Make Electronics

Getting Somewhat More Serious 119

Experiment 14: A Pulsing Glow

Resizing the Circuit

The first step is to look at the physical components and imagine how to fit them
into a small space. Figure 3-78 shows a 3D view of a compact arrangement. Check
this carefully, tracing all the paths through the circuit, and you’ll see that it’s the
same as the schematic. The trouble is that if we solder the components together
like this, they won’t have much strength. All the little wires can bend easily, and
there’s no easy way to mount the circuit in something or on something.

R4

R1

R2

R3

R5

C1

C2

Figure 3-78. This layout of components replicates their connections in the schematic
diagram while squeezing them into a minimal amount of space.

The answer is to put it on a substrate, which is one of those terms that people in
the electronics field like to use, perhaps because it sounds more technical than
“perfboard.” But perforated board is what we need, and Figure 3-79 shows the
components transferred onto a piece of board measuring just 1 inch by 0.8 inch.

The center version of this diagram uses dotted lines to show how the compo-
nents will be connected with each other underneath the board. Mostly the
leads that stick out from underneath the components will be long enough to
make these connections.

Finally, the bottom version of the perfboard diagram shows the perfboard
flipped left-to-right (notice the L and the R have been transposed to remind
you, and I’ve used a darker color to indicate the underside of the board).
Orange circles indicate where solder joints will be needed.

The LED should be unpluggable, because we may want to run it at some dis-
tance from the circuit. Likewise the power source should be unpluggable. For-
tunately we can buy miniature connectors that fit right into the perforated
board. You may have to go to large online retail suppliers such as Mouser.com
for these. Some manufacturers call them “single inline sockets and headers,”
while others call them “boardmount sockets and pinstrip headers.” Refer back
to Figure 3-29 and check the shopping list for more details.

This is a very compact design that will require careful work with your pencil-
style soldering iron. Because a piece of perforated board as small as this will
tend to skitter around, I suggest that you apply your miniature vise to one end
to anchor it with some weight while still allowing you to turn it easily.

R

L

R

L

R

L

Figure 3-79. Perforated board can be used

to support the layout of components. Their

leads are soldered together under the

board to create the circuit. The middle dia-

gram shows the wires under the board as

dashed lines. The bottom diagram shows

the board from underneath, flipped left to

right. Orange circles indicate where solder

joints will be necessary.