Reliability and Failure Prediction: A New Take

HALT methodology has been a popular way to test harsh environment reliability. A new approach involves PCB design simulation for vibration and acceleration for deeper yet faster analyses.

By Craig Armenti & Dave Wiens—Mentor Board Systems Division

Many electronic products today are required to operate under significant environmental stress for countless hours. The need to design a reliable product is not a new concept, however, the days of depending on a product’s “made in” label as an indicator of reliability are long gone. PCB designers now realize the importance of capturing the physical constraints and fatigue issues for a design prior to manufacturing to reduce board failure and improve product quality.

Simulation results should be available in a two-phase post-processor for each simulation, providing broad input on the PCB’s behavior under the defined conditions.

Simulation results should be available in a two-phase post-processor for each simulation, providing broad input on the PCB’s behavior under the defined conditions.

Although every product is expected to fail at some point. That’s inevitable. But premature failures can be mitigated through proper design when proper attention is paid to potential issues due to vibration and acceleration. ….

Read this article in the August 325 issue of Circuit Cellar

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The Perfect PCB Prototype

Interested in constructing perfect PCB prototypes? Richard Haendel has the solution for you. In this article, he explains how five simple steps—print, mount, punch, fit, and evaluate—can save you a lot of time and money.

The following article first appeared in Circuit Cellar 156.

Who designs and builds your prototype circuit boards? The other department? Oh. Well, in that case, nice seeing you. Just flip past this article and enjoy the rest of the magazine.

On the other hand, if you’re a do-it-yourself engineer like me, then perhaps my technique for prototyping prototypes will interest you (see Photo 1). It’s so easy, cheap, and obvious, I have trouble believing that no one else has done it before. If you have, please let me know. I’d love to compare notes. The entire process can be described in five words: print, mount, punch, fit, and evaluate.

Photo 1: It doesn’t get any easier than this (or cheaper). Just remember to print, mount, punch, stuff, and evaluate.

Photo 1: It doesn’t get any easier than this (or cheaper). Just remember to print, mount, punch, stuff, and evaluate.


Your printer must be able to print a full-scale, moderately accurate representation of your PCB layout. I say “moderately accurate,” because, after all, a 10% error on a 0.4″-spaced resistor is only 0.04″. That’s close enough for most through-hole designs. Surface mounting, however, can be a problem. But because I don’t normally do surface mounting, it’s not a problem for me.

I use two printers for development: a color ink-jet and a black and white laser-jet. Both are fairly old, but they still have more than enough accuracy for this purpose. The laser-jet is probably a little better, but not by much.

Your printed layout must show (at minimum) the holes and component layout. You may or may not need to see the traces; it depends on what you’re hoping to accomplish. The traces are superfluous for test fitting (e.g., to make sure that components don’t touch each other); however, if you’re building a full-scale concept model, you’ll need as much detail as is practical. In fact, with a little more effort, you could print the top traces on one sheet and the bottom traces on another, glue them to the foam board on opposite sides (taking care to line up the holes, of course), and make yourself a full-scale PCB model. Cool.


Trim the excess white space from the sheet containing your printed image, because it will just get in the way. Next, cut a piece of foam board slightly larger than your layout. A utility knife and metal ruler work well for this. Peel the backing from the foam board’s adhesive side; of course, if you don’t have the self-adhesive kind, simply apply dry glue (from a glue stick) to either the board or paper. After that, carefully position one corner of your image on the foam board and smoothen it. Rub gently but firmly with a soft cloth or paper towel to permanently “seat” the image.

If you get air bubbles or wrinkles, throw it away and start over. Remember, your pattern must be accurate. You can probably make a new one faster than you can fix a damaged one. A little practice goes a long way toward achieving perfect results.


Using a pushpin (or a similar instrument), carefully punch your holes. As you can see in Photo 2, I use metallic pushpins with longer-than-usual shafts. Naturally, the shorter plastic pushpins will work just as well. Thumbtacks, however, are not a good choice; they’re pretty rough on the fingernails.

Photo 2: A small pin is my favorite tool for punching holes in the foam board.

Photo 2: A small pin is my favorite tool for punching holes in the foam board.

Note that this stage can be tedious, especially if you have a large board with many holes. Take your time. The holes should be centered as accurately as possible. Also, don’t push the pin all the way through; it’s merely intended to puncture the paper front so the component’s pins can penetrate the foam and have it “grab” them. In other words, you want a snug fit so the pieces don’t (easily) fall off the board.

That’s how it works for IC sockets and connectors with short leads (i.e., less than the thickness of the board). However, resistors and other parts with longer leads are a different matter. In this case, you must either trim the leads—which is fine if you’re not planning to reuse the component—or extend the hole to the backside with something like a map pin. That’s what I usually do.


That’s right. Simply fit (or stuff) your components as you would a real circuit board. Components with short leads should be easy to fit; however, those with longer leads may need persuading. Simply insert the part, grab one lead close to the board’s surface with needle-nose pliers, and gently (but firmly) coax it through the hole. Sometimes this can be a pain, especially with small-gauge component leads (e.g., ceramic capacitors). You may need to enlarge the hole from the front or backside. Remember: practice, practice, practice.


In other words, use it for whatever purpose you need. Most of the time, I make these models just to test my board design and confirm that all parts will fit before committing to a manufactured prototype. After that, it’s trash. If the design is significant (pronounced “expensive to produce”), then I may make others until I’m confident of perfection.

I must confess, though, most of my models are nowhere near as neat and attractive as the one pictured in this article. Frequently, the images are slapped on a piece of scrap foam, tested, and tossed within 5 min. or less.


Not much. Just the other day, I purchased a 20″ × 30″, 3/16″ thick sheet of white self-adhesive foam board at a local hobby store for $4.99. (The nonadhesive type was about $1 less.) Therefore, the cost is $4.99 divided by 600 square inches, or a mere $0.00832 per square inch—that’s less than a penny. At that rate, this board cost only $0.07.


You bet! I’ve caught numerous board design and layout errors with this technique. I’ve also learned that legends on the silk-screen layer don’t always match the physical part as closely as you may expect. This is good to know when you’re tight on board space and need to fudge a little.

Photo 3: Notice that D1 will not actually touch J2, as the PCB layout program’s silkscreen outline indicates.

Photo 3: Notice that D1 will not actually touch J2, as the PCB layout program’s silkscreen outline indicates.

I was able to crowd D1 between J2 and J3, because J2 is 0.08″ smaller than its silkscreen outline (see Photo 3). So, even though D1 appears to touch J2, there’s actually 0.04″ between them, which is more than enough for my design.

So, did I lie? Is this not as simple as can be? And cheap! Try it yourself and see.—By Richard Haendel (Circuit Cellar 156)

Full Schematic and PCB Layout in One Project File

TARGET 3001! combines the full schematic and PCB layout in one project file. Schematic and layout are always in a consistent state. An embedded PSpice simulator enables the modeling of the electrical function of the circuit eliminating errors early in the design phase.

TARGET 3001! offers more than 38,000 components in a local MySql database. When placed on a server, an entire design team can simultaneously access the same component source. If a component is placed in a design, its drawing and all its properties still can individually be changed independent of the database. Most components are furnished with a 3-D model so that a PCB can be easily inspected in a live 3-D view. A STEP file import allows for the creation of custom 3-D models; the STEP export allows the 3-D printing of an exact model of your PCB with components.

Besides XGerber and Excellon, TARGET 3001! provides a wide range of industry standard manufacturing formats. It also includes a tool for isolation milling, outputting the data in G-Code and HPGL. Open and save Eagle projects. PCB sizes up to 47″ × 47″ and an embedded front-panel designer make TARGET 3001! the perfect tool for high-end makers as well as development pros who want to move quickly from design idea to finished product.

You can try a free version for double-sided projects up to 250 pins/pads at:

Source: Ing.-Buero FRIEDRICH

21st-Century Electronics Craftsman: Meet Saar Drimer

Saar Drimer (PhD, Cambridge) runs Boldport, a London-based hardware and prototyping consultancy that specializes in circuit boards. Wisse Hettinga recently met with Drimer to discuss PCB design, electronics craftsmanship, and his various engineering projects.

Saar Drimer, electronics craftman

Saar Drimer, electronics craftman

Hettinga writes:

The Art of Electronics is a book that’s well-known by many electronic engineers all over the world. Written by Horowitz and Hill, the first edition was published in 1980 and recently, in 2015, a third edition was released. Over the past 35 years, the book has been an inspiration and resource for many engineers eager to learn about the art of designing with electronics. But there is also a real art of electronics. To discover what that is, I traveled to London to meet up with Saar Drimer. His workplace was in one of the characteristic arches underneath London Bridge Station. With the constant rumble of the trains arriving and pulling out of the station in the background, he showed me some of his work.

Drimer’s designs are completely different from what we usually see on PCBs. Where most of our designs end up as small rectangles with only a few holes for the assembly screws, his boards take different shapes. Some are swirly, sometimes animal-like. At other times, he integrates components right into the board in special holes, as you can see in his Tiny Engineer Superhero Emergency Kit. Often there is no straight copper line to be found; they go all over the place and are a vital part of the total design.

Emergency kit

The Tiny Engineer Superhero Emergency kit

A PCB designed by Drimer asks for exposure and can be interesting for art’s sake only, but also for marketing purposes where drawing attention and presenting a surprise is required. One of his designs even features in the women’s magazine Marie Claire!

Where many of us try to put all the PCB and wiring in a (mostly) gray box and leave it out of sight, Drimer is doing exactly the opposite: he is trying to expose it. His end product is the PCB and that is where his art comes into the picture—in many exciting formats. In many ways, Saar is an engineer like many of us. He is extremely knowledgeable about electronics and designing. But when it comes to the latter, he is using unorthodox methods. Where we start with the schematics, Drimer starts with the form and shape of the final PCB—basically, he designs the other way around!

Working and designing in the opposite direction is not easy with existing PCB CAD programs like Eagle or Altium. They all start with a schematic and are using component libraries routing the final layout in the most effective or smallest footprint PCB. Their rigid, straightforward approach is excellent when designing for just another rectangle PCB. But if you want new and creative designs, you need to think of a different way of working and using other tools. If you want to change the way of thinking and designing, you need to be able to use free forms and the routing cannot be left to the CAD program. And that is exactly what Drimer is doing.

To be able to start with a different type of design, Drimer was left with no choice but to start developing his own PCB CAD design program. Unlike most of us who call ourselves “engineer,” Drimer calls himself ”craftsman”—and as a true craftsmen, he makes his own tools. PCBmodE is Drimer’s custom PCB CAD program. The “mod” in PCBmodE has a double meaning, Drimer explained. “The first is short for ‘modern’ in contrast to tired, old EDA tools. The second is a play on the familiar ‘modifications,’ or ‘mods,’ done to imperfect PCBs. Call it ‘PCB mode’ or ‘PCB mod E’, whichever you prefer,” he said.
PCBmodE is a PCB design Python script that creates an SVG from JSON input files. It then creates Gerber (the standard software to describe the PCB images: copper layers, soldering mask, legend, etc.) and Excellon files for manufacturing. With no graphical interface, PCBmodE enables you to place any arbitrary shape on any layer because it is natively vector-based. Most of the design is done in a text editor with viewing and some editing (routing) completed with Inkscape. (Inkscape is a professional vector graphics editor for Windows, Mac OS X, and Linux. It’s free and open source.) On his website, Drimer explains how to work with the program.

“PCBmodE was originally conceived as a tool that enables the designer to precisely define and position design elements in a text file, and not through a GUI. For practical reasons, PCBmodE does not have a GUI of its own, and uses an unmodified Inkscape for visual representation and some editing that cannot practically be done textually,” said Drimer.

A typical PCBmodE design workflow is as follows:

  • Edit JSON files with a text editor
  • “Compile” the board using PCBmodE
  • View the generated SVG in Inkscape
  • Make modifications in Inkscape
  • Extract changes using PCBmodE
  • Back to step 1 or step 2
  • Generate production files using PCBmodE

If you want to give PCBmodE a try, simply download it at It works with Linux, but Drimer is interested in results on other OS platforms as well. For starters, a “hello solder” design is currently available.

Hello Solder

Starter example: Hello Solder

Examples of Drimer’s work are posted on his website, I especially like the Tiny Engineer Superhero Emergency Kit’ design where the components are integrated into the PCB itself resulting in a very flat design. You will also notice he is not using straight lines and angles for the traces. It is more of a pencil drawing; the traces flow along the lines of the PCB and components.

You might ask why on earth someone would put so much effort into all of this? Don’t ask! But, if you like, here are a few answers. First, because it is an art. Second, it is Drimer’s full-time job and he hopes to expand the business. And third, working differently from the norm tends to generate fresh ideas and exciting solutions—and that is what we need more of.

This article appears in Circuit Cellar 306 (January 2016).

Interconnect Defects (ICDs) Explained

What is an Interconnect Defect (ICD)? An ICD is a condition that can interfere with the internal circuit connections in a printed circuit board (PCB). These internal connections occur where the innerlayer circuit has a drilled hole put through it. PCB processing adds additional copper into the drilled hole to connect the innerlayer circuits together and bring the circuit to the PCB board surface where connectors or components are placed to provide final function.

If there is a defect at or near this interconnect or plating and innerlayer copper, it could lead to failure of a specific circuit (or net). This defect typically causes open circuits, but could be intermittent at high temperatures. Of significant concern is that the functionality may be fine as the PCB is built, but will fail in assembly or usage, becoming a reliability risk. This latency for the defect has put ICDs on the serious defect list in the industry. Another item is that ICDs have increased in frequency over the past five to seven years, making this a higher priority issue.

The majority of ICDs fall into two categories: debris-based ICDs and copper bond failure ICDs. Debris-based ICDs are caused by material left behind by the hole drilling process. This material is supposed to be removed from the holes, but is not when ICDs are found. Some causes are drill debris residues, drill smear and particles (glass and inorganic fillers) embedded into the innerlayer copper surface. The increases in this ICD type seems to be related to the increased usage of low Dk/low Df materials that use inorganic filler types. These materials generate more drilling debris and are often more chemically resistant materials, compared to standard FR-4 epoxy materials. This combination of effects makes the drilled holes much more difficult to clean out completely.

Debris-based ICD

Debris-based ICD

Copper bond failure ICDs occur when the copper connection is physically broken. This can be due to high stress during assembly or use, or the copper bond being weak (or a combination). This failure mode is also design related, in particular, increased PCB thickness, increased hole size and wave soldering all tend to increase the risk of copper bond ICDs. It seems that there has been an increase in the rate of this ICD type, which is related to increased lead-free soldering temperatures and increased board thickness over the past 10 years. Note: This condition also occurs on HDI microvias. The causes are similar but the processing is different.

Copper bond failure ICD

Copper bond failure ICD

Reliability testing has been run on both types of ICDs. Copper bond type ICDs are a significant reliability issue. They show up as assembly failures and product with weakness may have increased tendency for field failures. Drill debris type ICDs have not been shown to be a significant reliability issue in several studies, but they are an industry specification failure, so they affect product yield and costs. Well run IST testing, using a valid coupon structure, has been a very valuable testing method for determining risk due to ICDs.

ICDs can be prevented by good PCB design and improved PCB processing methods. Debris type ICDs are a function of drilling parameters and desmearing. Many of the newer materials with fillers do not drill like standard FR-4. Instead of forming a chip during drilling, they break apart into small particles. These particles then tend to coat the drilled hole walls. One factor associated with debris ICDs is drill bit heating. Factors that result in hotter drill bits cause more debris formation and residues.
Desmearing, which is done to remove drilling residues, often needs to be more aggressive when using these material types. This has been effective at reducing or eliminating debris ICDs.

Copper bond failures are a little more complex. In PCB processing, the key factors are cleaning the innerlayer copper surface so that a strong bond can form. In addition, the electroless copper deposit needs to be in good control, having the correct thickness and grain structure, to have the required strength. Testing and experience show a good processing focus, along with appropriate reliability testing can result in consistently robust product.

Design factors also play a big role. As noted above, board thickness and hole size are key factors. These relate to the amount of stress placed upon the interconnect during thermal exposure. Eliminating soldered through-hole connectors is one of the major ways to reduce this issue, as these often contain most of the larger holes. If you need to have thick boards, look into the z-axis CTE and Tg of your material. Lower z-axis CTE values and higher Tg values will result in reduced stress.

With PCB performance requirements constantly on the rise, ICDs will remain an issue. A better understanding of ICDs will help designers reduce the impact that they have on the performance of the board. Better PCB processing practices in drilling and desmear and selecting electroless copper will improve quality. Implementing best practices will reduce opportunities for ICDs, particularly changing connector approaches. Finally, this issue is taken seriously by the PCB suppliers, many of which are working to combat the sources behind ICD failures.

Doug Trobough is the Corporate Director of Application Engineering at Isola Corp. Doug has worked introducing new material introduction and PCB processing enhancement with Isola for five years. Prior to Isola, Doug had almost 30 years of experience building a wide variety of PCB types and interconnections systems, for Tektronix and Merix Corp., in a variety of technical positions, including CTO for Merix Corp. 

This essay appears in Circuit Cellar 300 (July 2015).

Altium Launches Open Beta Program for PCB Design Tool

Altium recenlty announced an open beta program for its community-driven PCB design tool. CircuitMaker is intended to address the unique needs of the electronics maker and hobbyist community with a free software offering. Anyone interested in participating in the open beta can register now at

The open beta testing program enables designers to immediately download and begin using CircuitMaker while joining a collaborative electronics design community. The open beta process will also provide feedback and input to refine CircuitMaker.

CircuitMaker will be available at no cost to anyone interested in using the software, with no limits to design capability. This PCB design tool from Altium offers a polished and streamlined design tool for the maker community with features such as:

  • Comprehensive PCB design technology — Built from the foundation of existing Altium technology, all of the typical features needed for modern PCB design are built in to CircuitMaker. This includes schematic-PCB integration, interactive routing, and output generation tools.
  • Advanced community collaboration — With CircuitMaker, designers have the opportunity to collaborate in a community-driven design environment, with unlimited access to contributed design and component data. This collaboratively design process is made possible by combining an advanced, cloud-based platform and an industry-standard user experience in a native application-based design environment.
  • Streamlined interface — CircuitMaker is a native application, and provides a streamlined interface, allowing new and casual designers to create designs quickly. This removes the traditional, time-intensive learning curve usually required for new PCB design tools.

Open beta registrations for CircuitMaker begins today, and is freely available worldwide to all interested electronics designers. Those interested can register now for the open beta at the CircuitMaker website.

Source: Altium

Workspace for Open-Source Engineering

Christopher Coballes is a Philippines-based freelance R&D engineer and Linux enthusiast with more than a decade of experience in an embedded hardware/software and a passion for an open source design.

The nearby photo shows his home workspace, which includes handy tools such as a spectrum analyzer, digital oscilloscope, and a PCB etcher.

Source: Christopher Coballes

Source: Christopher Coballes

Here are some links to Coballes’s interests and work:

  • Engineering blog
  • Hi-Techno Barrio: A group of Filipino electronics enthusiasts who “aim to uncover the complexity of a modern technology and in turn make it simple, beneficial ,low-cost and free-ware resources.”

View other electrical engineering workspaces.

Automatic 3-D Data Conversion and 3D-MID Prototyping

Beta LAYOUT recently announced it is introducing 3D-MID prototypes. Molded Interconnect Device (MID) is the production of moldings with integrated conductive structures.BetaLayoutPCB

“In mass production, these moldings are manufactured using injection molding techniques, for prototyping purposes this method is not economically feasible,” Beta LAYOUT stated in a release.

In the near future, Beta LAYOUT will offer the ability to manufacture MID components in prototype and small batch quantities, including the production of formed components by 3-D printing, metallic coating, laser patterning, selective metallization, and mounting. Start of production is planned for the second quarter of 2015. For design of 3D-MID components, developers can download the free PCB – POOL edition of layout software TARGET 3001.

With “brd – to – 3D,” Beta LAYOUT offers a comprehensive 3-D package. The complete virtual circuit board package can be created directly from an EAGLE *.brd file. Features include photo realistic images of the PCB, SMD stencil and STEP file generation. In addition, a freely rotatable 3-D view in PDF format is created, which you can view with Adobe Reader. A link to order a laser sintered 3-D model of the assembled PCB is provided and a free 3-D model is offered with PCB-POOL prototype orders and can be used effectively for collision checking.

Visit Beta LAYOUT in hall A2, booth 357 at the upcoming Electronica trade show in Munich (November 11–14, 2014) for information on 3D-MID prototypes and other products.

Source: Beta LAYOUT

Bluetooth Haptic Kit

Texas Instruments recently introduced an innovative wireless haptic development kit. The DRV2605EVM-BT haptic Bluetooth kit comprises a 32-mm square PCB containing a DRV2605 haptic driver chip that controls an eccentric rotating mass motor (ERM) and a linear resonant actuator (LRA) to produce vibrations. The DRV2605 has an integrated library with more than 100 effects licensed from Immersion Corp.

Texas Instruments DRV2605EVM-BT haptic Bluetooth kit

Texas Instruments DRV2605EVM-BT haptic Bluetooth kit

You can use a circle of LEDs to display visual alerts. The board might be useful to speed up development times when designing and testing haptic effects in applications such as: watches, fitness trackers, wearables, portable medical equipment, touch screens, displays, and other devices requiring tactile feedback.

A SimpleLink Bluetooth low-energy CC2541 wireless microcontroller communicates with a free iOS app running on an iPhone or iPad. The app allows you to play predefined library waveforms, create new waveform sequences, and assign waveform sequences to in-app notifications. The app can also be used to quickly configure the DRV2605’s internal register settings: select between an ERM or LRA actuator, set the rated and overdrive voltages, configure and run autocalibration, send direct I2C commands, as well as set up the board to respond to a GPIO trigger.

The DRV2605EVM-BT haptic Bluetooth kit costs $99.

Source: Texas Instruments

Engineering Consultant and Roboticist

Eric Forkosh starting building his first robot when he was a teenager and has been designing ever since. This NYC-based electrical engineer’s projects include everything from dancing robots to remote monitoring devices to cellular module boards to analog signals—Nan Price, Associate Editor

NAN: Tell us about your start-up company, Narobo.


Eric Forkosh

ERIC: Narobo is essentially the company through which I do all my consulting work. I’ve built everything from dancing robots to cellular field equipment. Most recently I’ve been working with some farmers in the Midwest on remote monitoring. We monitor a lot of different things remotely, and I’ve helped develop an online portal and an app. The most interesting feature of our system is that we have a custom tablet rig that can interface directly to the electronics over just the USB connection. We use Google’s Android software development kit to pull that off.

ERIC: The DroneCell was my second official product released, the first being the Roboduino. The Roboduino was relatively simple; it was just a modified Arduino that made building robots easy. We used to sell it online at for a little while, and there was always a trickle of sales, but it was never a huge success. I still get a kick out of seeing Roboduino in projects online, it’s always nice to see people appreciating my work.


The DroneCell is a cellular module board that communicates with devices with TTL UARTs.

The DroneCell is the other product of mine, and my personal favorite. It’s a cellular module board geared toward the hobbyist. A few years ago, if you wanted to add cellular functionality to your system you had to do a custom PCB for it. You had to deal with really low voltage levels, very high peak power draws, and hard-to-read pins. DroneCell solved the problem and made it very easy to interface to hobbyist systems such as the Arduino. Putting on proper power regulation was easy, but my biggest design challenge was how to handle the very low voltage levels. In the end, I put together a very clever voltage shifter that worked with 3V3 and 5 V, with some calculated diodes and resistors.

NAN: Tell us about your first project. Where were you at the time and what did you learn from the experience?


Eric’s Butler robot was his first electronics project. He started building it when he was still in high school.

ERIC: The Butler robot was my first real electronics project. I started building it in ninth grade, and for a really stupid reason. I just wanted to build a personal robot, like on TV. My first version of the Butler robot was cobbled together using an old laptop, a USB-to-I/O converter called Phidgets, and old wheelchair motors I bought on eBay.

I didn’t use anything fancy for this robot, all the software was written in Visual Basic and ran on Windows XP. For motor controllers, I used some old DPDT automotive relays I had lying around. They did the job but obviously I wasn’t able to PWM them for speed control.

My second version came about two years later, and was built with the intention of winning the Instructables Robot contest. I didn’t win first place, but my tutorial “How to Build a Butler Robot” placed in the top 10 and was mentioned in The Instructables Book in print. This version was a cleaner version of everything I had done before. I built a sleek black robot body (at least it was sleek back then!) and fabricated an upside-down bowl-shaped head that housed the webcam. The electronics were basically the same. The main new features were a basic robot arm that poured you a drink (two servos and a large DC motor) and a built-in mini fridge. I also got voice command to work really well by hooking up my Visual Basic software with Dragon’s speech-to-text converter.

The Butler robot was a great project and I learned a lot about electronics and software from doing it. If I were to build a Butler robot right now, I’d do it completely differently. But I think it was an important to my engineering career and it taught me that anything is possible with some hacking and hard work.

At the same time as I was doing my Butler robot (probably around 2008), I lucked out and was hired by an entertainer in Hong Kong. He saw my Butler robot online and hired me to build him a dancing robot that was synced to music. We solved the issue of syncing to music by putting dual-tone multi-frequency (DTMF) tones on the left channel audio and music on the right channel. The right channel went to speakers and the left channel went to a decoder that translated DTMF tone sequences to robot movement. This was good because all the data and dance moves were part of the same audio file. All we had to do was prepare special audio files and the robot would work with any music player (e.g., iPod, laptop, CD, etc.). The robot is used in shows to this day, and my performer client even hired a professional cartoon voice actor to give the robot a personality.

NAN: You were an adjunct professor at the Cooper Union for the Advancement of Science and Art in New York City. What types of courses did you teach and what did you enjoy most about teaching?

ERIC: I will be entering my senior year at Cooper Union in the Fall 2014. Two years ago, I took a year off from school to pursue my work. This past year I completed my junior year. I taught a semester of “Microcontroller Projects” at Cooper Union during my year off from being a student. We built a lot of really great projects using Arduino. One final project that really impressed me was a small robot car that parallel parked itself. Another project was a family of spider robots that were remotely controlled and could shrink up into a ball.

Cooper Union is filled with really bright students and teaching exposed me to the different thought processes people have when trying to build a solution. I think teaching helped me grow as a person and helped me understand that in engineering—and possibly in life—there is no one right answer. There are different paths to the same destination. I really enjoyed teaching because it made me evaluate my understanding about electronics, software, and robotics. It forced me to make sure I really understood what was going on in intricate detail.

NAN: You have competed in robotics competitions including RoboCup in Austria. Tell us about these experiences—what types of robots did you build for the competitions?


Eric worked with his high school’s robotics team to design this robot for a RoboCup competition.

ERIC: In high school I was the robotics team captain and we built a line-following robot and a soccer robot to compete in RoboCup Junior in the US. We won first place in the RoboCup Junior Northeast Regional and were invited to compete in Austria for the International RoboCup Junior games. So we traveled as a team to Austria to compete and we got to see a lot of interesting projects and many other soccer teams compete. I remember the Iranian RoboCup Junior team had a crazy robot that competed against us; it was built out of steel and looked like a miniature tank.

My best memory from Austria was when our robot broke and I had to fix it. Our robot was omnidirectional with four omni wheels in each corner that let it drive at any angle or orientation it wanted. It could zigzag across the field without a problem. At our first match, I put the robot down on the little soccer field to compete… and it wouldn’t move. During transportation, one of the motors broke. Disappointed, we had to forfeit that match. But I didn’t give up. I removed one of the wheels and rewrote the code to operate with only three motors functional. Again we tried to compete, and again another motor appeared to be broken. I removed yet another wheel and stuck a bottle cap as a caster wheel on the back. I rewrote the code, which was running on a little Microchip Technology PIC microcontroller, and programmed the robot to operate with only two wheels working. The crippled robot put up a good fight, but unfortunately it wasn’t enough. I think we scored one goal total, and that was when the robot had just two wheels working.

After the competition, during an interview with the judges, we had a laugh comparing our disabled robot to the videos we took back home with the robot scoring goal after goal. I learned from that incident to always be prepared for the worst, do your best, and sometimes stuff just happens. I’m happy I tried and did my best to fix it, I have no regrets. I have a some of the gears from that robot at home on display as a reminder to always prepare for emergencies and to always try my best.

NAN: What was the last electronics-design related product you purchased and what type of project did you use it with?

ERIC: The last product would be an op-amp I bought, probably the 411 chip. For a current project, I had to generate a –5-to-5-V analog signal from a microcontroller. My temporary solution was to RC filter the PWM output from the op-amp and then use an amplifier with a
gain of 2 and a 2.5-V “virtual ground.” The result is that 2.5 V is the new “zero” voltage. You can achieve –5 V by giving the op-amp 0 V, a –2.5-V difference that is amplified by 2 to yield 5 V. Similarly, 5 V is a 2.5-V difference from the virtual ground, amplified by 2 it provides a 5-V output.

NAN: What do you consider to be the “next big thing” in the industry?

ERIC: I think the next big thing will be personalized health care via smartphones. There are already some insulin pumps and heart monitors that communicate with special smartphone apps via Bluetooth. I think that’s excellent. We have all this computing power in our pockets, we should put it to good use. It would be nice to see these apps educating smartphone users—the patients themselves— about their current health condition. It might inspire patients/users to live healthier lifestyles and take care of themselves. I don’t think the FDA is completely there yet, but I’m excited to see what the future will bring. Remember, the future is what you build it to be.

Experimentation and Engineering

Frederic Vecoven is software engineer living in Luxembourg who enjoys experimenting with everything from his home’s central heating controller to FPGAs. He has been designing micrcontroller-based projects for more than a dozen years and is currently working on an EPROM emulator.—Nan Price, Associate Editor


NAN: What is your current occupation?

FREDERIC:: I am a software principal engineer at Oracle.

NAN: Your website features projects involving capacitors, microcontrollers, and EEPROM and hardware emulators. Tell us a little about the projects and your design process.

vecovenFREDERIC: At work I design firmware for high-end servers. At home I like to design my own stuff, so I have full control and can create new devices and/or enhance existing ones. I work on various projects and I don’t find enough time to document all of them on the website. For example, I designed a controller for the central heating in my house, but never documented it (it’s too “custom”). I love retrocomputing, which is how my FreHD project started. This is a hard-drive emulator for TRS-80 computers.

My design process starts from an idea (I have too many, so I must carefully select one) then a lot of thinking about the future implementation (as always, designing something is about compromises). Once I have a clear view in my mind about how things should work, I start prototyping. If possible, I use a breadboard or I create a PCB. Sometimes I do a lot of simulation before starting the prototyping, as this will save a lot of time. However, that cannot be done for all projects.

NAN: How long have you been designing microcontroller-based systems?

FREDERIC: More than 15 years.

NAN: How did you become interested in technology?

FREDERIC: When I was 13 years old I fell in love with computers when I saw a TRS-80 model in high school. I am thankful to my parents, who gave me a computer one year later.
I went to college and got a master’s degree in computer science. But I wasn’t satisfied, so I studied some more years to get another master’s degree, this time in electrical engineering. The combination of software and hardware is really powerful. A few years later, I relocated to the San Francisco Bay Area, but I am back in Europe now.

NAN: Describe the first embedded system you designed. Where were you at the time? What did you learn from the experience?

FREDERIC: My first big experience with a real embedded system was when I was working for Sun Microsystems. My group was writing the firmware for the system controllers of the SunFire 3800-6900 line. The embedded system was a small SPARC CPU running Wind River Systems’s VxWorks and the firmware was almost entirely written in Java.

NAN: What was the last electronics design-related product you purchased and how did you use it?

FREDERIC: I bought some FPGAs recently. I haven’t released any project with it yet, it is still a work in progress. My hobby time is very limited.

My idea is to use a CPU core and enhance it with new instructions to enable the generation of real-time signals. FPGAs are very powerful in that area, where a microcontroller would spend most of its time processing interrupts.

NAN: Are you currently working on or planning any projects?


This is Frederic’s PWM prototype for his Roland Super JX synthesizer.

FREDERIC: Yes, I have rewritten the Roland JX-10/MKS-70 firmware from scratch because I wanted to add PWM waveforms. This quickly turned into a big project. Currently, the prototype setup involves a simulator running the “assigner” code on my laptop. The laptop sends the sound board commands in System Exclusive (SysEx) Musical Instrument Digital Interface (MIDI) messages, which go to a microcontroller that extracts the payload from the SysEx. The payload is then sent to the sound board, which believes it got its instructions directly from the assigner. The sound board (which runs its own microcontroller) uses an EPROM emulator connected over USB, so I can easily modify the assigner code (running in the simulator) or the sound board code (running in the EPROM emulator) without having to program any chip. Note that I didn’t have an EPROM emulator, so I designed mine.


This oscilloscope capture shows the generated PWM signal.

FREDERIC: The power of CPUs and GPUs are really exciting. You can pretty much do everything with software now (a 32-bit core costs less than $5).
On the other side, people don’t pay enough attention to optimization, so I am sad anytime I see poorly written code. I am also excited with all the tools and hardware available today for so little cost. That wasn’t the case in the past, so it opens door to students and hobbyists.

NAN: Last question. Let’s say you had a full year and a nice budget to work on any embedded design project you wanted. Call it your “dream project.” What would it be?

FREDERIC: I would love to do some robotic design, but I am not an expert in mechanics and I don’t have the tools (e.g., lathe, milling machine, etc.). That would fill the gap: hardware, software, and mechanics.

Build an Adequate Test Bench (EE Tip #127)

It’s in our makeup as engineers that we want to test our newly received boards as soon as possible. We just can’t wait to connect them to a power supply and then use our test bench equipment (e.g., generators, oscilloscopes, switches or LEDs, and so on) for simulation.

Circuit Cellar columnist Robert Lacoste's workspace in Chaville, France.

Circuit Cellar columnist Robert Lacoste’s clean, orderly workspace in Chaville, France.

But due to our haste, the result is usually a PCB under test lying on a crowded workbench in the middle of a mesh of test cables, alligator clamps, prototyping boards, and other probes. Experience shows that the probability of a short circuit or mismatched connection is high during this phase of engineering excitement.

Test Board

Rather than requiring a mesh of test wires, it is often wise to develop a small test PCB that will drastically simplify the test phase. Here the ancillary board provided a clean way to connect a Microchip Technology ICD3 debugger, a JTAG emulator, a debug analyzer, and a power supply input.

Take your time: prepare a real test bench to which you can connect your board. It could be as simple as a clean desk with properly labeled wires, but you might also need to anticipate the design of a test PCB in order to simplify the cabling.—Robert Lacoste, “Mixed-Signal Designs,” CC25:25th Anniversary Issue, 2013. 


Q&A: Hacker, Roboticist, and Website Host

Dean “Dino” Segovis is a self-taught hardware hacker and maker from Pinehurst, NC. In 2011, he developed the Hack A Week website, where he challenges himself to create and post weekly DIY projects. Dino and I recently talked about some of his favorite projects and products. —Nan Price, Associate Editor


NAN: You have been posting a weekly project on your website, Hack A Week, for almost three years. Why did you decide to create the website?

Dean "Dino" Segovis at his workbench

Dean “Dino” Segovis at his workbench

DINO: One day on the Hack A Day website I saw a post that caught my attention. It was seeking a person to fill a potential position as a weekly project builder and video blogger. It was offering a salary of $35,000 a year, which was pretty slim considering you had to live in Santa Monica, CA. I thought, “I could do that, but not for $35,000 a year.”

That day I decided I was going to challenge myself to come up with a project and video each week and see if I could do it for at least one year. I came up with a simple domain name,, bought it, and put up a website within 24 h.

My first project was a 555 timer-based project that I posted on April 1, 2011, on my YouTube channel, “Hack A Week TV.” I made it through the first year and just kept going. I currently have more than 3.2 million video views and more than 19,000 subscribers from all over the world.

NAN: Hack A Week features quite a few robotics projects. How are the robots built? Do you have a favorite?

rumblebot head

Dino’s very first toy robot hack was the Rumble robot. The robot featured an Arduino that sent PWM to the on-board H-bridge in the toy to control the motors for tank steering. A single PING))) sensor helped with navigation.

Rumble robot

The Rumble robot

DINO: I usually use an Arduino as the robot’s controller and Roomba gear motors for locomotion. I have built a few others based on existing wheeled motorized toys and I’ve made a few with the Parallax Propeller chip.

My “go-to” sensor is usually the Parallax PING))) ultrasonic sensor. It’s easy to connect and work with and the code is straightforward. I also use bump sensors, which are just simple contact switches, because they mimic the way some insects navigate.

Nature is a great designer and much can be learned from observing it. I like to keep my engineering simple because it’s robust and easy to repair. The more you complicate a design, the more it can do. But it also becomes more likely that something will fail. Failure is not a bad thing if it leads to a better design that overcomes the failure. Good design is a balance of these things. This is why I leave my failures and mistakes in my videos to show how I arrive at the end result through some trial and error.

My favorite robot would be “Photon: The Video and Photo Robot” that I built for the 2013 North Carolina Maker Faire. It’s my masterpiece robot…so far.

NAN: Tell us a little more about Photon. Did you encounter any challenges while developing the robot?

Photon awaits with cameras rolling, ready to go forth and record images.

Photon awaits with cameras rolling, ready to go forth and record images.

DINO: The idea for Photon first came to me in February 2013. I had been playing with the Emic 2 text-to-speech module from Parallax and I thought it would be fun to use it to give a robot speech capability. From there the idea grew to include cameras that would record and stream to the Internet what the robot saw and then give the robot the ability to navigate through the crowd at Maker Faire.

I got a late start on the project and ended up burning the midnight oil to get it finished in time. One of the bigger challenges was in designing a motorized base that would reliably move Photon across a cement floor.

The problem was in dealing with elevation changes on the floor covering. What if Photon encountered a rug or an extension cord?

I wanted to drive it with two gear motors salvaged from a Roomba 4000 vacuum robot to enable tank-style steering. A large round base with a caster at the front and rear worked well, but it would only enable a small change in surface elevation. I ended up using that design and made sure that it stayed away from anything that might get it in trouble.

The next challenge was giving Photon some sensors so it could navigate and stay away from obstacles. I used one PING))) sensor mounted on its head and turned the entire torso into a four-zone bump sensor, as was a ring around the base. The ring pushed on a series of 42 momentary contact switches connected together in four zones. All these sensors were connected to an Arduino running some simple code that turned Photon away from obstacles it encountered. Power was supplied by a motorcycle battery mounted on the base inside the torso.

The head held two video cameras, two smartphones in camera mode, and one GoPro camera. One video camera and the GoPro were recording in HD; the other video camera was recording in time-lapse mode. The two smartphones streamed live video, one via 4G to a Ustream channel and the other via Wi-Fi. The Ustream worked great, but the Wi-Fi failed due to interference.

Photon’s voice came from the Emic 2 connected to another Arduino sending it lines of text to speak. The audio was amplified by a small 0.5-W LM386 amplifier driving a 4” speaker. An array of blue LEDs mounted on the head illuminated with the brightness modulated by the audio signal when Photon spoke. The speech was just a lot of lines of text running in a timed loop.

Photon’s brain includes two Arduinos and an LM386 0.5-W audio amplifier with a sound-to-voltage circuit added to drive the mouth LED array. Photon’s voice comes from a Parallax Emic 2 text-to-speech module.

Photon’s brain includes two Arduinos and an LM386 0.5-W audio amplifier with a sound-to-voltage circuit added to drive the mouth LED array. Photon’s voice comes from a Parallax Emic 2 text-to-speech module.

Connecting all of these things together was very challenging. Each component needed a regulated power supply, which I built using LM317T voltage regulators. The entire current draw with motors running was about 1.5 A. The battery lasted about 1.5 h before needing a recharge. I had an extra battery so I could just swap them out during the quick charge cycle and keep downtime to a minimum.

I finished the robot around 11:00 PM the night before the event. It was a hit! The videos Photon recorded are fascinating to watch. The look of wonder on people’s faces, the kids jumping up to see themselves in the monitors, the smiles, and the interaction are all very interesting.

NAN: Many of your Hack A Week projects include Parallax products. Why Parallax?

DINO: Parallax is a great electronics company that caters to the DIY hobbyist. It has a large knowledge base on its website as well as a great forum with lots of people willing to help and share their projects.

About a year ago Parallax approached me with an offer to supply me with a product in exchange for featuring it in my video projects on Hack A Week. Since I already used and liked the product, it was a perfect offer. I’ll be posting more Parallax-based projects throughout the year and showcasing a few of them on the ELEV-8 quadcopter as a test platform.

NAN: Let’s change topics. You built an Electronic Fuel Injector Tester, which is featured on Can you explain how the 555 timer chips are used in the tester?

DINO: 555 timers are great! They can be used in so many projects in so many ways. They’re easy to understand and use and require only a minimum of external components to operate and configure.

The 555 can run in two basic modes: monostable and astable.

Dino keeps this fuel injector tester in his tool box at work. He’s a European auto technician by day.

Dino keeps this fuel injector tester in his tool box at work. He’s a European auto technician by day.

An astable circuit produces a square wave. This is a digital waveform with sharp transitions between low (0 V) and high (+ V). The durations of the low and high states may be different. The circuit is called astable because it is not stable in any state: the output is continually changing between “low” and “high.”

A monostable circuit produces a single output pulse when triggered. It is called a monostable because it is stable in just one state: “output low.” The “output high” state is temporary.

The injector tester, which is a monostable circuit, is triggered by pressing the momentary contact switch. The single-output pulse turns on an astable circuit that outputs a square-wave pulse train that is routed to an N-channel MOSFET. The MOSFET turns on and off and outputs 12 V to the injector. A flyback diode protects the MOSFET from the electrical pulse that comes from the injector coil when the power is turned off and the field collapses. It’s a simple circuit that can drive any injector up to 5 A.

This is a homebrew PCB for Dino's fuel injector tester. Two 555s drive a MOSFET that switches the injector.

This is a homebrew PCB for Dino’s fuel injector tester. Two 555s drive a MOSFET that switches the injector.

NAN: You’ve been “DIYing” for quite some time. How and when did your interest begin?

DINO: It all started in 1973 when I was 13 years old. I used to watch a TV show on PBS called ZOOM, which was produced by WGBH in Boston. Each week they had a DIY project they called a “Zoom-Do,” and one week the project was a crystal radio. I ordered the Zoom-Do instruction card and set out to build one. I got everything put together but it didn’t work! I checked and rechecked everything, but it just wouldn’t work.

I later realized why. The instructions said to use a “cat’s whisker,” which I later found out was a thin piece of wire. I used a real cat’s whisker clipped from my cat! Anyway, that project sparked something inside me (pun intended). I was hooked! I started going house to house asking people if they had any broken or unwanted radios and or TVs I could have so I could learn about electronics and I got tons of free stuff to mess with.

My mom and dad were pretty cool about letting me experiment with it all. I was taking apart TV sets, radios, and tape recorders in my room and actually fixing a few of them. I was in love with electronics. I had an intuition for understanding it. I eventually found some ham radio guys who were great mentors and I learned a lot of good basic electronics from them.

NAN: Is there a particular electronics engineer, programmer, or designer who has inspired the work you do today?

DINO: Forrest Mims was a great inspiration in my early 20s. I got a big boost from his “Engineer’s Notebooks.” The simple way he explained things and his use of graph paper to draw circuit designs really made learning about electronics easy and fun. I still use graph paper to draw my schematics during the design phase and for planning when building a prototype on perf board. I’m not interested in any of the software schematic programs because most of my projects are simple and easy to draw. I like my pencil-and-paper approach.

NAN: What was the last electronics-design related product you purchased and what type of project did you use it with?

DINO: An Arduino Uno. I used two of these in the Photon robot.

NAN: What new technologies excite you and why?

DINO: Organic light-emitting diodes (OLEDs). They’ll totally change the way we manufacture and use digital displays.

I envision a day when you can go buy your big-screen TV that you’ll bring home in a cardboard tube, unroll it, and place it on the wall. The processor and power supply will reside on the floor, out of the way, and a single cable will go to the panel. The power consumption will be a fraction of today’s LCD or plasma displays and they’ll be featherweight by comparison. They’ll be used to display advertising on curved surfaces anywhere you like. Cell phone displays will be curved and flexible.

How about a panoramic set of virtual reality goggles or a curved display in a flight simulator? Once the technology gets out of the “early adopter” phase, prices will come down and you’ll own that huge TV for a fraction of what you pay now. One day we might even go to a movie and view it on a super-huge OLED panorama screen.

NAN: Final question. If you had a full year and a good budget to work on any design project you wanted, what would you build?

DINO: There’s a project I’ve wanted to build for some time now: A flight simulator based on the one used in Google Earth. I would use a PC to run the simulator and build a full-on seat-inside enclosure with all the controls you would have in a jet airplane. There are a lot of keyboard shortcuts for a Google flight simulator that could be triggered by switches connected to various controls (e.g., rudder pedals, flaps, landing gear, trim tabs, throttle, etc.). I would use the Arduino Leonardo as the controller for the peripheral switches because it can emulate a USB keyboard. Just program it, plug it into a USB port along with a joystick, build a multi-panel display (or use that OLED display I dream of), and go fly!

Google Earth’s flight simulator also lets you fly over the surface of Mars! Not only would this be fun to build and fly, it would also be a great educational tool. It’s definitely on the Hack A Week project list!

Editor’s Note: This article also appears in the Circuit Cellar’s upcoming March issue, which focuses on robotics. The March issue will soon be available for membership download or single-issue purchase.


Arduino MOSFET-Based Power Switch

Circuit Cellar columnist Ed Nisley has used Arduino SBCs in many projects over the years. He has found them perfect for one-off designs and prototypes, since the board’s all-in-one layout includes a micrcontroller with USB connectivity, simple connectors, and a power regulator.

But the standard Arduino presents some design limitations.

“The on-board regulator can be either a blessing or a curse, depending on the application. Although the board will run from an unregulated supply and you can power additional circuitry from the regulator, the minute PCB heatsink drastically limits the available current,” Nisley says. “Worse, putting the microcontroller into one of its sleep modes doesn’t shut off the rest of the Arduino PCB or your added circuits, so a standard Arduino board isn’t suitable for battery-powered applications.”

In Circuit Cellar’s January issue, Nisley presents a MOSFET-based power switch that addresses such concerns. He also refers to one of his own projects where it would be helpful.

“The low-resistance Hall effect current sensor that I described in my November 2013 column should be useful in a bright bicycle taillight, but only if there’s a way to turn everything off after the ride without flipping a mechanical switch…,” Nisley says. “Of course, I could build a custom microcontroller circuit, but it’s much easier to drop an Arduino Pro Mini board atop the more interesting analog circuitry.”

Nisley’s January article describes “a simple MOSFET-based power switch that turns on with a push button and turns off under program control: the Arduino can shut itself off and reduce the battery drain to nearly zero.”

Readers should find the article’s information and circuitry design helpful in other applications requiring automatic shutoff, “even if they’re not running from battery power,” Nisley says.

Figure 1: This SPICE simulation models a power p-MOSFET with a logic-level gate controlling the current from the battery to C1 and R2, which simulate a 500-mA load that is far below Q2’s rating. S1, a voltage-controlled switch, mimics an ordinary push button. Q1 isolates the Arduino digital output pin from the raw battery voltage.

Figure 1: This SPICE simulation models a power p-MOSFET with a logic-level gate controlling the current from the battery to C1 and R2, which simulate a 500-mA load that is far below Q2’s rating. S1, a voltage-controlled switch, mimics an ordinary push button. Q1 isolates the Arduino digital output pin from the raw battery voltage.

The article takes readers from SPICE modeling of the circuitry (see Figure 1) through developing a schematic and building a hardware prototype.

“The PCB in Photo 1 combines the p-MOSFET power switch from Figure 2 with a Hall effect current sensor, a pair of PWM-controlled n-MOFSETs, and an Arduino Pro Mini into

The power switch components occupy the upper left corner of the PCB, with the Hall effect current sensor near the middle and the Arduino Pro Mini board to the upper right. The 3-D printed red frame stiffens the circuit board during construction.

Photo 1: The power switch components occupy the upper left corner of the PCB, with the Hall effect current sensor near the middle and the Arduino Pro Mini board to the upper right. The 3-D printed red frame stiffens the circuit board during construction.

a brassboard layout,” Nisley says. “It’s one step beyond the breadboard hairball I showed in my article “Low-Loss Hall Effect Current Sensing” (Circuit Cellar 280, 2013), and will help verify that all the components operate properly on a real circuit board with a good layout.”

For much more detail about the verification process, PCB design, Arduino interface, and more, download the January issue.

The actual circuit schematic includes the same parts as the SPICE schematic, plus the assortment of connectors and jumpers required to actually build the PCB shown in Photo 1.

Figure 2: The actual circuit schematic includes the same parts as the SPICE schematic, as well as the assortment of connectors and jumpers required to actually build the PCB shown in Photo 1.

PCB Design Guidelines (EE Tips #113)

Designing a matching printed circuit board (PCB) can be a challenge for many electronics enthusiasts. To help ease the process, Circuit Cellar and Elektor editors compiled a list of tips for laying out components, routing, and more.PCB1

  • When compactness is not a major consideration and the boards will be assembled by hand, through-hole components are the better choice. In this case you can use the pins of these components as “vias.”
  • On the other hand, surface-mount components can save a whole load of drilling on self-made PCBs. They make it simpler to achieve objectives such as minimum length for traces , minimal area inside trace loops, etc.
  • The orientation of components should consider not only simplicity of assembly but also the need to test the circuitry afterward. This is the time to remember the need for test points!
  • The place for switches, press buttons, plug-in connectors, LEDs and other user-interface components is outside the enclosure. Anything requiring subsequent access should be on the front panel of the case.
  • Components that require assembling with the right polarity should all have the same orientation.
  • Manual routing is preferable to using the autorouter. The latter has its uses nevertheless for discovering bottlenecks and other critical points.
  • When routing, never even think about giving up! Many PCBs appear “unroutable” at the outset, yet after a while it turns out you have plenty of space to spare.
  • If you’re not satisfied with your efforts, it’s better to go back a step or two rather than just muddle onwards.
  • Complete the routing for each of the functional groups of the circuit first. Link the groups together only after you have finished this stage.
  • Short traces are better than long ones. High impedance connections are more sensitive to interference and for this reason require to be kept as short as possible.
  • Where traces form a loop, their surface area should be kept to an absolute minimum.
  • Decoupling capacitors must be located as close as possible to the switching element that needs to be decoupled.
  • Traces carrying signals should be routed early on (first the short ones, then the long ones). Except, that is, when the power supply traces are particularly critical.
  • Bus lines should be routed alongside one another.
  • Separate analog circuitry from digital whenever possible.PCB2
  • On multilayer boards arrange traces carrying signals so that one of the layers hosts the vertical traces and another one accommodates the horizontal ones.
  • If possible, reserve one layer or side exclusively for a continuous ground plane. Only in exceptional situations, e.g. with high speed op-amps, is this undesirable.
  • Keep traces carrying heavy currents well away from sensitive pickups, sensors and so on.
  • Beginners should take special care with mains and high voltages!
  • Ground and earth traces require exactly the same consideration as the power supply traces. Electromagnetic interference can be minimized by keeping the power and ground traces parallel (or better still arranged over each other on either side of a double-sided board).
  • Bends should be no more than 45°. Sharp angles between the traces and the pads are also to be avoided.
  • Observe PCB manufacturers’ requirements without exception in order to avoid unpleasant surprises later.
  • If you are using software for checking conformity to specifications, carry out these checks regularly at each design phase.
  • A border of 0.12″ (approximately 3 mm) around the edge of the PCB should be kept entirely clear of components.
  • If components are to be inserted by machine you must provide at least three location marks.
  • Don’t forget the holes for fixing screws or pillars!
  • Don’t skimp on text markings on the PCB: indicate polarity, voltages, on-board functions, part designation, design date, version number…
  • Check not just twice but three times that all components will actually fit the PCB!
  • Leave time at the end of the process for tidying up and optimizing.

Good luck!