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A DC connector (or DC plug, for one common type) is an electrical connector that supplies direct current (DC) power.
Compared to domestic AC power plugs and sockets, DC connectors have many more standard types that are not interchangeable. The dimensions and arrangement of DC connectors can be chosen to prevent accidental interconnection of incompatible sources and loads. Types vary from small coaxial connectors used to power portable electronic devices from to connectors used for automotive accessories and for battery packs in portable equipment.
These plugs are intended for use on the cable connected to an external AC adapter (power supply). The matching jack or socket is permanently fitted to power the equipment. 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 battery recharging.
Cylindrical plugs usually have an insulated tip constructed to accept the insertion of a pin. The outer body of the plug is one contact, most often but not always the negative side of the supply. Inverted polarity plugs can and do damage circuitry when plugged in, even if the voltage is correct; not all equipment is equipped with protection. A pin mounted in the socket makes contact with a second internal contact. The outer plug contact is often called the barrel, sleeve, or ring, while the inner is called the tip.
There are a wide variety of sizes and designs for these power connectors, and many appear pretty similar to each other yet are not quite mechanically or electrically compatible. In addition to many generic designs (whose original designer is unknown), there are at least two national standards—EIAJ connector in Japan and DIN connector in Germany, plus the JSBP connector used on some laptop computers. The Japanese EIAJ standard includes five sizes, each supporting a specified range of voltages. However, most other coaxial DC power connectors have no specified voltage association. Generic plugs are often named for the pin diameter they are designed to take.
Many non-proprietary co-axial power plugs are in outside diameter (OD) and in length. Two pin sizes are standard in the jacks for this size plug body, and , and the plugs should match. If the size is not known, it is difficult to distinguish by eye or measurement between the 2.1mm and 2.5mm ID plugs; some suppliers suggest simple methods.
Maximum current ratings commonly vary from unspecified up to 5 A (11 A for unique high-power versions from some companies), with 1 A, 2 A, and 5 A being common values. The smaller types usually have lower ratings, both for current and voltage. The 'tip' (i.e., the inner conductor) usually carries the positive (+) pole, but some devices and their power supplies use the negative tip. The connector size does not usually indicate the voltage. It is not possible, except for some proprietary connectors, to reliably infer any information on power parameters (current, voltage, polarity, even whether AC or DC) by examining the connector.
Locking Molex connectors are available in 3, 4, and 6 terminal configurations.
The connector is circular, with the male connector having two pins placed symmetrically inside a circular shield, and the female connector having two receptacles surrounded by a circular groove to accept the male shield, in turn surrounded by a second circular shield which projects past the mating surface and encloses the male connector. (It somewhat resembles a smaller IEC 60309 connector.)
The dimensions are as follows:
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The male shield has two keys projecting inwards, which fit into notches in the female body. The larger key is at right angles to the pins, wide and ending at a radius of from the connector centre. The corresponding notch is wide and ends at a radius of from the connector centre.
The angle of the second key from the first indicates the voltage and current type. The eight permitted angles are multiples of 30° which are not multiples of 90°. Angles of ±30° and ±60° indicate alternating current (50 or 60 Hz), while angles of ±120° or ±150° indicate direct current with the pin at 90° being negative and the pin at 270° being positive.
The second key is smaller than the first, wide ending at a radius of from the connector centre. The corresponding notch in the female connector body is wide and ends at a radius of from the connector centre.
With the angles measured clockwise looking at the female connector (counter-clockwise looking at the male), the various key positions indicate:
| 6 V AC |
| 12 V AC |
| 6 V DC |
| 12 V DC |
| 24 V DC |
| 48 V DC |
| 24 V AC |
| 48 V AC |
The so-called "Mini IEC connectors" are unrelated and not even standardized by the IEC at all; they are called that because they resemble a smaller IEC C13 connector.
The International Electrotechnical Commission (IEC) has standardized a set of multi-pin screw plugs matching ISO metric screw thread, available in M5, M8 and M12 sizes. M5 connectors are very low current, typically only used for signal wiring, while some M8 pin arrangements are rated for up to 3 A, and some M12 arrangements are available up to 16 A. The multi-pin design caters for Ethernet, single and three-phase AC, as well as single or multiple voltage DC. The DC ratings are typically 60 V and below, however the F-coding is rated for 300 V (see #IEC 61076 (LV) below).
Usual pin assignment T-Plug: negative (-) is the parallel pin; positive (+) is the perpendicular pin.
Powerpole connectors are physically and electrically genderless, 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 genderless two-wire trailer plug.
Powerpoles have been adopted as a standard 12 VDC connector by most RACES Radio Amateur Civil Emergency Service organizations and ARES Amateur Radio Emergency Service units. They deliver good current capability for their sizes and facilitate very easy pluggability for those without good eyesight or good lighting. However, they can be damaged relatively quickly and, if not correctly crimped, can occasionally separate from each other easily with minimal force unless additional retaining measures are taken.
Although the plug is physically hermaphroditic, and any SAE connector can be connected to any other SAE connector, they are NOT electrically hermaphroditic, and care needs to be taken to maintain correct polarity when connecting different plugs.
This connector typically applies a maintenance charge to a vehicle battery. When installed in a vehicle and attached to a battery, the polarity of the connector is always such that no short circuit will occur if the exposed terminal touches the vehicle chassis. In most vehicles, this means that the exposed terminal connects to the battery's negative terminal. Conversely, the positive terminal on a battery charger is exposed to mate with the concealed one on the vehicle side. (This is reversed on vehicles with a positive-ground frame, such as vintage British motorcycles.)
Although there is a risk of Short circuit a battery charger, the risk is minimal and often mitigated by the circuitry of the battery charger itself. On the other hand, the short-circuit current 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 the charger.
Although the term "SAE connector" is commonly used to refer to the pictured two-pin connector, many different connector standards are designated by SAE International which may also be referred to by this term. Furthermore, while the design of the subject connector was inspired by and based on SAE Standards, the connector itself has no official SAE designation.
The SAE Specifications are available for J928 and J1239 but do require payment to be viewed.
These sockets were not originally designed to provide DC power, and are not an ideal DC connector for several reasons, but still widely used for compatibility to existing accessories. Three sizes exist, one for 6 VDC and two for 12 VDC and the mating of the different sized 12 VDC plugs and jacks is problematic. Because of this, and the small gauge wire sometimes used, they may provide unreliable power connections.
The polarity for 12 VDC sockets is center pin positive (+), outer collar negative (−). Reversed polarity will damage some electronic devices.
Although the nominal voltage of a 12 V lead acid battery is 12 VDC, when the engine is running the car's battery charging system will bring the system voltage to 13.8 VDC or higher. The possible range of battery voltages from 11–15 VDC must be taken into account by devices attached to the cigar lighter socket.
This connector is also often used for powering accessories on motorcycles, such as heated clothing (vests, gloves, etc.) or GPS units. This makes "plugging in" easier to manage while wearing gloves. As the accessory lacks any power of its own, there's no risk of "shorting" the exposed connector.
Found most frequently on motorcycles, it is also known as a "BMW Accessory", "Hella", "Merit", "Norm" or "Powerlet" connector.
The readily available XLR3 is also used by some manufacturers as power supply plugs despite their being a well-accepted standard for other purposes.
The connector pins are mutually perpendicular, and are usually oriented to look like a capital T. Polarity at the outlet can be random, and must be verified to avoid equipment damage.
In 2009, the EU created a common external power supply specification, a voluntary specification which encouraged mobile phone manufacturers to use the micro USB-B connector. As of 2016, most new mobile phones used this connector for charging.
In 2012, the USB Power Delivery (PD) specification was released. The USB PD specification provides the ability for 5 V devices to draw more than (the USB battery-charging specification limit of) 7.5 W of power from USB "PD-aware" ports when using PD-aware USB cables. The specification also allows USB PD ports to provide even greater power at higher voltages over PD-aware cables – up to 36 W at 12 V and 60 W at 20 V (for micro-USB connectors) and up to 60 W at 12 V and 100 W at 20 V (for standard USB A/B connectors).
After previous connectors were deprecated in USB 3.2, the new USB-C plug has become a new standard for charging (and data transfer) over USB.
In the European Union, the Radio Equipment Directive 2021/0291, requires new to use USB-C as a universal charger by the end of 2024, and laptops by 2026.
These connectors see use as battery bank connectors in higher power UPS systems, where the battery bank voltages are between 48 VDC and 500 VDC.
The International Electrotechnical Commission (IEC) has standardized a set of multi-pin screw plugs matching ISO metric screw thread, available in M5, M8 and M12 sizes (see #IEC 61076 (ELV) above). The M12 F-coding is rated for 300 V.
Designed primarily for supplying power to computer and communications equipment, these connectors are intended to allow to migrate towards supplying equipment with DC power as an alternative to AC.
Like the IEC 62735, this connector was designed to replace the IEC connector used in computer power supplies so that they can be operated from 380–400 VDC instead. Introduced in January 2009, Saf-D-Grid - Connector System for Higher Voltage Power Distribution it arrived before the competing IEC standard, however despite this it has not seen widespread use.
There are some competing standards:
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