Coaxial power connector

The connector pairs for barrel connectors are defined in terms of "plugs" and "receptacles"; receptacles are more commonly called "sockets" or "jacks" in the United States. Receptacles may be panel-mounted or circuit board-mounted. Plugs are on cables. Some in-line receptacles are also cable-mounted.

There is a long history in electrical engineering of referring to such power plugs — that is to say, plugs with holes instead of prongs — as female,[1] particularly regarding coaxial transmission of electricity,[2] and data communication and computer cables.[3] Type N connectors,[4][5] and all IEC 60320 "appliance coupler" plugs, and VGA cables with male connectors on the cable and female connectors on the devices[3] are examples of this. That said, while IEC 60320 provides gender-based standards for higher-voltage plugs (such as the cable plugged into a standard computer power supply), they have not yet defined gender-based standards for low-voltage coaxial power connectors such as those discussed herein; i.e., which component is "male" and which is "female". As a result, there are varying opinions in this regard. Many industrial suppliers avoid gender terminology[6] but many do not.[7] Similarly, some people view the corded plug as female[8] and some perceive it as male.[9] Some, after consideration and surveys, found that user perception of which was male and which female was evenly split.[10]

Regardless of user perception surveys, the connector that resembles the male sex organ is the male connector or plug, and the connector it is inserted in is the female connector or socket or receptacle.[3]

Power is generally supplied by a plug to a receptacle. Cables are available with one in-line receptacle fanning out to a number of plugs, so that many devices may be supplied by one supply. As the use of a plug implies a cable, even a short stub, some power supplies carry panel-mounted receptacles instead to avoid this cable, i.e., the normal convention of power from plug to receptacle is reversed. Cables for such cases are available with a plug at each end, although cables or adapters with two receptacles are not widely available.

There are many different sizes of coaxial power connectors. See the table at the end of this article.

Contact ratings commonly vary from unspecified up to 5 A (11 A for special high-power versions). Voltage is often unspecified, but may be up to 48 V with 12 V typical. The smaller types usually have lower current and voltage ratings.

It is quite possible that new sizes will continue to appear and disappear. One possible reason that a particular manufacturer may use a new size is to discourage use of third-party power supplies, either for technical reasons or to force use of their own accessories, or both.

The sizes and shapes of connectors do not consistently correspond to the same power specifications across manufacturers and models. Two connectors from different manufacturers with different sizes could potentially be attached to power supplies with the same voltage and current. Alternatively, connectors of the same size can be part of power supplies with different voltages and currents. Use of the wrong power supply may cause severe equipment damage, or even fire.

Some common DC power connectors

Generic plugs are often described by their inside diameter, such as 2.1 mm DC plugs and 2.5 mm DC (direct current) plugs.

After the two common 5.5 mm OD (Outer Diameter) plugs, the next-most common size is 3.5 mm OD with a 1.3 mm ID (Inner Diameter), usually about 9.5 mm in length, although both longer and shorter versions also exist. These 3.5 mm OD plugs are normally used for lower voltages and currents.

A ring-shaped "locking detent" or "high-retention feature", present on the barrel of some DC coaxial connectors, is a feature intended to prevent accidental disconnection. Typically, this feature is a conical cut-back section of the tip, just behind the insulator that separates the inner from outer contact surfaces.

A "lock-ring DC coaxial connector" uses a captive threaded ring or collar to secure the connection between the plug and jack. This design offers strong resistance to unplugging when used properly.

Lock-ring DC coaxial connectors. The knurled barrel allows the plug to be secured to jacks that have mating male threads.

A "lock-tab DC coaxial connector" (also called "bayonet lock") offers a compromise that resists unplugging, but which will disengage when pulled hard enough. This connector uses small metal tab protrusions on the connector barrel to lock the plug in place, requiring a special push-and-rotate motion to engage the locks.

Close-up of a yellow-tipped EIAJ connector. Note two round adapter pins on the opposite end.

There are several standards in existence, such as IEC, EIAJ in Japan and DIN in Germany. More recently, some manufacturers appear to have implemented their own system correlating voltage and plug size. In addition, there appears to be a trend to standardize DC connector to negative barrel (or sleeve) of a coaxial power connector.

This list attempts to show all known sizes, and is annotated with some manufacturers producing selected types, since each manufacturer makes its own unique subset of the known types. Note that the example part numbers given may have different connector barrel (sleeve) lengths, and are not necessarily exact equivalents. There are many more design variants than can be listed in this table, so only a small sampling of part numbers is given.

Connector size is often listed in the format OD (outer diameter) × ID (inner diameter) × L (length of barrel) and expressed in millimeters. Designations may vary between manufacturers.

Coaxial plugs that have a male center pin will have another measurement, Center Pin Diameter (CPD). These plugs are often used for higher power applications such as portable computers.

There are a number of sizes listed below that appear to be quite similar, and while the tolerances of these connectors are typically indicated as ±0.05 or ±0.03 mm by the manufacturers, there is still ambiguity as to whether two sizes differing by only 0.05 mm (or where the specification is only given to the nearest 0.10 mm) warrants listing them separately here.

RadioShack sold a line of adapter plugs for universal AC adapters. Each "Adaptaplug" had a single-letter code, but did not provide any other official designation, nor did RadioShack publish the complete specifications and tolerances on barrel and pin dimensions. RadioShack's Web site listed the diameters to the nearest 0.1 mm, and sometimes differs slightly from the official EIAJ RC-5320A standard dimensions. This list may include some parts RadioShack has discontinued but are retained here for completeness.[16]

• AC adapter
• Anderson Powerpole
• Cigarette lighter receptacle
• DC connector
• Gender of connectors and fasteners

• Guide to Understanding Power Conversion, RadioShack

Datasheets (drawings and dimensions)

• CUI Devices
• Hosiden
• Lumberg
• SMK
• West Side