A DC connector is an electrical connector for supplying direct current (DC) power. DC connectors in general are not standardized, compared to domestic AC power plugs and sockets. DC plug is a common name used for one common type of cylindrical two-conductor plug available in a range of sizes and used to power small pieces of electronic equipment. It is also used to describe some older multi-pin plugs.
Several competing standards exist for DC plugs, and in some cases incompatible plugs will fit together, to avoid damaging equipment these conditions must be true:
Also known as barrel connectors, concentric barrel connectors or tip connectors, small cylindrical connectors come in an enormous variety of sizes.
The intended use of these plugs is on the cable connected to a power supply. The matching jack or socket is then mounted in the equipment to be powered. Some of these jacks contain a normally closed contact, which can be used to disconnect internal batteries whenever the power supply is connected, avoiding the risk of battery leakage or explosion posed by incorrect recharging of the batteries.
Cylindrical plugs generally have an insulated tip constructed to accept insertion of a pin. The outer body of the plug is one contact, most often but not always the negative side of the supply. A pin mounted in the socket makes contact with a second internal contact. The outer plug contact is often called the sleeve, while the inner one is called the tip.
There are a wide variety of different sizes and designs for these power connectors, and many appear quite similar to each other yet are not quite mechanically or electrically compatible. In addition to a plethora of generic designs (whose original designer is unknown) there are at least two different national standards—EIAJ in Japan and DIN in Germany, plus the JSBP connector used on some laptop computers. The Japanese EIAJ standard includes five different sizes, with each supporting a specified range of voltages. Most of the other coaxial DC power connectors have no specified voltage association, however.
The most common plugs are 5.5 mm in outside diameter (OD) and 9.5 mm in length. Two pin sizes are common in the jacks for this size plug body, 2.1 mm and 2.5 mm, and the plugs should ideally match. Generic plugs are often named for the pin diameter they are designed to take, so these types will be seen described as "2.1 mm DC plugs" and "2.5 mm DC plugs" respectively. These two sizes are easily confused unless seen together.
Contact ratings vary from unspecified (and probably less than 1 A in practice) up to 5 A, with 2 A typical. Voltage is again often unspecified, up to 48 V with 12 V typical. The smaller types usually have lower ratings, both for current and voltage. The tip ie the inner conductor usually carry the positive (+) pole.
These connectors look similar to Mini-DIN connectors, but have either 3 or 4 thicker pins and a slightly larger mating shell. Because of this they do not mate with any of the Mini-DIN connectors. They can usually be identified by an engraved symbol on the backs of the plug, consisting of two wide arrows pointing in opposite directions, but parallel to each other, or sometimes one wide arrow inside a box, pointing towards the end of the male connector. Some devices, however, do use a standard 4-pin Mini-DIN connector, presenting the possibility for non-technical users to mate the connector with the wrong port (such as an S-Video output on a video card).
The connector design most commonly called Molex connector has frequently been used to supply DC power, most frequently on personal computers, for supplying power to drives and other peripherals.
The International Electrotechnical Commission (IEC) has produced a standard for a system of plugs and socket-outlets for household and similar purposes in fixed and portable applications. Safety extra-low voltage (SELV) plugs and socket-outlets for 16 amperes and 6, 12, 24, or 48 volts AC and DC. For use either indoors or outdoors.
The dimensions are as follows:
|Pin-2-Pin distance||7 mm ± 0.1 mm|
|Pin diameter||3.5 mm +0/-0.075 mm|
|Female sleeve||4 mm|
|Pin length||10 mm|
|Connector diameter||19.4 mm|
As shown, the usual wiring has the positive (red) wire running to the terminal with a square profile, and the negative (black) wire running to the half-circle, half-square terminal. This is true for both male and female connectors.
Some confusion exists in the market place between which is male or female. The male housing has female pins and the female housing has male pins. Some companies reference the housing gender while others reference the pin gender.
There are two sizes of Tamiya connectors, small and large. The rectangular portion of the small housing is approx 3/8" (9 mm) wide and the large is approx ½" (13 mm) wide. They are not compatible without an adapter.
Two different airline in-seat power supply system (ISPSS) standards for DC power have been used in the past.
American Airlines has in the past used an automotive cigar lighter socket, but using 14.7 V instead of the automotive 12 V.
Most other airlines that provide DC power use the EmPower system, which has a 4-pin Hypertronics' D-series connector smaller in diameter and overall size than a cigar lighter plug. It uses 15 volts maximum 5 amperes.
The Anderson Powerpole has been adopted by the amateur radio community as their standard 12-volt DC power connector for everything from radios to accessories. It is a bit more expensive than the older “standards” of the 2-wire trailer plug and Molex connector, but provides a more reliable electrical connection (both mechanically and electrically) and is easier to adapt to a wider range of wire gauges. Powerpole connectors are physically and electrically hermaphroditic, thus avoiding the need to worry about which end is the plug and which the socket, or which end has the correct polarity, as is the case with the physically but not electrically hermaphroditic 2-wire trailer plug.
For use in amateur radio, the community has adopted a standard polarity for assembling the Singlepole connectors, using one red and one black housing, as well as a mnemonic for remembering the arrangement: Red Right—Tongue Top. Before this polarity standard was adopted, some amateur radio groups had chosen the opposite polarity, so it is wise to double-check the polarity before blindly plugging devices together.
Although many sizes of the Powerpoles are available, the size most commonly used is the 15/30/45 ampere variety (but are available up to 180 A). These sizes all use the same plastic housing in multiple colors, differing only in the metal contact inserted into the housing (selected based on the current need and wire size). Larger Powerpole connectors (the SB/Multipole series) with 2 or 3 contacts in one molded housing are commonly used in various industrial settings, including as a battery connection for some UPS devices, removable truck/Jeep winches, many electric forklifts, and other electric powered vehicles.
For the larger Multipole design, each color is keyed so as to mate only with a like colored connector, and Anderson publishes a list of recommended voltages for each color:
Some manufacturers have ignored this color coding recommendation. One should always test the connection with a voltmeter if unsure. For example, winch manufacturer Warn uses a red housing for its winches, even though they are powered by 12 V DC, not 24 V DC.
The connectors are also starting to be used by Radio Control hobbyists, including robot builders and the R2-D2 Builders Club.
This connector design was created by Anderson, but the patent on its design has apparently lapsed, and there are other manufacturers of this connector now, including AMP and Sermos.
The SAE connector is a hermaphrodite two-conductor, DC connector commonly used for automotive applications (also motorcycles). It is so named for the Society of Automotive Engineers who created its specifications.
This connector is typically used for applying a maintenance charge to a vehicle battery. The polarity of the connector, when installed in a vehicle and attached to a battery, is always such that no short circuit will occur if the exposed terminal were to touch the vehicle chassis. In most vehicles, this means that the exposed terminal connects to the negative terminal of the battery.
Conversely, the positive terminal on a battery charger is exposed, to mate with the concealed one on the vehicle side.
Although there is a risk of short-circuiting a battery charger, the risk is minimal and often mitigated by the circuitry of the battery charger itself. On the other hand, the power-to-weight ratio of the lead-acid batteries installed in vehicles is sufficiently great, that a short circuit could result in a fire or explosion. The priority is therefore given to avoiding short circuits of the vehicle battery, rather than of the charger.
The car cigarette lighter socket is technically called a cigar lighter receptacle, since it was originally designed as a lighter for cigars—hence its rather large size (and unheated center barely large enough to light a cigarette).
These sockets were not originally designed to provide DC power, and are not an ideal DC connector for several reasons, notably the fact that three sizes exist (one for 6 V DC and two for 12 V DC) and the mating of the different sized 12 V DC plugs and jacks is problematic. Because of this, and the small gauge wiring sometimes used, they can sometimes provide only unreliable and current-limited power connections.
The polarity for 12 V DC sockets is center pin positive (+), outer collar negative (−). Reversed polarity will damage some electronic devices.
Similar in concept to an automotive cigar lighter, the DIN 4165 connector is shorter and smaller, and found most frequently on motorcycles.
In the broadcast, film and television industries, the 4-pin XLR connector is the standard for 12 V power. The connectors are wired pin 1 negative, pin 4 positive. Often pins 1 and 2 will be negative, 3 and 4 positive for a higher current rating. Female connectors are used as supply and male connectors are used on loads. Most battery belts and power supplies output 13.2 V, but equipment can usually handle a range of 11–18 volts to accommodate battery packs of varying voltages and charging while operating.
The readily available XLR3 is also used by some manufacturers as power supply plugs despite their being a well-accepted standard for other purposes.
In Australia, a T-configuration socket is used for DC power outlets, such as in stand-alone power systems (SAPS) or on boats. For this use, the horizontal slot is on top and is positive. This is also used for temporary equipment in emergency vehicles. In Victoria the top of the T is taken to look like a minus sign, and is therefore negative. Outside Victoria the vertical pin is meant to be earth/chassis ground, consistent with Australian Standards for Type I 240 volt outlets; therefore, the top of the T is positive on a negative-earth vehicle. Older positive-earth vehicles are still in service, so actual polarity at the outlet can be random.
Redirecting to DC connector