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Digital Logic Design

Breadboard Sockets

In order to temporarily construct a circuit without damaging the components used to build it, we must have some sort of a platform that will both hold the components in place and provide the needed electrical connections. In the early days of electronics, most experimenters were amateur radio operators. They constructed their radio circuits on wooden breadboards, which allowed them room to mount such things as vacuum tube sockets and larger, heavy components with sufficient room between them, and to connect components from pin to pin of the different sockets in order to complete the circuit.

Although more sophiticated techniques and devices have been developed to make the assembly and testing of electronic circuits easier, the concept of the breadboard remains, and the process of assembling components on a temporary platform is still known as "breadboarding."

The figure to the right shows a small, modern breadboarding socket. The socket itself is molded nylon; the actual device is 3" long and just about an inch and 3/8 wide. Along the center a groove is molded in, except for small sections in the middle and at either end, to maintain strength and stability. Above the groove you see a series of columns of five holes each, with a matching set of columns below the groove.

The holes on each side of the central groove are all spaced 0.1" apart; the groove separates the two sets of holes by 0.3". This makes this type of breadboard socket ideal for mounting integrated circuits (ICs) of the dual-in-line type.

The important factor here is that the five holes in each individual column are electrically connected to each other, but remain insulated from all other sets of holes. This is accomplished as shown to the right. This is an underside view of the breadboard socket with the insulating layer of paper removed. The nylon block contains a series of rectangular slots with thin walls between the slots. A prefabricated set of contacts, similar to the detail shown here, is inserted into each slot to provide the required electrical connections as well as to hold each component lead securely.

This breadboard socket is useful and works well for experiments of many kinds. However, it is limited is size and capability. A larger version is shown below:

This larger socket is 6" long and 3" wide. The middle area works just like a longer version of the smaller breadboard socket you saw first on this page: each column of five holes is electrically connected, but is also insulated from all other parts of the breadboard.

Beyond the main columns of holes, however, you'll note four sets or groups of holes along the top and bottom. Each of these consists of five separate sets of five holes each, for a total of 25 holes. These groups of 25 holes are all connected together. This makes them ideal for distributing power to multiple ICs or other circuits.

There are a number of variations on this breadboard socket arrangement, but they all serve the same functions of allowing individual components and ICs to be mounted on a stable platform, and then facilitating the interconnection of these components to form an electronic circuit that can be observed and tested while in operation.

These breadboarding sockets are sturdy and rugged, and can take quite a bit of handling. However, there are a few rules you need to observe, in order to extend the useful life of the electrical contacts and to avoid damage to components. These rules are:

    • Always make sure power is disconnected when constructing or modifying your experimental circuit. It is possible to damage components or incur an electrical shock if you leave power connected when making changes. 
    • Never use wire larger than AWG #22 solid hookup wire as jumpers. #24 wire (used for normal telephone wiring) is an excellent choice for this application. Observe the same limitation with respect to the size of component leads. 
    • Whenever possible, use watt resistors in your circuits. watt resistors may be used wnen necessary; resistors of higher power ratings should never be inserted directly into a breadboard socket. 
    • Never force component leads into contact holes on the breadboard socket. Doing so can damage the contact and make it useless. You may find it helpful to use diagonal cutters to cut off the very end of a component lead. This will leave a wedge-shaped end on a component lead, to make for easier insertion. 
    • Do not insert stranded wire or soldered wire into the breadboard socket. If you must have stranded wire (as with an inductor or transformer lead), solder (or use a wire nut to connect) the stranded wire to a short length of solid hookup wire, and insert only the solid wire into the breadboard. 

If you follow these basic rules, your breadboarding system will last indefinitely, and your experimental components will last a long time.

Source: A Useful Guide for using Breadboard
               (Taken from Play-Hookey.com)

 

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