Figure 3-14. X-Acto makes a range of small saw blades that are ideal for cutting square holes to mount components in plastic panels.
Recommended: Miniature vise
A miniature vise can do things that the helping hand cannot. I use mine when I’m sawing small pieces of plastic and as a dead weight to anchor a piece of perforated board while I’m working on it. See Figure 3-15.
Figure 3-15. This one-inch vise is available from the McMaster-Carr catalog.
Look for a cast-iron vise that is listed as being 1 inch or slightly larger, available from Megahobby, eBay, and other arts/crafts sources. Also consider the PanaVise, which has a tilting head to allow you to turn your work to any angle.
Recommended: Deburring tool
A deburring tool instantly smoothes and bevels any rough edge (when you have sawn or drilled a piece of plastic, for instance) and also can enlarge holes slightly. This may be necessary because some components are manufactured to metric sizes, which don’t fit in the holes that you drill with American bits. Your small local hardware store may not stock deburring tools, but they are very inexpensively available from Sears, McMaster-Carr, KVM Tools, or Amazon. See Figure 3-16.
Figure 3-16. This cunning little blade, safety-tipped with a round bump on the end, removes rough edges from saw cuts with a single stroke, and can enlarge holes that are almost big enough—but not quite.
Optional: Hand-cranked countersink
You need a countersink to bevel the edges of screw holes to accept flat-headed screws. If you use a countersink bit in an electric drill, it won’t give you precise control when you’re working with thin, soft plastic.
Handheld countersinks that you grasp and turn like a screwdriver are easy to find, but McMaster-Carr (catalog item 28775A61) is the only source I’ve found for a hand-cranked tool that is much quicker to use. It comes with a set of bits, as shown in Figure 3-17.
Optional: Pick and hook set
Made by Stanley, part number 82-115, available from Amazon and hardware stores. You can find imported imitations for a few dollars less. See Figure 3-18.
Optional: Calipers
These may seem like a luxury, but are useful for measuring the external diameter of a round object (such as the screw thread on a switch or a potentiometer) or the internal diameter of a hole (into which you may want a switch or potentiometer to fit).
I like Mitutoyo calipers, and the low-end model 505-611 (shown in Figure 3-19) does everything I need. You can find cheaper brands, but economizing on precision measuring tools may not be a wise policy in the long term. The manufacturer’s site will show you all their available models, after which you can Google “Mitutoyo” to find retail sources.
Figure 3-17. You spin this countersink tool like a hand crank to add just the right amount of bevel to a hole, so that it will accommodate a flat-head screw.
Figure 3-18. This pick-and-hook set is useful in many unexpected ways.
Figure 3-19. Calipers can be digital (which automatically convert from millimeters to 1/64 inch to 1/1,000 inch), or analog like these (so you never need to worry about a dead battery).
Supplies
Solder
This is the stuff that you will melt to join components together on a permanent (we hope) basis. You need some very thin solder, size 0.022 inches, for very small components, and thicker solder, 0.05 inches, for heavier items. Avoid buying solder that is intended for plumbers, or for craft purposes such as creating jewelry. A range of solder thicknesses is shown in Figure 3-20. You want to make sure to get lead-free solder.
Figure 3-20. Spools of solder in various thicknesses.
Electronics solder has a nonacidic rosin core that is appropriate for electronic components. Rolls of solder are available from all hobby-electronics sources including All Electronics, RadioShack, and Jameco, or search for “electronic solder” on Amazon.
Wire
You’ll need some stranded wire to make flexible external connections with the circuit that you’ll be building. Look for 22-gauge stranded hookup wire, in red, black, and green, 10 feet (minimum) of each.
If you want to install the intrusion alarm after completing that project in Experiment 15, you’ll need white-insulated two-conductor wire of the type sold for doorbells or furnace controls. This is available by the foot from Lowe’s, Home Depot, Ace Hardware, and similar stores. You’ll decide how much to buy after you measure the distances between the magnetic sensor switches that you decide to install.
Heat-shrink tube
For use in conjunction with your heat gun, described previously. You’ll need a range of sizes in any colors of your choice. See Figure 3-21. Check RadioShack part 278-1627, other electronics suppliers, or your local hardware store. Prices will vary widely. You can buy the cheapest.
Copper alligator clips
These absorb heat when you are soldering delicate components. The Mueller BU-30C is a full-size solid copper alligator clip for maximum heat absorption. RadioShack sells smaller clips (part number 270-373, shown in Figure 3-22) that are suitable for tiny components.
Figure 3-21. Slide heat-shrink tubing over a bare joint and apply heat from a heat gun to make a tight insulating seal around the joint.
Figure 3-22. These small clips absorb heat to protect components when you’re soldering them.
Perforated board
When you’re ready to move your circuit from a breadboard to a more permanent location, you’ll want to solder it to a piece of perforated board, often known as “prototyping board” but also called “perfboard.”
You need the type that has copper strips etched onto the back, in exactly the same “breadboard layout” as the conductors hidden inside a breadboard, so that you can retain the same layout of your components when you solder them into place. Examples are RadioShack part 276-150 (shown in Figure 3-23) for small projects and part 276-170 (in Figure 3-24) for larger projects, such as Experiment 15.
Figure 3-23. This perforated board has a pattern of copper traces similar to the pattern inside a breadboard, so that you can lay out the components with minimal risk of wiring errors, when you’re ready to create a permanently soldered version of your project.
For very small projects in which you will connect components using their wires alone, you need perfboard that isn’t etched with copper strips connecting the holes. I like the Twin Industries 7100 range (available from Mouser.com) or Vectorboard from Newark Electronics, shown in Figure 3-25. You use a saw to cut out as small a piece as you need. Cheaper options are RadioShack part 276-147 (shown in Figure 3-26), or PC-1 from All Electronics. These have little copper circles around each hole that are not necessary for our purposes, but not a problem, either.
Figure 3-24. A larger example of perforated board with breadboard geometry.
Figure 3-25. Plain perforated board (with no copper traces) can be used for mounting components when you want to do point-to-point wiring.
Figure 3-26. A small piece of perforated board with individual copper solder pads to assist you in mounting components.
Plywood
When you use a soldering iron, hot drops of solder tend to fall onto your table or workbench. The solder solidifies almost instantly, can be difficult to remove, and will leave a scar. Consider using a 2-foot square of half-inch plywood to provide disposable protection. You can buy it precut at Home Depot or Lowe’s.
Machine screws
To mount components behind a panel, you need small machine screws (or “bolts”). They look nice if they have flat heads that fit flush against the panel. I suggest stainless-steel machine screws, #4 size, in 1/2-, 5/8-, 3/4-, and 1-inch lengths, 100 of each, plus 400 washers and 400 #4 locknuts of the type that have nylon inserts, so that they won’t work loose. Check McMaster-Carr for a large and reasonably priced selection.
> Project boxes
A project box is just a small box (usually plastic) with a removable lid. You mount your switches, potentiometers, and LEDs in holes that you drill through the box, and you attach your circuit on a perforated board that goes inside the box. Search All Electronics for “project box” or RadioShack for “project enclosure.”
You need a box measuring approximately 6 inches long, 3 inches wide, and 2 inches high, such as RadioShack part 270-1805. Anything similar will do. I suggest you buy a couple other sizes as well, as they will be useful in the future.
Components
Power plugs, sockets, and binding posts
After you finish a project and put it in a box, you’ll need a convenient way to supply it with power. Buy yourself a pair of insulated binding posts, such as RadioShack part 274-661, shown in Figure 3-27. Also obtain a panel-mounted power jack, size N, such as RadioShack part 274-1583, and DC power plug, size N, such as RadioShack 274-1573. The plug-and-socket pair is pictured in Figure 3-28.
Finally, you will need interconnects that are sized to fit a perforated board that is drilled at intervals of 1/10 inch. Sometimes known as “single inline sockets and headers,” but also known as “boardmount sockets and pinstrip headers,” they come in strips of 36 or more, and you can snip off as many as you need. Examples are Mill-Max part numbers 800-10-064-10-001000 and 801-93-050-10-001000, or 3M part numbers 929974-01-36-RK and 929834-01-36-RK. You can buy them from the usual electronics suppliers. Figure 3-29 shows headers before and after being snapped into small sections. Make sure that the interconnects have a terminal spacing of 0.1 inch.
Figure 3-27. These terminals, also known as binding posts, enable a solderless connection with wires that have stripped ends. Also available in black.
Figure 3-28. The socket on the right can be mounted in a project box to receive power from the plug on the left.
Figure 3-29. Single inline sockets (top) and headers (middle) allow you to make very compact plug-and-socket connections to a PC board. They can be sawn, cut, or snapped into smaller sections (bottom). The terminals are 0.1 inch apart.
Battery
After you complete Experiment 15 at the end of this section of the book, if you want to use the project on a practical basis, you’ll need a 12-volt battery. Search online for “12v battery” and you’ll find many sealed, rechargeable lead-acid batteries that are designed for alarm systems, some measuring as small as 1×2×3-inch and costing under $10. You need a charger with it, which will probably cost you about $10.
Switches and relays
You will need the same DPDT relay and the same SPDT toggle switch that were mentioned in Chapter 2 shopping list.
For Experiment 15, you’ll need magnetic switches that you can apply to doors or windows, such as the Directed model 8601, available from dozens of sources online.
Also you will need a DPDT pushbutton switch, ON-(ON) type, with solder terminals. Examples are model MPG206R04 by Tyco or model MB2061SS1W01-RO by NKK (with optional cap). Or search eBay for “DPDT pushbutton.”
Diodes
Buy at least half-a-dozen red 5 mm LEDs rated for approximately 2 volts, such as the Optek part number OVLFR3C7, Lumex part number SSL-LX5093IT, or Avago part HLMP-D155. Buy half-a-dozen similar green LEDs at the same time.
In addition, you’ll need a signal diode, type 1N4001 (any brand will do). Figure 3-30 shows an example, highly magnified. They’re cheap, and likely to be useful in the future, so buy 10 of them.
Figure 3-30. This 1N4001 diode is about 1/4 inch long and can handle up to 50 volts.
Loudspeaker
To complete the project in Experiment 15, you’ll need a loudspeaker small enough to fit inside your project box but louder than the 1-inch speaker that you used previously. It should be 2 inches or 2.5 inches (50 to 60 mm) in diameter. If you can find a 100Ω speaker, it will give you more output, but an 8Ω speaker will be acceptable.
Experiment 12: Joining Two Wires Together
Your adventure into soldering begins with the prosaic task of joining one wire to another, but will lead quickly to creating a full electronic circuit on perforated board. So let’s get started!
You will need:
30-watt or 40-watt soldering iron
15-watt pencil-type soldering iron
Thin solder (0.022 inches or similar)
Medium solder (0.05 inches or similar)
Wire strippers and cutters
“Helping hand” gadget to hold your work
Shrink-wrap tubing, assorted
Heat gun
Something to protect your work area from drops of solder Soldering Irons Get Hot!
Please take these basic precautions:
Use a proper stand (such as the one incorporated in your helping hands) to hold your soldering iron. Don’t leave it lying on a workbench.
If you have infants or pets, remember that they may play with, grab, or snag the wire to your soldering iron. They could injure themselves (or you).
Be careful never to rest the hot tip of the iron on the power cord that supplies electricity to the iron. It can melt the plastic in seconds and cause a dramatic short circuit.
If you drop a soldering iron, don’t be a hero and try to catch it. Most likely you will grab the hot part, which hurts. (I speak from experience.) When you burn your hand, you will instinctively let go of the iron, so you may as well let it drop freely without the intermediate step of burning yourself while it’s on its way to the floor. Naturally, you should pick it up quickly after it does hit the floor, but by then you will have gained the necessary time in which to make a sensible decision to grab it by the cool end.
Always bear in mind that others in your home are more at risk of hurting themselves on a soldering iron than you are, because they won’t know that it’s hot. Most soldering irons have no warning lights to tell you that they’re plugged in. As a general rule, always assume that a soldering iron is hot, even if it’s unplugged. It may retain sufficient heat to burn you for longer than you expect.
Your First Solder Joint
We’ll start with your general-duty soldering iron—the one rated for 30 or 40 watts. Plug it in, leave it safely in its holder, and find something else to do for five minutes. If you try to use a soldering iron without giving it time to get fully hot, you will not make good joints.
Strip the insulation from the ends of two pieces of 22-gauge solid wire and clamp them in your helping hand so that they cross each other and touch each other, as shown in Figure 3-31.
To make sure that the iron is ready, try to melt the end of a thin piece of solder on the tip of the iron. The solder should melt instantly. If it melts slowly, the iron isn’t hot enough yet.
Figure 3-31. A helping hand work aid is shown here holding two wires with their stripped ends touching. The magnifying glass has been hinged out of the way.
Now follow these steps (shown in Figures 3-32 through 3-36):
1. Make sure the tip of the soldering iron is clean (wipe it on the moistened sponge in the base of your helping hand if necessary), then touch it against the intersection of the wires steadily for three seconds to heat them. If you have hard tap water, use distilled water to wet the sponge to avoid a buildup of mineral deposits on the tip of your soldering iron.
2. While maintaining the iron in this position, feed a little solder onto the intersection of the wires, also touching the tip of the soldering iron. Thus, the two wires, the solder, and the tip of the iron should all come together at one point. The solder should spread over the wires within another two seconds.
3. Remove the iron and the solder. Blow on the joint to cool it. Within 10 seconds, it should be cool enough to touch.
4. Unclamp the wires and try to tug them apart. Tug hard! If they defeat your best atte
mpts to separate them, the wires are electrically joined and should stay joined. If you didn’t make a good joint, you will be able to separate the wires relatively easily, probably because you didn’t apply enough heat or enough solder to connect them.
The reason I asked you to begin by using the higher-powered soldering iron is that it delivers more heat, which makes it easier to use.
Figure 3-32.
Figure 3-33.
Figure 3-34.
Figure 3-35. This and the preceding three figures illustrate four steps to making a solder joint: apply heat to the wires, bring in the solder while maintaining the heat, wait for the solder to start to melt, and wait a moment longer for it to form a completely molten bead. The whole process should take between 4 and 6 seconds.
Figure 3-36. The completed joint should be shiny, uniform, and rounded in shape.
Background
Soldering myths
Myth #1: Soldering is very difficult.
Make: Electronics Page 14
