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Wires & Cables



Wires & Cables



Wires


Wires are pretty simple devices. Most of the time. But there are some characteristics of wires that are important depending on the application.

Wire sizes

In the US wire size is expressed as a gauge number, the American Wire Gauge AWG. The smaller the AWG number the fatter the wire and thus the more current it can carry without overheating. For most electronics projects 20-26 AWG wire would be good choices.   

Stranded vs solid wire

Stranded wire: Stranded wire is the best choice for most wiring situations you are likely to encounter. Stranded is reasonably flexible and can survive some bending back and forth with much less chance of breaking. If you are wiring up two devices more than a couple of inches apart, use stranded wire.

Solid wire:  If you are wiring up a small test circuit on one of those white plastic protoboards (breadboard), solid 24 AWG wire is a good choice. By the way, here's how those things work. You can strip the insulation off easily, and the solid wire is readily inserted into the openings in the protoboard. This is actually about the only good application for solid wire. Suggestion: Don't build a project on a protoboard. Instead, once you have your circuit debugged, use a blank circuit board where you solder the components onto the board. This approach results in a much more reliable circuit.

Wire Colors

It's a great idea to use particular wire colors for different functions. Standardizing on a set of wire colors will make debugging your design much easier. Often red is used for power connections, black for ground. Signal wires should be some color other than red or black. The MAE170 lab has a set of recommended wire colors. Many companies have strict requirements for wire colors, so standardizing on wire colors is not a bad habit to get into.


Cables


       

 
    Multiconductor cables                                                                                                Multiconductor shielded cable


If you are making a 'run' between two devices with more than 2-3 wires, you should consider using a cable. Multiconductor cables are available with anywhere from 2 to 30 or more individual conductors, and come in a wide variety of AWG sizes. The cable assembly may consist of the conductors themselves enclosed in an outer plastic insulation or jacket, or the cable may be shielded, in which case the conductors are first surrounded by a flexible woven metal mesh or maybe metalized mylar, and then further surrounded by the plastic insulation. The shield connection is usually brought out at the ends of the cable as a bare section of wire. Shielded cables are commonly used in electrically noisy environments, such as the factory floor, where radiated electrical noise may interfere with the signals being carried by the cable, or where the cable may be subjected to physical abuse.   



Connectors



Interconnecting devices by means of cables involves connectors. There are hundreds if not thousands of different connector designs. Cost ranges from $1 to 10's or 100's of dollars.




                                                               DIN female panel mount connector 

For small projects using cables with a low conductor count, the so-called DIN-type connectors are useful, and not expensive.






        DB-15 male connector                                                                                                                 DB-15 Hood


For higher conductor counts, the "DB-type" connectors can be useful. These are also inexpensive, and can be had with up to 50 or so conductors. The usual designation is DB-xx where the xx refers to the number of connector pins in the part. These connectors come in male and female versions, and can be used as cable terminations or as panel-mounted connectors. When using a DB type connector to terminate a cable, you use a hood to protect the wiring and provide strain relief for the cable.


 

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