Test Equipment: What to Consider

Editor’s Note: Ian Broadwell, a postdoctoral fellow at the Department of Chemistry at Ecole Normale Superieure in Paris, wrote the following review of test equipment for circuitcellar.com readers. He is pursuing additional articles about making the right choices in equipment.

Whether you are setting up your own electronics workbench or professional design company, you certainly will be thinking about the test gear you should buy. With big-name brands such as Agilent, Fluke, Keithley, Tektronix, and LeCroy (to name a few) aggressively marketing their latest products, it’s easy to think you’ll have to start earning a pro soccer salary and work until you’re 150 to own some of these high-end products. But this is not necessarily true—if you’re prepared to wait and buy used equipment (I will revisit this point later).

The diverse spectrum of Circuit Cellar readers will have a wide variety of test and measurement requirements. In this first article about “making the right choice,” I want to introduce myself, the variety of test equipment available, and, finally, the rules I follow in buying test equipment for my electronics lab.

Introducing Myself

As a teenager, I had ambitious dreams of setting up an electronics laboratory. My journey started when I became involved with the local ham radio club, G4EKT, in Great Britain’s East Yorkshire County. At 17, I became a fully licensed A-class radio amateur and started to build some of my own equipment, such as a shortwave valve RF power amplifier (a tube amplifier in the US) and a dual-function standing wave ratio / power meter.

After joining G4EKT, I found flea markets and radio rallies a source of electronic and mechanical parts for constructing my own equipment. Money was tight as a teenager, so I could only dream of owning an oscilloscope; having a spectrum analyzer would be like standing on the moon (a very remote possibility). I came to realize it takes years to collect the equipment to set up your lab—and successful people rarely tell you this.

After my schooling, I followed the traditional university route—graduating with a BSc in Physics, MSc in Exploration Geophysics, and a PhD in Physical Chemistry. My professional experience has taken me from being a quality-control technician in an analytical chemistry lab to an offshore field geophysicist in northwest Australia. Eventually, I came full circle—back into academia with several postdoctoral positions in England, China, and now France. The diversity of working environments, locations, and multidisciplinary subjects has provided a unique window for viewing the tools-of-the-trade in different disciplines. My fascination with scientific instruments encompasses all domains.

Currently, I work in the Department of Chemistry at Ecole Normale Superieure in Paris as a Marie Curie Postdoctoral Fellow. My research interests include instrumentation and development of microfluidic tools for use at the interface between physics, chemistry and biology.

A Diversity of Available Equipment

Today we take test equipment for granted. We have testers for just about anything imaginable. Where there is something to be measured, there will be a machine to do so—along with 100 patents claiming rights to all the varied ways to measure what you want to quantify. There has never been a better time to find test equipment in the used market, a result of the global economic slowdown and the turnover and exploitation of new technologies. Consider the computer you bought last year; it’s already old, technologically speaking.

Technological progress has not always been this rapid. Historically, war or military endeavours have driven technological leaps. Remember the Cold War, the nuclear arms race between the US and USSR from 1947-1989? This period of sustained technological development spurred the Internet and the abundance of test equipment we see today. My favorite test-equipment manufacturer was Hewlett-Packard (HP), which produced a vast range of scientific and laboratory equipment from 1939 until 1999, when the company was restructured. Agilent Technologies continues to develop the company’s former test and measurement product lines, while the new HP primarily focuses on computer, storage and imaging products. Most of HP’s equipment is well-documented, with downloadable manuals. Meanwhile, Web-based user groups are continually contributing to online document repositories. And HP’s equipment was built to last, using military-grade components. That is why 20- or 30-year vintage test equipment is often found in working order.

At the high end, test equipment comes in many different forms—from stand-alone, high-precision single benchtop units to dedicated chassis and multifunction rack-mount instrument arrays. HP was one of the first companies to use instrument arrays. This has been further developed by companies such as National Instruments (NI), with its range of chassis and stand-alone data acquisition (DAQ) cards that fit into a desktop PC and form a virtual instrument using NI’s LabVIEW software. Industries often prefer to use modular measurement systems because of the inherent flexibility to tailor the functionality to meet their own specifications. They also conserve space and allow the test stand engineer to automate select tests.

At the low end, every electronics enthusiast should aim to have a basic handheld multimeter and an oscilloscope. This is essential equipment to start your hobby. Fluke, B&K Precision, and Extech Instruments are but a few of the established brands. Although company headquarters are usually located in Europe or the US, many companies have design and manufacturing units in Taiwan and mainland China (Hong Kong and Shenzhen). My experience working in China showed me that the mainland Chinese prefer electronic components and instruments made in Taiwan because of its longer history of Western investment. This is not to say mainland products are poor—Rigol is an excellent brand with top-quality components in its products.

The message is that you get what you pay for. So, whatever basic equipment you intend to buy, try to purchase it from an established brand that you know will provide at least a one-year guarantee and some sort of manufacturing quality control in its products. A Fluke 115 multimeter, for example, has the essential functions you’ll need and costs around $200. For this price, you should feel confident that the meter will last a very long time if used as intended.

Some of the best information sources for those interested in electronics are subscription electronics magazines such as Elektor, Circuit Cellar, Everyday Practical Electronics and Nuts and Volts. Article technical levels vary widely between the magazines, ranging from absolute beginner to seasoned professional. General magazines are a great introduction for beginners and offer a relatively cheap route into the electronics field or more focused areas. Specialized electronics areas such as audio or industrial have their own publications, including audioXpress, IEEE Industrial Electronics, and the free-subscription online EDN Network (www.edn.com).

Speaking to people can be better than wading through magazine pages. Local electronics or ham radio clubs are a rich knowledge source. In fact, they can be more informative than large professional-equipment suppliers who have commercial agreements or little knowledge of different test platforms. In Europe, a number of small equipment brokers survive. They can offer excellent advice on a wide range of equipment issues and projects, because their employees must multitask. Such companies have small profit margins, so their employees often work on projects outside their normal expertise. Brokers also tend to be professionals who have worked in the industry for 20 to 30 years before heading out on their own.

Rules I Use for Buying Test Equipment in My Electronics Lab

After determining your future test equipment needs and drawing up a short list of essential features, it’s time to focus on the brands, models, and vintages that will meet your minimum specifications. Some less obvious things to consider are: the physical volume and weight of the equipment and cooling and power requirements. My lab is situated in a 2-by-3-m room with minimal space and ventilation. Large rack-mounted instruments are heavy and take up a lot of space, which requires careful arrangement to accommodate all the equipment. Additional considerations include: electrical power ratings (daisy chaining too many instruments together from the same socket is a fire risk); sufficient room ventilation to remove hot air from the instruments’ cooling systems; and smells generated by aging, phenolic printed circuit boards.

In recent years, I have been collecting a wide range of instruments. My objective has been to build up a general-purpose electronics lab where overall functionality (i.e., the breadth of measurements I’m able to make) is more important than high resolution and cutting-edge accuracy (this is what calibration labs are for). General-purpose semi-professional labs should, in my opinion, be able to tackle a range of projects—be it RF, audio, or control.

One of the most expensive pieces of test equipment an RF lab should have is a spectrum analyzer. Recently, I spent a lot of time considering spending my money and realized that such a purchase could require remortgaging my house and would, at minimum, need the boss’s (wife’s) permission. In preparation to achieve the “minimum,” I drew up a series of feel good factors” to give weight to my case.

These factors amount to a list of things you should consider before a purchase (see Table 1). They can serve as a yardstick for reviewing a spectrum analyzer or other pieces of equipment.


Table 1

Feel good factor Description
a) Space utilization Keithley source meters have five instruments in one unit (i.e., one box replaces four or five boxes of its predecessors). This is efficient space utilization.
b) Connectivity Does the equipment come with all the latest LAN, Wi-Fi, GPIB, USB, and RS-232 protocols as standard?
c) Portability Is the equipment your lab doorstop, or is it small enough to be used in remote locations such as up a cellular phone mast?
d) Ease of use Is the equipment intuitive and easy to use, or do you need the latest version of the user guide and service manual (which may not be available) to get going?
e) Special features and add-ons/expansions Include extended memory depth or high-speed data streaming, automated test stand, hardware upgrades, and powerful proprietary software-analysis functions (i.e., modifications that allow uses with MATLAB or LabVIEW).
f) Resolution/accuracy How much resolution is required and what level of calibration/traceability?
g) Price vs. functionality You are either buying the latest feature-packed instrument or used equipment from a broker or eBay. Generally, money will be tight and buying high-end new equipment isn’t an option. Clearly, the used market can offer some good deals. You find two instruments that have nearly the same functionality and both are tempting. Which do you buy? At first, you may reply the more modern one, as there may be less risk of failure.Let’s now consider buying a 20 GHz vector network  analyzer. The Agilent 8510c is about half the price of the slightly more modern Agilent 8720a.  Both have nearly the same specifications. The 8720a is more compact. The 8510c is definitely larger, more modular (requiring an external signal generator and S-parameter test set), and better built. The latest versions of the 8510c are similar in vintage to the 8720a and differ by only a few years. Agilent repairs are prohibitively expensive for both. The modular nature of the 8510c and abundance of eBay modules translate into increased self-servicing of repairs. If 8510c spares were hard to find, then it would be a good reason for choosing more modern equipment (i.e., 10 years old rather than 25).
h) Disposal and small print issues Are there any toxic materials used in the instrument’s manufacturing that will cause future disposal issues? Is it going to cost you more to dispose of it than it did to buy it?EBay dealers only cover equipment faults detected within the initial weeks of a purchase. The buyer will be responsible for any repairs costs that fall outside of this guarantee period.
i) Overall value for money Does the equipment have a reputation for being reliable and consistently doing what is written on the packaging, year after year? What’s included with your purchase? Probes? Extended warranty? On-site maintenance? Service contracts?Often, eBay purchases come without peripherals (e.g., probes) and these need to be found elsewhere. Sometimes, there are lucky buys to be had. Generally, most traders only want to maximize their profits, so beware of this.
j) Deal or no deal 1) Does the equipment fit your test requirements?2) Is it within your budget?3) And finally, do you really need it?


Rules for reviewing equipment are often best understood by offering an example. To foster understanding, I have made a comparison between two spectrum analyzers—a used Agilent 8591a and a new Rigol DSA815-TG. Both have very similar specifications in terms of maximum frequency, dynamic range, and resolution. While the Rigol offers the latest color LCD, portability, and connectivity, the HP provides the reassurance that it still works after all these years. When new, the HP was a very high-end instrument (costing $18,000 in the 1980s). But evolving technology has enabled us to purchase entry-level spectrum analyzers, such as the Rigol DSA815-TG, with virtually the same specifications. This is really mind-blowing.

When considering instrument performance by comparing marketing data, you should keep in mind manufacturers will try to legitimately report best values for important parameters. Although the two analyzers appear identical, the phase noise performance of the HP is better than the Rigol. The phase noise represents the short-term stability of the frequency reference and the analyzer’s ability to distinguish weak signals next to a strong carrier. With my preference for high performance, value for money, and a hint of nostalgia, I would buy the HP 8591a rather than the Rigol DSA815-TG.

For a “feel good factor” comparison of the HP 8591a and Rigol’s DSA815-TG, see Table 2.

Table 2

Feel good factor Instrument 1: HP 8591a Instrument 2: Rigol DSA815-TG
a) Space utilization 163 mm x 325 mm x 427 mm 399 mm × 223 mm × 159 mmThe Rigol is approximately half the volume of the HP.
b) Connectivity GPIB, serial port, and analogue monitor output USB interface allows connection to PC and memory stick; LAN
c) Portability Not very portable at 15 kg and has no battery feature. It will accept 86-127/195-250 VAC; 47-66 Hz. Very portable at 7.5 kg including battery and also accepts 100-240 VAC, 45-440 Hz.
d) Ease of use Although the instrument is old, the menu system is easy to use. ROM updates for the software are available but no longer updated. The Rigol also has an excellent indexed menu system with hot keys on the side of the screen. The operating system can be switched instantly to a range of different languages
e) Special features and add-ons/expansions 004 precision frequency reference, 010 tracking generator, 101 fast time domain sweeps, 102 AM/FM demodulation Optional USB to GPIB; tracking generator and preamp are not standard features.
f) Resolution/accuracy Frequency resolution bandwidth 3 kHz to 3 MHz in a 1, 3, 10 sequence; 10 MHz frequency reference with option 4 has 0.2 ppm drift/year. The phase noise sidebands at 10 kHz offset from the carrier is <-90 dBc/Hz. Signal amplitude dynamic range of −115 dBm to 30 dBm from 1 MHz to 1.8 GHz and 0.01 dB resolution 100 Hz to 1 MHz in 1-3-10 sequence. Frequency reference has 2 ppm drift/year10 kHz offset from the carrier is <-80 dBc/Hz.−115 dBm to 20 dBm across 1 MHz to 1.5 GHz without preamplifier and 0.01 dB resolution
g) Price vs. functionality 9 kHz–1.8 GHz spectrum analyzer with tracking generator. This unit was originally sold from 1978 to 1990 for $18,000 including options. Today a good uncalibrated unit on eBay will fetch $1,750. 9kHz–1.5GHz spectrum analyzer with tracking generator currently sells for $2,000, including tax, from both eBay and directly from a Rigol supplier. With this, you are buying the latest instrument 2012 production date.
h) Disposal and small print issues Has beryllium oxide RF components inside, which could be a problem for disposal Repairs are only carried out by the manufacturer in Beijing. In 2010, I remember this was the situation.
i) Overall value for money Reliable and time-honored equipment made of excellent quality components and built to be repairable. Boasts 8″ WVGA 800 × 480 pixel screen. Has all the bells and whistles that your portable lab needs. Not really built to be repaired by the broker or individual, with all the FPGA and surface-mounted components.
j) Deal or no deal Personally, I would buy the used equipment, as there is more margin to negotiate the price and it is built to last. The product will not substantially depreciate, as with a new model such as the Rigol. This excellent equipment built from Analog Devices components is a budget spectrum analyzer and offered at the lowest price in the Rigol range.

The Key Questions

Always remember, making the right choice doesn’t have to be painful and costly. Just ask yourself the key questions:

1) Is the equipment a fit for your test requirements?

2) Is it within your budget?

3) Do you really need it?

If you manage to convince your line manager (or your spouse) that the answer to all three is “yes,” then you’re likely to get the thumbs up to make that important purchase.

Microcontroller-Based, Cube-Solving Robot

Cube Solver in ActionCanadian Nelson Epp has earned degrees in physics and electrical engineering. But as a child, he was stumped by the Rubik’s Cube puzzle. So, as an adult, he built a Rubik’s Cube-solving robot that uses a Parallax Propeller microcontroller and a 52-move algorithm to solve the 3-D puzzle.

Designing and completing the robot wasn’t easy. Epp says he originally used a “gripper”-type robot that was “a complete disaster.” Then he experimented with different algorithms–“human memorizable ones”—before settling on a solution method developed by mathematician Morwen Thistlethwaite. (The algorithm is based on the mathematical concepts of a group, a subgroup, and generator and coset representatives.)

Nelson also developed a version of his Rubik’s Cube solver that used neural networks to analyze the cube’s colors, but that worked only half the time.

So, considering the time he had to spend on project trial and error (and his obligations to work, family, and pets), it took about six years to complete the robot. He writes about the results in the September issue of Circuit Cellar magazine. 

Here, he describes some of the choices he made in hardware components.

“The cube solver hardware uses two external power supplies: 5 VDC for the servomotors and 12 VDC for the remaining circuits. The 12-VDC power supply feeds a Texas Instruments (TI) UA78M33 and a UA78M05 linear regulator. The UA78M05 regulator powers an Electronics123 C3088 camera board. The UA78M33 regulator powers a Maxim Integrated MAX3232 ECPE RS-232 transceiver, a Microchip Technology 24LC256 CMOS serial EEPROM, remote reset circuitry, the Propeller, a SD/MMC card, the camera board’s digital output circuitry, and an ECS ECS-300C-160 oscillator. The images at right show my cube solver and circuit board.
“The ECS-300C-160 is a self-contained dual-output oscillator that can produce clock signals that are binary fractions of the 16-MHz base signal. My application uses the 8- and 16-MHz clock taps. The Propeller is clocked with the 8-MHz signal and then internally multiplied up to 64 MHz. The 16-MHz signal is fed to the camera.

“I used a MAX3232 transceiver to communicate to the host’s RS-232 port. The Propeller’s serial input pin and serial output pin are only required at startup. After the Propeller starts up, these pins can be used to exchange commands with the host. The Propeller also has pins for serial communication to an EEPROM, which are used during power up when a host is not sending a program.

“The cube-solving algorithm uses the coset representative file stored on an SD card, which is read by the Propeller via a SparkFun Electronics Breakout Board for SD-MMC cards. The Propeller interface to the SD card consists of a chip select, data in, data out, data clock, and power. The chip select is fixed into the active state. The three lines associated with data are wired to the Propeller.

“The Propeller uses a camera to determine the cube’s starting permutation. The C3088 uses an Electronics123 OV6630 color sensor module. I chose the camera because its data format and clocking speed was within the range of the Propeller’s capabilities. The C3088 has jumpers for external or internal clocking.”

To read more about Epp’s design journey—and outcomes—check out Circuit Cellar’s September issue. And click here for a video of his robot at work.


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.


The Growing Importance of Control Theory for DIYers

Control system theory is a branch of engineering that handles how to manipulate a dynamical system’s inputs to change the behavior or outcome of the system to something that is desired. The concept is simple enough to understand. In fact, humans do it regularly and intuitively when walking, driving, or playing video games—though many find it difficult to apply in practice when developing control systems for their projects. Often DIYers will purchase a controller then resort to the manufacturers’ recommended controller gains or they will tune the gains through a cumbersome trial-and-error process. In general, this method works fine for the patient engineer as long as the system is sufficiently simple. However, this method breaks down with so-called multiple-input multiple-output (MIMO) systems whose dynamics are coupled in such a way that renders this method impractical. But do DIYers need to worry about designing and building such complicated MIMO systems any time soon? Absolutely! And current trends suggest we’re already there.

Control systems have been around at least as far back as the float-regulated water clock developed by the Greeks in the third century BC; however, control theory as a branch of mathematics wasn’t explored until much later in the mid-19th century. Since that time, the theory has been used almost entirely by professional engineers and mathematicians rather than DIY builders, but that trend is beginning to change. I’m not saying professionals with accredited degrees aren’t still the majority of control theory users; however, with the rise of inexpensive open-source development platforms, free online software libraries, and the vast array of available sensors and actuators, control theory is becoming a major requirement for part-time DIYers, as well.

The simplest control systems are open loop. An open-loop control system is one in which the change in the input is not a function of the measured output. Open-loop controllers work best on systems that are predictable, repeatable, and robust to disturbances. A good example of an open-loop control system is a stepper motor where the user only needs to command a set number of steps and does not need to measure the motor’s final position to know with great confidence that it is where it is supposed to be.

On the other hand, closed-loop control systems vary the input based on the measured output. To accomplish position control with a brushless DC motor for example, the user would need to feed back the measured position and adjust the input voltage appropriately. This closed-loop system is more robust to changes in the environment, but consequently introduces a whole new set of problems including stability, overshoot, settling time, and other loop performance measures. If you build a system with multiple closed-loop paths that must work together, you can see how the complexity grows.

Kits for DIY projects (e.g., robotic sumo cars, maze-following robotic mice, six-axis stabilized quadcopters, and auto-piloted model aircraft) are now easily accessible to the individual. All of these projects rely heavily on control-system theory because they require multiple sensors and actuators working closed loop in conjunction with each other. These are MIMO closed-loop systems and they require more than clunky guess-and-try design methods.

So where will DIYers turn to gain the knowledge necessary to develop the controllers for these complex systems in the future? Luckily, along with the capability for individuals to build these projects comes the means with which to learn the skills. With the rise of YouTube and other information-sharing sites, people now have access to more educational content than ever before. In addition to open-source hardware and software, there is also this “open-source” library of free knowledge where a creator can learn and share just about anything.

The potential for video-based education is limitless, but it will probably won’t replace traditional education in classrooms any time soon, if ever. However, it is already proving an invaluable resource to many people who are looking to increase their knowledge base to tap into their full project-building potential.

Continuing advances in hardware and software mean home projects are going to become more capable. With this capability comes a necessary complexity in their control systems. This should be celebrated because these projects come with a certain amount of pride, a sense of accomplishment, and valuable knowledge gained. The knowledge is generated and shared within the community, feeding back to a new generation of DIYers who, in turn, share their new gained knowledge. It’s a positive feedback system that shows no sign of slowing down.

Brian Douglas is a control systems engineer based in Seattle, WA. He holds an MS in Aerospace and Mechanical Engineering (Dynamics and Controls) from the University of Southern California. Brian is the content creator of the Control System Lectures YouTube channel, which is dedicated to providing an intuitive and practical understanding of control system theory (www.youtube.com/user/ControlLectures). He has worked at The Boeing Company since 2003 developing satellite and aircraft guidance, navigation, and control systems. He is also married to a wonderful wife who supports him with all of his numerous hobbies.

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.



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.