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*STANDARD ‘OUTER DIAMETER’* —>
*5.5 milli-meters*
*0.0055 meters*
(requires ‘5 round up’ to get to 1/100th of a meter)
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*STANDARD ‘INNER DIAMETERS* –>
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*STANDARD ‘BARREL LENGTH’* –>
*9 milli-meters*
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*the 2 most common ‘inner diameters’ are ‘2.1 mm’ + ‘2.5 mm’*
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*to differentiate them, find the ‘brass housing’ of a ‘ballpoint pen’*
(standard diameter of 2.2 mm)
(meaning it will not fit in a ‘2.1 mm inner diameter barrel jack’)
(but it will fit in a ‘2.5 mm inner diameter barrel jack’)
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*the standard diameter of a toothpick is ‘2.1 mm’*
(so sticking it into a ‘2.1 mm inner diameter barrel jack’ and it will fit snug)
(but it will fall out of a ‘2.5 mm inner diameter barrel jack’)
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*the standard diameter of a ‘multi-meter probe’ is ‘1.9 mm’*
*so it will fit snugly in the ‘2.1 mm inner diameter barrel jack’*
(but it will be loose in a ‘2.5 mm inner diameter barrel jack’)
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*8-in-1 ADAPTER*
*amazon iink*
*mintata 2019*
$7
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*ordered ’25 APRIL 2022’*
*the 8 ‘female bases’ are standard*
*5.5 mm outer diameter*
*2.1mm inner diameter*
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*8 male ‘jacks’*
(think ‘dick’)
6 mm / 1.4 mm
6.3 mm / 3 mm
5.5 mm / 2.5 mm
5.5 mm / 2.1 mm
5.5 mm / 1.7 mm
4.8 mm / 1.7 mm
4.0 mm / 1.7 mm
3.5 mm / 1.35 mm
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Barrel connectors are perhaps the most common design for dc power connectors because they are inexpensive to manufacture due to loose mechanical tolerances and have no required orientation when plugging them together.
The most common form of barrel connectors has plugs constructed with concentric metal sleeves (barrels) separated by an insulator.
Many standard diameters are available for both the inner and the outer sleeves and the length of the plug barrel.
Common combinations of the diameters and length exist,
but the design engineer will still need to specify the desired dimensions for the plugs used in their products
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Illustration of barrel plug with dimensions
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Barrel Plug with 2.1 mm inner diameter, 5.5 mm outer diameter, 9.5 mm barrel length
The corresponding barrel jack has a pin, which fits into the inner sleeve of the plug, often with a loose mechanical clearance and a cantilevered spring which contacts the outer sleeve of the plug.
Like the barrel plug, the barrel jack will have dimensions for the central pin diameter, the inner case diameter, and the plug insertion depth
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Barrel Jack illustration
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Barrel Jack
When the barrel plug is inserted into the jack the spring in the jack pushes against the outer sleeve of the plug and forces the central pin on the jack to contact the inner sleeve of the plug.
The selection of plug and jack dimensions needs to ensure the desired mechanical fit is achieved and the proper electrical connections are established
Illustration showing barrel plug and jack electrical connections
Barrel plug and jack electrical connections
Although the features of the barrel connector make them appropriate for many applications, there are also some issues caused by the design of barrel connectors.
The mechanical tolerance between the central pin on the jack and the inner sleeve on the plug is not standardized.
Similarly, the force with which the cantilevered spring in the jack pushes against the outer sleeve of the plug is not standardized.
This lack of standardizations means that the insertion and retention forces between the plug and the jack are difficult to specify and vary over a wide range.
In standard barrel connectors there is no mechanical retention mechanism for the connection and thus the connection can accidently come apart.
A solution to ensure the connection is retained is to use locking barrel connectors.
Locking barrel connectors are available with either threaded or twist locking features.
Threaded and twist locking barrel connectors illustration
Threaded and twist locking barrel connectors
The current rating of barrel connectors is determined by the force and surface area between the cantilevered spring and the outer sleeve and between the inner pin and the inner sleeve.
The light forces and small surface areas limit the current ratings of the connectors.
Barrel connectors are available in a range of both inner and outer conductor diameters.
Although there are no standards for the combinations of inner and outer diameters, product designers may choose to specify dimensions to either match existing products or to be unique from other products.
The two most common barrel connector sizes are 5.5 mm outer sleeve diameter with 2.1 mm inner sleeve diameter and 5.5 mm outer sleeve diameter with 2.5 mm inner sleeve diameter
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Illustration showing CUI’s standard barrel plug offerings
CUI’s standard barrel plug offering: (top) outer diameter (middle) inner diameter (bottom) CUI part number designation
Convention has evolved with the outer conductor as the ground or negative voltage and the inner conductor as the positive voltage.
The advantage of this configuration is if the outer plug of the sleeve touches an exposed conductor then the exposed conductor will be connected to ground rather than to any other electrical potential.
This convention is not always followed, and some product design teams place the positive potential on the outer conductor and the negative potential on the inner conductor
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Barrel plug polarity symbols
Barrel plug polarity symbols
Selecting the power cord to be in-line with the power connector is the most common configuration used in the industry.
This configuration is easy to manufacture and makes it more convenient for the user to align the connector when mating.
However, there are applications where a right-angle plug configuration may be preferred.
One reason for selecting a right-angle plug may be to allow the dc power cable to remain closer to the chassis as it feeds into the plug and thus allowing the physical footprint of the product to be smaller.
Another reason for selecting a right-angle plug is to provide for retention between the two halves of the barrel connection.
Because the power cord is at right angles to the connector, a force putting tension on the cord will force a torque on the barrel connector which will make it more difficult to disengage the connector.
It is also possible to secure the cord under a hook or latch on the product case such that none of the tension force on the cable is transferred to the plug
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*👨🔬🕵️♀️🙇♀️*SKETCHES*🙇♂️👩🔬🕵️♂️*
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💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
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*🌈✨ *TABLE OF CONTENTS* ✨🌷*
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🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥