Ribbon Cable And You

By Author: Sam Inci
Total Articles: 13
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With so many cables associated to the interworkings of a computer, or any other hardware, what do they all mean? What are the main differences? As we take a look into the specifications of a cable we will explore the reason, purpose and definition of a ribbon cable and what role they play overall. To begin with, a ribbon cable (also known as multi-wire planar cable, and/or flat cable) is a cable with many conducting wires running parallel to each other on the same flat plane. As a result the cable is wide and flat rather than round. Its name comes from the resemblance of the cable to a piece of ribbon (which is likewise wide and flat).
Ribbon cables are commonly seen for internal peripherals in computers, such as hard drives, CD drives and floppy drives. On some older computer systems (such as the BBC Micro) they were commonly used for external connections as well. Unfortunately the ribbon like shape makes them awkward to handle especially when there are a lot of them and so round cables have almost entirely replaced ribbon cables for external connections.
Flat cables, also known as ribbon cables, use a variety of ...
... cable shielding and cable conductor materials. Cable shielding is an envelope of wires or metal foil that covers the dielectric and center conduction. Typically, shielding for flat cables consists of copper braids; however, another common type is aluminum foil applied to both sides of a supporting mylar or polyester film. Cable conductors are wires or combinations of wires that are not insulated from one another, and that are suitable for carrying electric current. Cable conductors for flat cables are made out of aluminum, aluminum alloys, aluminum-clad steel, copper-clad steel, copper, and copper alloys. Aluminum, a metal characterized by high resistance to corrosion, provides good electrical and thermal properties and a density that is about one-third less than steel, copper, or nickel.
Copper is the most widely used electrical conductor and offers excellent corrosion resistance and high thermal conductivity. Flat cables use a variety of cable shielding and cable conductor materials. Cable shielding is an envelope of wires or metal foil that covers the dielectric and center conduction. Typically, shielding for flat cables consists of copper braids; however, another common type is aluminum foil applied to both sides of a supporting mylar or polyester film. Cable conductors are wires or combinations of wires that are not insulated from one another, and that are suitable for carrying electric current. Cable conductors for flat cables are made out of aluminum, aluminum alloys, and aluminum-clad steel, copper-clad steel, copper, and copper alloys. Aluminum, a metal characterized by high resistance to corrosion, provides good electrical and thermal properties and a density that is about one-third less than steel, copper, or nickel. Copper is the most widely used electrical conductor and offers excellent corrosion resistance and high thermal conductivity.
The main point of ribbon cables is to allow mass termination to specially designed insulation displacement connectors (IDC connectors) in which the ribbon cable is forced onto a row of sharp forked contacts. (The phrase "IDC connector" is widely used, even though it is redundant - an example of RAS syndrome.) Most commonly this is done at both ends of the cable though sometimes (for example when making a lead that needs to change wiring between the two connectors) only one end will be IDC terminated with the other end being terminated in a regular crimp or solder bucket connection. Although it is sometimes possible to dismantle and re-use IDC connectors, they are not designed to allow this.
Popular types of connectors available with IDC termination suitable for ribbon cable include:
BT224 connector - these are the type used on ATA cables and are often simply called "IDC connectors". They mate with either a purpose-made plug or a two-row grid of header pins with 0.1 inch (2.54 mm) spacing.
D-subminiature connector - used for serial ports and printer ports (however IDC D connectors are far less common than crimp and solder bucket types).
DIN41612 connector - used for Eurocard buses.
PCB transition headers - has two rows of pins with the same spacing's as BT244 connectors. Intended to be soldered directly into a PCB.
DIL headers - Has pins with the same spacing's as standard DIL ICs. Generally used where for some reason it is desired to replace an IC with a connection to an external device (e.g. in-circuit emulators). Can also be used like a PCB transition header especially on strip board. (Fitting a standard spacing header to strip board is tricky because you have to cut the tracks between two holes rather than on a hole.)
FFCs are miniature versions of flat-ribbon cables, but require a totally different set of equipment to produce. Conventionally utilized for signal transmissions, FFCs are now used as power supply and internal wiring for electronic equipment such as PCs, printers and mobile phones. FFC applications are expanding and in the near future, foreseen to include EMI, wireless local loop (WLL), and medical and automotive applications.