Coaxial DC Power Connectors

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Common DC power connectors

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 (but note also the internal pin in the larger size EIAJ plugs). 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, and the inner the tip, although the tip itself is actually non-conductive.

At least two different national standards exist, EIAJ in Japan and DIN in Germany. As well several conventions have been adopted by specific manufacturers, notably by Sony, to indicate voltage by plug size.

Some manufacturers use opposite polarity standards, and some generic power supplies cater for this by allowing the polarity to be reversed by use of a switch or an unpolarised two-pin plug and socket arrangement. These two-pin plugs seem to be standardized but official specifications are hard to find. The pins are 1.5 mm in diameter, 6 mm long and spaced 4.2 mm apart. (see Egston connector overview, page 6, number 230)

Some power supplies allow the voltage to be switched. Four-way X connectors or six-way star connectors, also known as spider connectors, with multiple plug sizes and types are common on generic power supplies. On others there are arrangements for changing the connector, with from four to nine different connectors available.

A six-way connector on a 'universal' DC power supply, consisting of a 4-way X connector and two individual connectors. The X-connector here provides 3.5 and 2.5 mm jack plugs and two sizes of cylindrical connector

It is quite possible that new sizes will continue to appear and disappear. The most likely reason for a new size is that a particular manufacturer wishes to discourage use of third-party power supplies, either for technical reasons or to promote use of their own products or both. At the same time there is a trend for newer equipment of a particular type to be more tolerant of its power supply than older designs, making previous standards and conventions unnecessary.

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.

[edit] Generic types

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.

Slightly smaller 5.0 mm OD plugs are sometimes used in both 2.1 mm and 2.5 mm pin sizes, as are longer or shorter 5.5 mm OD plugs. All are typically 8 mm to 14 mm in length. There are also 6.5 mm OD plugs taking a 3 mm pin, 3.8 mm OD plugs taking either a 1.35 mm or a 1.05 mm pin, 3.5 mm plugs for a 1.3 mm pin, and many less common sizes.

Use of a plug designed for a larger pin, for example a 2.5 mm pin plug in a 2.1 mm pin jack, may work perfectly depending on the design of the jack, but often the result is an unreliable contact or occasionally no contact at all. A pin that is too large for the plug will not allow insertion of the plug at all. Similarly, a larger plug body (OD) may not fit at all, a smaller one may fit but may not make a reliable contact. Length is less critical than the diameters but is sometimes a consideration, in general a longer plug is no great problem but a shorter one may fail to contact the pin reliably or at all.

After the two common 5.5 mm OD plugs the next most common size is 3.5 mm OD to take a 1.3 mm pin, commonly 9.5 mm in length but both longer and shorter versions also exist. These 3.5 mm OD plugs are normally used for lower voltages and currents.

This list shows all known generic types, and is annotated with the manufacturers each is available from (based on those found in the Mouser and Digi-Key catalogs), since not all make all sizes. It should be further noted that a circular locking detent is present on some of these barrel connectors, and its presence or absence should be a clue in distinguishing very similar sizes. This is not to be confused with the locking DC connectors which use threaded fittings to secure the connection between the plug and jack.

Some of these sizes always include a high-retention feature, while others feature it only in designs from certain manufacturers. Typically, this is a connical cut-back section of the tip, just behind the insulator that separates the inner from outer contact surfaces.

There are a number of sizes below that appear to be quite similar, and while the tollerances of these connectors is typically indicated as +/- 0.05 or 0.03 mm by the manufacturers, there is still sufficient ambiguity in whether two sizes differing by only 0.05 mm (or where the specification is only to the nearest 10th of a mm) to warrant listing them separately here. Further work should be done to determine the original specification for the size, and then list the similar sizes that are intended to be compatible.

Bold items are connectors with known originating standards.

• outside diameter × inside diameter × length [pin diameter]
• 2.35 mm OD × 0.70 mm ID × 9.5 mm (EIAJ-01)
• 2.40 mm OD × 0.70 mm ID (Egston 212, perhaps rounded-off representation of EIAJ-01 plug)
• 2.40 mm OD × 0.80 mm ID (Egston 213)
• 3.00 mm OD × 1.00 mm ID
• 3.00 mm OD × 1.10 mm ID (Egston 214, Adaptaplug G)
• 3.40 mm OD × 1.30 mm ID (Adaptaplug H, KOBICONN)
• 3.40 mm OD × 1.35 mm ID (Egston 218 Medical, 220)
• 3.40 mm OD × 1.40 mm ID NES/J 135
• 3.50 mm OD × 1.30 mm ID (Egston 238)
• 3.50 mm OD × 1.35 mm ID (CUI Inc. P7) (KOBICONN) (Egston 215)
• 3.60 mm OD × 1.15 mm ID (Egston 216)
• 3.80 mm OD × 1.10 mm ID (Adaptaplug I, CUI Inc. P9 but with 1.05 mm ID)
• 3.80 mm OD × 1.30 mm ID (Egston 217)
• 3.80 mm OD × 1.35 mm ID (CUI Inc. P8)
• 4.00 mm OD × 1.70 mm ID × 9.5 mm (EIAJ-02, Adaptaplug B)
• 4.75 mm OD × 1.70 mm ID × 9.5 mm (EIAJ-03, Adaptaplug C)
• 4.75 mm OD × ?.?? mm ID × 2.5 mm protruding pin (EIAJ RC-5321)
• 4.80 mm OD × 1.70 mm ID (KOBICONN)
• 5.00 mm OD × 1.50 mm ID (Adaptaplug J)
• 5.00 mm OD × 2.00 mm ID (Egston 206, 207, 219)
• 5.00 mm OD × 2.10 mm ID (Adaptaplug K, CUI Inc. P3)
• 5.00 mm OD × 2.50 mm ID (Adaptaplug L, CUI Inc. P4)
• 5.50 mm OD × 1.50 mm ID with 1.80 mm pin (Adaptaplug S)
• 5.50 mm OD × 2.10 mm ID—2.1 mm DC plug (Adaptaplug M, CUI Inc. P5/P10 locking, KOBICONN) (available in high-retention versions, and threaded collar locking versions)
• 5.50 mm OD × 2.50 mm ID—2.5 mm DC plug (Adaptaplug N, CUI Inc. P6/P11 locking, KOBICONN, Egston 222) (available in threaded collar locking versions)
• 5.50 mm OD × 2.80 mm ID (Adaptaplug O, used on some Toshiba laptop computers)
• 5.50 mm OD × 3.30 mm ID × 9.5 mmwith 1.00 mm pin (EIAJ-04, Adaptaplug D)
• 5.50 mm OD × 3.80 mm ID with 1.80 mm center pin (Adaptaplug P)
• 6.30 mm OD × 3.00 mm ID (Adaptaplug Q)
• 6.50 mm OD × ?.?? mm ID (EIAJ RC-5322)
• 6.50 mm OD × 3.00 mm ID
• 6.50 mm OD × 3.10 mm ID with 1.00 mm center pin (Philmore 285 plug)
• 6.50 mm OD × 4.10/3.10 mm ID with 1.00 mm center pin (Adaptaplug U, same as Philmore 285?)
• 6.50 mm OD × 4.30 mm ID × 9.5 mm with 1.40 mm center pin (EIAJ-05, Adaptaplug T)
• 6.90 mm OD × 4.20 mm ID with 0.70 mm center pin (Adaptaplug R)
• 7.00 mm OD × ?.?? mm ID with 1.00 mm center pin (Philmore 48-412 cable)

[edit] EIAJ standards

Five plug and matching socket or jack designs are defined by the EIAJ standard RC-5320A (a.k.a. JEITA RC-5320A). Each of these plugs is used with a specified voltage range. Most manufacturers use a yellow insulating material to distinguish these plugs from other similar-looking DC plugs.

• EIAJ-01 for 0-3.15 V
• EIAJ-02 for 3.15-6.3 V
• EIAJ-03 for 6.3-10.5 V
• EIAJ-04 for 10.5-13.5 V (a.k.a. JSBP 4)
• EIAJ-05 13.5-18 V (a.k.a. JSBP 5)

Unlike most DC plugs, the larger two IEAJ sizes have an internal pin in the plug. The smaller three do not and are similar to the generic plugs in structure. The plug length is 9.5 mm in all cases, and current rating 2 A.

There are two other, less common, connectors defined by EIAJ; RC-5321 ane RC-5322. The latter is designed for both 12 V and 24 V automotive applications.

[edit] DIN 45323 Power Connectors

The German national standard DIN (Deutsches Institut für Normung) DIN 45323 apparently defines two DC power plug sizes. The information below is inferred from catalog references, as the German standard has not been translated into English as of yet.

• 5.00 mm OD, 2.00 mm ID, 14 mm long?
• 6.00 mm OD, 1.98 mm ID [1]
• Connectors for coupling an external low-voltage power to portable entertainment equipment

[edit] Guidelines for selection

With more than 30 different designs of coaxial power connectors in existance and use to power electronic products, the lack of a clear starting point for selecting one has helped lead to the wide incompatibilities between power plugs and devices.

Here are some guidelines that can be drawn from the few power connector designs that have clear specifications associated with them.

• 1.5 V devices
  • EIAJ-01
• 3.0 V devices
  • EIAJ-01
• 4.5 V devices
  • EIAJ-02
  • EIAJ RC-5321
• 6.0 V devices
  • EIAJ-02
  • EIAJ RC-5321
• 7.5 V devices
  • EIAJ-03
• 9.0 V devices
  • EIAJ-03
• 10.5 V devices
  • EIAJ-03
• 12.0 V devices, including automotive electrical systems
  • EIAJ-04
  • ARINC 628/EmPower for automotive or airplane use
  • EIAJ RC-5322 for automotive use
• 13.5 V devices
  • EIAJ-04
  • EIAJ RC-5322 for automotive use
  • ARINC 628/EmPower for automotive or airplane use
• 15.0 V devices
  • EIAJ-05
  • ARINC 628/EmPower for automotive or airplane use
• 16.5 V devices
  • EIAJ-05
• 18.0 V devices
  • EIAJ-05

[edit] RadioShack Adaptaplug Conversion Matrix

RadioShack sells adapter plugs that convert from the above-described two-pin non-polarized connector to various DC power plugs. RadioShack, in particular, has assigned a single-letter code to each plug, but has not provided the official name for each plug, nor often their complete specifications on barrel and pin diameter. Here is a complete list:

• Size A: 2.35mm OD × 0.70mm ID (EIAJ-01 for up to 3.15 V; yellow ring RS #273-1704)
• Size B: 4.00mm OD × 1.70mm ID (EIAJ-02 for 3.15–6.3 V; yellow ring—RS #273-1705)
• Size C: 4.75mm OD × 1.70mm ID (EIAJ-03 for 6.3-10.5 V; yellow ring—RS #273-1706)
• Size D: 5.50mm OD × 3.30mm ID with 1.0mm pin (EIAJ-04 for 10.5-13.5 V; yellow ring RS #273-1707)
• Size E: 2.50mm (3/32"2.5mm) submini plug (black ring—RS #273-1708)
• Size F: 3.50mm (1/8"/3.5mm) mini plug (black ring RS #273-1709)
• Size G: 3.00mm OD × 1.10mm ID (Turquoise ring—RS # 273-1710)
• Size H: 3.40mm OD × 1.30mm ID (Orange ring RS #273-1711)
• Size I: 3.80mm OD × 1.10mm ID (Pink ring—RS #273-1712)
• Size J: 5.00mm OD × 1.50mm ID (Red ring—RS #273-1713)
• Size K: 5.00mm OD × 2.10mm ID (Purple ring—RS #273-1714)
• Size L: 5.00mm OD × 2.50mm ID (Dark Green ring—RS #273-1715)
• Size M: 5.50mm OD × 2.10mm ID (Navy ring—RS #273-1716)
• Size N: 5.50mm OD × 2.50mm ID (White ring—RS #273-1717)
• Size O: 5.50mm OD × 2.80mm ID (Brown ring—RS #273-1718)
• Size P: 5.50mm OD × 3.80mm ID with 1.80 mm pin (no specified color—RS #273-1719)
• Size Q: 6.30mm OD × 3.00mm ID (Yellow-Green ring—RS #273-1720)
• Size R: 6.90mm OD × 4.20mm ID with 0.70 mm pin (no specified color—RS #273-1721)
• Size S: 5.50mm OD × 1.50mm ID with 1.80 mm pin (Gray ring—RS #273-1722)
• Size T: 6.50mm OD × 4.30mm ID with 1.40 mm pin (EIAJ-05 for 13.5-18.0 V; yellow ring—RS #273-1723)
• Size U: 6.50mm OD × 4.10mm/3.10mm ID with 1.00mm pin (Light-Yellow ring—RS #273-1724)

[edit] References

• Digi-Key Catalog #T053; Sept-Dec 2005
• Mouser Electronics Catalog #624; Nov. 2005–Jan. 2006
• Mouser catalog page [2]
• RadioShack Web site (online descriptions of Adaptaplugs)
• Simple low voltage connection basics for everybody[3]
• Understanding the Radioshack Adaptaplug System*
• Hosiden
• [4]
• [5]
• [6]
• [7]
• [8]
• [9] shows a connector not yet covered here.