DC connector

DC connector

A DC connector (or DC plug, for one common type of connector) is an electrical connector for supplying direct current (DC) power. Unlike domestic AC power plugs and sockets, DC connectors are not generally standardized.

The dimensions and arrangement of DC connectors can be chosen to prevent accidental interconnection of incompatible sources and loads.


Cylindrical connectors

Common DC power connectors shown with a rule marked in cm/mm

Small cylindrical connectors come in an enormous variety of sizes. They may be known as coaxial power connectors, barrel connectors, concentric barrel connectors or tip connectors.

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 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 (0.22 in) in outside diameter (OD) and 9.5 mm (0.37 in) in length. Two pin sizes are common in the jacks for this size plug body, 2.1 mm (0.083 in) and 2.5 mm (0.098 in), and the plugs should ideally match. Generic plugs are often named for the pin diameter they are designed to take.

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 (i.e. the inner conductor) usually carries the positive (+) pole.

Snap and lock DC power connectors

A Mini-DIN male 4-pin power connector

Snap and lock DC power 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 users to mate the connector with the wrong port (such as an S-Video output on a video card).

  • Also known as Power Mini-DIN or Power DIN
  • The male plug's mating shell outer diameter is 10 mm (0.39 in), and the pins are 1.5 mm (0.059 in) diameter
  • Standard may include a limit of 20 V at 7.5 amperes[1]
  • 3-pin
    • Hosiden part number TCP8927-53
    • Kycon part number KPP-3P (obsolete) or KPPX-3P (RoHS)[2]
  • 4-pin
    • Kycon part number KPP-4P[3][4] (obsolete) or KPPX-4P (RoHS)[5]

Molex connector

A Molex connector

The connector design most commonly called a Molex connector has frequently been used to supply DC power, most frequently on personal computers, for supplying power to drives and other peripherals. It has four pins, +5 V (red), 2 com/ground (black), and +12 V (yellow).

Locking Molex connectors are available in 3, 4, and 6 terminal configurations.[3]

IEC 60906-3:1994

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 amps and 6, 12, 24, or 48 volts AC and DC. For use either indoors or outdoors.

The dimensions are as follows:

Parameter Value
Pin to pin distance 7 mm (0.28 in) ± 0.1 mm (0.0039 in)
Pin diameter 3.5 mm (0.14 in) + 0 / -0.075 mm (0.0030 in)
Female sleeve 4 mm (0.16 in)
Pin length 10 mm (0.39 in)
Connector diameter 19.4 mm (0.76 in)

There are also Mini IEC connectors.[6]

Tamiya connectors

Tamiya connector

Tamiya connectors are commonly used on radio-control (toy) vehicle battery packs and chargers.[7] They are also commonly used on airsoft guns.[8]

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. 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 0.375 in (9.5 mm) wide and the large is approx 0.5 in (13 mm) wide. They are not compatible without an adapter.[9]

Tamiya connectors are useful because they do not come undone easily, and are therefore child-safe, hence their use in remote-controlled cars and the like.[citation needed]

Deans connectors

Deans connectors are popular with higher-end radio-control vehicle battery packs and chargers.[10]

JST RCY connector

The JST [11] connector is also known in RC circles as the BEC connector, or the P connector. JST also produces other types of connectors that are used in RC and hobby electronics.

Inverter tabs/lugs

Inverter lugs

Inverter tabs/lugs are available in 2, 4, and 8 gauge.[clarification needed] Designed to pass very high currents at voltages up to 600 V DC to and from battery packs, inverters, and other high-current loads to a terminal bus.

Airline in-seat power supply system

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.

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.

Anderson Powerpole connectors

Anderson Powerpole connectors with crimping tool

The Anderson Powerpole has been adopted by some segments of the amateur radio community as their standard 12-volt DC power connector for everything from radios to accessories.[12] It is more expensive than the older de facto standard 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 for the positive connector: Red Right—Tongue Top. The ham standard is nominal 12 volts (actually 13.8 volts), with red positive and black negative.

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 ampacity 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 vehicle winches, many electric forklifts, and other electric powered vehicles.

For the larger Multipole design, which is available in up to 700 A sizes, 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:

  • 12 V: Yellow
  • 18 V: Orange
  • 24 V: Red
    • Used by Warn for its 12 V winches (should have used yellow multipole)
    • Used by Tripp-Lite for some of its 24 V external UPS battery packs
    • Used by FIRST Robotics Competition for 12V battery connection (should have used yellow multipole)
  • 36 V: Gray
    • Used by Tripp-Lite for some of its 38 V external UPS battery packs
    • Used by APC for some of its 24 V external UPS battery packs (should have used red multipole)
  • 48 V: Blue
    • Used by Tripp-Lite and APC for 48 V external UPS battery packs
  • 72 V: Green
  • 80 V: Black
  • 96 V: Brown
  • 120 V: Purple
  • 144 V: White

The connectors are also starting to be used by Radio Control hobbyists, including robot builders and the R2-D2 Builders Club.

In model railways, the NTRAK Modular Railroading Society has since 2005 recommended the use of the Powerpole PP30 as an alternative to the Cinch Jones connector, while retaining the widely-used latter within its standards.

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.

400V-DC rated connectors

Buildings such as data centres are starting to be designed for 380V-DC power distribution as a way of improving electrical efficiency.[13] DC power distribution has resulted in the need to standardise a Low Voltage (LV) connector with an integral ground conductor, and that is safe for use by untrained personnel. The tendency of LV connectors to arc when disconnected from a capacitive load requires the connector's insulation to contain the plasma arc in addition to normal requirements such as preventing accidental finger contact. Examples are the Anderson Powerpole® Pak connectors[14] and SDG connector,[15] designed with the form factor of an IEC C15 connector.

SAE connector

An SAE Connector

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 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 of the charger.

Cigar lighter sockets and plugs

A 12 volt cigar lighter plug

The car cigarette lighter socket is also 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.

Although the nominal voltage of a 12 V lead acid battery is 12 volts, when the engine is running the car's alternator and/or battery charging system will often bring the system voltage to 13.8 volts or higher.[16] The possible range of battery voltages from 11–15 volts must be taken into account by devices attached to the cigar lighter socket.

DIN 4165 connector

Similar in concept to an automotive cigar lighter, the DIN 4165 connector is shorter and smaller, and found most frequently on motorcycles.

It is also known as Powerlet connector, BMW Accessory connector or Hella plug

XLR connectors used for power

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.

Other DC connectors

Weatherproof DC connectors designed for connecting photovoltaic panels
DC plug, not wired. Flat pin connectors in T configuration. Often used for extra-low voltage in stand-alone power system (SAPS) or on boats
  • Fly RC magazine: Connectors Connection describes most or all of the connectors used by RC users.
  • There are a number of similar design PC board power connectors, including Molex Mini-Fit SR, Molex Mini-fit jr., MOLEX MICROFIT and Molex SABRE connectors, and AMP DUAC connectors that look similar to each other.
  • Some plugs with three, four, five or more pins are also called DC plugs. These were common on vacuum tube equipment and continue to be used where several voltages are supplied. On vacuum tube equipment the pins are normally on the equipment side of the join for safety reasons.
  • Many mobile phones use DC connectors that are unique to the manufacturer, or even a specific phone. In the interest of improved interoperability of phone battery chargers, major manufacturers have agreed to standardize on the micro-USB connector for new phone chargers from 2010.[17]
  • Many manufactures make special-purpose DC power connectors for battery packs, instruments, medical equipment, communications equipment and other devices.
  • Power Pack (PP) series of batteries such as the PP3 nine-volt battery have circular and hexagonal terminals which mate with a "snap" connector with physically identical (but opposite-polarity) terminals.

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.[citation needed]

See also


  1. ^ Hosiden product guide
  2. ^ http://anacapa.kycon.com/Pub_Eng_Draw/KPPX-3P.pdf
  3. ^ a b Adapters: output plug/cord options See for pin configuration
  4. ^ "Access Communications Snap and Lock plug information". Accesscomms.com.au. 2007-07-10. http://www.accesscomms.com.au/reference/outputplugsdc.htm. Retrieved 2011-06-22. 
  5. ^ http://anacapa.kycon.com/Pub_Eng_Draw/KPPX-4P.pdf
  6. ^ "Mini-IEC Output Plug reference sheet". Accesscomms.com.au. 2007-07-10. http://www.accesscomms.com.au/reference/outputplugsiec.htm. Retrieved 2011-06-22. 
  7. ^ ElectriFly: Adapters and Connectors shows converter cables for connectors commonly used in the RC community.
  8. ^ "Battery Junction". Battery Junction. http://www.batteryjunction.com/onetacoforai.html. Retrieved 2011-06-22. 
  9. ^ "Chargers and Dischargers shows a converter between the two sizes of Tamiya connector". Trinity Airsoft. http://www.trinityairsoft.com/p-19-battery-adaptor-large-to-mini-tamiya.aspx. Retrieved 2011-06-22. 
  10. ^ "W.S. Deans". W.S. Deans. http://www.wsdeans.com/index.html. Retrieved 2011-06-22. 
  11. ^ RCY
  12. ^ [1][dead link]
  13. ^ "Researchers Flip the Switch to Test Energy Saving in Data Centers Using DC Power Directly". Anderson Power Products Inc. http://www.calit2.net/newsroom/release.php?id=1730. Retrieved 16 June 2011. 
  14. ^ "Powerpole® Pak Connectors". Anderson Power Products Inc. http://andersonpower.com/products/powerpak-powerpole-pak.html. Retrieved 16 June 2011. 
  15. ^ "Saf-D-Grid® Connector". Anderson Power Products Inc. http://www.andersonpower.com/products/sdg.html. Retrieved 16 June 2011. 
  16. ^ http://www.familycar.com/Classroom/charging.htm
  17. ^ Common charging and local data connectivity, Open Mobile Terminal Platform, February 2009

External links

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