P R OTO
BY JIM STEWART
For those just getting started in electronics as a hobby, a solderless
breadboard (SBB) is the perfect platform for building those first circuits.
Also known as a solderless proto board, an SBB has rows
of springy metal contacts embedded in a plastic base.
The contacts hold components in place and the rows can be
interconnected with wires. Changing a circuit is quick and
easy. And when done, the circuit can be disassembled and
the components can be saved for reuse in the next circuit.
Figure 1 is a photograph of a typical SBB while Figure 2 is
a simplified drawing showing how an SBB is wired internally.
An SBB can be purchased from Jameco (part #194299),
Electronix Express (part #03MB102), and other vendors.
A pair of contact strips marked by red and blue lines run
along both of the long sides. The plus and minus signs show
that those strips are often used as power buses. (Not all SBBs
have those stripes or +/- signs.) In the center are many short
contact strips on either side of the groove that run down the
middle of the SBB. The connections do not span the groove.
mounted on a solderless breadboard. Note how the IC is
inserted so that its rows of pins are on either side of the
groove. The SBB is designed for easy use of DIP (dual
inline package) ICs such as the one shown. The contact
holes are spaced 0.1 inches apart from each other and
0.300 inches across the groove.
It's easy to mount leaded parts such as resistors,
capacitors, diodes, and ICs on an SBB. However, switches
can be a problem; many are not designed to fit an SBB.
It's also difficult to connect stranded wire leads such as
on a battery connector to an SBB. For stranded wire,
something like a screw-terminal would be handy. This is
where the Proto Buddy comes in.
The Proto Buddy
Components on an SSB
Figure 3 is a detailed view of components
■ FIGURE 1
The Proto Buddy board (PRB) is shown in Figure 4. It
has two SPST switches, two N.O. momentary pushbutton
switches, two LEDs with 1K current limiting resistors, and a
three-position terminal-block for stranded wire. It uses
three sets of pins along one edge to plug
into the connector strip on one edge of
the SBB as shown. All components on the
PRB are wired to pin jacks along its edge.
Pieces of solid hook-up wire are used to
connect the PRB to the SBB. A Proto
Buddy attached to an SBB costs a lot less
than the powered breadboards sold by
many vendors but with a battery or two
attached to it the combo has a lot of
the same functionality as those
Figure 5 is the schematic of the PRB.
The two pushbutton switches are
connected by a removable jumper, as are
the two LED circuits. The jumpers are
there for convenience. For pushbutton
switches, it's often the case that both
connect to ground. For LEDs, it's often the
case that both anodes are connected to
+V through resistors. The jumpers can
eliminate a few wires in
■ FIGURE 2