Molex connector

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A Molex connector is the vernacular term for a two-piece "pin and socket" interconnection. Pioneered by Molex Products Company, the two-piece design became an early electronic standard. Molex developed and patented the first exemplars of this connector style in the late 1950s and early 1960s. First used in home appliances, other industries soon began designing it into their products from automobiles to vending machines to mini-computers.

In such a connector, cylindrical spring-metal pins fit into cylindrical spring-metal sockets. The pins and sockets are held in a rectangular matrix in a nylon shell. The connector typically has 2, 3, 4, 5, 6, 9, 12, or 15 circuits. Pins and sockets can be arranged in any combination in a single connector, and the housing separately has male and female gender.

There are three typical pin sizes: .062" (1/16"), .093" (3/32"), and .084". The .062" pin can carry 5A of current, while the .093" can carry 8.5A. Because the pins have a large contact surface area and fit tightly, these connectors are typically used for power.

This style of connector was first used as a computer disk drive connector in the late 1970s, initially on the Shugart floppy disk drive. It is in this role, that the vernacular term "molex connector" is most frequently used. This is somewhat ironic, as it was AMP (now a division of Tyco International) that developed the Mate-n-lok connector that was used on these disk drives, and is now the established standard for disk drive power connectors.

1 Desktop PC Use
2 References

[edit] Desktop PC Use

Several types of "pin and socket" connector have become established for power connections in desktop PCs, because of the simplicity and reliability of the design. Molex connectors are used for providing power to the motherboard, fans, and floppy disk drives.

In practice, compatible connectors are available from many manufacturers, not just Molex and AMP.

PC power supply with several connectors. From left to right: Molex Mini-fit Jr 20 and 4 pin, Molex KK, SATA connector, AMP Mate-n-lok, Molex mini-spox

[edit] Motherboard power connector (Molex Mini-fit Jr.)

In 20/24 pin configurations, the Mini-fit Jr. connector is used by ATX motherboards as the main power connector. 4 and 6 pin configurations of the same style of connector are used for additional CPU power and graphics card power.

These connectors are polarised so that they cannot be inserted incorrectly, and lock into position using a latch.

Standard pinout:

	Function	Pins (20 pin connector)	Pins (24 pin connector)
Yellow	+12V	10	10, 11
Black	Ground	3, 5, 7, 13, 15 - 17	3, 5, 7, 15, 17 - 19
Red	+5V	4, 6, 19, 20	4, 6, 21 - 23
Orange	+3.3V	1, 2, 11	1, 2, 12, 13
Blue	-12V	12 (not always present)	14 (not always present)
White	-5V	18 (not always present)	20 (not always present)
Grey	Power OK	8	8
Green	Power control	14	16

[edit] Fan power connector (Molex KK)

These 3 and 4 pin connectors are used to power small fans (e.g. for CPU cooling). They are polarised and are friction locked. Some connector pairs have locking hook tabs. Rather unusually for power connectors, power is supplied via the male connector, with the fan being fitted with a female connector. Fans usually include a tachometer, from which a signal is sent through a lead to register RPM.

[edit] Disk drive connector (AMP Commercial MATE-N-LOK)

AMP MATE-N-LOK connector (female). Although not developed by Molex, this is frequently called a 'Molex' connector by casual PC builders

AMP MATE-N-LOK connector (male)

The desktop computer hard-drive connector is pictured here. It has 4 circuits, with the standard pinout as follows:

1: 12 volts (yellow)
2 and 3: ground (black)
4: 5 volts (red).

Sometimes, especially in older computers, the colors differ. The pins are .200" (5.08mm) apart (center to center). The connector housing has chamfered corners on one side to prevent the user from plugging it in incorrectly. The connector that provides power (e.g. on a power supply) has female pins and a male housing; the connector that receives power (e.g. on a peripheral) has male pins and a female housing.

The connector is standard on all PATA disk drives and low-end SCSI disk drives; however, newer disk drives will employ a more advanced integrated serial interconnection. These new, advanced connection systems are being developed by Molex and other connector companies, often working together to develop interconnection standards.

Despite its widespread adoption, the connector has problems as a 40-year-old product. It is cumbersome and difficult to remove because it is held in place by friction instead of a latch. It is specific to this one application, so it is not as widely available as most electronic connectors, and is more expensive.