Circuitbuilding Projects: The Solderless Breadboard

Using a breadboard is one of the basic starting points for the design of many types of circuits and projects. Also known as a plugboard or prototyping board, this miniature workbench allows you to whip up a circuit or try a new design in just minutes!

You can probably pick one up at your local RadioShack store. Models are available from postage stamp sizes used for trying small circuits inside equipment, all the way to foot-square models on which entire complex circuits can be built. A small one will do just fine as you start out, but it's a good idea to buy one size bigger than you think you need.

A solderless breadboard consists of plastic strips with small holes into which the leads of electronic components are inserted. Brass strips under the holes connect each short row of openings together. Any two leads inserted into the same row of holes will be connected together electrically. The plastic body keeps adjacent strips from shorting together.

Up to four leads can be connected together in this way. If more common connections are required, a short piece of wire can be used to connect two (or more) rows together, creating a common electrical contact between all the holes in those rows. The slot between halves of the plastic strip is an insulating gap between the two sides so that integrated circuits with a DIP (Dual In-line Package) can be inserted with one row of pins on each side of the strip.

Most breadboards have areas for point-to-point circuit wiring and areas for distributing power and ground. These are called rails, and they run the length of the breadboard's plastic strips. For analog circuits, these are generally used for positive and negative power supplies, plus a common ground or return to the power supply. Builders of digital circuits that operate from a single voltage find it easier to "double up" and use the extra rail for a duplicate power supply connection. Breadboards with more than one strip, each with its own set of rails, are easy to use for circuits that have both analog and digital circuitry.

If you are just getting started, you might consider purchasing a breadboard that comes with its own power supplies and possibly even some limited test capabilities. More expensive models even have test meters and test signal generators. Although separate power supplies and test equipment might be more flexible and have additional features, the convenience of always having the test equipment connected and ready will be appreciated.

In keeping with the theme of convenience, breadboards hardly need any special materials to use! You'll need some test equipment to power and measure your circuits, certainly, but aside from the components themselves, here is a short list of things you'll need:

• Insulated jumpers (20- to 24-gauge solid, insulated wire in various colors): They don't have to be tinned (coated with solder); bare copper is fine.

• Bare jumpers (20- to 24-gauge solid bare wire): These are used to connect adjacent rows of contacts, to create connection points for external equipment, or to make leads for items that don't have suitable leads for insertion into the breadboard sockets. Save the clipped-off pieces of component leads to create a bountiful supply!

• Leaded components: It's very difficult, if not impossible, to use surface-mount technology (SMT) components with a breadboard. Make the task easier by purchasing and stocking only leaded components.

That's it! No special tools other than needle-nose pliers and a small pair of wire cutters are needed. You may also want to augment your eyesight by purchasing a pair of head-mounted magnifier glasses from a local craft store.

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