Chapter 3
Getting Parts

Exactly where do you find robot parts? Your friendly neighborhood robot store would be a good place to start—if only such a store existed! Fortunately, other local and online retail stores are there to fill in the gaps.

The fundamental stuff of bots includes:

Basic electronic parts to control your robot. These include core electronic components such as resistors and capacitors, switches, wire, and relays.

Specialized electronic modules to complete circuits that you connect with the rest of your robot. The options here are nearly limitless, but the main modules you’ll be interested in include a microcontroller (holds programs for your robot, operates motors and other parts) and sensors.

Motors and wheels for making your robot go.

Construction materials for building the body, or base, of your robot. You can make the base from found material (old CDs, small plastic containers) or from wood, plastic, metal, foam, even heavy cardboard.

Fasteners, adhesives, and other building parts to put everything together. These might include small screws and nuts, but also cable ties, Velcro, and glue.

In this chapter we review where you can find these and other parts for your robot projects.

Local Electronics Stores

Not long ago most towns had at least one local electronic parts store. Even some automotive outlets carried a full range of tubes, specialty transistors, and other electronic gadgets. Now, RadioShack remains as the only U.S. national electronics store chain. In many cities across the country, it’s the only thing going.

The situation is much the same for those in other countries. There’s Maplin Electronics and Farnell in the United Kingdom; in Australia and New Zealand you’ll find Dick Smith.

Most of the nationwide chains like RadioShack continue to support electronics experimenters. But they stock only the very common components. They’re great for getting emergency replacement parts or filling in the odds and ends. If your needs extend beyond common-value components, wire, and switches, you must turn to other sources—and for the best selection that means going online.

Online Electronics Outlets

There’s no shortage of choices for online electronics stores. While you have to wait for the parts to ship to you, the selection is better, and (often) so are the prices.

Some of the online outlets are so vast you’ll be hard-pressed to just “browse the aisles.” Their catalogs are extensive, numbering hundreds of pages. You really need to know what you’re looking for, and fortunately they all provide a search function on their Web sites. You may look for specific parts or search by category.

Here are some of the key online electronics retailers in North America that you’ll want to know about:

All Electronics: www.allelectronics.com (they also have a retail store in the Los Angeles area)

DigiKey: www.digikey.com

Jameco Electronics: www.jameco.com

Mouser Electronics: www.mouser.com

RadioShack: www.radioshack.com

This is only a short list, and there are others, including those outside the United States. See Appendix B, “Internet Parts Sources,” for more.

Using FindChips.com to Locate Parts

If you’re looking for a particular electronic component, use the specialized search at www.FindChips.com (Figure 3-1). Enter the part number or part reference, and the site will search over a dozen online electronics specialty retailers. You can compare prices and availability. Using the FindChips.com search is free.

Figure 3-1 Use Findchips.com to locate electronic components. The free site searches numerous online parts retailers and displays availability, price, and stocking levels.

Specialty Online Robotics Retailers

With robotics now a hot hobby, a new type of online retailer has sprung up: the specialty robotics site. These sites offer one-stop-shopping for all—or nearly all—of the parts you need to build your robots.

Inventory differs from one site to the next, and some products are exclusive to one company. No doubt you’ll develop your favorite haunts. I regularly shop at several of these, looking for what’s new and who has the best prices.

Acroname Robotics: www.acroname.com

Lynxmotion: www.lynxmotion.com

Parallax: www.parallax.com

Pololu: www.pololu.com

RobotShop: www.robotshop.com

SparkFun Electronics: www.sparkfun.com

See Appendix B, “Internet Parts Sources,” for more.

Hobby and Model Stores

Hobby and model stores are the ideal sources for small parts, including lightweight plastic, brass rod, servo motors for radio control (R/C) cars and airplanes, gears, and construction hardware. Most of the products available at hobby stores are designed for building specific kinds of models and toys. But that shouldn’t stop you from raiding the place with an eye to converting the parts for robot use.

In my experience, many hobby store owners and salespeople are not up to speed on using their products in robotic applications. Your best bet is to browse the store and look for parts that you can put together to build a robot. Some of the parts, particularly those for R/C models, will be behind a counter, but they should still be visible enough for you to conceptualize how you might use them.

If you don’t have a well-stocked hobby store in your area, there’s always mail order through the Internet. Here are a few of the larger eHobby outlets:

Hobby Lobby: www.hobbylobby.com

Hobby People: www.hobbypeople.net

Horizon Hobby: www.horizonhobby.com

Tower Hobbies: www.towerhobbies.com

Craft Stores

Craft stores sell supplies for home crafts and arts. As a robot builder, you’ll be interested in some of the aisles with:

Foam rubber sheets. These come in various colors and thicknesses and can be used for pads, bumpers, nonslip surfaces, tank treads, and lots more. The foam is very dense; use a sharp scissors or knife to cut it (I like to use a rotary paper cutter to get a nice, straight cut).

Foamboard. Constructed of foam sandwiched between two heavy sheets of paper, foam-board can be used for small, lightweight robots. Foamboard can be cut with a hobby knife and glued with paper glue or hot-melt glue. Look for it in different colors and thicknesses.

Parts from dolls and teddy bears. These can often be used in robots. Fancier dolls use something called armatures—movable and adjustable joints—that can be applied to your robot creations. Look also for linkages, bendable posing wire, and eyes (great for building robots with personality!).

Electronic light and sound buttons. These are designed to make Christmas ornaments and custom greeting cards, but they work just as well in robots. Electric light kits come with low-voltage LEDs or incandescent lights, often in several bright colors. Some flash at random, some in sequence. Sound buttons have a built-in song that plays when you depress a switch. You could use these buttons as touch sensors, for example, or as a “tummy switch” in an animal-like robot.

Plastic crafts construction material. This can be used in lieu of more expensive building kits. For example, many stores carry the plastic equivalent of that old favorite, the Popsicle stick. (You can also get the original wooden ones, but they aren’t as strong.) The plastic sticks have notches in them so they can be assembled to create frames and structures.

Model-building supplies. Many craft stores have these, sometimes at lower prices than the average hobby-model store. Look for assortments of wood and metal pieces, adhesives, and construction tools.

There are, of course, many other interesting products of interest at craft stores. Visit one and take a stroll down its aisles. Don’t have a craft store nearby? There are plenty online. See Appendix B, “Internet Parts Sources,” for several of the larger outlets.

Hardware and Home Improvement Stores

Hardware stores and builder’s supply outlets are a good source for hand tools for building your robots. They’re also good for screws, nuts, and other fasteners, adhesives, and the materials for bot bases.

As you tour your neighborhood hardware store, keep a notebook handy and jot down what they offer. Then, when you find yourself needing a specific item, you have only to refer to your notes. Take an idle stroll through your regular hardware store haunts on a regular basis. You’ll always find something new and laughably useful for robot design each time you visit. I know I do.

Samples from Electronics Manufacturers

Shhhh! I’m not supposed to tell you this, but a number of electronics manufacturers will send you free samples, just for the asking.

Okay, it helps if you’re an instructor at a school or an engineer working for a company building millions of units of some gizmo. But the truth is, some semiconductor and electronics makers will send free samples to students and hobbyists, too. Just don’t be greedy, and observe limits to their kindness.

Availability of freebies is especially useful, as the newest semiconductors may not yet be carried by distributors and wholesalers, making it hard to purchase these products. You can get a jump ahead by asking for free samples and incorporating them in your work.

Sample kits are also occasionally available from wholesalers, distributors, and resellers. Look for kits of parts, fasteners, or various hardware. The kits are limited and are obviously meant to entice you into buying more, but they’re free, and you never know when some piece from a kit will come in handy.

If you belong to a school or a robotics club, send your request (preferably on professional-looking letterhead) under the auspices of your organization. Be sure you have permission from the school or club! Most electronics manufacturers realize that today’s robotics students and hobbyists are tomorrow’s engineers, and they want to actively foster a good working relationship with them (er, you).

Finding What You Need on the Internet

The Internet has given a tremendous boost to the art and science of robot building. Through the Web, you can now search for and find the most elusive part for your robot. Moreover, with the help of Web search engines—such as Google (www.google.com) or Bing (www.bing.com)—you can look for topics of interest from among the millions of Web sites throughout the world.

Remember that the Internet is worldwide. Some of the sites you find may not be located in your country; many Web businesses ship internationally, but not all do. Check for any specific payment requirements and shipping restrictions. If they accept checks or money orders, the denomination should be in the company’s native currency.

Shop Once, Shop Smart

Whether buying locally or through mail order—and that includes the Internet—you’ll want to get as many of the parts as you need at once. This saves time, trouble, and expense.

When getting parts locally, there’s the hassle of returning to the store for last-minute additions. That costs you time and gas. And when buying through the mail, repeat orders pile up the shipping costs. A transistor may cost only 25 cents, but add order minimums and shipping fees and you could easily be looking at $5 or $10 on your credit card.

Some ideas for savvy shopping:

Keep an inventory of what you have, and think ahead. Plan your next several projects, and get as many of the parts for them at the same time as you can.

Try to group purchases together when buying from the same store, even if the store doesn’t have the lowest price. If the difference is minor, consider the additional costs of driving or shipping from another source.

For very basic electronic parts try to get an assortment of standard values. Things like resistors and capacitors (discussed in Chapter 31, “Common Electronic Components for Robotics”) are just pennies each. A $10 (or whatever) assortment of the most common values will save you time and money.

Don’t forget what you already have! See “Getting Organized,” later in this chapter, on how to keep a good inventory of your stock.

Haunting the Surplus Store

Surplus is a wonderful thing, but most people shy away from it. Why? If it’s surplus, the reasoning goes, it must be worthless junk. That’s simply not true. Surplus is exactly what its name implies: extra stock. Because the stock is extra, it’s generally priced accordingly—to move it out the door.

Surplus stores that specialize in new and used mechanical and electronic parts are a pleasure to find. (Don’t confuse these with stores that sell surplus clothing, camping, and government equipment. Completely different animal.) Many urban areas have at least one mechanical/electronics surplus store. Bear in mind that surplus stores don’t have mass-market appeal, so finding them is not always easy. Start by looking in the phone company’s business directory under Surplus.

Surplus parts are also available through the mail. There’s a limited number of mail-order surplus outfits that cater to the hobbyist, but you can usually find everything you need if you look carefully enough and are patient. See Appendix B, “Internet Parts Sources,” for leads.

While surplus is a great way to stock up on mechanical parts such as big DC motors and gears, you must shop wisely. Just because the company calls the stuff surplus doesn’t mean that it’s cheap—or even reasonably priced. A popular item in a surplus catalog may sell for top dollar, simply because of high demand.

Getting Parts from Specialty Stores

Specialty stores are outlets open to the general public that sell items you won’t find in a regular hardware or electronic parts store. These don’t include surplus outlets, which were discussed in the previous section.

What specialty stores are of use to robot builders? Consider:

Toy stores. Look for construction toys like Erector, Meccano, LEGO, and others. Check out their battery-operated toy vehicles, such as motorized tanks. Raid the motors and rubber treads, like the ones in Figure 3-2, for your robot. This is how I get parts for most of my tracked robots.

Sewing machine repair shops. These are ideal for finding small gears, cams, levers, and other precision parts. Some shops will sell broken machines to you. Tear them to shreds and use the parts for your robot.

Auto parts stores. The independent stores tend to stock more goodies than the national chains, but both kinds offer surprises in every aisle. Keep an eye out for small switches, wire, and tools.

Junkyards. If you’re into building bigger robots, old cars are good sources for powerful DC motors, which are used to drive windshield wipers, electric windows, and automatic adjustable seats (though take note: such motors tend to be terribly inefficient for battery-based bots).

Lawn mower sales-service shops. Lawn mowers use all sorts of nifty control cables, wheel bearings, and assorted odds and ends. Pick up new or used parts for a current project.

Bicycle sales-service shops. I don’t mean the department store that sells bikes, but a real professional bicycle shop. Items of interest: control cables, chains, brake calipers, wheels, sprockets, brake linings, and more.

Figure 3-2 Toys are among the best sources for robotic parts, especially motorized military tanks or construction vehicles. These can be turned into robots with tracks.

Industrial parts outlets. Some places sell gears, bearings, shafts, motors, and other industrial hardware on a one-piece-at-a-time basis. The penalty: fairly high prices and often the requirement that you buy a higher quantity of an item than you really need.

Scavenging: Making Do with What You Already Have

You don’t need to buy new (or used or surplus) to get worthwhile robot parts. In fact, some of the best parts for hobby robots may already be in your garage or attic. Consider the typical used VCR. It’ll contain at least one motor—and possibly as many as five—numerous gears, and other electronic and mechanical odds and ends.

Depending on the brand and when it was made, it could also contain belts and pulleys, miniature push buttons, infrared light emitting diodes and detectors, and even wire harnesses with reusable connectors. Any and all of these can be salvaged to help build your robot. All told, the typical discarded VCR may have over $30 worth of parts in it.

Likewise, make a point of visiting garage sales and thrift stores from time to time, and look for parts bonanzas in used—and perhaps nonfunctioning—goods. I regularly scout the local resale stores and for very little money come away with a trunk full of valuable items that I can salvage for parts. Goods that are still in functioning order tend to cost more than the broken stuff, but for robot building the broken stuff is just as good. Be sure to ask the store personnel if they have any nonworking items they will sell you at a reasonable cost.

Here is just a short list of the electronic and mechanical items to be on the lookout for and the primary robot-building components they have inside:

VCRs are perhaps the best single source for parts, and they are in plentiful supply. As discussed, you’ll find motors, switches, cable harnesses, and other useful goodies.

CD players have optics you can gut out if your robot uses a specialty vision system. Apart from the laser diode, CD players have focusing lenses and other optics, as well as miniature motors.

Old fax machines contain numerous motors, gears, small switches, and other mechanical parts.

Mice, printers, old scanners, disk drives, and other discarded computer add-ons contain valuable optical and mechanical parts. Mice contain optical encoders that you could use to count the rotations of your robot’s wheels; printers contain motors and gears; disk drives contain motors; and so on.

Mechanical toys, especially the motorized variety, can be used either for parts or as a robot base. When looking at motorized vehicles, favor those that use separate motors for each drive wheel.

Getting Organized

Over his 20 years in the military, one of the principal jobs my father had was taking charge of supplies. He had the knack for organizing where everything went—from huge trucks and airplanes to miniscule ball bearings.

If apple trees are organizational traits, this apple (me) fell far from the tree: I inherited virtually none of my dad’s mind-set to keep things in their place. All while growing up—and even now as an adult—I’d forget to put things back where they belonged. I’ve often ended up buying the same thing two and even three times because I’d lost track of my garage inventory.

So, knowing my shortcomings, I now make a conscious effort to maintain order in the shop, or else things rapidly get messy and increasingly expensive. It gets old taking a half hour just to find a part.

While my shop is far from a Robotics Eden, it’s now more or less well organized, and this with the help of some small parts cabinets, a few plastic parts bins, and zipper-style plastic bags. My system works for me, but you’ll undoubtedly want to improvise your own.

SMALL PARTS DRAWER CABINETS

Plastic drawer cabinets are really the mainstay for any activity that deals with small parts. You can get them in all styles and sizes, from little units with just a half dozen 1″ × 2″ drawers (these fit on bookshelves quite well) to much larger parts chests, with 20, 30, even 40 drawers of different shapes and sizes. These won’t fit on a bookshelf—unless your shelves are for very large books!—but are ideal for workbenches and assembly tables.

I like the cabinets with several drawer sizes, which accommodate parts of different bulks. For example, the cabinet might sport 24 or 30 small drawers of about 1.5″ × 2″ and 6, 9, or 12 large drawers of about 2″ × 4″. You might, for instance, place individual values of resistors in the smaller drawers and large capacitors in the large drawers.

HEAVY-DUTY STORAGE DRAWERS

A step up the size and cost ladder is the plastic heavy-duty storage bin. These are 1-to 3-foot-high units that sport between three and six large, heavy-duty plastic drawers. The drawer sizes may be different or all the same; find a model that suits your needs. The most robust models can readily hold heavy motors, metal gears, and other construction parts.

Larger still (and somewhat more flexible) are stacking drawers, with sizes big enough to hold bulky sweaters and pants. They’re made to stack on top of one another, so you can get as few or as many as you want. (Avoid overdoing the height of your Tower of Babel, or else things could topple if you open a heavy drawer near the top of your stack.)

TOOLBOXES AND TOTES

Sometimes you have to build while on the go, and you’ll need to bring your tools and supplies with you. For the big stuff, a standard metal or heavy-duty plastic toolbox is the best choice. I still have my Sears Craftsman 24″ steel toolbox that I bought over 30 years ago, and I use it regularly.

Figure 3-3 A plastic toolbox or tote helps you keep all your robot-building supplies in one convenient location. Get one with several compartments for storing small parts.

For lighter jobs, a plastic fishing tackle box or tote (see Figure 3-3) makes it easy to lug your supplies. The typical tackle box has a storage drawer on the top for small parts. When you open the top, the drawer slides up and over, and you can reach into the bottom of the box for larger tools and supplies.

KEEPING TRACK OF YOUR INVENTORY

Unless you have perfect memory you’ll need some system to keep track of what has gone where. On the low end of the scale is the old “Magic-Marker-on-the-side-of-the-parts-bin trick.” (You can use any type of felt-tip marker; a Sharpie is my favorite.)

Instead of writing directly on the plastic, you can instead tape an index card to the container and write on the card. If you change the contents of the container, just peel the card off and start over. Wide clear packing tape works well, too.

For smaller parts drawers, an electronic labeler is the absolute best way to keep track of parts. (Think of Vanessa Kensington from the movie Austin Powers, and how her suitcase was full of labeled bags.) Larger machines can accommodate labels of many different widths.

AD-HOC STORAGE SOLUTIONS

Not everything needs a fancy plastic storage bin. Sometimes simple—and free—is better. Here are some storage ideas for when you don’t need a fancy solution.

Cardboard shoe boxes still make great storage containers. Keep the lid so you can stack up the boxes, or just use the box open if you need quick access.

Zipper locking food storage bags, particularly the heavy-duty ones for freezer use, make ideal containers for odd-sized items. Mark the contents with a Sharpie. Tip: The wide-bottom bags stand up on their own.

Baby food jars, plastic or glass, are still an excellent storage solution for very small parts, such as 2–56 size hardware. (If you can get ’em, use the glass jars for electronics parts, as they don’t generate static.)

Empty egg crates and egg boxes are also useful for holding small parts, but take care not to overturn the crate or box, as the lid doesn’t close over the hollow for the egg. If you’re not careful, your parts may spill out or get mixed up.