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.
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.
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).
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.
