Make: Electronics

by Charles Platt

  5. What Next?

  At this point, we can branch out in numerous directions. Here are some possibilities:

  Audio electronics

  This is a field in itself, including hobby projects, such as simple amplifiers and “stomp boxes,” to modify guitar sound.

  Radio-frequency devices

  Anything that receives or transmits radio waves, from an ultra-simple AM radio to remote controllers.

  Motors

  The field of robotics has encouraged the growth of many online sites selling stepper motors, gear motors, synchronous motors, servo motors, and more.

  Programmable microcontrollers

  These are tiny computers on a single chip. You write a little program on your desktop computer, which will tell the chip to follow a series of procedures, such as receiving input from a sensor, waiting for a fixed period, and sending output to a motor. Then you download your program onto the chip, which stores it in nonvolatile memory. Popular controllers include the PICAXE, BASIC Stamp, Arduino, and many more. The cheapest ones retail for a mere $5 each.

  Obviously, I don’t have space to develop all of these topics fully, so what I’m going to do is introduce you to them by describing just one or two projects in each category. You can decide which interests you the most, and then proceed beyond this book by reading other guides that specialize in that interest.

  I’m also going to make some suggestions about setting up a productive work area, reading relevant books, catalogs, and other printed sources, and generally proceeding further into hobby electronics.

  Shopping List: Experiments 25 Through 36

  Tools

  You won’t need any new tools for this section of the book.

  Supplies and Components

  As we have progressed to the point where you may want to pick and choose which projects you attempt, I will list the supplies and components at the beginning of each experiment.

  Customizing Your Work Area

  At this point, if you’re getting hooked on the fun of creating hardware but haven’t allocated a permanent corner to your new hobby, I have some suggestions. Having tried many different options over the years, my main piece of advice is this: don’t build a workbench!

  Many hobby electronics books want you to go shopping for 2×4s and plywood, as if a workbench has to be custom-fabricated to satisfy strict criteria about size and shape. I find this puzzling. To me, the exact size and shape of a bench is not very important. I think the most important issue is storage.

  I want tools and parts to be easily accessible, whether they’re tiny transistors or big spools of wire. I certainly don’t want to go digging around on shelves that require me to get up and walk across the room.

  Figure 5-1. The ideal work area: surrounded by storage. Never again will you need to get out of your chair!

  This leads me to two conclusions:

  1. You need storage above the workbench.

  2. You need storage below the workbench.

  Many DIY workbench projects allow little or no storage underneath. Or, they suggest open shelves, which will be vulnerable to dust. My minimum configuration would be a pair of two-drawer file cabinets with a slab of 3/4-inch plywood or a Formica-clad kitchen countertop placed across them. File cabinets are ideal for storing all kinds of objects, not just files.

  Of all the workbenches I’ve used, the one I liked best was an old-fashioned steel office desk—the kind of monster that dates back to the 1950s. They’re difficult to move (because of their weight) and don’t look beautiful, but you can buy them cheaply from used office furniture dealers, they’re generous in size, they withstand abuse, and they last forever. The drawers are deep and usually slide in and out smoothly, like good file-cabinet drawers. Best of all, the desk has so much steel in it that you can use it to ground yourself before touching components that are sensitive to static electricity. If you use an antistatic wrist strap, you can simply attach it to a sheet-metal screw that you drive into one corner of the desk.

  What will you put in the deep drawers of your desk or file cabinets? Some paperwork may be useful, perhaps including the following documents:

  Product data sheets

  Parts catalogs

  Sketches and plans that you draw yourself

  The remaining capacity of each drawer can be filled with plastic storage boxes. The boxes can contain tools that you don’t use so often (such as a heat gun or a high-capacity soldering iron), and larger-sized components (such as loudspeakers, AC adapters, project boxes, and circuit boards). You should look for storage boxes that measure around 11 inches long, 8 inches wide, and 5 inches deep, with straight sides. Boxes that you can buy at Wal-Mart will be cheaper, but they often have tapering sides (which are not space-efficient).

  The boxes that I like best are Akro-Grids, made by Akro-Mils (see Figures 5-2 and 5-3). These are very rugged, straight-sided, with optional transparent snap-on lids. You can download the full Akro-Mills catalog from http://www.akro-mils.com and then search online for retail suppliers. You’ll find that Akro-Mils also sells an incredible variety of parts bins, but I don’t like open bins because their contents are vulnerable to dust and dirt.

  Figure 5-2. Akro-Grid boxes contain grooves allowing them to be partitioned into numerous compartments for convenient parts storage.

  Figure 5-3. Lids are sold separately for Akro-Grid boxes to keep the contents dust-free. The height of the box in Figure 5-2 allows three to be stacked in a typical file-cabinet drawer. The box shown here allows two to be stacked.

  For medium-size components, such as potentiometers, power connectors, control knobs, and toggle switches, I like storage containers measuring about 11 inches long, 8 inches wide, and 2 inches deep , divided into four to six sections. You can buy these from Michaels (the craft store), but I prefer to shop online for the Plano brand, as they seem more durably constructed. The Plano products that are most suitable for medium-size electronic parts are classified as fishing-tackle boxes, and you’ll see them at http://www.planomolding.com/tackle/products.asp.

  For undivided, flat-format storage boxes, the Prolatch 23600-00 is ideally sized to fit a file-cabinet drawer, and the latches are sufficiently secure that you could stack a series of them on their long edges. See Figure 5-4.

  Figure 5-4. This Plano brand box is undivided, making it useful for storing spools of wire or medium-size tools. When stacked upright on its long edge, three will fit precisely in a file-cabinet drawer.

  Plano also sells some really nicely designed toolboxes, one of which you can place on your desktop. It will have small drawers for easy access to screwdrivers, pliers, and other basics. Because you need a work area that’s only about three feet square for most electronics projects, surrendering some desk space to a toolbox is not a big sacrifice.

  If you have a steel desk with relatively shallow drawers, one of them can be allocated for printed catalogs. Don’t underrate the usefulness of hard copy, just because you can buy everything online. The Mouser catalog, for instance, has an index, which is better in some ways than their online search feature, and the catalog is divided into helpful categories. Many times I’ve found useful parts that I never knew existed, just by browsing, which is much quicker than flipping through PDF pages online, even with a broadband connection. Currently, Mouser is still quite generous about sending out their catalogs, which contain over 2,000 pages. McMaster-Carr will also send you a catalog, but only after you‘ve ordered from them, and only once a year.

  Now, the big question: how to store all those dinky little parts, such as resistors, capacitors, and chips? I’ve tried various solutions to this problem. The most obvious is to buy a case of small drawers, each of which is removable, so you can place it on your desk while you access its contents. But I don’t like this system, for two reasons. First, for very small components, you need t
o subdivide the drawers, and the dividers are never secure. And second, the removability of the drawers creates the risk of accidentally emptying the contents on the floor. Maybe you’re too careful to allow this to happen, but I’m not!

  My personal preference is to use Darice Mini-Storage boxes, shown in Figure 5-5. You can find these at Michaels in small quantities, or buy them more economically in bulk online from suppliers such as http://www.craftamerica.com. The blue boxes are subdivided into five compartments that are exactly the right size and shape for resistors. The yellow boxes are subdivided into ten compartments, which are ideal for semiconductors. The purple boxes aren’t divided at all, and the red boxes have a mix of divisions.

  Figure 5-5. Darice Mini-Storage boxes are ideal for components such as resistors, capacitors, and semiconductors. The boxes can be stacked stably or stored on shelves, with their ends labeled. The brand sticker is easily removed after being warmed with a heat gun.

  The dividers are molded into the boxes, so you don’t have the annoyance associated with removable dividers that slip out of position, allowing components to mix together. The box lids fit tightly, so that even if you drop one of the boxes, it probably won’t open. The lids have metal hinges, and a ridge around the edge that makes the boxes securely stackable.

  I keep my little storage boxes on a set of shelves above the desk, with a gap of 3 inches between one shelf and the next, allowing two boxes to be stacked on each shelf. If I want to work with a particular subset of boxes, I shift them onto the desktop and stack them there.

  Labeling

  No matter which way you choose to store your parts, labeling them is essential. Any ink-jet printer will produce neat-looking labels, and if you use peelable (nonpermanent) labels, you’ll be able to reorganize your parts in the future, as always seems to become necessary. I use color-coded labels for my collection of resistors, so that I can compare the stripes on a resistor with the code on the label, and see immediately if the resistor has been put in the wrong place. See Figure 5-6.

  Figure 5-6. To check that resistors are not placed in the wrong compartments, print the color code on each label.

  Even more important: you need to place a second (non-adhesive) label inside each compartment with the components. This label tells you the manufacturer’s part number and the source, so that reordering is easy. I buy a lot of items from Mouser, and whenever I open their little plastic bags of parts, I snip out the section of the bag that has the identifying label on it, and slide it into the compartment of my parts box before I put the parts on top of it. This saves frustration later.

  If I were really well organized, I would also keep a database on my computer listing everything that I buy, including the date, the source, the type of component, and the quantity. But I’m not that well organized.

  On the Bench

  Some items are so essential that they should sit on the bench or desktop on a permanent basis. These include your soldering iron(s), helping hands with magnifier, desk lamp, breadboard, power strip, and power supply. For a desk lamp, I prefer the type that has a daylight-spectrum fluorescent bulb, because it spreads a uniform light and helps me to distinguish colors of adjacent stripes on resistors.

  The power supply is a matter of personal preference. If you’re serious about electronics, you can buy a unit that delivers properly smoothed current at a variety of properly regulated and calibrated voltages. Your little wall-plug unit from RadioShack cannot do any of these things, and its output may vary depending on how heavily you load it. Still, as you’ve seen, it is sufficient for basic experiments, and when you’re working with logic chips, you need to mount a 5-volt regulator on your breadboard anyway. Overall, I consider a good power supply optional.

  Another optional item is an oscilloscope. This will show you, graphically, the electrical fluctuations inside your wires and components, and by applying probes at different points, you can track down errors in your circuit. It’s a neat gadget to own, but it will cost a few hundred dollars, and for our tasks so far, it has not been necessary. If you plan to get seriously into audio circuits, an oscilloscope becomes far more important, because you’ll want to see the shapes of the waveforms that you generate.

  You can try to economize on an oscilloscope by buying a unit that plugs into the USB port of your computer and uses your computer monitor to display the signal. I have tried one of these, and was not entirely happy with the results. It worked, but did not seem accurate or reliable for low-frequency signals. Maybe I was unlucky; I decided not to try any other brands.

  The surface of your desk or workbench will undoubtedly become scarred by random scuffs, cut marks, and drops of molten solder. I use a piece of half-inch plywood, two feet square, to protect my primary work area, and I clamp a miniature vise to its edge. To reduce the risk of static electricity when working with sensitive components, I cover the plywood with a square of conductive foam. This is not cheap, but offers advantages in addition to protecting chips from being zapped. Instead of scattering stray components, I can stick them into the foam, like plants growing in a garden. And like a garden, I can divide it into sections, with resistors on one side, capacitors on the other, and chips straight ahead.

  Inevitably, during your work you’ll create a mess. Little pieces of bent wire, stray screws, fasteners, and fragments of stripped insulation tend to accumulate, and can be a liability. If metal parts or fragments get into a project that you’re building, they can cause short circuits. So you need a trash container. But it has to be easy to use. I use a full-size garbage pail, because it’s so big that I can’t miss it when I throw something toward it, and I can never forget that it’s there.

  Last, but most essential: a computer. Now that all data sheets are available online, and all components can be ordered online, and many sample circuits are placed online by hobbyists and educators, I don’t think anyone can work efficiently without quick Internet access. To avoid wasting space, I suggest you use a small, cheap laptop that has a minimal footprint. A possible workbench configuration, using a steel desk, is shown in Figure 5-7.

  Figure 5-7. An old steel office desk can be as good as, if not better than, a conventional workbench when building small electronics projects. It provides a large work area and ample storage, and has sufficient mass for you to ground yourself when dealing with components that are sensitive to static electricity.

  Reference Sources

  Online

  My favorite educational and reference site is Doctronics (http://www.doctronics.co.uk). I like the way they draw their schematics, and I like the way they include many illustrations of circuits on breadboards (which most sites don’t bother to do). They also sell kits, if you’re willing to pay and wait for shipping from the UK. Part of a page from the doctronics website is reproduced in Figure 5-8.

  Figure 5-8. A sample page from http://www.doctronics.co.uk shows their detailed instructional approach. This is a valuable free online resource.

  My next favorite hobby site is also British-based: the Electronics Club (http://www.kpsec.freeuk.com). It’s not as comprehensive as Doctronics, but very friendly and easy to understand.

  For a more theory-based approach, try http://www.electronics-tutorials.ws. This will go a little farther than the theory sections I’ve included here.

  For an idiosyncratic selection of electronics topics, try Don Lancaster’s Guru’s Lair (http://www.tinaja.com). Lancaster wrote The TTL Cookbook more than 30 years ago, which opened up electronics to at least two generations of hobbyists and experimenters. He knows what he’s talking about, and isn’t afraid of getting into some fairly ambitious areas such as writing his own PostScript drivers and creating his own serial-port connections. You’ll find a lot of ideas there.

  Books

  Yes, you do need books. As you’re already reading this one, I won’t recommend other beginners’ guides. Instead, in keeping with t
he orientation of this chapter, I’ll suggest some titles that will take you farther in various directions, and can be used for reference. I own all of these myself, and find them valuable:

  Practical Electronics for Inventors, by Paul Scherz (McGraw-Hill, Second Edition, 2007)

  This is a massive, comprehensive book, well worth the $40 cover price. Despite its title, you won’t need to invent anything to find it useful. It’s my primary reference source, covering a wide range of concepts, from the basic properties of resistors and capacitors all the way to some fairly high-end math. If you buy only one book (in addition to this one, of course!), this would be my recommendation.

  Getting Started with Arduino, by Massimo Banzi (Make: Books, 2009)

  If you enjoy the simplicity and convenience of the PICAXE programmable microcontroller that I describe later in this chapter, you’ll find that the Arduino can do a lot more. Getting Started is the simplest introduction around, and will help to familiarize you with the Processing language used in Arduino (similar to the C language, not much like the version of BASIC used by the PICAXE).

  Making Things Talk, by Tom Igoe (Make: Books, 2007)

  This ambitious and comprehensive volume shows how to make the most of the Arduino’s ability to communicate with its environment, even getting it to access sites on the Internet.

  TTL Cookbook, by Don Lancaster (Howard W. Sams & Co, 1974)

  The 1974 copyright date is not a misprint! You may be able to find some later editions, but whichever one you buy, it will be secondhand and possibly expensive, as this title now has collectible value. Lancaster wrote his guide before the 7400 series of chips was emulated on a pin-for-pin basis by CMOS versions, but it’s still a good reference, because the concepts and part numbers haven’t changed, and his writing is so accurate and concise.