05-05-2012, 02:33 PM
Making prototype circuits using a solderless breadboard
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Many people are confused the first time that they have to build a circuit. How to connect the components together? The easiest way to get started is by 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 right is a typical breadboard. There are several rows of holes for components. 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.
The pattern varies from model to model; some breadboards have only one strip down each side (like this model from Radio Shack), others have multiple side rows, and so forth. The basic model, with many horizontal rows separated by a central divider and one or two long side rows, is what we’ll focus on.
On each side of the 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.
This image of the back of a breadboard may help to clear up how the holes on the front of the board are connected. The backing of the board has been removed (don’t remove the backing on your own board! It will make the board useless) to expose the metal strips connecting the holes. You can clearly see the short strips in the center separated by the divider, and the long strips down the side. The detail photo to the right illustrates how the holes and strips are related.
The reason for the center divider is so that we can mount integrated circuit 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.