

MARY: What new skills or technologies did you learn from the project, if any?

KEVIN: Along the way to creating the gloves, I learned a great deal about modern electronics. My previous skills in electronics were learned in the ’70s with single-sided circuits with through-hole components and pre-made circuit boards. I can now design and create double-sided circuit boards with primarily surface-mounted components. For initial prototype designs, I use double-sided photosensitized circuit boards and etch them at home.

Learning to program Arduino boards and Arduino clones has been incredible. The fact that the boards can be programmed using C in a nice IDE with lots of support libraries for common programming tasks makes the platform an incredibly efficient tool. Having an enormous following makes it very easy to find technical support for solving problems with Arduino products and making Arduino clones.

Wireless networking is a key component for the success of the project. I was lucky to have a course in wireless sensor network design at UConn, which taught me how to leverage wireless technology and avoid many of the pitfalls. That, combined with some excellent reference books I found, insured that the networking is stable. The network design provides for more network bandwidth than a single pair of data gloves require, so it is feasible to have multiple people collaborating manipulating the same on the same project.

Designing microcontroller circuits using EAGLE has been an interesting experience. While most of the new components I use regularly in designs are available in libraries from Adafruit and SparkFun, I occasionally have to design my own parts in EAGLE. Using EAGLE to its fullest potential will still take some time, but I have become reasonably proficient with it.

For soldering, I mostly still use a standard temperature controlled soldering iron with a standard tip. Amazingly, this allows me to solder 0402 resistors and capacitors and up to 100 pitch chips. When I have components that need to be soldered under the surface, I use solder paste and a modified electric skillet. This allows me to directly control the temperature of the soldering and gives me direct access to monitoring the process.

The battery charger circuit on my data glove is hand soldered and has a number of 0402-sized components, as  well as a micro USB connector, which also is a challenge to hand solder properly.

MARY: Are there similar “data gloves” out there? How are yours different?

There are a number of data glove projects, which can be found on the Internet. Some are commercial products, while others are academic projects.

My gloves are unique in that they are lightweight and self-contained on the cotton glove. All other projects that you can find on the Internet are either hard-wired to a computer or have components such as the microcontroller, batteries, or radio strapped to the arm or body.

Also, because the main structure is a self-contained cotton glove; the gloves do not interfere with other activities such as typing on a keyboard, using a mouse, writing with a pen, or even drinking from a glass. This was quite handy when developing the software for the glove because I could test the software and make programming corrections without having the inconvenience of putting the gloves on and taking them off repeatedly.

MARY: Are you working on any other projects you’d like to briefly tell us about?

KEVIN: At UConn, we are lucky to have one of the few academic programs in puppetry in the US. In the spring, I plan on taking a fine arts course at UConn in designing and making marionette puppets. This will allow me to expand the use of my data gloves into controlling and manipulating puppets for performance art.

I am collaborating on designing circuit boards with a number of people in Hartford. The more interesting collaborations are with artists, where they think differently about technology than I do. Balam Soto of Open Wire Labs is a new media artist and one of the creative artists I collaborate with regularly. He is also a member of MakeHartford and presents at Maker Faires.

MARY: What was the response to the wireless data gloves at World Maker Faire New York?

KEVIN: The response to the data gloves was overwhelmingly positive. People were making comparisons to the Nintendo Power Glove and to the movie “Minority Report.” Several musicians commented that the gloves should be excellent for performing and recording virtual musical instruments such as a guitar, trumpet and drums.

For the demonstration, I showed a custom application; which allowed both hands (or two people) to interactively manipulate points and lines on a drawing. Many people were encouraged to use the gloves for themselves, which enhanced the quality of the feedback I received.

The gloves are large-sized to fit my hands, which was quite a challenge for younger children to use because their hands were “lost” in the gloves. Even with the size challenge, it was fun watching younger children manipulating the objects on the computer screen.

I look forward to the Maker Faire next year, when I will have implemented the newer design for the data gloves and will have additional software to demonstrate. I plan on trying to put together a presentation on some form of performance art using the data gloves.

Two Campuses, Two Problems, Two Solutions

In some ways, Salish Kootenai College (SKC)  based in Pablo, MT, and Penn State Erie, The Behrend College in Erie, PA, couldn’t be more different

SKC, whose main campus is on the Flathead Reservation, is open to all students but primarily serves Native Americans of the Bitterroot Salish, Kootenai, and Pend d’Orellies tribes. It has an enrollment of approximately 1,400. Penn State Erie has roughly 4,300.

But one thing the schools have in common is enterprising employees and students who recognized a problem on their campuses and came up with technical solutions. Al Anderson, IT director at the SKC, and Chris Coulston, head of the Computer Science and Software Engineering department at Penn State Erie, and his team have written articles about their “campus solutions” to be published in upcoming issues of Circuit Cellar.

In the summer of 2012, Anderson and the IT department he supervises direct-wired the SKC dorms and student housing units with fiber and outdoor CAT-5 cable to provide students better  Ethernet service.

The system is designed around the Raspberry Pi device. The Raspberry Pi queries the TMP102 temperature sensor. The Raspberry Pi is queried via the SNMP protocol.

The system is designed around the Raspberry Pi device. The Raspberry Pi queries the TMP102 temperature sensor. The Raspberry Pi is queried via the SNMP protocol.

“Prior to this, students accessed the Internet via a wireless network that provided very poor service.” Anderson says. “We wired 25 housing units, each with a small unmanaged Ethernet switch. These switches are daisy chained in several different paths back to a central switch.”

To maintain the best service, the IT department needed to monitor the system’s links from Intermapper, a simple network management protocol (SNMP) software. Also, the department had to monitor the temperature inside the utility boxes, because their exposure to the sun could cause the switches to get too hot.

This is the final installation of the Raspberry Pi. The clear acrylic case can be seen along with the TMP102 glued below the air hole drilled into the case. A ribbon cable was modified to connect the various pins of the TMP102 to the Raspberry Pi.

This is the final installation of the Raspberry Pi in the SKC system. The clear acrylic case can be seen along with the TMP102 glued below the air hole drilled into the case. A ribbon cable was modified to connect the various pins of the TMP102 to the Raspberry Pi.

“We decided to build our own monitoring system using a Raspberry Pi to gather temperature data and monitor the network,” Anderson says. “We installed a Debian Linux distro on the Raspberry Pi, added an I2C Texas Instruments TMP102 temperature sensor…, wrote a small Python program to get the temperature via I2C and convert it to Fahrenheit, installed SNMP server software on the Raspberry Pi, added a custom SNMP rule to display the temperature from the script, and finally wrote a custom SNMP MIB to access the temperature information as a string and integer.”

Anderson, 49, who has a BS in Computer Science, did all this even as he earned his MS in Computer Science, Networking, and Telecommunications through the Johns Hopkins University Engineering Professionals program.

Anderson’s article covers the SNMP server installation; I2C TMP102 temperature integration; Python temperature monitoring script; SNMP extension rule; and accessing the SNMP Extension via a custom MIB.

“It has worked flawlessly, and made it through the hot summer fine,” Anderson said recently. “We designed it with robustness in mind.”

Meanwhile, Chris Coulston, head of the Computer Science and Software Engineering department at Penn State Erie, and his team noticed that the shuttle bus

The mobile unit to be installed in the bus. bus

The mobile unit to be installed in the bus.

introduced as his school expanded had low ridership. Part of cause was the unpredictable timing of the bus, which has seven regular stops but also picks up students who flag it down.

“In order to address the issues of low ridership, a team of engineering students and faculty constructed an automated vehicle locator (AVL), an application to track the campus shuttle and to provide accurate estimates when the shuttle will arrive at each stop,” Coulston says.

The system’s three main hardware components are a user’s smartphone; a base station on campus; and a mobile tracker that stays on the traveling bus.

The base station consists of an XTend 900 MHz wireless modem connected to a Raspberry Pi, Coulston says. The Pi runs a web server to handle requests from the user’s smart phones. The mobile tracker consists of a GPS receiver, a Microchip Technology PIC 18F26K22 and an XTend 900 MHz wireless modem.

Coulston and his team completed a functional prototype by the time classes started in August. As a result, a student can call up a bus locater web page on his smartphone. The browser can load a map of the campus via the Google Maps JavaScript API, and JavaScript code overlays the bus and bus stops. You can see the bus locater page between 7:40 a.m. to 7 p.m. EST Monday through Friday.

“The system works remarkably well, providing reliable, accurate information about our campus bus,” Coulston says. “Best of all, it does this autonomously, with very little supervision on our part.  It has worked so well, we have received additional funding to add another base station to campus to cover an extended route coming next year.”

The base station for the mobile tracker is a sandwich of Raspberry Pi, interface board, and wireless modem.

The base station for the mobile tracker is a sandwich of Raspberry Pi, interface board, and wireless modem.

And while the system has helped Penn State Erie students make it to class on time, what does Coulston and his team’s article about it offer Circuit Cellar readers?

“This article should appeal to readers because it’s a web-enabled embedded application,” Coulston says. “We plan on providing users with enough information so that they can create their own embedded web applications.”

Look for the article in an upcoming issue. In the meantime, if you have a DIY wireless project you’d like to share with Circuit Cellar, please e-mail editor@circuitcellar.com.





MIT’s Self-Assembling Robots

Calling it a low-tech solution to a high-tech challenge, MIT researchers have received a lot of attention recently for their modular system of self-assembling robot cubes. The video of the so-called M-Blocks in action, which MIT posted earlier this month on YouTube, has also become high profile. A recent tally has the video at nearly 1.5 million views and counting.


The text accompanying the video explains how the cubes are able to move around and climb over each other,  jump into the air, and roll across surfaces as they connect in a variety of configurations. And they do all this without any external moving parts. Instead, each M-Block contains a flywheel that can reach speeds of 20,000 rpm. When the flywheel brakes, it imparts angular momentum to the cube.  Precisely placed magnets on every face and edge of each M-Block enable any two cubes to attach to each other.

The simple design holds short- and long-term promise.  According  to an October 4 article by Larry Hardesty of the MIT News Office, it is hoped that the blocks can be miniaturized someday, perhaps to swarming microbots that can self-assemble with a purpose. Even at their current size, further development of the M-Blocks might lead to “armies of mobile cubes” that can help repair bridges and buildings in emergencies, raise scaffolding, reconfigure into heavy equipment or furniture as needed, or head in to environments hostile to humans to diagnose and repair problems, the article suggests.

While it may not rise to “cooperative group behavior,”  the ability of one cube to drag another and influence its alignment is impressive. What could 100 or more of these robots accomplish as MIT researchers continue to develop algorithms to control them?

A prototype of the new modular robot, with its flywheel exposed. (Photo: M. Scott Brauer)

A prototype of the new modular robot, with its interior and flywheel exposed.
(Photo: M. Scott Brauer)

Battery Basics (Part 2): Battery Back-Up Power

Circuit Cellar columnist George Novacek has been “burned” more than once by manufacturers of battery-powered devices that include chargers poorly suited for the batteries required.

To get the full life out of a rechargeable battery, the charger must be “specifically designed” for the battery type, Novacek says in his October issue column “Battery Basics (Part 2): Battery Back-Up Power.”

The charger schematic diagram is shown.

The charger schematic diagram is shown.

When cordless phone, lawn mower, or power tool batteries die before their time, it gets expensive.

“The replacement cost of battery packs in my equipment represents about 50% of the equipment’s purchase price,” Novacek says. “Consequently, I would have expected the supplied or built-in chargers to be optimized for the batteries. Unfortunately, this is just wishful thinking. I have spent a fortune on replacement power packs for several of my battery-operated devices.”

Novacek’s column discusses what causes short battery life, how to purchase the right charger, and tips on building your own charger.

“As an engineer, if I can’t buy what I need or have been burned by commercial,off-the-shelf equipment, I design my own solution to the problem,” he says. “Building a good battery charger is easy these days because many ICs are specifically designed for battery chargers.

“The plethora of available ICs—together with exhaustive application notes—enables you to design a charger with minimal external parts for almost any battery type. The resulting circuits are often small enough to fit inside enclosures of your original, poorly designed chargers.”

You can also build a good charger out of parts found in your component box, Novacek says. In fact, he did just that when he needed a reliable floating backup power source for the fans of his home’s gas-fired Franklin stove. “I selected two 12-V/7-Ah sealed lead-acid batteries connected in parallel. They are widely available, reasonably priced, and have adequate capacity for my needs. I also built the charger with components I had lying around my workbench.”

Photo 1: The charger is built on a small piece of a perforated board. An ample heatsink is needed during constant current mode. The six-pin header on the right side is used to in-circuit program the Atmel ATtiny85 microcontroller.

Here is a small portion of his description the charger design.

Figure 1 shows the charger schematic diagram… Series regulator U1, a Texas Instruments LM117 adjustable regulator, works as a current source with R4 determining the 1.5-A current. When the battery voltage reaches 14.5 to 14.7 V, MOSFET Q1 is turned on, changing U1 to a constant voltage source. Potentiometer R1 trims the voltage to 13.6 V, which is crucial for long battery life.

“U2 is a 5-V regulator that feeds the microcontroller U3, an Atmel ATtiny85, which monitors the charger’s status and switches between the operating modes. Zener diodes D7 and D8 and signal diodes D9, D10, and D11 together with JFET Q3 serve as a level shifter to monitor the battery voltage. They subtract 10.5 V from the battery voltage to place it within the 5-V input range of the ATtiny’s ADC.JFET Q3 ensures constant current through the diodes and the voltage drop across the diodes is essentially independent of the battery voltage.”

Photo 1 shows the charger construction. “The header at the right-hand edge is for the ATtiny85’s in-circuit programmer,” he says. “Also, notice that the ATtiny85 inputs are protected by Schottky diodes and 10-kΩ series resistors to prevent its input pins’ excursion beyond 5 V.”

Novacek’s column goes on to explain how you can change a few components of the charger to make it work with different lead-acid battery types.

For those details and others, check out Novacek’s full column in the October issue.


Maker Faire in Rome Highlights Big News For Arduino Fans

If you like working on Arduino projects, you probably welcome some big news on two Linux-capable boards that came out of the recent Maker Faire in Rome.

Arduino founder Massimo Banzi announced a new collaboration with Intel called the Intel Galileo, an Arduino-compatible microcontroller board that uses Intel’s 32-bit Pentium-class




With the Galileo’s small, 32-bit Quark processor, the collaboration gives Intel a toehold in the low-power device market, while providing Arduino-compatible boards that have more processing power. (Arduino devices currently use Atmel’s 8-bit microcontrollers.)

An October 3 Arduino blog post by Zoe Romano says the Galileo is “a great tool for quickly prototyping simple interactive designs like LED light displays that respond to social media, or for tackling more complex projects from automating home appliances to building life-size robots that you control from your smartphone.”

Also at the Maker Faire, Banzi and Texas Instruments spokesmen discussed their collaboration on Arduino TRE, a next-generation Arduino SBC based on TI’s Sitara AM335x ARM Cortex-A8 processor.

Arduino TRE is the “most powerful Arduino to date” and will be able to run full Linux, according to another Arduino blog post by Romano.

“Arduino developers will get up to 100 times more performance with the Sitara-processor-based TRE than they do on the Arduino Leonardo or Uno,”  Romano says. For example, the Linux Arduino will be able to run high-speed communications and high-performance desktop applications.

Intel may be closely  following  news about the Arduino TRE, Stephen Shankland suggests in his October 5 article on the c/net website.

“The Arduino Tre speed boost comes from its Texas Instruments Sitara AM335x processor, which is based on the Cortex-A8 design from ARM Holdings,” Shankland’s article says. “Because ARM chips are nearly universal in the smartphone market that Intel has been struggling to penetrate, they’re a top competitive concern for Intel, and TI’s move means it might not be Intel’s Pentium-derived Quark chips that hobbyists end up with when looking for their next widget.”

However the competition plays out, it all seems nothing but good news for electronics tinkerers, hardware hackers, hobbyists, and designers who want more choices and more processing power for their Arduino-based projects.

CC280: Analog Communications and Calibration

Are you an analog aficionado? You’re in luck. Two articles, in particular, focus on the November issue’s analog techniques theme. (Look for the issue shortly after mid-October, when it will be available on our website.)

Block Diagram

Data from the base adapter is sent by level shifting the RS-232 or CMOS serial data between 9 and 12 V. A voltage comparator at the remote adapter slices the signal to generate a 0-to-5-V logic signal. The voltage on the signal wire never goes low enough for the 5-V regulator to go out of regulation.

These adapters use a combination of tricks. A single pair of wires carries full-duplex serial data and a small amount of power to a remote device for tasks (e.g., continuous remote data collection and control). The digital signals can be simple on/off signals or more complex signals (e.g., RS-232).

These adapters use a combination of tricks. A single pair of wires carries full-duplex serial data and a small amount of power to a remote device for tasks (e.g., continuous remote data collection and control). The digital signals can be simple on/off signals or more complex signals (e.g., RS-232).

Dick Cappels, a consultant who tinkers with analog and mixed-signal projects, presents a design using a pair of cable adapters and simple analog circuits to enable full-duplex, bidirectional communications and power over more than 100 m of paired wires. Why bother when Power Over Ethernet  (PoE), Bluetooth, and Wi-Fi approaches are available?

“In some applications, using Ethernet is a disadvantage because of the higher costs and greater interface complexity,” Cappels says. “You can use a microcontroller that costs less than a dollar and a few analog parts described in this article to perform remote data gathering and control.”

The base unit including the 5-to-15-V power supply is simple for its functionality. The two eight-pin DIP ICs are a voltage comparator and the switching regulator.

The base unit including the 5-to-15-V power supply is simple for its functionality. The two eight-pin DIP ICs are a voltage comparator and the switching regulator.

Cappels’s need for data channels to monitor his inground water tank inspired his design. Because his local municipality did not always keep the tank filled, he needed to know when it was dry so his pumps wouldn’t run without water and possibly become damaged.
“Besides the mundane application of monitoring a water tank, the system would be excellent for other communication uses,” Cappels says, including computer connection to a home weather station and intrusion-detection systems. Bit rates up to 250 kHz also enable the system to be used in two-way voice communication such as intercoms, he says.

Retired engineer David Cass Tyler became interested in writing his series about calibration while working on a consulting project. “I came to realize that some people don’t really know how to approach the issue of taking an analog-to-digital value to actual engineering units, nor how to correct calibration factors after the fact,” Tyler says

In Part 1 of his article series, Tyler notes: “Digital inputs and digital outputs are pretty simple. They are either on or off. However, for ADCs and DACs to be accurate, they must first be calibrated. This article addresses linear ADCs and DACs.” Part 2, appearing in the December issue, will discuss using polynomial curve fitting to convert nonlinear data to real-world engineering values.

In addition to its analog-themed articles, the November issue includes topics ranging from a DIY solar array tracker’s software to power-capped computer systems.

Editor’s Note: Learn more about Circuit Cellar contributors Dick Cappels and David Cass Tyler by reading their posts about their workspaces and favorite DIY tools.

Solar Array Tracker (Part 1): SunSeeker Hardware

Figure 1: These are the H-bridge motor drivers and sensor input conditioning circuits. Most of the discrete components are required for transient voltage protection from nearby lightning strikes and inductive kickback from the motors.

Figure 1: These are the H-bridge motor drivers and sensor input conditioning circuits. Most of the discrete components are required for transient voltage protection from nearby lightning strikes and inductive kickback from the motors.

Graig Pearen, semi-retired and living in Prince George, BC, Canada, spent his career in the telecommunications industry where he provided equipment maintenance and engineering services. Pearen, who now works part time as a solar energy technician, designed the SunSeeker Solar Array tracker, which won third place in the 2012 DesignSpark chipKit challenge.

He writes about his design, as well as changes he has made in prototypes since his first entry, in Circuit Cellar’s October issue. It is the first part of a two-part series on the SunSeeker, which presents the system’s software and commissioning tests in the final installment.

In the opening of Part 1, Pearen describes his objectives for the solar array tracker:

When I was designing my solar photovoltaic (PV) system, I wanted my array to track the sun in both axes. After looking at the available commercial equipment specifications and designs published online, I decided to design my own array tracker, the SunSeeker (see Photo 1 and Figure 1).

I had wanted to work with a Microchip Technology PIC processor for a while, so this was my opportunity to have some fun. I based my first prototype on a PIC16F870 microcontroller but when the microcontroller maxed out, I switched to its big brother, the PIC16F877. Although both prototypes worked well, I wanted to add more features and

The SunSeeker board, at top, contains all the circuits required to control the solar array’s motion. This board plugs into the Microsoft Technology chipKIT MAX32 processor board. The bottom side of the SunSeeker board (green) with the MAX32 board (red) plugged into it is shown at bottom.

The SunSeeker board, at top, contains all the circuits required to control the solar array’s motion. This board plugs into the Microchip Technology chipKIT MAX32 processor board. The bottom side of the SunSeeker board (green) with the MAX32 board (red) plugged into it is shown at bottom.

capabilities. I particularly wanted to add Ethernet access so I could use my home network to communicate with all my systems. I was considering Microchip’s chipKIT Max32 board for the next prototype when Circuit Cellar’s DesignSpark chipKIT contest was announced.

I knew the contest would be challenging. In addition to learning about a new processor and prototyping hardware, the contest rules required me to learn a new IDE (MPIDE), programming language (C++), schematic capture, and PCB design software (DesignSpark PCB). I also decided to make this my first surface-mount component design.

My objective for the contest was to replicate the functionality of the previous Assembly language software. I wanted the new design to be a test platform to develop new features and tracking algorithms. Over the next two to three years of development and field testing, I plan for it to evolve into a full-featured “bells-and-whistles” solar array tracker. I added a few enhancements as the software evolved, but I will develop most of the additional features later.

The system tracks, monitors, and adjusts solar photovoltaic (PV) arrays based on weather and atmospheric conditions. It compiles statistics on these conditions and communicates with a local server that enables software algorithm refinement. The SunSeeker logs a broad variety of data.

The SunSeeker measures, displays, and records the duration of the daily sunny, hazy, and cloudy periods; the array temperature; the ambient temperature; daily minimum and maximum temperatures; incident light intensity; and the drive motor current. The data log is indexed by the day number (1–366). Index–0 is the annual data and 1–366 store the data for each day of the year. Each record is 18 bytes long for a total of 6,588 bytes per year.

At midnight each day, the daily statistics are recorded and added to the cumulative totals. The data logs can be downloaded in comma-separated values (CSV) format for permanent record keeping and for use in spreadsheet or database programs.

The SunSeeker has two main parts, a control module and a separate light sensor module, plus the temperature and snow sensors.

The control module is mounted behind the array where it is protected from the heat of direct sunlight exposure. The sensor module is potted in clear UV-proof epoxy and mounted a few centimeters away on the edge of, and in the same plane as, the array. To select an appropriate potting compound, I contacted Epoxies, Etc. and asked for a recommendation. Following the company’s advice, I obtained a small quantity of urethane resin (20-2621RCL) and urethane catalyst (20-2621CCL).

When controlling mechanical devices, monitoring for proper operation, and detecting malfunctions it is necessary to prevent hardware damage. For example, if the solar array were to become frozen in place during an ice storm, it would need to be sensed and acted upon. Diagnostic software watches the motors to detect any hardware fault that may occur. Fault detection is accomplished in several ways. The H-bridges have internal fault detection for over temperature, under voltage, and shorted circuit. The current drawn by the motors is monitored for abnormally high or low current and the motor drive assemblies’ pulses are counted to show movement and position.

To read more about the DIY SunSeeker solar array tracker, and Pearen’s plans for further refinements, check out the October issue.


Q&A: Krystal Horton, the Raspberry Pi Kid

Eben Upton and Krystal met in October at the Broadcom MASTERS

Krystal Horton is the clever kid behind the blog Raspberry Pi Kid: An 11-Year-Old’s Adventures with Raspberry Pi.  Since starting her blog in January 2013, her entries have covered everything from unpacking her first Pi, to projects she has created with the SBC, to her recent dinner with Eben Upton, founder and trustee of the Raspberry Pi Foundation, and his wife, Liz Upton, who oversees the foundation website.

Krystal met the couple in October 2013 in Washington, D.C., as one of 30 finalists competing in the 2013 Broadcom MASTERS, a national science, technology, engineering, and math competition for middle school students.  (At the competition, Krystal was named one of two Rising Stars students who will represent Broadcom MASTERS at the 2014 International Science and Engineering Fair, the world’s largest international high school science fair competition.)

“They also gave each of the finalists their own Raspberry Pi,” Krystal says in her October 2 blog entry from Washington, D.C.  “I’m hoping to have each of the finalists guest post on my blog after they’ve had a chance to try out the RPi.”

Liz Upton describes Krystal as “brilliant.” Recently, Circuit Cellar Managing Editor Mary Wilson asked the seventh-grader several questions about her interest in the Raspberry Pi and the blog she created to complement it.

Krystal and her oak borer beetle infestation science project.

Krystal and her oak borer beetle infestation science project.

MARY: Tell us a little bit about yourself and why you became interested in working with the Raspberry Pi.

KRYSTAL: I am an 11-year-old seventh-grader in Southern California. I have been interested in science and technology ever since I can remember. My cousin got a Raspberry Pi for Christmas and my uncle saw how curious I was. So, he gave me one for New Year’s. He gave me some basic lessons on how to hook it up, turn it on, and type into Vim. That and some YouTube videos, tutorials, and eBooks and I was off and running. I now blog at http://raspberrypikid.wordpress.com and sometimes I tweet through @kid_pi.

MARY: Why did you decide to start your blog Raspberry Pi Kid? What type of feedback/comments have you gotten from visitors to your site? Will you rename the blog and keep posting when you’re 12?

KRYSTAL: I’ve learned so much from other people’s blogs, but they’re written for adults and are very hard for a kid to understand. So, I thought that I could put things in kid language and in simple steps so that other kids would be inspired and learn from what I’ve done. I want to give back to the Raspberry Pi and blogging communities.

On my blog, I’m often talking about problems that I’m having (I still haven’t figured out analog to digital conversion) and a lot of people offer to help me out. Others congratulate me and wish that they’d had an RPi when they were my age. I’ve also heard from other kids my age who are learning to code. I put my dad’s email address on the account and he gets invitations for me to Skype with CoderDojos and to guest blog for people. I have over 52,000 views to my blog right now. I hadn’t even thought about whether the name would change when I turn 12, but I’ll definitely keep blogging.

MARY:  Was the SBC difficult to set up? What was the first project you worked on with it?

KRYSTAL: The only hard thing about setting it up is all of the accessories that you need. It doesn’t even come with a power supply, keyboard, or mouse. My uncle gave me some of the stuff (power supply, wireless keyboard/mouse, breadboard), I had some stuff at home (memory card, network cable), and I bought some stuff from Adafruit’s very useful website (wireless adapter, ADC chip, breadboard accessories).

I really like the idea of programming the computer to do things. So, the first thing I did was start programming in Python through Vim and IDLE. I got a book from the library, read tutorials online, and emailed my uncle questions.

MARY: Can you tell me about some other Pi-based projects you have finished or are working on? Do you have something you would like to do next? Where do you get your ideas? Where do you go for guidance?

Krystal and her robot

Krystal and her robot

KRYSTAL: I love playing Minecraft, so when I saw that there’s a Pi version, I installed it and blogged about it. I’ve also used the Scratch programming language to create games and blink LEDs. I’ve used RPi as a Linux computer with the Wheezy version. I just wish that Midori would play YouTube videos so that I could watch Pi tutorials on my Pi. I have also installed OpenELEC (Open Embedded Linux Entertainment Center) so that I can stream HD video to my TV. I’ve also used PuTTY to control the Pi with a laptop (my uncle showed me that one).

In the future, I want to keep working with Scratch, a free visual programming language for kids from MIT (where I want to go to college). I want to figure out analog to digital so that I can connect sensors. And I want to use the RPi to do a science fair project. I really, really want to get a 3-D printer and connect it to the Pi.  I’m planning to order a MakiBOX soon, but it’ll take six-10 weeks to arrive and then I have to build it and learn how to use it.

When I don’t know how to do something, my dad helps me find answers on YouTube or other people’s blogs. He’s a scientist, not a programmer, so he learns with me sometimes. If he can’t help me, I email my uncle who does know how to program. He has automated his house with a RasPi. If I can’t get in touch with him, then I post a question on a forum and wait for answers.

Close up view of the credit-card sized Pi

Close up view of the credit-card sized Pi

MARY: What were some of the challenges you had to overcome with the Pi? What, if anything, would you change about it?

KRYSTAL: One of the problems I’ve had is when things don’t work for me as the blogs say they should. I had a really hard time getting Wi-Fi to work even though I followed the instructions exactly.

If I could change anything, I’d label the GPIO pins right on the board. I’ve had to look up that diagram soooo many times. There are several versions now, so I’d recommend marking them to make it easier to tell which one it is when getting a case for it. I’ve read stories about people breaking off the connector where the memory card goes. That’s scary, I hope they fix that if they can.

MARY: What do you think are the SBC’s best features?

KRYSTAL: Everyone says that the price and size are the Pi’s best features and I agree. But I also like that it’s so open to let me put any kind of Linux I want on it. Some people have even put the Android Operating System on it. Not me… yet.

MARY: What new skills/tools have you learned about through your Pi?

KRYSTAL: Some of the things I’ve learned through using my Pi are: coding in Python and Scratch, basic electronics (how to use a breadboard, multimeter, LEDs, etc.), and using Linux and all of the absolutely free software for it. These are very valuable skills for anyone to learn. I’ve learned about IP addresses and using a computer without the graphical interface at times also.

MARY: What advice would you give to another kid (or adult tinkerer) who is interested in getting started with the Raspberry Pi?

KRYSTAL: The advice that I’d give is to work on fun projects. This shouldn’t feel like boring work. Also, don’t get frustrated if things don’t work right the first time. That’s just part of coding. Most big cities also have groups of computer users. Find one and connect with them.

MARY: How many other 11-year-old girls do you know who are drawn to the Raspberry Pi? Any thoughts about that?

KRYSTAL: I’ve met online several kids who are using Pi. I spoke through Skype with a group in Washington, D.C., one Saturday morning. There were probably 15 kids and many were girls. I watched a video of a girl who tests all of the Raspberry Pis that get sent back as broken.

I think that computers and technology are going to be incredibly important to my generation. It is very scary that so few (girls or boys) are learning how technology works and how to code. Coders are going to rule the future, and I want be a part of that. All kids should. And their parents need to encourage it.  Websites like code.org and adafruit.com and devices like Raspberry Pi are helping.

CC279: Working with RobotBasic

In Circuit Cellar’s October issue, columnist Jeff Bachiochi introduces readers to RobotBasic, a free robot control programming language that you can use to control real or simulated robots, and provides a detailed explanation on how to use it.

Photo 1: This army of robots all use the RobotBASIC Robot Operating System (RROS). Note the large robot has an arm located just above the wheels that is controlled by a second RROS. It uses an on-board laptop running a RobotBASIC (RB) application. The small robots are all controlled via a Bluetooth link from an external PC running an RB application.

Photo 1: This army of robots all use the RobotBASIC Robot Operating System (RROS). Note the large robot has an arm located just above the wheels that is controlled by a second RROS. It uses an on-board laptop running a RobotBASIC (RB) application. The small robots are all controlled via a Bluetooth link from an external PC running an RB application.

“About five years ago, John Blankenship and Samuel Mishal coauthored Robot Programmer’s Bonanza, a book explaining the freely available RobotBASIC IDE they offer. RobotBASIC (RB) is a powerful language that enables you to use standard BASIC syntax (or a modified C-style syntax ( i.e., ++, +=, !=, and &&) to quickly write a program to control and simulate a robot with many types of sensors,” Bachiochi says. “This is a great tool to teach programming.”

RB, with more than 800 commands and functions, can also be a tool for non-robotic applications such as tackling tough engineering problems or creating animated simulations, Bachiochi says.

It’s likely that anyone who starts out simulating with RobotBasic will eventually want to control real robot hardware.

“There is no need to worry,” Bachiochi says. “RB was written to make use of a PC’s I/O. The parallel port is a good source for digital I/O and the serial port is well suited for external communication. The same commands used for robot movement in the simulator can alternatively be sent to a serial port establishing a sort of serial robot command protocol. But, tethered robots aren’t so cool, and many robots are too small to tote around a PC as their “great and powerful Oz.”

“Luckily, much has changed since RB’s original concepts were put into practice,” he adds. “We all know what has happened to these PC ports. They’ve fallen under the USB’s mighty power. RB doesn’t care whether it is talking with a serial port or a USB virtual serial port. USB offers inexpensive Bluetooth dongles and can create wireless serial communication to external devices.”

Bachiochi also discusses the RobotBASIC Robot Operating System (RROS), created to support RB’s serial robot command protocol. The module is available from RB’s website.

“The RROS is a preprogrammed module that can receive communication from RB, interpret commands, and directly interface to hardware,” Bachiochi says. “The module is a Pololu Baby Orangutan robot controller, consisting of an Atmel ATmega328P microcontroller and a Pololu TB6612 dual motor driver carrier in a DIP24 form factor. You can use the module (which comes preprogrammed with the RROS) to build robots like those shown in Photo 1.”

Bachiochi’s look at RB and RROS is a two-part series. In Part 2, appearing in Circuit Cellar’s November issue, Bachiochi will explain how to translate between RROS and the iRobot Create Open Interface.

So, if you want explore a programming language that can take you from simulated to real-world robotics control, check out the October and November issues.


CC279: What’s Ahead in the October Issue

Although we’re still in September, it’s not too early to be looking forward to the October issue already available online.

The theme of the issue is signal processing, and contributor Devlin Gualtieri offers an interesting take on that topic.

Gualtieiri, who writes a science and technology blog, looks at how to improve Improvig Microprocessor Audio microprocessor audio.

“We’re immersed in a world of beeps and boops,” Gualtieri says. “Every digital knick-knack we own, from cell phones to microwave ovens, seeks to attract our attention.”

“Many simple microprocessor circuits need to generate one, or several, audio alert signals,” he adds. “The designer usually uses an easily programmed square wave voltage as an output pin that feeds a simple piezoelectric speaker element. It works, but it sounds awful. How can microprocessor audio be improved in some simple ways?”

Gualtieri’s article explains how analog circuitry and sine waves are often a better option than digital circuitry and square waves for audio alert signals.

Another article that touches on signal processing is columnist Colin Flynn’s look at advanced methods of debugging an FPGA design. It’s the debut of his new column Programmable Logic in Practice.

“This first article introduces the use of integrated logic analyzers, which provide an internal view of your running hardware,” O’Flynn says. “My next article will continue this topic and show you how hardware co-simulation enables you to seamlessly split the verification between real hardware interfacing to external devices and simulated hardware on your computer.”

You can find videos and other material that complement Colin’s articles on his website.

Another October issue highlight is a real prize-winner. The issue features the first installment of a two-part series on the SunSeeker Solar Array Tracker, which won third SunSeekerplace in the 2012 DesignSpark chipKit challenge overseen by Circuit Cellar.

The SunSeeker, designed by Canadian Graig Pearen, uses a Microchip Technology chipKIT Max32 and tracks, monitors, and adjusts PV arrays based on weather and sky conditions. It measures PV and air temperature, compiles statistics, and communicates with a local server that enables the SunSeeker to facilitate software algorithm development. Diagnostic software monitors the design’s motors to show both movement and position.

Pearen, semi-retired from the telecommunications industry and a part-time solar technician, is still refining his original design.

“Over the next two to three years of development and field testing, I plan for it to evolve into a full-featured ‘bells-and-whistles’ solar array tracker,” Pearen says. “I added a few enhancements as the software evolved, but I will develop most of the additional features later.”

Walter Krawec, a PhD student studying Computer Science at the Stevens Institute of Technology in Hoboken, NJ, wraps up his two-part series on “Experiments in Developmental Robotics.”

In Part 1, he introduced readers to the basics of artificial neural networks (ANNs) in robots and outlined an architecture for a robot’s evolving neural network, short-term memory system, and simple reflexes and instincts. In Part 2, Krawec discusses the reflex and instinct system that rewards an ENN.

“I’ll also explain the ‘decision path’ system, which rewards/penalizes chains of actions,” he says. “Finally, I’ll describe the experiments we’ve run demonstrating this architecture in a simulated environment.”

Videos of some of Krawec’s robot simulations can be found on his website.

Speaking of robotics, in this issue columnist Jeff Bachiochi introduces readers to the free robot control programming language RobotBASIC and explains how to use it with an integrated simulator for robot communication.

Other columnists also take on a number of very practical subjects. Robert Lacoste explains how inexpensive bipolar junction transistors (BJTs) can be helpful in many designs and outlines how to use one to build an amplifier.

George Novacek, who has found that the cost of battery packs account for half the DIY Battery Chargerpurchase price of his equipment, explains how to build a back-up power source with a lead-acid battery and a charger.

“Building a good battery charger is easy these days because there are many ICs specifically designed for battery chargers,” he says.

Columnist Bob Japenga begins a new series looking at file systems available on Linux for embedded systems.

“Although you could build a Linux system without a file system, most Linux systems will have some sort of file system,” Japenga says. “And there are various types. There are files systems that do not retain their data (volatile) across power outages (i.e., RAM drives). There are nonvolatile read-only file systems that cannot be changed (e.g., CRAMFS). And there are nonvolatile read/write file systems.”

Linux provides all three types of file systems, Japenga says, and his series will address all of them.

Finally, the magazine offers some special features, including an interview with Alenka Zajić, who teaches signal processing and electromagnetics at Georgia Institute of Technology’s School of Electrical and Computer Engineering. Also, two North Carolina State University researchers write about advances in 3-D liquid metal printing and possible applications such as electrical wires that can “heal” themselves after being severed.

For more, check out the Circuit Cellar’s October issue.



CC279: A Fresh Focus on Programmable Logic

We’re not finished adding new features to our magazine. Last month, we rolled out our redesign and told you a bit about Ayse K. Coskun, who is writing a new bimonthly Green Computing column. This month, we introduce you to columnist Colin O’Flynn.

Colin’s bimonthly column, Programmable Logic in Practice, debuts in this issue. His first article focuses on integrated logic analyzer tools and methods of debugging your FPGA designs (p. 46).

Future articles will continue to feature “advanced information about FPGAs,” Colin says. “I will cover topics including debugging tools, high-level synthesis, high-speed serial interfaces, hard-core processors, interfacing to memory, and so forth.

“To keep this column practical, I’m going to focus on real hardware and tools you will be using. When it comes to programmable logic, there is always a choice of vendors—and I don’t work for any of them.”

Colin is definitely “multimedia.” To help readers better understand each article’s topic, he has set up a companion website, ProgrammableLogicInPractice.com. He wants to avoid too many step-by-step instructions in print. Instead, such steps will be posted on the website, along with example project files and videos, where applicable.

Many Circuit Cellar readers are already familiar with Colin. Since 2002, we have published five articles from this Canadian electrical engineer, who is also a product developer and a lecturer at Dalhousie University in Halifax, NS. Colin earned his master’s degree in applied science from Dalhousie and has also pursued graduate studies in cryptographic systems.
The topics he is pondering for future articles include circuit board layout for high-speed FPGAs, different methods of configuring an FPGA, designing memory into FPGA circuits, and use of vendor-provided and open-source soft-core microcontrollers.

Any designer or engineer interested in programmable logic technologies should check out Colin’s column in this and future issues.

Mary Wilsoneditor@circuitcellar.com

CC278: Evolving Neural Networks in Robotics

ccpostrobotAre you curious about how an evolving neural network helps a robot learn about itself and its environment?


A neural network with two inputs, one output, and three hidden neurons.

In the September issue of Circuit Cellar, Walter O. Krawec begins a two-part series that describes an ENN he uses in robot development experiments, explains how short-term memory (STM) evaluates a network’s conditions and how to add data to STM, and discusses how an ENN uses a robot’s minimalistic “instincts” and “reflexes” to guide a robot’s evolution.

Krawec, who has been building robots since 1999, is a research assistant and PhD student in Computer Science at the Stevens Institute of Technology in Hoboken, N.J. The work presented in his two-part series is based on a paper published in the proceedings of the 13th International Artificial Life Conference in 2012.

The overall goal of the Krawec’s experiments in developmental robotics is to enable a robot to learn on its own without human intervention. “An ENN is used to accomplish this,” he says.  “This network will be capable of growing and learning in real time as the robot operates.”

In his series, Krawec presents an architecture he says “enables a robot to ‘grow’ from a naive individual with no knowledge of itself (i.e., no notion of what its sensors are reporting or what its outputs actually do) to one that can operate in an environment.”

“This architecture will consist of an evolving neural network (ENN), a short-term memory (STM), and simple instincts and reflexes.

“Despite a minimal set of instincts, which provide penalties and rewards for certain actions (e.g., crashing into a wall, the robots described in this article sometimes develop complicated and unexpected behaviors. Such behaviors range from following walls (despite the robots’ binary proximity sensors) to games of ‘follow the leader.’…

“This article explores basic artificial neural network (ANN) concepts and outlines the ENN I’m using in this project. This is a neural network that, over time, learns not only by adjusting synaptic weights but also by growing new neurons and new connections (generally resulting in a recurrent neural network). Finally, I’ll discuss the STM system and how it is used to evaluate a network’s fitness.”

The second article in Krawec’s series appears in Circuit Cellar’s October issue.

“In Part 2, I’ll examine the reflex and instinct system, which feeds reward information to an ENN and the ‘decision path’ system, which rewards or penalizes chains of actions,” Krawec says. “Finally, I’ll discuss experiments conducted to demonstrate this architecture in a simulated environment. In particular, I’ll describe some interesting behaviors that robots have developed in trial runs.”

For more, check out Krawec’s articles on “Experiments in Developmental Robotics” in the September and October issues. You will also find information and videos about his work with robots on his website.


One Desk Serves Two Roles for Professor and Designer

Chris Coulston, head of the Computer Science and Software Engineering department at Penn State Erie, The Behrend College, has a broad range of technical interests, including embedded systems, computer graphics algorithms, and sensor design.

Since 2005, he has submitted five articles for publication in Circuit Cellar, on projects and topics ranging from DIY motion-controlled gaming to a design for a “smart” jewelry pendant utilizing RGB LEDs.

We asked him to share photos and a description of the workspace in his Erie, PA, home. His office desk (see Photo 1) has something of an alter ego. When need and invention arise, he reconfigures it into an “embedded workstation.”

Coulston's workspace configured as an office desk

Photo 1: Coulston’s workspace configured as an office desk

When working on my projects, my embedded workstation contains only the essential equipment that I need to complete my project (see Photo 2).  What it lacks in quantity I’ve tried to make up for in quality instrumentation; a Tektronix TDS 3012B oscilloscope, a Fluke 87-V digital multimeter, and a Weller WS40 soldering iron.  While my workstation lacks a function generator and power supply, most of my projects are digital and have modest power requirements.

Coulston can reconfigure his desk into the embedded workstation pictured here.

Photo 2: Coulston can reconfigure his desk into the embedded workstation pictured here.

Coulston says his workspace must function as a “typical office desk” 80 percent of the time and electronics station 20 percent of the time.

It must do this while maintaining some semblance of being presentable—my wife shares a desk in the same space. The foundation of my workstation is a recycled desk with a heavy plywood backing on which I attached shelving. Being a bit clumsy, I’ve tried to screw down anything that could be knocked over—speakers, lights, bulletin board, power strip, cable modem, and routers.

The head of a university department has different needs in a workspace than does an electronics designer. So how does Coulston make his single office desk suffice for both his professional and personal interests? It’s definitely not a messy solution.

My role as department chair and professor means that I spend a lot time grading, writing, and planning. For this work, there is no substitute for uncluttered square footage—getting all the equipment off the working surface. However, when it’s time to play with the circuits, I need to easily reconfigure this space.

I have found organization to be key to successfully realize this goal. Common parts are organized in a parts case, parts for each project are put in their own bag, the active project is stored in the top draw, frequently used tools, jumper wires, and DMM are stored in the next draw. All other equipment is stored in a nearby closet.

I’ve looked at some of the professional-looking workspaces in Circuit Cellar and must admit that I am a bit jealous. However, when it comes to operating under the constraints of a busy professional life, I have found that my reconfigurable space is a practical compromise.

To learn more about Coulston and his technical interests, check out our Member Profile posted earlier this year.


Chris Coulston

Chris Coulston

CC278: Serial Displays Save Resources (BMP Files)

In Circuit Cellar’s September issue, columnist Jeff Bachiochi provides his final installment in a three-part series titled “Serial Displays Save Resources.” The third article focuses on bitmap (BMP) files, which store images.


A BMP file has image data storage beginning with the image’s last row. a—Displaying this data as stored will result in an upside-down image. b—Using the upsidedown=1 command will rotate the display 180°. c—The mirror=1 command flips the image horizontally. d—Finally, an origin change is necessary to shift the image to the desired location. These commands are all issued prior to transferring the pixels, to correct for the way the image data is stored.

LCDs are inexpensive and simple to use, so they are essential to many interesting projects, Jeff says. The handheld video game industry helped popularize the use of LCDs among DIYers.

Huge production runs in the industry “made graphic displays commonplace, helping to quickly reduce their costs,” Jeff says. “We can finally take advantage of lower-cost graphic displays, with one caveat: While built-in hardware controllers and drivers take charge of the pixels, you are now responsible for more than just sending a character to be printed to the screen. This makes the controllers and drivers not work well with the microcontroller project. That brings us to impetus for this article series.

“In Part 1 (‘Routines, Registers and Commands,’ Circuit Cellar 276, 2013), I began by discussing how to use a graphic display to print text, which, of course, includes character generation. In essence, I showed how to insert some intelligence between a project and the display. This intermediary would interpret some simple commands that enable you to easily make use of the display’s flexibility by altering position, screen orientation, color, magnification, and so forth.

“Part 2 (‘Button Commands,’ Circuit Cellar 277) revealed how touch-sensitive overlays are constructed and used to provide user input. The graphic display/touch overlay combination is a powerful combination that integrates I/O into a single module. Adding more commands to the interface makes it easier to create dynamic buttons on the graphic screen and reports back whenever a button is touched.

The prototype PCB I used for this project mounts to the reverse side of the thin-film transistor (TFT) LCD. The black connector holds the serial and power connections to your project. The populated header is for the Microchip Technology MPLAB ICD 3 debugger/programmer.

“Since I am using a graphic screen, it makes sense to investigate graphic files. This article (Part 3, ‘BMP Files,’ Circuit Cellar 277) examines the BMP file makeup and how this relates to the graphic screen.”

To learn more about the BMP graphical file format and Jeff’s approach to working with a graphic icon’s data, check out the September issue.


CC278: Battery Basics

Front of a battery analyzer

The University of Washington recently announced its engineers have created a wireless communications system that enables everyday devices to power up and connect to the web without the use of batteries. Instead, such devices would tap the energy available in wireless signals.

According to an August article on the university’s website,  engineers have developed a communication system that takes advantage of what they call  “ambient backscatter,”  the TV and cellular transmissions all around us. You can read more about the breakthrough by checking out the university article.

It will be some time before such an approach becomes commercially viable. In the meantime, we’ll still be relying heavily on batteries. With that in mind, you should check out columnist George Novacek’s article in Circuit Cellar’s September issue. Novacek goes “back to the basics” of batteries in this first installment of a two-part series.

“Battery usage has increased due to the proliferation of mobile and cordless devices,” Novacek says in Part 1. “This article describes battery types generally available in retail stores. I’ll discuss their features, operation, and usages. While many exotic batteries and custom packages are available, this article focuses on standard batteries, which are the type you are most likely to encounter.”

He opens his discussion by distinguishing between batteries vs. cells and describing common battery packages.

“Although we tend to use the words ‘battery’ and ‘cell’ interchangeably, there is a difference,” Novacek says. “Batteries comprise cells (e.g., the well-known 9-V battery contains six 1.5-V cells, while the omnipresent AA ‘battery’ and many others are just single cells). I will use the common terminology, even though it may be at times technically incorrect.

“Batteries store chemical energy. When activated, the chemical process occurring internally converts the chemical into electrical energy. Alessandro Volta, an Italian physicist, is credited with inventing the “voltaic pile” in the early 19th century, although archeological discoveries suggest that some form of an electrical battery was known in ancient Babylon. National Carbon Company, known today as Eveready, began marketing a precursor of the ubiquitous carbon-zinc battery in 1896…

“According to Wikipedia, the most common battery packages available today include AA, AAA, C, D, 9-V pack, and different types of “button cells”. There is also a plethora of custom-made battery packs for power tools, cordless telephones, and so forth. No matter what kind of packaging, the battery principles for the given type remain the same.

“There are two categories of batteries: primary (i.e., single use) and rechargeable. Carbon-zinc is the oldest—and at one point the most common—primary battery. They are available in standard packages and inexpensive. Consequently, carbon-zinc batteries are often included by original equipment manufacturers (OEM) with devices (e.g., TV remote controls, portable radios, etc.). Although they have been improved over the years, some significant shortcomings remain, so I avoid using them.”

Novacek goes on to examine the drawbacks and advantages of carbon-zinc, alkaline, lithium, mercuric-oxide, silver-oxide button cell, lead-acid, nickel-cadmium (NiCad), and nickel-metal hydride (NiMH) batteries.

To learn more about what may be powering your handheld or other device, check out the September issue.