Making prototype circuits
using a solderless breadboard
A breadboard is a tool for holding the
components of your circuit, and connecting them together.
It's got holes that are a good size for hookup wires and the ends
of most components, so you can push wires and components in and pull
them out without much trouble.
At left is a typical breadboard. The holes on the breadboard are separated by
0.1-inch spaces, and are organized in many short rows in the center,
and in two long rows down each side of the board. The short horizontal
rows in the middle are separated by a center divider.
On each side of our board are two long rows of holes, with a
blue or a red line next to each row. All the holes in each of
these lines are connected together with a strip of metal in the back.
In the center are several short rows of holes separated by a central
divider. All of the five holes in each row in the center are connected
with a metal strip as well. This allows you to use the holes in any
given row to connect components together. To see which holes are
connected to which, take a multimeter and a couple of wires, set
the multimeter to measure continuity, stick the two wires in two
holes, and measure them with the multimeter. If the meter indicates
continuity, then the two holes in question are connected.
The reason for the center divider is so that we can mount integrated
circuit (
IC) chips, like a microprocessor, on the breadboard.
IC chips typically have two rows of pins that we need to connect other
components to. The center row isolates the two rows from each other,
and gives us several holes connected to each pin, so we can connect
other components.
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When you start to put components on your breadboard,
avoid adding, removing, or changing components on a breadboard
whenever the board is powered. You risk shocking yourself and
damaging your components. |
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At left is a typical use of a breadboard.
- An IC chip
(in this case a BX-24 microcontroller) straddling the center divider,
connected to several of the rows of middle holes.
- At the top, a 7805 5V DC
voltage regulator is connected to three of the middle rows
- Ground pin is connected to the
blue rows of holes
- +5V output is connected to the red rows of holes.
- LED and resistor connected to the BX-24's bottom left pin (pin 12) in series.
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A second row of middle
holes is used to connect the LED to the resistor.
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At left,
the
three LED's are connected in series using two rows. They are then connected to
power and ground by connecting the rows to the red power row and the blue ground
row.
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Many options are possible using a breadboard,
which is what makes them very useful and convenient
for building circuits. Once you understand which holes
are connected to each other (and which ones are not),
you can build any circuit very quickly.
Wiring basics
You need to add a
voltage regulator to your breadboard because you only want to allow
5 volts into your circuit. We will use the LM7805 :
Output is what you want to link to your power line of your breadboard.
Front view
Back view
Also you want to connect both power and ground sides together:
Class Assignment— Your First Circuit
