It’s no secret that the Arduino development board has changed the way we look at working with electronics. All over the world, the little board has enabled millions of engineers, students, artists, and makers to get electronics projects up and going. We recently traveled to DotDotDot in Milan, Italy, to chat with Arduino codeveloper Massimo Banzi, who talked about the history of Arduino, the importance of makerspaces, and more.
The proliferation of open-source hardware and software has made do-it-yourself electronics accessible to both professional electrical engineers and newbies. Today we’re just at the start of an exciting DIY revolution that promises innovation, adventure, and new social, creative, and business opportunities. How will you get involved? In this essay, Adafruit founder Limor Fried offers her thoughts on the present and future of open-source technology.
I’m an MIT-trained electrical engineer and founder of Adafruit Industries, an open-source hardware (OSH) company in New York City. Normally, I tell people that we design and manufacture electronic gadgets—mostly kits and parts for students who are learning to become engineers—or project packs for people who didn’t realize that they wanted to get into electronics. But really what we do is teach, and we do that by creating OSH. Every design we make is fully documented and given away for free—to anyone, for any purpose. But we also sell completely assembled designs as products. Most people just buy from the Adafruit store or from one of our many distributors, but there are still thousands who look at what we create as points of origin for their own businesses or products.
Another way to put it: we’re basically like a test kitchen with a restaurant attached to it. We come up with new dishes, write the recipes up for others to follow at home (or in their own restaurants), and also serve up the dishes to those who don’t have all the equipment and ingredients—they just want to chow down. Other aspiring chefs look at our videos and recipes and adapt them for their own kitchens all over the world. And, once in a while, those same cooks turn around and give away one of their techniques or recipes to the community. Not everyone gives back, but that’s OK. Enough people contribute to create a vibrant culture of sharing.
The best part about talking about OSH is how easy it is. So much has happened with OSH in the last few years that it’s not like I need to sell a pipe dream. It’s not some “experimental future” or “speculative fiction” about what could occur. OSH is already happening, so all I have to do to predict its future is to accurately describe what’s going on right now. But first, a brief introduction.
Nearly everyone knows about open-source software (OSS). Sure, you may not be a coder, but you’ve used the Internet, which is pretty much fully made of OSS: websites running the ubiquitous Apache webserver software, displaying customized sites written in Ruby or PHP, drawing on pools of data stored in MySQL databases all running on server computers running the open-source Linux operating system.
The fantastic thing about all this free OSS is how it has helped proliferate the Internet, improving the functionality of the web through rapid mutations in code (that’s the free-as-in-speech part) and driving down the cost to commodity levels (that’s the free-as-in-beer part). The commodification of the Internet—that is, the marginal cost of an blog or email account is so low that it’s essentially free—and indeed nearly all computer software and hardware would not be possible without OSS.
OK, so that’s the state of the Internet as of circa 1995. Although the details have evolved, the essence of OSS is the same. But something interesting started happening a few years ago in the hardware world (i.e., atoms instead of bits): stuff started getting both complex and cheap. Suddenly, everything had a microcomputer inside of it, and if you had a microcomputer, you needed data to crunch. The market for sensors—what would normally be shoved into extremely expensive military hardware—started ballooning. (When I was in college, a triple-axis accelerometer motion sensor would cost $60. Now it costs less than $1.) Once low-cost sensors and easily reprogrammable logic chips started flooding the market, online communities of engineering geeks started to take notice. Engineers start using what they had learned at work to build hobby projects. The parts were finally cheap enough. And as a result, they started laying down the groundwork: compilers, simulators, and toolchains. That was the mid-1990s. Soon thereafter, geek artists started taking a look and liked what they saw. They started designing interactive art, building on some of the great electronic art concepts of the 1970s. And finally, non-geeks had a crack at it. Complex electronics and electrical engineering went from something requiring years of differential equations to weekend fun.
While all this was happening, something cool began occurring. Just as code geeks created OSS to help commodify the Internet, solder geeks decided to apply the same principles to the creation of hardware (both mechanical and electronic). They started sharing schematics, CAD files, and layouts on social websites. Today, designers use a variety of sites (e.g., Instructables.com, Thingiverse.com, and LetsMakeRobots.com) and via various social services (e.g., Flickr, Twitter, Facebook, and Google+) to give away inventions and post tutorials and instructions for free.
The Proliferation of OSH
The first response we can have is this: OK. Free and OSS erased the costs of software while also increasing demand (and thus lowering the price) for desktop computers. Then followed laptops (say, OLPC, which runs exclusively OSS) and finally cell phones (e.g., Android). So, we’ll also see OSH reduce costs and simultaneously speed up iterations of new and better devices by separating the IP control (say, patents) from the ability to manufacture.
There’s also another response we can take to the proliferation of OSH. Not only is it making it easier than ever to design and manufacture original products to fit a group’s needs, it’s also providing a broad curriculum to the world. Someone who has the desire to learn how to build and repair electronics will not learn much by taking apart a modern cell phone—everything is too small, poorly documented, and hidden. But with OSH, documentation is an essential part of the process—describing why a certain component is chosen and possible alternatives gives insight. The student is empowered to trace the design from thought-process to mathematical analysis to specifications to fabrication.
Let’s consider some examples of what is happening in OSH right now. First of all, I’m sure you’ve already heard about 3-D printing from MakerBot. It used to be a technology only available to high-end prototyping houses that could spend the tens of thousands of dollars on both machinery and upkeep. But then about five years ago, a few different groups such as Fab@Home and RepRap decided they wanted create low-cost home versions as well as make the projects OSH. So they gave away all the plans with the hopes that others would build, improve, and proliferate the basic plan of low-cost 3-D printing. Now there are over 100 low-cost 3-D printer design variations available for anyone to make. In addition, a massive community is constantly improving the quality, lowering the price, and simplifying things. It’s possible that within a few years we could see 3-D printers that cost $100 and are built of common hardware store parts.
Another example that has promise is the Global Village Construction Set, which is a “manual” of simple, easy-to-repair construction equipment. Instead of high-cost specialized tools from John Deere or Caterpillar, each of a dozen machines can be fabricated using basic steel welding, electrical wiring, and some basic common components. The hope is not that it would replace the many powered tools already available, but that it would enable people to approach the design of new tools without fear that they had nowhere to start from. That is to say, by being broad and simple, it can encourage specialization when needed, whereas most equipment manufacturers would not be interested in selling something unless they had tens of thousands of customers.
Finally, one of my favorite projects is the Dili Village Telco project. There are no phone lines in the East Timor village. There is a cell network, but it’s expensive and not very useful for making calls within the village. David Rowe, a telephony engineer, designed a sort of “micro cell” so that the Timorese in the village could use regular phones to call each other, basically like a little version of AT&T. Rowe designed the very complex hardware, which not only has to work but also has to work well in the difficult environment of a village without cables or consistent power. What I thought was most interesting about the project is how he was giving away the years’ worth of work, posting up schematics, DSP code, filters, and more with the hope that some company would come by and rip him off. The best thing that could happen for the project is to have the design mass manufactured because then he could get on with the work of deploying and configuring the network boxes instead of figuring out how to get them made.
The Speed & Power of OSH
Now I’ll share personal example of the speed and power of open-source hardware and software. About a year ago, I was mucking about with trying to design a low-cost, high-efficiency solar battery charger. Solar panels are really annoying to deal with, and although there are lots of off-the-shelf solutions for big solar panels—say, over 50 W—there isn’t a lot available for 5 W or under. I ended up designing what I thought was a pretty clever battery charger that used off-the-shelf parts and then began selling it in the Adafruit store. A few months later, I got an e-mail from a fellow who had designed a solar-powered cell phone charger and liked the design and efficiency. He had a Kickstarter going to sell them, and just wanted me to know that he had taken the design and remixed it. Some people would consider such a scenario a nightmare: I spent months in the sun tweaking the design and some guy just rips it off to make money. But I thought it was great. In fact, nothing would make me happier than to hear that every design I’ve worked on and published was used to create a useful product.
Share Knowledge, Share Success
So, on to the future! One thing that makes me most excited is the proliferation of low-cost cell phones that are easy to program (Android in particular). Once you take a programmable cell phone and connect ultra-low-cost sensors, you’ve got a global sensor network—a very powerful tool that enables anyone to measure and monitor the environment.
More sensors, more things talking. You’ll hear about the “Internet of Things” a lot more in the future. A lot of OSH makers cross-pollinate from hobbyist projects to manufacturer products to other industries. For instance, you’ll see medical devices get smarter. Quickly being able to pull from a library of open-source projects and make a Kickstarter or some other crowd-funded service will lower the entry barrier for many engineers and makers. Sure, there are challenges once you actually get the funding, but it’s never been a better time to work on OSH and get your designs out there. Previously, capital needed to be raised via venture capitalists, loans, or friends and family.
What I like about the future of electronics—and DIY electronics in particular—is that it’s more than just about the physical bits. The OSH movement has a built-in cause: sharing knowledge. If we can all provide a little more value when we make something, we can develop more things by standing on each other’s shoulders and make more engineers who share the same values.
Limor Fried founded Adafruit Industries in 2005. She earned a Bachelor’s in EECS and a Master’s of Engineering from MIT This essay first appeared in CC25 (2011).
Bernard Hiew sure knows how to get the most of his Penang, Malaysia-based “humble” electrical engineering workspace. He turned the third room of his apartment into a complete innovation space that’s used for everything from engineering to 3-D printing to playing music to woodworking.
I spend my most of my time here, my little humble workspace. This room is not a dedicated workshop at somewhere else but is in my house. Half of the room is my workspace … The other half of the room is the main table where we do most of office work and surfing. Recently my wife is working from home, so she is occupying this table most of the time.
Hiew proves that with a little planning and ingenuity, you can create a fully functional workspace complete with essential engineering equipment and tools. His space includes a soldering station, a PCB UV box, multimeter, power station, computer, book shelves, and even a couch for relaxing and playing music. He also makes great use of storage containers for his electrical components.
In the spirit of DIY engineering and solar power innovation, we’re re-releasing Circuit Cellar founder Steve Ciaria’s three-part series, “Solar-Powering the Circuit Cellar.”
An excerpt from the first article in the series appears below. And for a limited time, you can download the entire series for free. Enjoy!
The photos show the roof-mounted solar panels that produce approximately 40% of the total PV power. I know it sounds like a joke that the first PV system consideration is walking around the house and looking for the sun, but you can’t generate much energy if your panels are always shaded. When you live in the middle of the woods, finding the sun is often easier said than done.
Array orientation determines how much energy you can produce. Solar panels are typically aimed due south at a specific tilt angle that optimizes the incidence angle of the sunlight striking the panel. Maximum energy is produced when this tilt angle is equal to the latitude of the location (reduced by a location correction factor). Typically, the optimal tilt angle during the summer is the latitude minus 15°, and the optimal angle for the winter is the latitude plus 15°. Hartford, CT, is located at 42° latitude and the optimum tilt angle (minus an 8° correction factor) ranges from 19° in the summer (34° – 15°) to 49° in the winter (34° + 15°). The Connecticut rebate program suggests that if a fixed tilt is used, it be set at 35°. Of course, these are computer-generated optimizations that don’t necessarily accommodate real-world conditions. While it requires some nontrivial computer calculations to show authenticity, it is my understanding that as long as the non-optimal differences in azimuth and tilt are less than 20°, the loss in maximum power production is typically only about 5%. It is exactly for that reason that the most cost-effective PV installation is typically a fixed-pitch roof-mounted array.
My system includes both variable and fixed-pitch arrays. The roof-mounted panels are located on the solarium roof and oriented at a fixed pitch of 17.5° facing SSW (see Photo 1). According to Sunlight Solar Energy’s calculations, efficiency is still about 92% of the desired maximum because the 17.5° roof angle actually allows higher efficiency during longer summer hours even though it isn’t the optimum tilt for winter.
Pole-mounted arrays are more efficient than a fixed-pitch roof array by design. My configuration is single-axis adjustable. The pole-mounted arrays are oriented due south and enable seasonal adjustment in the tilt angle to optimize the incidence angle of the sun. For everyone ready to e-mail me asking why I didn’t put in a tracking solar array since this is a pole mount, let me just say that you can also send me financial contributions for doing it via the magazine.—Steve Ciarcia, “Solar-Powering the Circuit Cellar (Part 1: Preparing the Site),” Circuit Cellar 209, 2007.
Check out some of Circuit Cellar’s other solar power-related articles and projects:
Micrcontrollers and electrical engineering probably don’t come to mind when you flip through an IKEA product catalog. But when you think about it, IKEA has plenty of easy-to-assemble tables, cabinets, and storage containers that could be handy for outfitting a electronics workspace or “circuit cellar.”
Sweden-based Patrik Thalin built a workspace within an IKEA Husar cabinet. The setup is compact, orderly, and well-planned. He noted:
It has a pull-out keyboard shelf that I use it as an extension of the workspace when the doors are open. My inspiration came from a friend that had built his lab in a two door closet. The main idea is to have a workspace that can be closed when not used and to be able to resume my work later. I have used this lab for nearly ten years and I am still happy with it!
In the upper part of the cabinet I keep commonly used tools and instruments. On the top shelf are two PSUs, a signal generator, assortment boxes with components, the SMD component kit and shelf trays with cables and small tools. On the lower shelves are things like multimeter, callipers and a power drill. At the bottom is the work space with a soldering station. On the left wall are screwdrivers,wrenches and pliers. To the left are cables hanging on hooks.The thing hanging under the shelf is an old radio scanner. You can also see a small vise hanging on the front of the workspace.
The lower part of the cabinet is for additional storage, he noted.
The information and images were submitted by Patrik Thalin. For more information about his space and work, visit his blog.
Cornell University students Sean Hubber and Crystal Lu built an Arduino-based electrocardiography (ECG) system that enables them to view a heart’s waveform on a mini TV. The basic idea is straightforward: an Arduino Due converts a heartbeat waveform to an NTSC signal.
In their article, “Hands-On Electrocardiography,” Hubber and Lu write:
We used the Arduino Due to convert the heartbeat waveform to an NTSC signal that could be used by a mini-TV. The Arduino Due continuously sampled the input provided by the voltage limiter at 240 sps. Similar to MATLAB, the vectorized signal was shifted left to make room at the end for the most recent sample. This provided a continuous real-time display of the incoming signal. Each frame outputted to the mini-TV contains two waveforms. One has a 1-s screen width and the other has a 5-s screen width. This enables the user to see a standard version (5 s) and a more zoomed in version (1 s). Each frame also contains an integer representing the program’s elapsed time. This code was produced by Cornell University professor Bruce Land.
As you can see in the nearby block diagram, Hubber and Lu’s ECG system comprises a circuit, an Arduino board, a TV display, MATLAB programming language, and a voltage limiter.
The system’s main circuit is “separated into several stages to ensure that retrieving the signal would be user-safe and that sufficient amplification could be made to produce a readable ECG signal,” Hubber and Lu noted.
The first stage is the conditioning stage, which ensures user safety through DC isolation by initially connecting the dry electrode signals directly to capacitors and resistors. The capacitors help with DC isolation and provide a DC offset correction while the resistors limit the current passing through. This input-conditioning stage is followed by amplification and filtering that yields an output with a high signal-to-noise ratio (SNR). After the circuit block, the signal is used by MATLAB and voltage limiter blocks. Directly after DC isolation, the signal is sent into a Texas Instruments INA116 differential amplifier and, with a 1-kΩ RG value, an initial gain of 51 is obtained. The INA116 has a low bias current, which permits the high-impedance signal source. The differential amplifier also utilizes a feedback loop, which prevents it from saturating.
Following the differentiation stage, the signal is passed through multiple filters and receives additional amplification. The first is a low-pass filter with an approximately 16-Hz cutoff frequency. This filter is primarily used to eliminate 60-Hz noise. The second filter is a high-pass filter with an approximately 0.5-Hz cutoff frequency. This filter is mostly used to eliminate DC offset. The total amplification at this stage is 10. Since the noise was significantly reduced and the SNR was large, this amplification produced a very strong and clear signal. With these stages done, the signal was then strong enough to be digitally analyzed. The signal could then travel to both the MATLAB and voltage limiter blocks.
Hubber and Lu’s article was published in Circuit Cellar 289, 2014. Get it now!
Want an electronic tachometer to display the RPM of a lathe or milling machine? If so, Elektor has the project for you.
The electronics tachometer design features an Arduino micro board and a 0.96″ OLED display from Adafruit for instantaneous readout. The compact instrument also has a clock displaying the equipment running time.
When electrical engineer Bill Porter isn’t working on unmanned systems projects for the Navy, he spends a great deal of engineering time at his workspace in Panama City Beach, FL. Bill submitted the interesting images that follow (along with several others) for an interview we plan to run an upcoming issue of Circuit Cellar magazine. Once we saw his workspace images, we knew we had to feature it on our site as soon as possible.
Check out Bill working on a project. He told us: “I am a hardware guy. I love to fire up my favorite PCB CAD software just to get an idea out of my head and on the screen.”
Interesting the sorts of things Bill designs? Check out his wedding-related projects.
You’ll be able to learn more about his innovations in a future issue of Circuit Cellar magazine.
Share your space! Circuit Cellar is interested in finding as many workspaces as possible and sharing them with the world. Email our editors to submit photos and information about your workspace. Write “workspace” in the subject line of the email, and include info such as where you’re located (city, country), the projects you build in your space, your tech interests, your occupation, and more. If you have an interesting space, we might feature it on CircuitCellar.com!
Traditional RS-232 communication needs one transmit line (TXD or TX), one receive line (RXD or RX), and a Ground return line. The setup allows a full-duplex communication. However, many applications use only half-duplex transmissions, as protocols often rely on a transmit/acknowledge scheme. With a simple circuit like Figure 1, this is achieved using only two wires (including Ground). This circuit is designed to work with a “real” RS-232 interface (i.e., using positive voltage for logic 0s and negative voltage for logic 1s), but by reversing the diodes it also works on TTL-based serial interfaces often used in microcontroller designs (where 0 V = logic 0; 5 V = logic 1). The circuit needs no additional voltage supply, no external power, and no auxiliary voltages from other RS-232 pins (RTS/CTS or DTR/DSR).
Although not obvious at a first glance, the diodes and resistors form a logic AND gate equivalent to the one in Figure 2 with the output connected to both receiver inputs. The default (idle) output is logic 1 (negative voltage) so the gate’s output follows the level of the active transmitter. The idle transmitter also provides the negative auxiliary voltage –U in Figure 2. Because both receivers are connected to one line, this circuit generates a local echo of the transmitted characters into the sender’s receiver section. If this is not acceptable, a more complex circuit like the one shown in Figure 3 is needed (only one side shown). This circuit needs no additional voltage supply either. In this circuit the transmitter pulls its associated receiver to logic 1 (i.e., negative voltage) by a transistor (any standard NPN type) when actively sending a logic 0 (i.e., positive voltage) but keeps the receiver “open” for the other transmitter when idle (logic 1). Here a negative auxiliary voltage is necessary which is generated by D2 and C1. Due to the start bit of serial transmissions, the transmission line is at logic 1 for at least one bit period per character. The output impedance of most common RS-232 drivers is sufficient to keep the voltage at C1 at the necessary level.
Note: Some RS-232 converters have quite low input impedance; the values shown for the resistors should work in the majority of cases, but adjustments may be necessary. In case of extremely low input impedance, the receiving input of the sender may show large voltage variations between 1s and 0s. As long as the voltage is below –3 V at any time these variations may be ignore.— Andreas Grün, “One Wire RS-232 Half Duplex,” Elektor July/August 2009.
In the early 1990s, nostalgic users wrote software emulators to relive the “vintage” experience of their old Commodore 64 or Apple II. Others preferred the actual hardware and began collecting classic computers. As their old machines occasionally broke down, people began cultivating the art of computer diagnosis and repair into a new form of retrocomputing.
Next to software emulation and hardware maintenance, a third strain of retrocomputing has emerged: designing and building your own system from a “bag of chips” and a circuit board. It is easy to create a functional computer on a little circuit board—considering all the information now available on the Internet. These retro machines may not have much practical use, but the learning experience can be tremendously valuable (see Photo 1).
Hobbyists with no background in electronics somehow pick up the required skills, and they often share their homebrewing experiences online. Although some of their creations are stunningly exotic, 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.
Still, one challenge remains: If you want homebrewing to be an enduring hobby instead of a one-off project, you should have some perspective beyond putting together a minimal computer and switching it on. 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).
This is where the N8VEM Google group comes in. In 2006, Andrew Lynch published his own single-board CP/M design to engage and involve others. He intended the N8VEM (named after his ham radio license) to be expandable with add-on cards. Soon after, an informal collaborative effort emerged around a Google mail group. A website was set up to share the hardware and software produced.
Builders with a range of skills became involved, from well-known systems builders to beginners. They bought Lynch’s $20 circuit board and ordered the required electronic components and a soldering iron from an online electronics distributor. After two days of wielding the soldering iron, they could create a CP/M computer that uses ROM and RAM disks for storage and has plenty of built-in vintage software.
The design can be expanded into a “powerful” (we use the term lightly here) multiprocessor system with “blinkenlights,” hard disks, graphics subsystems, and various OSes. People also started to build miniaturized variants, PC/XT clones, and 32-bit machines.
However, 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.
There is nothing preventing you from plugging in your own CPU board design. But if you do, you’re not forced to develop all the other expansion boards on your own.
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.
THE N8VEM SBC
At 10-cm × 16-cm (roughly 4” × 6”), the N8VEM computer does not look particularly impressive (see Photo 2). However, it provides all the capabilities of an early 1980s commercial microcomputer. In fact, thanks to CP/M, it is software-compatible with those microcomputers, offering a range of good programming languages (e.g., BASIC, C, Pascal, and Assembler). Excellent editors (e.g., ZDE) and word processors (e.g., WordStar) are also available. You could also run simple spreadsheets, databases and interactive games (e.g., Zork).
The small-sized N8VEM makes one concession to modern-day electronics: It uses a single, high-capacity RAM chip. All the other electronics are components that would have been used “back in the day” (e.g., simple 74LS logic chips, a Z80 microprocessor, and classic interface chips). A battery backs up the N8VEM’s memory; therefore, the RAM disk is a practical storage mechanism, especially because a ROM disk comes with most essential software installed. Use the N8VEM with a serial terminal, or (more likely) with a PC terminal program. The XMODEM protocol enables files to be transferred to and from the N8VEM.
GETTING STARTED: BOOKS AND TOOLS
Homebrewing is straightforward once you figure out how to do things. That is why homebrewing as a group is so practical. Still, two pieces of background information will prove indispensable for any builder: an understanding of basic computer hardware and Assembly language. Reading up on these topics will not only make things easier, but will also help you understand what you are putting together. (See the Resources section at the end of this article for helpful information.)
Only a few tools are necessary. Although, for many, building an electronics lab is part of the fun. A good soldering iron, an inexpensive “solder sucker” to correct mistakes, and a multi-meter are absolute requirements. A secondhand oscilloscope is a useful additional tool. A logic analyzer can also be a big help by enabling you to simultaneously inspect multiple signals and determine what is wrong. Old logic probes are expensive and cumbersome. New designs (e.g., Saleae’s Logic 8-channel USB logic analyzer) are inexpensive and better.
At some point you will need an EPROM programmer, unless you want to depend on others to burn EPROMs for you. Ensure you have a programmer that can deal with a range of (E)EPROMs, as N8VEM boards use many types. Finally, a laboratory power supply is a wise investment, mostly because it has a current limiter that cuts power when a short circuit could otherwise blow up your board.
Editor’s Note: This is an excerpt from an article written by Oscar Vermeulen and Andrew Lynch, “DIY Single-Board Computers (Part 1): Design and Expansion Options,” Circuit Cellar 276, 2013.
If your project needs a higher voltage rail than is already available in the circuit, you can use an off-the-shelf step-up device. But when you want a variable output voltage, it’s less easy to find a ready-made IC. However, it’s not complicated to build such a circuit yourself, especially if you have a microcontroller board that’s as easy to program as an Arduino. And this also lets you experiment with the circuit so you can get a better understanding of how it works.
No surprises in the circuit—a largely conventional boost converter. The MOSFET is driven by a pulse width modulated (PWM) signal from the microcontroller, and the output voltage is measured by one of the microcontroller’s analog inputs. The driver adjusts the PWM signal according to the difference between the output voltage measured and the voltage wanted.
We don’t have enough space here to go into details about how this circuit works, but it’s worth mentioning a few points of special interest.
The small capacitor across the diode improves the efficiency of the circuit. The load is represented by R3. The components used make it possible to supply over 1 A (current limited by the MSS1260T 683MLB inductor from Coilcraft), but maximum efficiency (89%) is at around 95 mA (at an output voltage of 10 V). To avoid damaging the controller’s analog input (≤5 V), the output voltage may not exceed 24 V. For higher voltages, the values of resistors R1 and R2 would need to be changed.
The MOSFET is driven by the microcontroller, which is nothing but a little Arduino board. The Arduino’s default PWM signal frequency is around 500 Hz—too low for this application, which needs a frequency at least 100 times higher. So we can’t use the PWM functions offered by Arduino. But that’s no problem, as the Arduino can also be programmed in assembler, allowing a maximum frequency of 62.5 kHz (the microcontroller runs at 16 MHz). To sample the output voltage, a frequency of 100 Hz is acceptable, which means we can use Arduino’s standard timers and analog functions. The Arduino serial port is very handy: we can use it for sending the output voltage set point (5–24 V) and for collecting certain information about the operation. Thanks to the Arduino environment, it only took about half an hour to program. Software is available. — Clemens Valens (Elektor, April 2010)
Whether you are professional electrical engineer or part-time DIYer, before you start your next project, read through this primer on grounding. This short survey covers one of the most fundamental topics in electronics: grounding.
Electronics Signal Ground or Circuit Common
Signal ground is the current return to the power supply. Current leaves the power supply, passes through the various electronic components, and then returns to the supply. The typical symbol for signal ground is shown in Figure 1.
Chassis Ground or Earth Ground
Chassis ground is an electrical safety requirement to prevent an electrical or electronic device’s chassis from delivering an electrical shock. A long copper rod is driven into the ground outside of the building, and a wire connects the metal chassis to the rod which is at the approximate 0 V potential of the earth. The symbol for earth ground is shown in Figure 2.
Consider the following two details about ground. First, ground is not exactly 0 V. And second, two physically different ground points will not be at the same voltage potential.
By definition, current will flow in an electrical conductor connected to a difference in voltage potential between two points. Because two physically different ground points are not at the same potential, current will flow through an electrical conductor connected between those two points. This is a ground loop.
Notice this current flowing between these two different ground points is not related to or correlated to any electronic data or message signal. This is noise or garbage that will interfere and distort any information contained in the electronic system.
Note: While “noise” can be added to systems on occasion, it is specifically controlled and the exact quantity is regulated.
Given: A ground loop producing 610 μV of ground noise. It’s a very small quantity. You have a 16-bit A/D converter with a 0- to 10-V input. The smallest voltage it can resolve is:
= 10 V/16 exp 2
= 10 V/65,536
Note that the ground loop noise is four times greater than the actual data, so that A/D converter loses two bits of resolution, and it is now a 14-bit converter.
Connect with Single-Ended/Unbalanced Amps
Connect with Transformers
When connecting with transformers, keep the following in mind:
- There is no ground connection, so there can be no Ground Loop.
- Common-mode rejection of RF interference.
- Signals are AC coupled, so of limited use for circuits with DC data such as accelerator focus and bend magnets (see Figure 5).
Connect with Differential Amps
Refer to Figure 6 for connecting two systems with differential amplifiers.
- There is no ground connection, so there can be no Ground Loop.
- Common-mode rejection of RF interference (see Figure 7).
- Signals are DC coupled, so this is the perfect solution for circuits with DC data.
Note: This article first appeared in audioXpress (June 2011). It is from a class that Dennis Hoffman teaches at the SLAC National Accelerator Laboratory (Menlo Park, CA). Like Circuit Cellar, audioXpress is Elektor International Media Publication.
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.
“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.
“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.
ALTSpace is a Community Art Workshop in Seattle. Creative people of all kinds share this spacious workshop, teaching, experimenting, making and learning. Members can spend time bouncing ideas off one another, hold or attend classes, work away from home and have the space to get even large projects done.
|Location||2318 E. Cherry Street, Seattle, WA|
Co-founder Mike tells us about his space:
Tell us about your meeting space!
We have a total of about 2800 sq ft. We have two garage spaces for industrial machines, loud and dirty operations. (about 700 sq ft total) The rest of the space is for personal workspaces and public areas for working, meeting, hanging out. We have 2 showers, 2 bathrooms, a kitchen, a laundry room and an outdoor patio.
What tools do you have in your space? (Soldering stations? Oscilloscopes? 3-D printers?)
Are there any tools your group really wants or needs?
A laser cutter would be our next purchase.
Does your group work with embedded tech (Arduino, Raspberry Pi, embedded security, MCU-based designs, etc.)?
Yes, we do quite a bit of electronics. One of our more well known projects, the Groovik’s Cube (A 30ft playable Rubik’s Cube) is an arduino driven project.
Can you tell us about some of your group’s recent tech projects?
We first built the cube as an art project for Burning Man 2009 and we’ve since been working hard to try and bring this project to the general public. We’ve been collaborating with the Science Center since summer ’10 and we’ve been doing a number of refurbishments including a brand new light-weight aluminum structure to create a neater look suitable for an indoor museum environment.
Groovik’s cube is a fully playable, LED driven Rubik’s cube, hung from the ceiling, corner down. (the motion is of course simulated, not mechanical, i.e. the colors move around, not the structure itself). It can be played and solved by the visitors. A particularly interesting feature is that we have split the controls into 3 stations placed around the cube, each allowing only one axis of rotation. This means 3 people have to collaborate together to solve it. The stations are ~30-50 ft apart from each other. This makes the puzzle considerably harder with a current record solution time of 50 minutes (achieved on Friday night @ Burning Man 09). It also turns a very introverted game into a collaborative challenge which is fun to watch. Imagine people shouting instructions to each other and running around checking on the state of the cube from different angles.
Temple of Shame:
by Alissa Mortenson, Nebunele Theatre, The Temple of Shame was a 6ft wide, 18ft tall wooden Temple dedicated to the collection of shame from the participants of Black Rock City. The temple was ceremonially burned on the last night of the festival to symbolically release all the shame collected.
From shameproject.org: “The experience of shame is part of our shared humanity, yet paradoxically, the times when we are ashamed are the times when we feel most alone. But within shame lies a capacity for human connection. The Shame Bearers seek to explore this emotion as a powerful medium for reaching a state of shared vulnerability. In order to make connection –the core human desire– we must believe that we are enough, that we are worthy of love and acceptance. In our vulnerability and our recognition of our mutual imperfections, we can find worthiness and connection. That is the power of this project.”
What’s the craziest project your group or group members have completed?
Groovik’s cube for sure.
Do you have any events or initiatives you’d like to tell us about? Where can we learn more about it?
Indeed: http://lsc.org/grooviks. We’re trying to raise funding for a new Groovik’s cube that will travel the World for 7 years together with Liberty Science Center and Erno Rubik!
What would you like to say to fellow hackers out there?
Hack more! Not satified with availability of hackerspaces near you ? Start one! It’s easier than you think and people come out of the woodwork to come and help and donate time and tools.
- 2HP Metal Mill & Lathe
- Lincoln 220 MIG Welder (up to 1/4″ steel)
- TIG 200Amp DC/AC (i.e. Steel, Aluminum & other non-ferrous)
- Plasma Torch (Up to 1″ steel or aluminum)
- Stick Welder
- Metal Grinding wheels, belt sanders
- 4×6 Metal Bandsaw
- Deburring wheel and 2 buffers
- Wire bender
- Abrasive metal chop saw
Machine Shop (Wood):
- 3/4HP Table saw
- Router table & Hand Router
- Various Sanders (Orbital & Belt)
- Miter Chop saw
Other Machine Shop amenities:
- 90 PSI Compressor
- 3/4HP 1/2″ Shank Drill press
- Hand drills, Sander
- 110V/230V Power (50A)
- Glass fusing/slumping/casting kiln, up to 1600 deg F
- Small Propane/Oxygen torch for soldering/annealing
- Flexshaft Rotary grinder
- Rolling Mill
- Disc Die Cutter & Hemisphere punch
- Maker bot
- Soldering station with fume extractor and static pad
- 100 Mhz Oscilloscope (Techronix)
- Basic tools (snippers, strippers, screwdrivers, etc)
- Variable voltage / current power supply
- Stock of common components
- Anti-static worktop
- Pfaff industrial sewing machine
- Janome domestic sewing machine
- Hoseki HK757G is a 5-thread industrial serger
- White domestic 4-thread serger
- irons, cork-topped layout table, digitizing table, pattern plotter
- Janome Computerized domestic sewing machine
- Rowenta domestic iron
- Sleeve board
- Tailor’s ham
- Pattern Drafting Rulers and curves
- Costuming books
You can read about more of ALTspace’s projects on their art page.
Show us your hackerspace! Tell us about your group! Where does your group design, hack, create, program, debug, and innovate? Do you work in a 20′ × 20′ space in an old warehouse? Do you share a small space in a university lab? Do you meet at a local coffee shop or bar? What sort of electronics projects do you work on? Submit your hackerspace and we might feature you on our website!
Alpha One Labs is a very active hackerspace located in Brooklyn. They frequently host events and offer many services to their members.
|Location||657 Meeker Ave #1L
Brooklyn NY, 11222
Mary Auriti is co-founder and secretary at Alpha One Labs. We ask her what she has to tell us about her space:
What’s your meeting space like?
Approximately 900 sq. ft. with 18 ft. ceilings which could accommodate a second floor. We have a wall of pegboard with tools and custom built shelves with clear containers for supplies as well as small bins for little items. There is eight heavy duty desks, a taller work table and an adjustable height desk/work table. In the front area of our space we have a little lounge area with a small sofa, book shelf, fridge, coffee maker, big flat screen TV, twitter LED scroller, old school video consoles and games, and a gallery wall featuring a local artist’s work.
What tools do you have in your space? (Soldering stations? Oscilloscopes? 3-D printers?)
We have a JCUT 6090 laser cutter, a RepRap, drill press, saws, a Dremel, and other hand tools. Also, oscilloscopes and soldering irons.
If you could add three more tools, what would they be?
Welder, Epilogue laser cutter, and a CNC 5 axis mill
Does your group work with embedded tech (Arduino, Raspberry Pi, embedded security, MCU-based designs, etc.)?
We use Arduinos and are getting into Raspberry Pi.
Can you tell us about some of your group’s recent tech projects?
We have had a wide range of projects come through our lab as well as the ongoing big project of the physical lab space itself. Some projects from the past four years are:
- the “Twitmas Tree” (ornaments that light up every time someone tweets a holiday related word)
- butter churning with kosher cream from bed sty
- self-watering rooftop veggie garden
- LED hat displaying preset or dynamic messages
- Internet time piece
- and a stair climbing wheelchair — to name few
What’s the craziest project your group or group members have completed?
“Shot in the Dark” — A laser pointing to the center of the toilet bowel so men have a target.
Where can the CC Community learn more about it?
We post all our events on our web site alphaonelabs.com and host a few meetups from time to time as people contact us. We like to be there for any group that needs us and shares our interests in the great wide space of making, art, technology, science, education, environmentalism, hacking.
What would you like to say to fellow hackers out there?
Come on down! We are open to all and love the diversity of people who come through our lab. We are consistently working on making our lab a place to encourage innovation and give people what they need to get their projects off the ground.