Follow along with this series!
Joe’s book & kits are available in our
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with the Arduino
Projects Kit by Joe Pardue
■ The ALP (AVR Learning Platform).
Introduction to Breadboards
Itend to write this stuff with the idea that the reader
already knows a bit about electronics. But that isn’t
always a valid assumption. For instance, some folks
have never used a solderless breadboard. I tried to
remember the first time I used one and it just seems like
I was born knowing how these things work. I do have
vague recollections, however, of using an ohmmeter to
figure out that the + and – power busses run horizontally
the entire length of the board and that the two grids in
the middle of the board have vertical five-position clips.
If you have already used one of these things, then skip
over this section.
How a Breadboard Works
In the good old days, electronics experimenters would
build prototypes by nailing components to an actual
■FIGURE 1. Breadboard front and back.
wooden breadboard and then soldering wire between
connection points. Today’s solderless breadboards are
made of plastic blocks with holes on 0.1 inch centers that
allow you to insert jumper wires (usually 22 AWG) into
hidden clips below the holes. The vertical ‘terminal’ blocks
let you connect up to five points on each of the 63 double
sets of columns. These columns are separated by a 0.4
inch gutter over which you can place an IC or DIP package.
You also have four horizontal power bus rows with 50
point clips on each … Oh, who am I kidding? There is no
way you can really understand what is going on by reading
a written description. It is even hard to take decent photos
and have it be clear what I’m talking about. So, I decided
to take some photos and get out the crayons and draw
some pretty pictures that might just make things clearer.
Figure 1 shows the top and bottom of a solderless
breadboard (the bottom has the foam tape stripped off to
show the connections. Figure 2 shows the clips pulled
out. Figure 3 shows how a clip grabs a wire and Figure 4
shows a cutaway drawing with an LED, 1K resistor,
and a jumper wire all connected such that if you
have + 5 volts in the upper + channel and GND in
the lower – channel, the LED should light up.
The clips should handle about one amp at five
volts. Breadboards only work for relatively low
frequency devices ( 10 MHz or less) due to high
and variable stray capacitance and inductance.
Also, the jumpers don’t always maintain a solid
connection. I can’t count the times that I’ve had a
circuit go weird until I jiggled a few wires and the
weirdness went away. However, I’ve gotten microcontrollers to work with 16 MHz external clocks
on breadboards, but it isn’t something that you
can be totally confident in so caution is advised.
You are trading off reliability for flexibility (and