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Working with the Boxes that Contain Your Projects

In most cases, you’ll want to put the breadboard on which you build your circuit into some kind of container. A container can make toting around your breadboard easier, help prevent little bits from falling off, and make your project look better. You might also want to add mechanisms for controlling your circuit in a box. For example, you might operate a remote control device by disconnecting and connecting wires on a breadboard, but wouldn’t it be easier to put the breadboard in a box and then add switches and buttons you can use to make it work?

In this section, we give you some advice about basic skills you need to work with these containers for your projects.

Working with boxes

Essentially, using a box involves finding the right type of box and then drilling or cutting holes in it to poke wires and items such as switches or speakers through.

Choosing plastic or wood

You could build your own boxes, but you can find a large variety of containers that you can simply buy cheaply and put right to work, including plastic and wooden boxes in various shapes. We typically put remote control circuits in plastic boxes to make the control light and compact for handling. And we typically use wooden boxes to house other circuits because we can make them look a little more stylish than the plastic boxes.

Drilling and cutting holes

We use a drill to make holes up to 1⁄2" diameter in boxes. There’s nothing complicated about using an electric drill, but if you’re new to this tool, have someone at your local home improvement center walk you through it. Here’s an easy way to decide what size drill bit to use. Try slipping drill bits through the nut used to secure the screws or electrical component you’re drilling the hole for. Choose a drill bit that’s too big to fit through the hole in the nut and smaller than the outside of the nut. Drill bits sometimes bind in the material you’re drilling. When a drill bit binds, the box gets kind of edgy and begins to spin with the drill. That’s why it’s important that you clamp the box you’re drilling to your worktable or secure it in a vise. We’ve found that drill bits bind more often in plastic boxes than in wooden ones.

Mounting your project in a box

After you build your circuit and drill or cut holes in your box to accommodate anything you want to feed through from inside to outside, actually mounting things in the box has a few ins and outs, too.

Working with switches, potentiometers, and other panel-mount components

Many switches, potentiometers, and other components have a threaded shaft, a nut, and possibly washers that are meant to be mounted through a hole in a panel. Here’s the drill (pun intended):

1. Drill a hole in your box where you want to mount the component.

2. Clean up any debris around the hole from the drilling.

3. Slide the threaded shaft through the hole and tighten a nut on the threads. If the hole turns out to be a little too big, slip a washer under the nut.

Some components, such as speakers or buzzers, have holes in flanges that you can use to secure the component to the wall of the box with screws. Use the flange holes as a template to mark the locations to drill holes. Some components are meant to be panel-mounted but don’t have threads. For example, in Chapter 11, we use a two-piece, LED panel-mount socket in which one part of the socket slides through the hole and onto the other half and snaps in place, securing the LED.

In some cases, you have to mount microphone cartridges that don’t come with threads or snap sockets in the walls of boxes. Simply drill a hole that’s just big enough in diameter to slip the cartridge in with a snug fit. If you’re using a wooden box, the wall of the box should be thick enough to secure the microphone cartridge. If you’re using a plastic box, you’ll probably need to secure the microphone cartridge with glue.

Sticking things on the box

If you use screws to attach a component to a wooden box and you want to put something else over the screw head, use a flathead screw, as shown in Figure 4-16. When you don’t need to keep the surface flush, panhead screws are just fine.

figure 4-16

When stranded wire works

If you’re connecting a component in the lid of your box to a terminal block on the breadboard in the bottom of the box, that wire will be bent back into the box when you close the lid. In this case, it’s best to use stranded wire, which is more flexible than solid wire. (Refer to Figure 4-9 for a comparison.) Be sure to leave enough length of wire for the box to open and lightly solder the strands at the end of the wire together before inserting them into the terminal block so none of them poke out and short the circuit.

For items with flat surfaces such as breadboards or battery packs, Velcro or similar materials are useful to secure them in your box. However, if you remove breadboards that you have secured in a box with Velcro, be careful. Breadboards have a thin sheet of plastic or paper on the back that can peel off if you’re not careful.

You can make custom mounts out of metal bars, screws, and nuts, as shown in Figure 4-17, which shows also how we mount the motors in "Sensitive Sam Walks the Line" project.


figure 4-17

You can also use wooden dowels and cable ties as we did to mount the microphone in Chapter 6 (see Figures 4-18 and 4-19).

figure 18/19

You can use wire clips to secure wires to the side of boxes so they are out of the way as you work, as shown in Figure 4-20.

figure 4-20