Electronics Workspace: Pure Function, Minimal Form

Engineering consultant Steve Hendrix of Sagamore Hills, OH, says the “corporate headquarters” of Hx Engineering, LLC, pictured below, “is pure function, minimal form, and barely fits.”

This basement workspace reflects Steven's diverse projects and clients.

This basement workspace reflects Steve’s diverse projects and clients.

It’s a home basement workspace that reflects a variety of projects and clients. “I do a range of design work, from transistor-level hardware design through microcontrollers and FPGAs, as well as the embedded firmware and PC-side software to run the products,” Hendrix says. “Most of my clients are small to medium businesses in northeast Ohio, although I’ve done designs for companies as far west as New Mexico, as far south as Florida, and as far east as Cypress.”

Hendrix describes a workspace layout that stresses utility and a certain attention to thriftiness:

As I look through my equipment, probably the central theme is cost-effective solid equipment, without necessarily being the ‘first kid on the block.’ I learned long ago to be the second kid on the block with the newest toy… er… TOOL. The early bird gets the worm, but the second mouse gets the cheese.

He provides the following detailed description of his equipment and desk, which is a very large, solid-core door purchased cheaply from a lumberyard because it had been damaged:

Being natural wood and not plastic, it makes an inherently anti-static workstation. I used a router to round the front edge to be a bit friendlier to elbows, and carefully trimmed it and wedged it between the wall on the right and the utility room wall on the left, supported by vertical plywood against the walls. My PCs are in the adjacent utility room so I don’t have to listen to fans all day and they’re up on custom brackets on the wall so I don’t have to shinny under the desk to get to them. All the wires pass through plumbing fittings in the wall. The main work computer runs the lower dual monitors. The next-older work computer is still used for some specialized hardware, via the monitor above and an extra mouse. Under the left monitor is an all-band receiver that I sometimes use to monitor equipment under development, but also listen to broadcast music.

My late father-in-law was always extremely thrifty, and salvaged the flatbed scanner at the top left from a dumpster. It’s turned out to be the best scanner I’ve seen, and I used it to scan their family pictures. There’s also an HP Photosmart scanner that’s excellent on slides and negatives.

The middle stack has a parts cabinet that I really should retire, holding mainly SN74 series dual in-line packages (DIPs) that I very rarely use these days. Below that is an Ethernet-enabled power switch that controls various equipment. Next down is my trusty old Tektronix TDS-220 oscilloscope

I was pleased to note that past contributors to [Circuit Cellar’s Workspace feature] also use that same scope. It was the first digital scope I ever encountered that wouldn’t fib to me about aliasing, and it’s still a real workhorse. The ability to do screen captures with the free PC software helps a lot in documenting a finished product and in discussing problems remotely. Below that is a very solid bench multimeter. If it just had a capacitance function, I could abandon my Fluke 12! Then there’s a basic analog function generator, and some manual switches for AC.

Over on the far right are some more parts cabinets, several power supplies (including the ±5V/±12V supply my dad helped me build during my very first excursions into the then-new SN74 series of logic), an RF signal generator, and a good old boat-anchor Hewlett-Packard (HP) spectrum analyzer. I got that one off eBay, and spent as much again to get it repaired and calibrated. It’s in many ways better than the newer instruments. If it had a synthesized local oscillator and a computer interface, it would do it all. Actually, I have on occasion faked a computer interface by connecting the video outputs on its front panel to my TDS-220, and then capturing the resulting waveform.

In front of that is my solder station and stereo zoom microscope. Sitting on its stage is a backup prototype identical to the one currently controlling 4,800 W of my total 6,800 W of installed solar capacity. I routinely do prototypes using 0603 parts and recently more 0402 parts, with occasional 0201 parts. Don’t sneeze around those! The cabinets on the right wall are mainly connectors and surface-mount parts.

I needed some more bench space for a project, so I added a “temporary” shelf between the right end of my bench and the bookshelves on the wall to the right. As you can imagine, the “temporary” part of that wasn’t. So now it holds a voltage standard, on which sits my solder station and a ham radio. The latter is powered directly by 12-V solar power. At the extreme right are an inverter connected to the same solar batteries and the side of a breaker panel that allows me to safely connect to those same batteries when I need a heavy-duty 12-V power supply.

The whole office is lighted by strips of white LEDs run directly by 12-V solar power. The self-adhesive strips are just stuck to the drop-ceiling rails on each side of the standard florescent fixture. The standard fixture is still present and functional as a backup, but the solar lights are actually brighter and don’t flicker like a florescent. The 12-V solar is also wired to the rear jacks of the HP multimeter, so I can get an instant reading on the battery charge state. I have future plans to move some or all of my office circuits to the 120 VAC solar power that runs a portion of our home.

To the right and out of the picture is a solid wall of bookshelves that I built to hold databooks when I first set up this office over 20 years ago. The Internet and PDFs have pretty much made that obsolete, so those shelves now hold various supplies, projects in various states of completion, and some archival data. Behind me as I take this picture is a long table, made of another big door sitting atop filing cabinets. My original intent was for the desk to be for software/firmware, and the long table to be for hardware. Indeed, there are still a couple of RS-232 lines up through the ceiling and down to the table. However, now it serves as an assembly area when I have contractors doing assembly, as well as for storage and general workspace. But there’s Ethernet available on both the desk and the bench, for connecting Ethernet-enabled prototypes.

The biggest drawback to this office comes on a clear, cold, sunny day. The upstairs has lots of glass, so it absorbs lots of free solar heat. However, that means the furnace doesn’t run at all (even near zero outside), so the office and the rest of the basement get really cold. But since the furnace blower is on solar power, which is abundant under those conditions, I just force the blower on to share some of that heat!

If you’re interested in learning more about Hendrix’s work, check out our member profile posted last year. Also, be sure to pick up Circuit Cellar‘s upcoming July and August issues, which will include Hendrix’s two-part series on his personal solar-power setup.

These solar panels are mounted on Steve's east-facing roof.

These solar panels are mounted on Steve’s east-facing roof.


Q&A: Robotics Mentor and Champion

Peter Matteson, a Senior Project Engineer at Pratt & Whitney in East Hartford, CT, has a passion for robotics. We recently discussed how he became involved with mentoring a high school robotics team, the types of robots the team designs, and the team’s success.—Nan Price, Associate Editor


NAN: You mentor a FIRST (For Inspiration and Recognition of Science and Technology) robotics team for a local high school. How did you become involved?

Peter Matteson

Peter Matteson

PETER: I became involved in FIRST in late 2002 when one of my fraternity brothers who I worked with at the time mentioned that FIRST was looking for new mentors to help the team the company sponsored. I was working at what was then known as UTC Power (sold off to ClearEdge Power Systems last year) and the company had sponsored Team 177 Bobcat Robotics since 1995.

After my first year mentoring the kids and experiencing the competition, I got hooked. I loved the competition and strategy of solving a new game each year and designing and building a robot. I enjoyed working with the kids, teaching them how to design and build mechanisms and strategize the games.

The FIRST team’s 2010 robot is shown.

The FIRST team’s 2010 robot is shown.

A robot’s articulating drive train is tested  on an obstacle (bump) at the 2010 competition.

A robot’s articulating drive train is tested on an obstacle (bump) at the 2010 competition.

NAN: What types of robots has your team built?

A temporary control board was used to test the drive base at the 2010 competition.

A temporary control board was used to test the drive base at the 2010 competition.

PETER: Every robot we make is purposely built for a specific game the year we build it. The robots have varied from arm robots with a 15’ reach to catapults that launch a 40” diameter ball, to Frisbee throwers, to Nerf ball shooters.

They have varied in drive train from 4 × 4 to 6 × 6 to articulating 8 × 8. Their speeds have varied from 6 to 16 fps.

NAN: What types of products do you use to build the robots? Do you have any favorites?

PETER: We use a variant of the Texas Instruments (TI) cRIO electronics kit for the controller, as is required per the FIRST competition rules. The motors and motor controllers we use are also mandated to a few choices. We prefer VEX Robotics VEXPro Victors, but we also design with the TI Jaguar motor controllers. For the last few years, we used a SparkFun CMUcam webcam for the vision system. We build with Grayhill encoders, various inexpensive limit switches, and gyro chips.

The team designed a prototype minibot.

The team designed a prototype minibot.

For pneumatics we utilize compressors from Thomas and VIAIR. Our cylinders are primarily from Bimba, but we also use Parker and SMC. For valves we use SMC and Festo. We usually design with clipart plastic or stainless accumulator tanks. Our gears and transmissions come from AndyMark, VEX Robotics’s VEXPro, and BaneBots.

The AndyMark shifter transmissions were a mainstay of ours until last year when we tried the VEXPro transmissions for the first time. Over the years, we have utilized many of the planetary transmissions from AndyMark, VEX Robotics, and BaneBots. We have had good experience with all the manufacturers. BaneBots had a shaky start, but it has vastly improved its products.

We have many other odds and ends we’ve discovered over the years for specific needs of the games. Those are a little harder to describe because they tend to be very specific, but urethane belting is useful in many ways.

NAN: Has your team won any competitions?

Peter’s FIRST team is pictured at the 2009 championship at the Georgia Dome in Atlanta, GA. (Peter is standing fourth from the right.)

Peter’s FIRST team is pictured at the 2009 championship at the Georgia Dome in Atlanta, GA. (Peter is standing fourth from the right.)

PETER: My team is considered one of the most successful in FIRST. We have won four regional-level competitions. We have always shined at the competition’s championship level when the 400 teams from the nine-plus countries that qualify vie for the championship.

In my years on the team, we have won the championship twice (2007 and 2010), been the championship finalist once (2011), won our division, made the final four a total of six times (2006–2011), and were division finalists in 2004.

A FIRST team member works on a robot “in the pits” at the 2011 Hartford, CT, regional competition.

A FIRST team member works on a robot “in the pits” at the 2011 Hartford, CT, regional competition.

Team 177 was the only team to make the final four more than three years in a row, setting the bar at six consecutive trips. It was also the only team to make seven trips to the final four, including in 2001.

NAN: What is your current occupation?

PETER: I am a Senior Project Engineer at Pratt & Whitney. I oversee and direct a team of engineers designing components for commercial aircraft propulsion systems.

NAN: How and when did you become interested in robotics?

PETER: I have been interested in robotics for as long as I can remember. The tipping point was probably when I took an industrial robotics course in college. That was when I really developed a curiosity about what I could do with robots.

The industrial robots course started with basic programming robots for tasks. We had a welding robot we taught the weld path and it determined on its own how to get between points.

We also worked with programming a robot to install light bulbs and then determine if the bulbs were working properly.

In addition to practical labs such as those, we also had to design the optimal robot for painting a car and figure out how to program it. We basically had to come up with a proposal for how to design and build the robot from scratch.

This robot from the 2008 competition holds a 40” diameter ball for size reference.

This robot from the 2008 competition holds a 40” diameter ball for size reference.

NAN: What advice do you have for engineers or students who are designing robots or robotic systems?

PETER: My advice is to clearly set your requirements at the beginning of the project and then do some research into how other people have accomplished them. Use that inspiration as a stepping-off point. From there, you need to build a prototype. I like to use wood, cardboard, and other materials to build prototypes. After this you can iterate to improve your design until it performs exactly as expected.

Issue 284: EQ Answers

Can you name all of the signals in the original 25-pin RS-232 connector?

Pins 9, 10, 11, 18, and 25 are unassigned/reserved. The rest are:

Pin Abbreviation Source Description
1 PG - Protective ground
2 TD DTE Transmitted data
3 RD DCE Received data
4 RTS DTE Request to send
5 CTS DCE Clear to send
6 DSR DCE Data Set Ready
7 SG - Signal ground
8 CD DCE Carrier detect
12 SCD DCE Secondary carrier detect
13 SCTS DCE Secondary clear to send
14 STD DTE Secondary transmitted data
15 TC DCE Transmitter clock
16 SRD DCE Secondary received data
17 RC DCE Receiver clock
19 SRTS DTE Secondary request to send
20 DTR DTE Data terminal ready
21 SQ DCE Signal quality
22 RI DCE Ring indicator
23 - DTE Data rate selector
24 ETC DTE External transmitter clock


What is the key difference between a Moore state machine and a Mealy state machine?

The key difference between Moore and Mealy is that in a Moore state machine, the outputs depend only on the current state, while in a Mealy state machine, the outputs can also be affected directly by the inputs.


What are some practical reasons you might choose one state machine over the other?

In practice, the difference between Moore and Mealy in most situations is not very important. However, when you’re trying to optimize the design in certain ways, it sometimes is.

Generally speaking, a Mealy machine can have fewer state variables than the corresponding Moore machine, which will save physical resources on a chip. This can be important in low-power designs.

On the other hand, a Moore machine will typically have shorter logic paths between flip-flops (total combinatorial gate delays), which will enable it to run at a higher clock speed than the corresponding Mealy machine.


What is the key feature that distinguishes a DSP from any other general-purpose CPU?

Usually, the key distinguishing feature of a DSP when compared with a general-purpose CPU is that the DSP can execute certain signal-processing operations with few, if any, CPU cycles wasted on instructions that do not compute results.

One of the most basic operations in many key DSP algorithms is the MAC (multiply-accumulate) operation, which is the fundamental step used in matrix dot and cross products, FIR and IIR filters, and fast Fourier transforms (FFTs). A DSP will typically have a register and/or memory organization and a data path that enables it to do at least 64 MAC operations (and often many more) on unique data pairs in a row without any clocks wasted on loop overhead or data movement. General-purpose CPUs do not generally have enough registers to accomplish this without using additional instructions to move data between registers and memory.

Electrical Engineering Crossword (Issue 285)

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


2.    STOKESSHIFT—Can reduce photon energy [two words]
8.    HYSTERESISLOOP—Its area measures the energy dispersed during a magnetization cycle [two words]
11.    NANDGATE—A shoe in when playing “true or false?” [two words]
13.    YOCTOPROJECT—An open-source alliance designed to help Linux aficionados [two words]
15.    RANKINE—°R
17.    INTERNALNET—A network that resides in and around you
18.    SEQUENTIALCIRCUIT—Dependent on past input [two words]
19.    NANOHENRY—Its abbreviation is the same as the state bordered by Massachusetts, Maine, and Vermont
20.    BINARYCODEDDECIMAL—Makes good use of a 4- or 8-bit nibble [three words]


1.    BIREFRINGENCE—Divides light into ordinary and extraordinary rays
3.    SQUIRREL—An object-oriented programming language
4.    SMARTMETER—Records and shares energy usage information [two words]
5.    MESHANALYSIS—A circuit evaluation method [two words]
6.    LYOTFILTER—Uses [1. Down] to produce a narrow frequency range of wavelengths [two words]
7.    LINEARREGULATOR—Keeps things steady [two words]
9.    BRAGGDIFFRACTION—Occurs when electromagnetic radiation disperses [two words]
10.    AUTODYNE—An amplifying vacuum tube-based circuit
12.    FEMTOWATT—10–15 W
14.    UNIJUCTION—Can be used to measure magnetic flux
16.    PEAKER—Increases gain at higher frequencies

Electrical Engineering Crossword (Issue 284)

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



1.    CROSSEDFIELDAMPLIFIER—This vacuum tube is capable of high output power [three words]
3.    HYPERVISOR—Produces and runs virtual machines
5.    DYNATRON—Uses negative resistance to keep a tuned circuit oscillating
8.    ULTRAVIOLETLIGHT—Gives some substances “a healthy glow” [two words]
13.    ZEROMOMENTPOINT—A moment of respite for robots [three words]
14.    THERMOSONIC—Connects to silicon ICs
17.    CATSWHISKER—An outdated electronic component mainly used in antique radios [two words]
18.    FLEMINGVALVE—Invented in the early 1900s, this was known as the first vacuum tube [two words]
19.    BACKBONE—Makes LANs connect


2.    DEMODULATOR—Recovers information from a regulated waveform
4.    SQUEGGING—This type of circuit oscillates erratically
5.    DOWNMIXING—Audio manipulation process
6.    REYNOLDSNUMBER—Used for flow pattern predictions [two words]
7.    LATENCY—Used with bandwidth to ascertain network connection speed
9.    THICKFILM—This type of chip resistor is commonly used in electronic and electrical devices [two words]
10.    DYNAMIC—Its memory is volatile
11.    CRYOTRON—Operates via superconductivity
12.    NETMASK—Creates neighborhoods of IP addresses
15.    HOROLOGY—E.g., clepsydras, chronometers, and sundials
16.    SEEBECK—An effect that creates electricity