The D-subminiature or d-sub connectors are popular connectors. They were among the smallest connectors connecting to computers at the time of their advent. But how do these connectors come into being, and what are the applications?
Let’s begin with its basics.
As the design suggests, the d-sub has two or more sockets or pins around which a metal shield is present. This metal shield is in a D shape, and it ensures that the pins are in the correct orientation. Moreover, it may screen the electromagnetic interference coming towards the connecting point.
Usually, D-subminiature connectors are comprised of genders. The part where pins are present is the male counterpart or plugs. At the same time, the other with socket contacts is the female connectors or Plugs. The socket’s shield fits perfectly in the plug’s shield.
Moreover, the panel connectors have 4 to 40 jackscrews that will allow the insertion of screws from the cable end connectors. That way, both the counterparts will be locked with each other, lessening the mechanical strain in the series of connectors.
Caption: Subminiature connector pin
Cannon first introduced the d-sub connector series in 1952. Their part numbering system had the alphabets to tag the plugs. For example, the 25-pin female (DB-25F) connector has D-sub shelling with a 25-position shell size and 25-position contact configuration.
Formerly, the manufacturers adjusted the pins with the spacing called normal density. Later on, they added more pins to the same D-sub series models. For example, the DE-15 connector, usually in the VGA cables, has a 15 pin count spaced at 0.090 inches horizontally and 0.078 inches vertically, all in three rows of pins. This type of pin layout is known as high density.
Despite having a naming convention, the manufacturers never followed it completely. Because when the PCs started using 9-pin connectors with E shell, the makers labeled them DB-9 instead of DE-9. Whether it was a manufacturer’s mistake or printer’s, it has become the convention. In the same way, connectors with denser arrangements are named Db-15HD, DB-26HD (HD-26), DB-44HD, and DB-78HD.
Now, the manufacturers name the D-subminiature connectors under the international standards, IEC 60807-3 / DIN 41652.
Micro-D and Nano-D
With time, there are two more variants of the D-sub connectors derived. These are the micro-D (microminiature D) and the nano-D (nano miniature D), sold under the trademarks of ITT Cannon.
Micro-D is about half of the length of the original D-sub, and Nano-D is half of the micro-D. Their most common use is in the military and space-grade industry. For instance, the military spec of Micro-D is MIL-DTL-83513 and for Nano-D is MIL-DTL-32139.
Caption: Comparison of microminiature D connector and male DE-9
Applications of D-Sub connectors
Caption: Computer Monitor Port
Here are the typical applications of the D-sub ports
RS-232 serial communication has the largest use of D-sub connector, though there was no specific point in the standard, which made the use mandatory. Typically, these devices used DB25, but people started using DE-9 Connectors as communications ports as the signals were lost.
There should be a male connector for the terminals and female connectors on the modems as the standard calls. However, there are many variations. For example, the IBM PC uses the male connector and the female connectors on the modem. Similarly, Apple Macintosh uses DE-9 for the multi-drop serial interface.
There was a time when the DE-9 connectors were using some Token Ring networks and other types of networks.
The attachment unit interfaces used in the 1980s had a DA15 connector. The sliding latch offered much more reliability in such designs than jackscrew in those times. Moreover, it offered to lock the electrical connectors with the plug through a sliding latch to engage quicker and disengage.
Computer Video Ports
The IBM PC used a female 9-pin connector as a video output display. The same connector could be connected to the different types of outputs. But the interface may get damaged if the incompatible versions are placed at both ends of the connector.
The Apple IIC used DA15F for the auxiliary video port, which might not be an RGB port. Hence, the VGA cables later came to light as they comprised DE15 high-density sockets. Many Apple Macintosh models also added “D-Sub 15-pin” connector sockets for the RGB video output.
Game Controller Ports
Atari’s first gaming console used a DE9 connector for its game controller. It didn’t have the jackscrews to fasten it with the socket, and it entirely made it of plastic. Later on, other gaming consoles followed the same connector as the game ports.
The gaming ports and the DE-9 also supported the joysticks, light pen, and mouse. Thus you needed one port for many devices.
The early Macintosh and late Apple II used the D-sub ports for attaching the external floppy discs. Not only Apple, but the Atari Computer System Interface also added these ports to their 16-bit computer range where you can connect the hard disk drives and the printers using the D-sub connectors.
Moreover, some companies also made the D-sub ports a part of their audio and video sending devices.
D-Sub Cable Attachment Types
Six types are in everyday practice to attach the wires in D-sub connectors are
- Insulation Displacement contacts in which you will insert a ribbon cable onto sharp tines present on the back of the contacts. This way, you can pierce the insulation of all the wires simultaneously. It is a rapid process, either by hand or by machine.
- Solder-Bucket has a cavity into which you will insert the stripped wire and hand-soldered.
- Wire wrap connections will wrap the solid wire around the square post with a wire-wrapping tool. This type often comes in handy when you are developing prototypes.
- Crimp Contacts insert the wire into the cavity inside the rear of contact and then crush the cavity with a crimp tool. That way, the cavity grips the wire efficiently at many points. Then you will insert the crimped contact into the connector and remove it later using special tools and techniques.
- PCB pins you solder directly on the PCB board and not on a wire. THP board-style pins were initially in use, but as they came under mechanical stress, the system caused problems. Hence, later on, PCB connectors were popular among the masses. Furthermore, these connectors are available in different variants with typically large tolerances so that you can mount the smaller connectors with them. However, it may not hold for the larger connectors.
Caption: A male PCB mounting DD50 plug
D-sub ports are standard when connecting the devices. Be it for making a network or sending audio-video signals from one device to another, you can see the D-sub ports on every device.
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