Experiment 14: A Pulsing Glow
120 Chapter 3
When I’m working on this kind of project, I like to place it (with the vise at-
tached) on a soft piece of polyurethane foam—the kind of slab that is nor-
mally used to make a chair cushion. The foam protects the components from
damage when the board is upside-down, and again helps to prevent the work
from sliding around unpredictably.Step by Step
Here’s the specific procedure for building this circuit:- Cut the small piece of perfboard out of a sheet that has no copper traces
on it. You can cut the section using your miniature hobby saw, or you may
be able to snap the board along its lines of holes, if you’re careful. Alter-
natively, use a small ready-cut piece of perfboard with copper circles on it
that are not connected to one another. You’ll ignore the copper circles in
this project. (In the next experiment, you’ll deal with the additional chal-
lenge of making connections between components and copper traces on
perforated board.) - Gather all the components and carefully insert them through holes in the
board, counting the holes to make sure everything is in the right place.
Flip the board over and bend the wires from the components to anchor
them to the board and create connections as shown. If any of the wires
isn’t long enough, you’ll have to supplement it with an extra piece of
22-gauge wire from your supply. You can remove all the insulation, as we’ll
be mounting the perfboard on a piece of insulating plastic. - Trim the wires approximately with your wire cutters.
- Make the joints with your pencil soldering iron. Note that in this circuit,
you are just joining wires to each other. The components are so close to-
gether that they’ll prevent each other from wiggling around too much. If
you are using board with copper pads (as I did), and some solder connects
with them, that’s OK—as long as it doesn’t creep across to the neighbor-
ing component and create a short circuit. - Check each joint using a close-up magnifying glass, and wiggle it with
pointed-nosed pliers. If there isn’t enough solder for a really secure joint,
reheat it and add more. If solder has created a connection that shouldn’t
be there, use a utility knife to make two parallel cuts in the solder, and
scrape away the little section between them.
Generally, I insert three or four components, trim the wires approximately, sol-
der them, trim their wires finally, then pause to check the joints and the place-
ment. If I solder too many components in succession, there’s a greater risk of
missing a bad joint, and if I make an error in placing a component, undoing
it will be much more problematic if I have already added a whole lot more
components around it.
Figures 3-80 and 3-81 show the version of this project that I constructed, be-
fore I trimmed the board to the minimum size.
Figure 3-80. Components mounted on a
piece of perforated board.
Figure 3-81. The assembly seen from
below. The copper circles around the holes
are not necessary for this project. Some of
them have picked up some solder, but this
is irrelevant as long as no unintentional
short circuits are created.