Molex connector
Molex connector is the vernacular term for a two-piece "pin and socket" interconnection, most frequently disk drive connectors. Pioneered by Molex Products Company, the two-piece design became an early electronic standard. Molex developed and patented the first examples 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 each housing can be either male or female.
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 as well as Atari (1979) on its path to becoming a de facto standard. It is in this role, that the vernacular term "molex connector" is most frequently used. AMP (now a division of Tyco International) developed the Mate-n-lok .084 pin connector that was used on many of these disk drives. This interconnection configuration is now the established standard for disk drive power connectors.
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. Certain Molex connectors are used for providing power to the motherboard, fans, and floppy disk drives; and hundreds of others.
In practice, compatible connectors are available from myriad manufacturers, not just Molex and AMP.
Motherboard power connector (Molex Mini-fit Jr.)
In 20/24 pin configurations, the Mini-Fit Jr. connector may be used on ATX motherboards as the main power connector. 4, 6 and 8 pin configurations of the same style of connector are used for additional CPU power and graphics card power. This is changing as power, signal and speed requirements increase in sophistication and electronic requirements. More commonly, the Mini-Fit, Jr. can be found in consumer applications, such as white goods, requiring high density and high current.
These connectors are polarised so that they cannot be inserted incorrectly, and lock into position using a latch.
Standard pinout:
| Color | 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, 24 | |
| 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 | |
| Purple | Standby +5V (10mA max) | 9 | 9 | |
Power OK goes high to indicate that voltages are stabilised and ready for use.
Power Control is typically connected to Standby +5V, with a switch causing momentary connection to Ground, switching the power supply on.
Disk drive connector (AMP Commercial MATE-N-LOK)
| Type | Electrical | ||
|---|---|---|---|
| Production history | |||
| Designer | Molex | ||
| General specifications | |||
| Width | 21 mm | ||
| Height | 6 mm | ||
| Pins | 4 | ||
| Electrical | |||
| Signal | Yes | ||
| Max. voltage | 12 V | ||
| Pinout | |||
| Pin | Color | Type | |
| Pin 1 | Yellow | +12V | |
| Pin 2 | Black | Ground | |
| Pin 3 | Black | Ground | |
| Pin 4 | Red | +5V | |
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 30-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.
| Color | Function | |
|---|---|---|
| Yellow | +12V | |
| Black | Ground | |
| Black | Ground | |
| Red | +5V | |