Cables & Connectors Study Guide

Transcription

1 Cables & Connectors Study Guide When you look inside a computer, you will not only see the motherboard, devices, adapter cards, and other components; you will also see an array of cables, wires, and connectors that make everything work together. However, the cables and connectors inside the computer are not the only ones that are needed for a computer to work. There are also cables and connectors outside of the computer. The combination of these are used to connect: Hard drives, floppy drives, and CD-ROMs (internal and external) Display Monitors Keyboards The Mouse Printers Sound Card to Speakers Other devices and components Cable Sets Cable Sets When you begin to gather the materials, components and devices for building, repairing, or upgrading a computer, you will need to make sure that you have all the correct cables and connectors. After all, the computer will not work unless everything is connected together. Below, you will see a common cable set for computers. The price for these range anywhere from $6 to $20, depending on where you buy them, and the manufacturer. Interface Cable - Red Stripe The most common cables in this set are ribbon cables. What they have in common are the fact that they are thin, flat, and have multi-connector functions. This means that many parts of a device can be connected by one cable, rather than many separate wires. The colors that they come in are usually gray or tan, but I have also seen them in white, blue and multicolored. Every ribbon cable has a unique identifying mark on it that is very important when it comes time to use the cable to connect a device or component inside a computer. The identifying mark is that only one side has a red stripe imprinted on and traversing down the cable. Sometimes this stripe is blue. The red stripe must always line up with the #1 or #2 pin on the device connector that you are attaching it to. Cables & Pin Setup When the cable is attached to the device or component, it needs to be attached according to the pin setup. In other words, the number 1 pin on the device needs to connect to the number one pin on the adapter card or motherboard, the number 2 pin to number 2 pin, and so on. If you connect these in the wrong way, you risk the chance of burning out the device, components, motherboard, etc. Even if it did not burn or

2 damage anything, the device would not work. An example of a device that will not become damaged is the floppy disk drive. If the cable is plugged in backwards, the floppy drive LED (Light Emitting Diode ) light will stay on, and BIOS will recognize an error when the computer boots up. The floppy disk will not immediately become damaged, however, it will not function. Most connectors will only fit one way. However, some that will fit either way, so it is important to make sure of the pin configuration. Understanding Cable Wiring To understand why it is important to use the appropriate cable and to make sure that they are attached properly, look at this diagram of a simple DB9 serial connector (9-pin male to 25-pin female cable). This shows that all wires do not always connect in a straight line from one cable end to the other. Additionally, it shows that not all pins have a wire connected to them. Flat Ribbon Interface Cables (1) The flat ribbon interface cable will usually come folded with a small rubber band holding it in place They are called ribbon cables because they look like ribbons. It is a good idea to store them the same way when they are not in use. You will notice that the folds are not creased. This is important, because inside the plastic covering that encompasses the cable are fine wires. If they are bent or twisted they can break, and they will no longer be functional. Additionally, they will no longer be able to make a complete circuit from one end to the other. If this happens, the device that you are connecting to the computer will no longer work properly either. Look at the cross section view to see how thin these wires can be. Flat Ribbon Interface Cables (2) Flat ribbon interface cables can have a connector on each end, or they can also have an additional connector in the middle of the cable. Ribbon cables that have connectors only on the ends run directly from the device to the adapter card or motherboard. However, some ribbon cables can connect more than one device to a computer. Examples of this are hard drives, floppy drives, and CD-ROMs. Sometimes cables that are longer than normal will have plastic bars clipped over sections of the cable. The main function of the plastic bar is to keep the cable flat. The pictures below show the varieties of flat ribbon interface

3 cables. This is what a typical ribbon cable connector end looks like. Sometimes there will be a tiny plug in one of the holes to aid in connecting the end to a device. Power Supply & Connectors In this picture you see a power supply box with the power connectors used for distributing power to the motherboard, switches, and various devices inside a computer, such as the floppy drives, hard drives, and CD-ROM. The power supply is a very important component in the computer, as without it nothing would work. The duty of a power supply is to transform the voltage coming from your wall outlet (110V or 230V) into the various DC power levels that are needed by the motherboard and devices attached to it. It transforms AC (alternating current) to DC (direct current). Y-Connectors with corresponding male and female ends are sometimes attached to the individual connectors coming from the power supply box, and enables more devices to be connected when there are not enough available. However, it is important not to overload the power supply box by adding too many Y- connectors. The power supply also connects to additional fans inside of the computer case. These extra fans are used to help remove the extra heat produced by modern computers. Sometimes the power supply connects directly to the 2-wire connection to the fan that cools the CPU, and sometimes this wire is attached directly to the motherboard. If the fan connects directly to the motherboard, the heat of the CPU can be monitored by special software. For example, American Megatrends has special software, ADCM or AMI Desktop Client Manager, which remotely provides insight into computer system and hardware and monitors the temperature. Optionally, it will telephone or page you at another location to let you know if something critical has happened that urgently needs your attention. Of course, the computer must have a modem installed, and the modem must be connected to a live phone line. Power Supply Differences You would think that the power supply is the simplest component to deal with in a PC, however, there are important differences and issues that you must understand about the main power connector from the power supply to the motherboard. The connector itself depends on whether or not the system is or X. Once you understand this, you acknowledge the fact that & X power supplies cannot be interchanged with each other. With the (older) system, you must pay particular attention to not only the connectors (there are 2) itself, but also to the way that you plug them both into the mainboard. The rule here is to make sure

4 that the black wires on each connector meet in the middle. This means that when you plug in each connector you must plug them in so that the connector end with the black wires will be side-by-side with the end of the black wires on the second connector. With the X (newer) system, you must pay attention to the direction that you plug the connector into the mainboard. However, it is only one connector, so it is not as complicated. Power Supply Form Factors There are many power supply form factors in the computer industry. Each of them are different, and have different configurations and power levels. The form factors changed with each new upgrade in computer designs, such as the PC/XT,, Baby and LPX. Their connectors, configurations and voltages are different from each other. Additionally, the case and motherboard are designed to match up to particular form factors, along with the power supply. The most important thing you need to remember about this is the fact that the power supplies associated with these form factors are all different and cannot be interchanged with each other. Below is a chart for reference. Form Factor Case Motherboard Motherboard Connector PC/XT Desktop PC/XT PC/XT Desktop & Tower, Baby Baby Desktop & Tower, /X Combination, Baby, /X Combination, Baby LPX Desktop /X Combination, Baby, LPX, /X Combination, Baby, LPX X/NLX Desktop & Tower X, Extended X, /X Combination, Micro X, Mini-X, NLX X, Extended X, Flex X, Micro X, Mini-X, NLX X SFX Desktop & Tower X, Flex X, Micro X, Mini- X, NLX X, Flex X, Micro X, Mini- X, NLX X, Flex X, Micro X, Mini-X, NLX WTX Tower WTX WTX WTX External Connectors As was briefly described in the introduction to this unit, there are many different kinds of connectors used externally on a computer. They all have one main purpose, and that is to connect external peripherals to the computer. Additionally, the connectors all use thumb screws or clips as supplementary help in keeping them secure once they are connected to the computer. However, there are differences in the external connectors, that being the amount of wires used, the size and pin configuration, and the design. Furthermore, there are adapters and gender changers that are used on the

5 cabling ends, which help to further modify the connector for variations in the designs of computers and peripherals. All connectors come with male or female ends. This means that one connector end is meant to match and connect to the other. The male connector will have pins, and the female connector will have socket holes that the pins fit into. All connectors must meet safety standards. In the following paragraphs, I will introduce the most common of these connectors and their use. D Shell Connectors D Shell or D-Sub Connectors If you look at this connector, it looks similar to a CAPITOL D. Most times, you will hear these connectors referred to as their individual names rather than a D Shell Connector. The design on these pins are all basically the same, with the exception of manufacturer shell colors. The difference is the amount of pins or sockets that they have. DB-9 (9 pins or sockets) - serial port connector on IBM, PS/2 and compatible computers for connecting modems and other RS-232 serial devices, serial mouse & printer, mono monitor. DB-15 (15 pins or sockets) - joystick port on IBM,, PS/2 and compatible computers, video connector on most Macintosh computers, and Ethernet cards. HDDB-15 High Density (15 pins or sockets) - VGA or SVGA video connector on IBM,, PS/2 and compatible computers. DB-25 (25 pins or sockets) - parallel port connector on IBM,, PS/2 and compatible computers (IEEE 1284 Type A), and SCSI connector on most Macintosh computers. Male end - serial port connector on older IBM,, PS/2 and compatible computers, and for attaching modems and RS-232 serial peripherals. DB-37 (37 pins or sockets) - older CD-ROM s, and Bernoulli Box. DB-50 (50 pins or sockets - also called an HP connector) - SCSI I Connector DB-50-Half Pitch (50 pins or sockets) - SCSI II Connector DB-68-Half Pitch (68 pins or sockets) - SCSI III Connector D Shell Connectors - Images DB-9 DB-15 HDDB-15 High Density DB-25 DB-37 DB-50 DB-50-Half Pitch DB-68-Half Pitch The male connectors are identical, except that they have pins in place of socket holes.

6 Centronics Connector The Centronics Connector has the same type shell case as the D Shell Connector. However, once you see this connector you will not forget what it looks like. Click on image or HERE for larger view of connector. The area inside the shell where you would expect to see holes or pins is what makes it look so different. It looks more like an edge connector for an adapter card, except that it is a little wider. This type of connector is used on printers and in SCSI devices. The male end fits snug into the female end, as on the back of a printer, and is usually held in place by clips rather than thumb screws. The Centronics Connector actually comes in several different sizes, however, I will only show the most common one used. All sizes are similar in how they look, the difference being how many contact point are incorporated. (Versions - Centronics 24, Centronics 36 - Parallel & IEEE 1284 Type B, Centronics 50 - SCSI I Connector, Centronics Half Pitch 36 - IEEE 1284 Parallel Type C, Centronics Half Pitch 50 - SCSI & Think pad SCSI Connector, Centronics Half Pitch 60 - RS/6000 & Think pad SCSI connector, and Centronics Half Pitch 68 - RS/6000 Connector. Centronics Half Pitch 36 - IEEE 1284 Parallel Type C showing side clips. Besides the Centronics cable, there are other cables that have been used for connecting printers to computers. They are: Serial cable - DB-9 (see above in D-Shell connectors) Parallel cable - DB-25 (see above in D-Shell connectors) RJ cables - (see below in the RJ connector section) DIN Connectors The acronym "DIN" stands for Deutsche Industrie Normen (German Industrial Standard), and the connector is a high-frequency coaxial connector. The connector has various uses throughout the electronic industry, which includes computers. It is round and has a notch to make sure that the pins line up correctly. DIN connectors have three (3) to seven (7) pins, and and sizes range from approximately 5/8 to just under 1 in diameter. There are both male and female ends for this connector. The number next to DIN tells how many pins (male) or socket holes (female) are incorporated into the DIN connector. The connector ends are attached to a coaxial cable. The connector ends are attached to a cable that contains the same amount of wires as the DIN name. The DIN connector names are: DIN-3 MINI - Apple Talk & Local talk Connector DIN-4 MINI - Apple ADB Port for Mouse & Keyboard DIN-5 - PC Keyboard Connector & Apple II serial Connector. DIN-6 MINI - PS/2 Keyboard & Mouse Connector DIN-8 MINI - Image/Laser Writer & Serial Printers Modems DIN-9 MINI - PS/2 Keyboard & Bus Mouse Connector

7 BNC & BNC T-Connectors BNC Connector BNC stands Bayonet Neill-Concelman (the inventors). Also known as Barrel Nut Connector and British Naval Connector, Coaxial, Thinnet, 10base2, and RG 58 cable. It is of the male type connectors. This type of connector is mounted on each end of a coaxial cable, is barrel shaped, and has a pin protruding from the center. However, the pin protruding from the center is actually a part of the coaxial cable and not the connector itself. The outer metal tube of the connector is attached to the outer braided cable shield of the Coaxial Cable, which also has a rotating ring that screws onto the designated female adapter to hold it in place. This is the same type of connector that is used for cable television, VCR's, citizen band and amateur radio connections. In the computer industry, it is used for primarily for coaxial networking. BNC T-Connectors are female devices that are used to connect two BNC connectors to a NIC (Network Interface Card). Sometimes BNC connectors are used for making a connection to a particular type of monitor. In this setup, it helps to increase the accuracy of the signals that are being transported from the video display adapter to the monitor, but is only used where very high accuracy is needed. BNC & BNC T-Connectors - Images ===> Coaxial Cable BNC Connector on Coaxial Cable Click image or HERE for larger view. BNC-T Connector RJ-11 & RJ-45 Connectors RJ-11 & RJ-45 Connectors - RJ stands for Registered Jack. Therefore, RJ-11 is called Registered Jack-11, and RJ-45 is Registered Jack-45. All of the RJ series connectors are used for communication, but on a few occasions, I have seen them used for other purposes in special setups. You will probably only see them used for telephones, modems, and NIC s (Network Interface Cards). RJ-11 4 or 6 wires standard telephone equipment connectors used mostly for telephone cords, but sometimes used for LAN's (Local Area Network). Wires are used in pairs of 2 in the connector. RJ-45 8 wires in pairs of 2 - it is almost identical to the RJ-11 except that it is slightly wider and uses more wires. Most Networks use the RJ-45 connector to link computers to a LAN (Local Area Network).

8 Null-Modem & Laplink Cables Null-Modem Cable This cable is an RS-232 serial cable that is designed to link two computers together, through the serial port for sharing files and data. They can be used to connect any two computers together, but are more often used for connecting a laptop computer to a full-sized computer. This cable can have DB-9 or DB-25 connectors at the cable ends. Laplink Cable - A Null modem looks similar, but only has the 2 connector ends, instead of 4. Laplink "Serial" Cables This cable is actually a special combination cable with four female connector ends; two DB-9 s and two DB-25 s. It is designed to enable computers that have different sized serial port adapters (DB-9 or DB- 25) to be able to connect together. At each end of the cable there is one DB-25 and one DB-9 connector. Laplink "Parallel" Cables only have 2 connector ends. Gender Changers & Configurable Connectors Gender Changers are connectors that make it possible to change the connector end of a cable into another type. Simply put, it is a double-ended connector that enables converting a male connector into a female connector, and vice versa. Configurable Connectors make it possible to configure the pin or socket connector according to what is needed. These types of connectors come in pieces that need to be assembled, and attached to the cable, and come in male and female versions. They also come in handy for when you just need to repair the end of a cable rather than to buy an entire new one. Have you ever seen a hose repair kits for the garden hose, where you could splice two hoses together or repair a broken end? Well, configurable connectors are the electrical world equivalent of the hose repair kits. Jumpers Jumpers are the simplest type of connectors. They usually consist of a very small plastic shell with two or more holes. Inside of the holes are metal sleeves, which are permanently connected to each other. They are designed so that they can slide onto two or more pins on a circuit board to make a closed circuit. Jumpers are used to change the parameters of a circuit board. Parameters are characteristics that make it possible to change what can or can not happen in software or circuits. For example, connecting pins 1 and 2 could be designated for making a particular adapter card to use IRQ-1 (INTERRUPT REQUEST LINE ). If pins 3 & 4 were designated for IRQ-3, then putting a jumper on those two pins would make the adapter use IRQ-3 instead of IRQ-1, and so on. Before PnP (Plug-and-Play), most adapter cards or devices needed to be configured with jumpers or switches. Since PnP came into use, the computer's system automatically decides and configures the parameters that are to be used. However, this does not always work optimally. Because of this, many adapter cards and devices still incorporate pins so that you can optionally use jumpers to manually set the parameters to what is needed to make it work.

9 USB Connectors USB (Universal Serial Bus) - USB is an interface that uses an external bus standard, and is used to connect peripherals to a computer. It is much faster than serial and parallel connectors, and supports data transfer rates of 12 Mbps or more. Up to 127 peripheral devices can be connected to a single USB port. These devices include mice, modems, keyboards, scanners, printers, digital cameras, etc. Additionally, USB supports Plug-and-Play. It also permits you to be able to connect peripherals "on the fly". This means that as long as you already have the USB device set up with your Windows operating system, you can connect it while Windows is running, without having to reboot or shutdown your computer. Since the inception of USB, many devices have changed over to its interface. For devices that do not have a USB interface, you can usually purchase an adapter that will enable a USB connection along with its speed. For instance, let's say you have a digital camera, and it only has a serial connector for your PC. A serial connection is extremely slow for downloading the very large image files from your camera to your PC. To solve this problem, USB card readers were designed so that you could take the memory card from the camera and insert it into the USB cable that has a memory card adapter attached to it. The difference in transfer times can change to seconds as opposed to an hour or more, for transferring images to your PC. Power Cable Connectors Power Cable (plug/cord) - There is not anything special about a PC power cable, except maybe the fact that the end that connects to the computer usually isn't used in any other industry besides computers. The standard AC power cord for computers is of the 3-prong variety (third prong is ground), with one end being male and one end female. The female end plugs into the computer, monitor or other peripheral, and the male end into the surge-protected wall outlet. They come in various colors and lengths, and a few even have extension cord adaptors built into the wall outlet end. However, the one seen in the picture here, is the one that you will most likely be using for most of your computer projects. Click HERE to see a full-sized image. Internal Y Connectors Internal Power Supply Y-Connectors with corresponding male and female ends are sometimes attached to the individual connectors coming from the power supply box, and enables more devices to be connected when there are not enough available. However, it is important not to overload the power supply box by adding too many Y-connectors. Your power supply can only put out so much power, and if you over-do it, you can crash your computer, or not let it start at all. Viewed here, you see the 5.25" (Molex Connector - larger) power supply connector and a 3.5" (FDD/HDD/CD-ROM - smaller) power connectors. The main end attaches to an existing connector coming off of the power supply. Also see topic above on Power Supplies.

10 Twisted-Pair Cable Twisted-Pair Cable is a cable that has two wires (both have individual insulated jackets). One of the wires carries the signal or current, and the other is a ground wire. The ground wire absorbs surrounding signal interference. The reason they are called Twisted-Pair Cables is that the two wires twist around each other. This type of cable has been used in telephone and LAN (Local Area Network) networks, is of the older type, and the quality is not as good as the other cables. Notice in the image that there are two sets of cables that are twisted together. Fiber Optics Cables Fiber Optics Cables use glass, silica fiber or plastic threads to transmit signals or data. These threads are as thin as a human hair and are bundled and wrapped in an insulated jacket. Fiber optics cables are used to carry digital information over very long distances. The information or signals are carried in the form of pulses of light. These newer type cables are more efficient and can carry more data much faster than the other forms of cables. They are used as the medium for transmitting, receiving and converting electrical input signals into modulated light, using transmitters and receivers via LEDs and LDs (Light Emitting Diodes and Laser Diodes), and are used mostly in communications systems. Since light can travel faster than electrical signals, you can understand why fiber optics are a faster and more efficient mode of transferring data and information. Additionally, they are lightweight, thinner, use less power to operate, are flexible and less susceptible to corrosion and signal interference than metal wires. Pictured here is a commonly used fiber optic cable. The cables themselves, consist of hundreds to thousands of fiber optic strands. Each strand consists of basically three components, the core, cladding and the buffer coating. The core is made of the thin and fragile glass fiber strands by which the light signals travel. The cladding is a special material that is used to reflect the light back into the core of the glass fibers. The buffer coating is made of plastic, and is used to protect the cables from damage such as moisture. In addition to this the sets of bundles are enclosed in a protective jacket. However, they are still very fragile, and can break easily. Although fiber optics are currently in use, it is because of this fragile condition that they are very expensive to install. The reason why it is taking time to change over to fiber optics is due to the cost of replacing all of the existing copper cables that have been used in the past. Infrared IrDA Infrared Connectors (Infrared Data Association) Infrared is a standard used for transmitting information and data by using infrared light waves. IRDA transmits at about the same rate as parallel ports. It was designed for transferring information and data, or for communication between the computer and an external device. Some devices that use infrared connectors and adapters are printers, remote controls, cameras and digital equipment, keyboards, mice and laptops. There are special connectors and adapters that can be purchased to convert a non-infrared device to infrared through its existing port connector. The infrared adapter/connector contain infrared receiving transmitters which transmit and receive data via infrared light flashes in the form of wave bands, which can not normally be seen by the human eye. Using infrared makes it possible to transmit data or information without having to make a physical connection to the computer, but you must connect the connectors and adapter to the port and have the devices and software already installed for this to work. The PC and the infrared device have distance limits of a few feet, and there cannot be any obstacles in-between them that would block the transmission of infrared light

11