PRACTICAL FILE

OF

COMPUTER HARDWARE &

TROUBLESHOOTING LAB

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SUBMITTED TO: SUBMITTED BY:Er. Ashish Vashisht Ravi Jindal(Lect. In C.S.E. Deptt.) Roll No.-2907140

Branch- C.S.E.

KURUKSHETRA INSTITUTE OF TECHNOLOGY & MANAGEMENTPehowa Road, Bhor Saidan

Kurukshetra

S.NO. EXPERIMENT NAME DATE REMARKS

INDEX

EXPERIMENT NO. - 1

AIM: - To assemble a PC.

Requirement: - Cabinet, Motherboard, RAM, Heat Sink, VGA, SMPS, screw driver,

Hard Disk,

Steps for assembling the PC: Locate the CPU socket on the motherboard. Pentium motherboards have a ZIF (Zero Insertion Force) socket that lets you mount a processor with minimum force. The ZIF socket has a little lever, lifted and aligns the CPU chip with the socket. You will notice that the CPU chip has on corner marked distinctively as a stubbed corner, small dot or tiny groove. This marked corner must correspond to a similar marking on the socket. The CPU goes into the socket on the way only and this marking will ensure correct alignment. Place the CPU into the socket and push down the lever. Now mount the CPU FAN on it and lock it, also connect the power cable to the power supply that can add later. Fix the SIMM or DIMM insert them in vertical position so that the plastic locks that hold the module snap in place. Never apply too much force while inserting RAM modules. Fix the plastic spacers provided with the cabinet to the motherboard. To attach the motherboard to the chassis, press the spacers to the socket at the bottom of the chassis. Unpack all the components and lay them out carefully on the table. Check that all the components and cables. Keep the screws and motherboard spacers in a bowl. The plastic spacers provide maintain a distance between a motherboard and chassis. Then fix the two screws from top to secure the motherboard in place. Attach the power supply to the chassis and connect the power cables to the motherboard. The cables supplying the power to motherboard have flat connector’s p8.There are two connectors (each having six wires) and they have to be plugged in a certain way. The sequence of wires on one connector begins with an orange wire and ends with a black wire. On the second connector, the sequence begins with a black wire and ends with a red wire. Holding the two connectors together the sequence should be orange –black, black-red.

The serial and parallel ports are integrated on the new motherboards. Using cables, these must be connected to external ports mounted on back plates at the near of the PC.Remove the plastic plates near the drive bays in the front of the cabinet. Attach the hard disk in the lower drive bay. In some cases the hard disk is screwed down directly to the bottom of chassis. Otherwise you have to mount the hard drive on the slide rails using mounting brackets.

Add the CD-ROM drive in the top bay and the floppy drive sideward. The arrangement of drives differs, depending on the case design. Connect the power cable to the drives and the data cables. Again you will have to watch out for polarity. The flat data cable has a red stripe on one end that indicates pin number one. The power connector also has a red wire on one end. These two red wires must face each other. First attach the power connector in the D type slot.

The data cables from the floppy drives, CD-ROM drive and Hard disk drives connect directly to marked connectors on the motherboards. Connect the audio cable from the CD-ROM drive to the sound cars that can add next. Remove the metal covers near the expansion slots at the back of the cabinet. Attach the VGA card and sound card or cable provided. Check each component and examine all cable connections before switching on. Need not to close the cabinet for the moment. Plug in the monitor power lead to the power supply. The monitor data lead plugs in to the VGA port on the graphics card. Plug in the keyboard and mouse. Finally connect the system power lead to the AC wall outlet.Switch on the unit. If there is a single brief beep and a whirring sound from the drives. Let the boot process continue. If there are multiple beeps look out for error messages on the screen.

The POST (power on self test) program will occur followed by a memory check and drive detection. Finally you will get a message prompting for the operating system. Insert the bootable floppy and reboot the computer. Then install configure the operating system on to the disk.

Precautions:-

Before Assembling the CPU1. Ensure the power supply is disconnected from the mains.2. Do not drop any screws or other conducting material on the PC’s motherboard as that might cause short circuit of pins and tracks of the motherboard.3. Make sure that must have a large, flat surface area to work on. That will reduce the chances of small screws etc. falling and getting lost.4. While screwing components on to the chassis, do not use excessive force as that may damage the screws or their grooves/holes.5. The motherboard contains sensitive components; which can be easily damaged by static electricity. Therefore the motherboard should remain in its original antistatic envelope until it is required for installation. When it is taken out from the envelope, it should be immediately placed on the suitable grounded conductive surface. The motherboard itself should be held from the edges and the person taking it out should wear an antistatic wrist strap that is properly grounded. In the absence of the proper wrist strap,

you may make one on your own using a peeled off multi-strand copper cable and ground it properly. Similar handling precautions are also requires for DIMM and cards.

Experiment No. - 2

AIM: - To study about different types of RAM.

RAM: - Random-access memory (usually known by its acronym, RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

Types of RAM: - There are 2 types of RAM which have appeared over the years and it is often difficult knowing the difference between them both performance wise and visually identifying them. This article tells a little about each RAM type, what it looks like and how it performs.

1. SRAM: - Static RAM. It is primarily used as cache memory. SRAM is faster than DRAM. It is more expensive, takes up a lot more space, requires more power, dissipates more heat ,therefore it is not used as primary system memory. It uses only transistors in its circuitry. 2. DRAM: - Dynamic RAM. It consists of an array of transistors coupled with capacitors. When fully charged, one of these capacitors represents a 1 in binary. To prevent this from happening, we have to recharge the individual cells. This process is called the Refresh.

FPM RAM: - FPM RAM, which stands for “Fast Page Mode RAM” is a type of Dynamic RAM (DRAM). The term “Fast Page Mode” comes from the capability of memory being able to access data that is on the same page and can be done with less latency. Most 486 and Pentium based systems from 1995 and earlier use FPM Memory.

EDO RAM: - EDO RAM, which stands for “Extended Data Out RAM” came out in 1995 as a new type of memory available for Pentium based systems. EDO is a modified form of FPM RAM which is commonly referred to as “Hyper Page Mode”. Extended Data Out refers to fact that the data output drivers on the memory module are not switched off when the memory controller removes the column address to begin the next cycle, unlike FPM RAM. Most early Pentium based systems use EDO. This is now obsolete. EDO DRAM gave people up to 5% system performance increase over DRAM.

SDRAM :- SDRAM , which is short for Synchronous DRAM (Dynamic Random Access Memory) is a type of DRAM that runs in synchronization with the memory bus.

Beginning in 1996 most Intel based chipsets began to support SDRAM which made it a popular choice for new systems in 2001. It has a different paging system, for those of you who don’t know what paging is, it is the swapping of files from your hard drive to your RAM Module. This type of memory synchronizes the input and output signals with the system board. SDRAM is capable of running at 133MHz which is about three times faster than FPM RAM and twice as fast as EDO RAM. Most Pentium or Celeron systems purchased in 1999 have SDRAM. SDRAM has 168 pins and two notches at the connector, which prevents it from being used in a DDR SDRAM motherboard and vice versa. It comes mainly in PC66, PC100 and PC133; the bus speeds of the RAM in MHz.

1. It is quicker than DRAM.2. Access time than 60seconds.

SDRAM has 4 types:-

1 DDR2 DDR13 DDR24 DDR3

DDR RAM :- DDR RAM, which stands for “Double Data Rate” which is a type of SDRAM and appeared first on the market around 2001 but didn’t catch on until about 2001 when the mainstream motherboards started supporting it. Dynamic Random Access Memory is used to temporarily store information on computers. its paging system swaps 2 pieces of data at a time. DRAM is made up of many cells and each cell is referred to as a bit. A cell contains a capacitor and a transistor. The difference between SDRAM and DDR RAM is that instead of doubling the clock rate it transfers data twice per clock cycle which effectively doubles the data rate. DDRRAM has become mainstream in the graphics card market and has become the memory standard. It is current technology. Basically a pumped up version of SDRAM. DDR SDRAM has 184 pins and a single notch at the connector. It comes in speeds of PC1600 (166 MHz), PC1800 (200 MHz), PC2100 (266 MHz), PC2700 (333 MHz), PC3200 (400 MHz), and PC4400 (550 MHz). The numbers represent the theoretical maximum bandwidth of the DDR SDRAM in Megabytes per second (MB/s). For example, PC2100 has a theoretical maximum bandwidth of 2100 MB/s.

1. Contents are constantly refreshed 100times per second. 2. Access time 60-70 nanoseconds. 3. A nano second is equal to 1billionth of a second.

DDR1:- It is also known as DDR. Double Data Rate interfaces provide two data transfers per differential clock. Compared to the preceding single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals. Implementations often have to use schemes such as phase-locked loops and self-calibration to reach the required timing accuracy. The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to lower the clock frequency. One advantage of keeping the clock frequency down is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a single data rate (SDR) SDRAM running at the same clock frequency, due to this double pumping. With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.

DDR2:- DDR2 stores memory in memory cells that are activated with the use of a clock signal to synchronize their operation with an external data bus. Like DDR before it, DDR2 cells transfer data both on the rising and falling edge of the clock (a technique called "dual pumping"). The key difference between DDR1 and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. DDR2 consumes less power as compared to the DDR memory. DDR2 speeds range between 400 MHz (DDR2-400) and 800 MHz (DDR2-800)... DDR2-800 transfers 6400 MB/s. DDR2 SDRAM is now available at a clock rate of 533 MHz generally described as DDR2-1066 and the corresponding DIMMS are known as PC2-8500 (also named PC2-8600 depending on the manufacturer). DDR2 allows higher bus speed and requires lower power by running the internal clock at one

quarter the speed of the data bus. The two factors combine to require a total of 4 data transfers per internal clock cycle. With data being transferred 64 bits at a time, DDR2 SDRAM gives a transfer rate of (memory clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR2 SDRAM gives a maximum transfer rate of 3200 MB/s.

DDR3:- DDR3 memory comes with a promise of a power consumption reduction of 30% compared to current commercial DDR2 modules due to DDR3's 1.5 V supply voltage, compared to DDR2's 1.8 V or DDR's 2.5 V. This supply voltage works well with the 90 nm fabrication technology used for most DDR3 chips. Some manufacturers further propose to use "dual-gate" transistors to reduce leakage of current. The main benefit of DDR3 comes from the higher bandwidth made possible by DDR3's 8 bit deep prefetch buffer, whereas DDR2's is 4 bits, and DDR1's is 2 bits deep. In theory DDR3 is supposed to act twice as fast as DDR2 memories.. DDR3 continues the trend, doubling the minimum read or write unit to 8 consecutive words. This allows another doubling of bandwidth and external bus rate without having to change the clock rate of internal operations, just the width. To maintain 800 M transfers/s (both edges of a 400 MHz clock), the internal RAM array has to perform 100 M fetches per second. Again, with every doubling, the downside is the increased latency. As with all DDR1 SDRAM generations, commands are still restricted to one clock edge and command latencies are given in terms of clock cycles, which are half the speed of the usually quoted transfer rate (a CAS latency of 8 with DDR3-800 is 8/(400 MHz) = 20 ns, exactly the same latency of CAS2 on PC100 SDR SDRAM).DDR3 memory chips are being made commercially, and computer systems are available that use them as of the second half of 2007, with expected significant usage in 2008. Initial clock rates were 400 and 533 MHz, which are described as DDR3-800 and DDR3-1066 (PC3-6400 and PC3-8500 modules), but 667 and 800 MHz, described as DDR3-1333 and DDR3-1600 (PC3-10600 and PC3-12800 modules) are now common. With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.

EXPERIMENT NO. - 3

AIM: - Cables and Connectors Used in Networking.

Generally speaking, the cabling systems described in the next few sections use one of three distinct cable types. These are twisted-pair (in shielded and unshielded varieties known as STP and UTP, 10BaseT, or 100BaseT), coaxial in thin and thick varieties (known as 10Base2 and 10Base5, respectively), and fiber optic. The kind of cable you use depends mostly on the data link layer protocol that you elect to use, the conditions at the network site, and of course, your budget. The entire major data link layer protocols used on LANs (such as Ethernet and Token Ring) includes highly specific guidelines for the installation of the network cable as part of their specifications. Technically, these guidelines are part of the physical layer, but this is one example of how protocols in the real world do not conform exactly to the OSI model.

Twisted-Pair Cable

Twisted-pair cable is just what its name implies: insulated wires within a protective casing with a specified number of twists per foot. Twisting the wires reduces the effect of electromagnetic interference (that can be generated by nearby cables, electric motors, and fluorescent lighting) on the signals being transmitted. Shielded twisted pair (STP) refers to the amount of insulation around the cluster of wires and therefore its immunity to noise. You are probably familiar with unshielded twisted-pair (UTP) cable; it is often used for telephone wiring.

Unshielded twisted pair cable

Shielded Versus Unshielded Twisted Pair When cabling was being developed for use with computers, it was first thought that shielding the cable from external interference was the best way to reduce interference and provide for greater transmission speeds. However, it was discovered that twisting the pairs of wires is a more effective way to prevent interference from disrupting transmissions. As a result, earlier cabling scenarios relied on shielded cables rather than the unshielded cables more commonly in use today.

Shielded cables also have some special grounding concerns because one, and only one, end of a shielded cable should be connected to an earth ground; issues arose where people inadvertently caused grounding loops to occur by connecting both ends or caused the shield to act as an antenna because it wasn’t grounded. Grounding loops are situations where two different grounds are tied together. This is a bad situation because each ground can have a slightly different potential, resulting in a circuit that has very low voltage but infinite amperage. This causes undue stress on electrical components and can be a fire hazard.

Definition: - CAT5 (also, CAT 5) is an Ethernet network cable standard defined by the Electronic Industries Association and Telecommunications Industry Association (commonly known as EIA/TIA). CAT5 is the fifth generation of twisted pair Ethernet technology and the most popular of all twisted pair cables in use today. CAT5 cable contains four pairs of copper wire. It supports Fast Ethernet speeds (up to 100 Mbps). As with all other types of twisted pair EIA/TIA cabling, CAT5 cable runs are limited to a maximum recommended run length of 100m (328 feet). Although CAT5 cable usually contains four pairs of copper wire, Fast Ethernet communications only utilize two pairs. A newer specification for CAT5 cable - CAT5 enhanced ("CAT5e" or "CAT 5e") - supports networking at Gigabit Ethernet [ speeds (up to 1000 Mbps) over short distances by utilizing all four wire pairs, and it is backward-compatible with ordinary CAT5. Twisted pair cable like CAT5 comes in two main varieties, solid and stranded. Solid CAT5 cable supports longer length runs and works best in fixed wiring configurations like office buildings. Stranded CAT5 cable, on the other hand, is more pliable and better suited for shorter-distance, movable cabling such as on-the-fly patch cabling. Though newer cable technologies like CAT6 and CAT7 are in

development, CAT5 / CAT5e Ethernet cable remains the popular choice for most wired local area networks (LANs), because Ethernet gear is both affordable and supports high speeds.

Definition: - CAT6 is an Ethernet cable standard defined by the Electronic Industries Association and Telecommunications Industry Association (commonly known as EIA/TIA). CAT6 is the sixth generation of twisted pair Ethernet cabling. CAT6 cable contains four pairs of copper wire like the previous generation CAT5. Unlike CAT5, however, CAT6 fully utilizes all four pairs. CAT6 supports Gigabit Ethernet speeds up to 1 gigabit per second (Gbps) and supports communications at more than twice the speed of CAT5e, the other popular standard for Gigabit Ethernet cabling. An enhanced version of CAT6 called CAT6a supports up to 10 Gbps speeds. As with all other types of twisted pair EIA/TIA cabling, individual CAT6 cable runs are limited to a maximum recommended length of 100m (328 feet). Printing along the length of the cable sheath identifies it as CAT6. A registered jack (RJ) is a standardized physical network interface — both jack construction and wiring pattern — for connecting telecommunications or data equipment to a service provided by a local exchange carrier or long distance carrier. The standard designs for these connectors and their wiring are named RJ11, RJ14, RJ21, RJ48, etc. Many of these interface standards are commonly used in North America, though some interfaces are used world-wide. The physical connectors that registered jacks use are mainly of the modular connector and 50-pin miniature ribbon connector types. For example, RJ11 uses a 6 position 4 conductor (6P4C) modular plug and jack, while RJ21 uses a 50-pin miniature ribbon connector.

Coaxial Cable Coaxial cable is fairly prevalent in your everyday life, as it is the standard medium used both by cable TV networks and for antenna connections. Thin and thick, of course, refer to the diameter of the coaxial cable itself. Standard Ethernet cable (Thick Ethernet), rarely used for networking today is as thick as your thumb. Thin Ethernet cable (sometimes called Thin net or Cheaper Net; RG-58) is slightly narrower than your little finger. The thick cable has a greater degree of noise immunity, is more difficult to damage, and requires a vampire tap (a connector with teeth that pierce the tough outer insulation) and a drop cable to connect to a workstation. Although thin coaxial cable carries the signal over shorter distances than the thick cable, it is lower in cost (hence the name Cheaper Net) and uses a simple, bayonet-locking connector called a BNC (Bayonet-Neill-Concelman) connector to attach to workstations. Thin Ethernet was at one time the standard for Ethernet networking, but it has since been replaced by 10BaseT (unshielded twisted pair). Thin net is wired directly to the back of each computer on the

network and generally installs much more easily than Thick net, but it is more prone to signal interference and physical connection problems.

Fiber-Optic Cable Fiber-optic cable uses pulses of light rather than electrical signals to carry information. It is therefore completely resistant to the electromagnetic interference that limits the length of copper cables. Attenuation (the weakening of a signal as it traverses the cable) is also less of a problem, enabling fiber to send data over huge distances at high speeds. It is, however, very expensive and difficult to install and maintain. Splicing the cable, installing connectors, and using the few available diagnostic tools for finding cable faults are skills that very few people have. Fiber-optic cable is often used to connect buildings together in a campus network environment for two very important reasons. One is that fiber can travel approximately 2.2km, whereas copper-based technologies are significantly more restricted. The other reason is that because fiber does not use electrical signals, it eliminates the problems with differing ground sources. Fiber-optic cable is simply designed but unforgiving of bad connections. It usually consists of a core of glass thread with a diameter measured in microns (millionths of a meter), surrounded by a solid glass cladding. This, in turn, is covered by a protective sheath. The first fiber-optic cables were made of glass, but plastic fibers also have been developed. The light source for fiber-optic cable is a light-emitting diode (LED); information usually is encoded by varying the intensity of he light. A detector at the other end of the cable converts the incoming signal back into electrical impulses. Two types of fiber-optic cable exist: single mode and multimode. Single mode has a smaller diameter, is more expensive, and can carry signals over a greater distance.

Figure illustrates fiber-optic cables and their connectors.

Multimode has a diameter five to ten times greater than single mode, making it easier to connect. This ease of use makes it the most commonly used fiber. However, multimode suffers from higher distortion and lower bandwidth.

EXPERIMENT NO. - 4

AIM: - To Solder & Desolder various components.

Requirement:- Soldering Iron, Desoldering Machine, Solder Wire, Flux & Different components.

Theory

Soldering is defined as "the joining of metals by a fusion of alloys which have relatively low melting points". In other words, you use a metal that has a low melting point to adhere the surfaces to be soldered together. Consider that soldering is more like gluing with molten metal, unlike welding where the base metals are actually melted and combined. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and developed with practice.

The first thing you will need is a soldering iron, which is the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and you risk damaging either the component or the board. If you intend to solder heavy components and thick wire, then you will want to invest in an iron of higher wattage (40W and above) or one of the large soldering guns. The main difference between an iron and a gun is that an iron is pencil shaped and designed with a pinpoint heat source for precise work, while a gun is in a familiar gun shape with a large high wattage tip heated by flowing electrical current directly through it.

Solder is an alloy (mixture) of tin and lead, typically 60% tin and 40% lead. It melts at a temperature of about 200°C. Coating a surface with solder is called 'tinning' because of the tin content of solder. Lead is poisonous and you should always wash your hands after

using solder. Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex. The flux is corrosive, like an acid, and it cleans the metal surfaces as the solder melts. This is why you must melt the solder actually on the joint, not on the iron tip. Without flux most joints would fail because metals quickly oxidize and the solder itself will not flow properly onto a dirty, oxidized, metal surface. The best size of solder for electronics is 22swg (swg = standard wire gauge).

How to Solder

First a few safety Precautions:

Never touch the element or tip of the soldering iron. They are very hot (about 400°C) and will give you a nasty burn.

Take great care to avoid touching the mains flex with the tip of the iron. The iron should have a heatproof flex for extra protection. An ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock.

Always return the soldering iron to its stand when not in use. Never put it down on your workbench, even for a moment!

Work in a well-ventilated area. The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work.

Wash your hands after using solder. Solder contains lead which is a poisonous metal.

Preparing the soldering iron:

Place the soldering iron in its stand and plug in. The iron will take a few minutes to reach its operating temperature of about 400°C.

Dampen the sponge in the stand. The best way to do this is to lift it out the stand and hold it under a cold tap for a moment, then squeeze to remove excess water. It should be damp, not dripping wet.

Wait a few minutes for the soldering iron to warm up. You can check if it is ready by trying to melt a little solder on the tip.

Wipe the tip of the iron on the damp sponge. This will clean the tip.

Melt a little solder on the tip of the iron. This is called 'tinning' and it will help the heat to flow from the iron's tip to the

joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the tip clean on the sponge.

Some components require special care when soldering. Many must be placed the correct way round and a few are easily damaged by the heat from soldering. Appropriate warnings are given in the table below, together with other advice which may be useful when soldering.

  Components Pictures Reminders and Warnings

1ICHolders(DIL sockets)

Connect the correct way round by making sure the notch is at the correct end. Do NOT put the ICs (chips) in yet.

2 Resistors No special precautions are needed with resistors.

3Small value capacitors(usually less than 1µF)

These may be connected either way round. Take care with polystyrene capacitors because they are easily damaged by heat.

4Electrolytic capacitors(1µF and greater)

Connect the correct way round. They will be marked with a + or - near one lead.

5 Diodes

Connect the correct way round. Take care with germanium diodes (e.g. OA91) because they are easily damaged by heat.

6 LEDs

Connect the correct way round. The diagram may be labelled a or + for anode and k or - for cathode; yes, it really is k, not c, for cathode! The cathode is the short lead and there may be a slight flat on the body of round LEDs.

7 Transistors

Connect the correct way round. Transistors have 3 'legs' (leads) so extra care is needed to ensure the connections are correct. Easily damaged by heat.

8Wire Links between points on the circuit board. single core wire

Use single core wire, this is one solid wire which is plastic-coated. If there is no danger of touching other parts you can use tinned copper wire, this has no plastic coating and looks just like solder but it is stiffer.

9Battery clips, buzzers and other parts with their own wires

  Connect the correct way round.

10

Wires to parts off the circuit board, including switches, relays, variable resistors and loudspeakers.

stranded wire

You should use stranded wire which is flexible and plastic-coated. Do not use single core wire because this will break when it is repeatedly flexed.

11 ICs (chips)

Connect the correct way round. Many ICs are static sensitive. Leave ICs in their antistatic packaging until you need them, then earth your hands by touching a metal water pipe or window frame before touching the ICs. Carefully insert ICs in their holders: make sure all the pins are lined up with the socket then push down firmly with your thumb.

You are now ready to start soldering:

Hold the soldering iron like a pen, near the base of the handle. Imagine you are going to write your name! Remember to never touch the hot element or tip.

Touch the soldering iron onto the joint to be made. Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and...

Feed a little solder onto the joint. It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron.

Remove the solder, then the iron, while keeping the joint still. Allow the joint a few seconds to cool before you move the circuit board.

Inspect the joint closely. It should look shiny and have a 'volcano' shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before applying solder

Desoldering At some stage you will probably need to desolder a joint to remove or re-position a wire or component.

With a desoldering pump (solder sucker)

Set the pump by pushing the spring-loaded plunger down until it locks. Apply both the pump nozzle and the tip of your soldering iron to the joint. Wait a second or two for

the solder to melt. Then press the button on the

pump to release the plunger and suck the molten solder into the tool.

Repeat if necessary to remove as much solder as possible.

The pump will need emptying occasionally by unscrewing the nozzle.Using a desoldering pump (solder sucker)

PRACTICAL No. - 5

Aim :- To check and measure power supply

If the SMPS has an AC input, then its first job is to convert the input to DC.

Computer power supply units (PSU) deliver the power to the PC hardware via a number of cables with connectors. The generic specifications for various PSU form factors intended for use with desktop systems are defined in Intel's design guides, which are periodically revised. Standard power supplies for desktop PCs typically have the main power connector and additional 12V connectors, as well as peripheral, floppy drive, serial ATA, and PCI Express connectors. To support 75W PCI Express requirements, in the new ATX-style systems the old 20-pin main power connector has been replaced by a 24-pin connector. See the diagram for pin outs of the old and new power connectors. The colors represent recommended colors of the wires in the PSU power cables. The diagrams show the front (pin-side) view. The colors are shown just for reference, but you need to look from the back of the connector to see them. Main connector uses Molex Housing Mini-Fit Jr. P/N# 39-01-2240 or equivalent (old part number 5557-24R), contacts: Molex

44476-1112 or equivalent, mating motherboard connector is Molex 44206-0007. The old 20-pin ATX connector was Molex 39-01-2200 or equivalent, mating motherboard part was Molex 39-29-9202.

To power up a stand alone PSU for testing purposes, you need to short PS_ON pin with one of the common pins. Normally, PS_ON is activated when you press and release the computer power button while it is in standby mode. All voltages are referenced to the same common (if you need to measure a voltage, connect the return lead of your voltmeter to any of the COM pins).

Note that between 1996 and 2000 Dell used proprietary (non-standard) power supplies and motherboards with entirely different pinouts.

The current rating of the main Molex power connector is 6A/pin. In early 2000's, some motherboards with 3.3V >18A and 5V >24A (mainly dual CPU AMD systems) used an auxiliary 6-pin power cable. It was removed from ATX12V spec v2.0 in 2003 because extra pins were added to the main connector. When the industry began using voltage regulation modules (VRM) running off 12V2 to power CPU and other motherboard components, the bulk of the power shifted to 12 volt bus. Most of today's motherboards power their CPU with a separate 12 volt cable, which has 4 pins for ATX style (sometimes called P4) or 8 or more pins for EPS and non-standard high-power systems. Some PSUs may have three or four 12 volt 4-pin connectors. The standard 4-pin connector is Molex 39-01-2040 or equivalent. 4-pin peripheral power connects go to disk drives, fans, and other smaller devices. The floppy drive power connector as the name implies powers the floppy drive. Pin numbers and wire numbers in Serial Power ATA (SATA) connector are not 1:1. There are three power pins for each voltage. One pin from each voltage is used for pre-charge in the backplane. Mating serial connector of ATA devices contains both signal and power segments. Some units may also have an optional 2x3 connector that can be used for ancillary functions, such as fan monitoring and control, IEEE-1394 power source, and a remote sense of 3.3 V.

Power Supply Types :-

There are two basic types of power supplies. There are AT power supplies, which are older and in older computers, and ATX power supplies, which you will find in virtually every new computer you can buy. There are two fundamental differences between AT and ATX power supplies. First, the switch mechanism is different. AT power supplies use a normal on-off switch, which directly turns the power supply on or off. ATX power supplies use a momentary switch which does not directly control the power. Instead, the switch signals the motherboard, which performs one of three actions:

1. If the computer is off, the power supply is turned on (which turns the computer on).

2. If the computer is on, the computer goes into power-saving mode (standby).3. If the switch is held for more than 4 seconds, the power is cut and the computer

turns off.

Because of this difference, ATX power supplies are better for projects that require the second power supply to turn on automatically when the computer is turned on. The second difference is in the motherboard connector: AT power supplies provide two 6-pin connectors (figure 1), which are easy to insert backwards. The ATX connector is a single 20-pin connector that only plugs in one way (below figure).

Figures : The difference between AT (left) and ATX (right) motherboard connectors.

AT power supplies come with an on/off switch. An ATX power supply is not necessary. The on/off switch of ATX units is controlled through the motherboard. However, some models of ATX power supply do come with it. The difference between ATX and Micro-ATX are the form factor and output voltage. Micro-ATX provides 4-output voltage (+5V, +12V, -12V, and +3.3V). ATX provides 5-output voltage (+5V, +12V, -5V, -12V, and +3.3V).

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Experiment No. - 6

Aim:- To study Components and Functions of Motherboard.

Introduction

The motherboard is the main circuit board inside the PC which holds the processor, memory and expansion slots and connects directly or indirectly to every part of the PC. It's made up of a chipset (known as the "glue logic"), some code in ROM and the various interconnections or buses. PC designs today use many different buses to link their various components. Wide, high-speed buses are difficult and expensive to produce: the signals travel at such a rate that even distances of just a few centimeters cause timing problems, while the metal tracks on the circuit board act as miniature radio antennae, transmitting electromagnetic noise that introduces interference with signals elsewhere in the system. For these reasons, PC design engineers try to keep the fastest buses confined to the smallest area of the motherboard and use slower, more robust buses, for other parts.This section focuses on basic functionality and layout - the motherboard's various interfaces, buses and chipsets being covered elsewhere.

Evolution

The original PC had a minimum of integrated devices, just ports for a keyboard and a cassette deck (for storage). Everything else, including a display adapter and floppy or hard disk controllers, were add-in components, connected via expansion slots.The basic changes in motherboard form factors over the years are covered later in this section - the diagrams below provide a detailed look at the various components on two motherboards. The first a Baby AT design, sporting the ubiquitous Socket 7 processor connector, circa 1995. The second is an ATX design, with a Pentium II Slot 1 type processor connector, typical of motherboards on the market in late 1998.Motherboard development consists largely of isolating performance-critical components from slower ones. As higher speed devices become available, they are linked by faster buses - and the lower-speed buses are relegated to supporting roles. In the late 1990s there was also trend towards putting peripherals designed as integrated chips directly onto the motherboard. Initially this was confined to audio and video chips - obviating the need for separate sound or graphics adapter cards - but in time the peripherals integrated in this way became more diverse and included items such as SCSI, LAN and even RAID controllers. While there are cost benefits to this approach the biggest downside is the restriction of future upgrade options

The Motherboard

The motherboard (sometimes called the main board) contains connectors to receive power from the power supply and other connectors to host a variety of plug-in devices.  The bus (a set of many parallel lines on the motherboard (wires) enables communication among the plug-in devices by providing paths for electrical current.  The chief plug-in devices are the, processor, memory, and input/output connectors.  A Pentium 4 motherboard appears below.

A. Processor One of the easiest items to recognize on the motherboard is the processor. The processor is usually the largest chip on the system board and can be identified generally because it often has a heat sink or fan located on top of it.Classic Pentium motherboards typically have a socket 7 slot that the processor is inserted into. This socket is implemented as a ZIF (zero insertion force) socket, which means that the processor chip can be removed or added to the socket with very little effort. ZIF sockets typically have a lever that you pull to pop the processor out of the socket.Pentium II system boards had to implement a different socket for the Pentium II chip because the Pentium II chip was designed with a single edge connector and was inserted into the board standing up. The processor socket for Pentium II chips is called slot 1.

B. SIMM/DIMM socketsWhen you look at a system board, one of the first items that should stand out is the processor or its socket; the next thing that you will usually take notice of is the memory slots that are used to install RAM.There are typically two types of sockets to install memory: SIMM (Single Inline Memory Module) sockets and DIMM (Dual Inline Memory Module) sockets. Original Pentium systems typically have either four 72-pin SIMM sockets, or two 168-pin DIMM sockets to install memory. When installing SIMMs in Pentium motherboards, you have to install them in pairs, but when installing DIMMs, you can install them individually. The reason for the difference in the installation process is that when installing memory, you must fill a memory bank, which is the size of the processor’s data path. That is, if you install 72-

pin (32-bit) SIMMs onto a Pentium (64-bit) motherboard, then you have to install two modules to fill the 64-bit data path of the processor. DIMMs are 64-bit memory modules, which is why you only have to install one at a time

C. Cache memoryCache memory increases performance by storing frequently used program code or data. Because cache memory is faster than RAM, the system can store information accessed from RAM in cache memory when the data is accessed the first time. The processor can then retrieve the information from the faster cache memory for subsequent calls. All the processors today have integrated cache memory, which is known as level-1 cache. The types of cache are as follows:L1 (level-1) cache: Cache that is integrated within the processor. L2 (level-2) cache: Cache that is located outside the processor, like on the motherboard.Older motherboards implemented cache memory as rows of DIP chips placed directly on the motherboard. This area was sometimes even labeled “cache.” Labels on a motherboard seem to be something that you cannot always rely on though—if they are there, considers it an added bonus!Newer systems have implemented the cache as a memory module, so you may see an empty slot on the motherboard that looks like a place where you would install a SIMM, but it will really hold a cache module. A lot of times this will be labeled as cache on the system board.

D. Expansion slotMost motherboards have one or more expansion slots, which serve the purpose of adding functionality to the computer. Even if, for example, your computer doesn’t have sound capability right now, you can install a sound card into the expansion slot to add that capability.Expansion slots come in different varieties on systems today, and it is extremely important to understand the benefits of each type. If you look at the system board, you can see a number of expansion slots. There are probably some white narrow slots on the board, which are the PCI slots. You may also see some larger black slots; these are ISA slots.

E. Communication portsCommunication ports newer system boards have communication ports integrated directly into the board. The communication ports are also known as the COM ports. Typically, there are two COM ports on each system, COM1 and COM2.COM ports are also known as serial ports. The reason that they are called serial ports is because they send data in a series—a single bit at a time. If eight bits of data are being delivered to a device connected to the COM ports, then the system is sending the eight bits of data, one at a time. You usually connect an external modem, or a serial mouse, to these ports. Each of these devices is used for communication; a modem is used to allow your computer to talk to another computer across phone lines, while a serial mouse is a communication device that allows you to communicate with the system. Serial ports on the back of the system board are one of two types:DB9-male is a male serial port with 9 pins. DB25-male is a male serial port with 25 pins.

F. Parallel port

Another type of connector that you will have on the back of the motherboard is the parallel port. The parallel port is also known as the printer port, or LPT1. The parallel port gets its name by being able to send information eight bits at a time. Whereas serial ports only send one bit at a time in single file, parallel ports send can send eight bits in one operation—side-by-side rather than single file. The parallel port is a female port located on the back of the system board with 25 pins, which is known as DB25-female. You connect the parallel port to a printer by using a parallel cable that has a different type of connector at each end. On one end of the cable is a DB25 connector that attaches to the parallel port on the back of the computer (that makes sense—a female DB25 port has a cable with a DB25 male connector on it). On the other end of the cable (the end that connects to the printer) you will have a 36-pin Centronics connector.

G. Keyboard/mouse connectorMost motherboards today have mouse and keyboard connectors that are most likely PS2 style connectors. Older motherboards may have an older DIN keyboard connector, which you can see on baby AT motherboards. These systems may or may not have a mouse port on the system board. If not, the mouse connector was located on the case that the system board was inserted into; the mouse connector would connect by wires to the system board.

H. Power connector Located on the system board, you should see a type of connector that you can use to connect the power supply to the motherboard. All of these devices connected to the motherboard need to get power from somewhere, so the power supply is connected to theMotherboard , which supplies power to the board and its components. There are power cables coming from the power supply to connect to the motherboard with very unique connectors on the end, these may be labeled as P1 and P2, or on some systems, P8 and P9. You have to be extremely careful to make sure that these connectors are inserted properly, or you could damage the motherboard. Often, the connectors are keyed (meaning that they can only go in one way) so that you cannot put both of the connectors in the wrong way.

I. Video adapterMany motherboards today come with a built-in video adapter, sometimes called a video card or video controller.

J. Hard Disk ControllerA controller is a device that is responsible for controlling data flow, so a hard drive controller is responsible for both of the following: 1. Receiving information from the processor and converting or interpreting the information into signals that the hard disk can understand 2. Sending information back to the processor and converting the information into signals that the processor can understand.Older drives implemented the controller as an expansion card installed into the system that connected to the hard disk via a cable connection. Today, however, hard disk controllers are integrated into the hard disks. You can also find either one or two hard disk controllers on newer motherboards (for more information, see the section titled “EIDE/ATA-2”). The controller on the motherboard has 40 pins and connects to the drive using a 40-wire ribbon cable.

K. Floppy disk controller

Located very close to the hard disk controllers, you should see a smaller floppy drive controller that connects the floppy drive to the motherboard. This controller supports a 33-wire ribbon cable, which connects the floppy drive to the motherboard. When connecting the floppy drive to the system, you will notice that the ribbon cable for the floppy drive has one end where the wires are twisted. This is the end of the ribbon cable that must be connected to the floppy drive. The opposite end is connected to the controller on the motherboard.

L. SCSI controllerSome high-end machines, particularly those designed for use as servers, may have a controller on the motherboard with 50 pins on it. This is the footprint of a SCSI (SmallComputer System Interface) controller on the motherboard. Because SCSI devices outperform IDE devices, SCSI controllers are extremely popular for use in servers (which have greater hard-disk access and storage needs than regular desktop computers).The following list compares the various flavors of SCSI. Know them for the exam: SCSI: SCSI is an example of a technology that has been out for many years and has progressed within those years. The original version of SCSI, also known as SCSI-1 was an 8-bit technology with a transfer rate of 5 Mbps. One of the major benefits of SCSI is that you are not limited to two devices in a chain like you are with IDE SCSI-1 allows you to have eight devices in the chain, with the controller counting as one. Fast SCSI-2: Fast SCSI-2 increases the performance of SCSI by doubling the transfer rate. Fast SCSI-2 devices transfer information at 10 Mbps, as opposed to 5 MBPS (SCSI-1). Fast SCSI-2 is still an 8-bit technology and supports eight devices in the chain. Wide SCSI-2: Wide SCSI-2 takes the data path of SCSI (8-bit) and doubles it to 16 bits; because the width of Wide SCSI-2 has been doubled the transfer rate is also 10 Mbps. The number of devices in a Wide SCSI-2 chain is 16. Fast Wide SCSI-2: Fast Wide SCSI-2 is the combination of Fast SCSI-2 and Wide SCSI-2. The data path of Fast Wide SCSI-2 is 16 bits, the transfer rate is 20 Mbps, and the number of devices that is supported in the chain is 16.Ultra SCSI: Ultra SCSI takes the transfer rate of 10 Mbps and doubles it again to 20 Mbps! With Ultra SCSI, the bus width is only eight bits, and the number of devices that exist in the chain is eight. Ultra Wide SCSI: Ultra Wide SCSI is Ultra SCSI with the bus width increased to 16 bits and the number of devices in the chain is increased to 16! The transfer rate of Ultra Wide SCSI has been increased to 40 Mbps. LVD (Ultra2): Low Voltage Differential, also known as Ultra2 SCSI, has a bus width of 16 bits and supports up to 16 devices. LVD gets its reputation from having a transfer rate of 80 Mbps.

M.BIOS Chip Locating the BIOS chip on the system board is easy; it is usually rectangular in shape and generally features the manufacturer’s name as a label on the chip. Some of the popular manufacturers are AMI, AWARD, and IBM. The Basic Input Output System (BIOS) is the low-level program code that allows all the system devices to communicate with one another. This low-level program code is stored in the BIOS chip on the motherboard.The BIOS chip is a ROM (read only memory) chip, which means that you can read information from the chip, but you cannot write to the chip under normal circumstances. Today’s implementation of BIOS chips is EEPROM (Electrically Erasable

Programmable ROM), which means that you can get special software from the manufacturer of the BIOS to write to the chip.Why would you want to erase the BIOS? Suppose, for example, that your BIOS is programmed to support a hard disk up to 2GB in size, but that you want to install a new, larger hard disk instead. What can you do about it? You can contact the BIOS manufacturer and get an update for your BIOS chip, which is usually a software program today (in the past, you generally had to install a new chip). Running the software program writes new instructions to the BIOS to make it aware that there are hard disks bigger than 2GB and provides instructions for dealing with them. But before new instructions can be written, the old instructions need to be erased. The BIOS chip also contains code that controls the boot process for your system. It contains code that will perform a power on self test (POST), which means that the computer goes through a number of tests, checking itself out and making sure that it is okay. Once it has made it past the POST, the BIOS then locates a bootable partition and calls on the master boot record, which will load an operating system.

N. BatteryThe computer keeps track of its inventory in what is known as Complementary Metal Oxide Semiconductor (CMOS). CMOS is a listing of system components, such as the size of the hard disk that is installed in the computer, the amount of RAM, and the resources (IRQs and IO addresses) used by the serial and parallel ports. This inventory list is stored in what is known as CMOS RAM, which is a bit of a problem because RAM loses its content when the power is shut off. You don’t want the computer to forget that it has a hard disk or forget how much RAM it has installed. To prevent this sort of problem, a small watch-like battery on the system board maintains enough energy so that CMOS RAM does not lose its charge. If CMOS RAM loses its charge, it results in the CMOS content being lost.

 

Experiment No. - 8

Aim:- To study various cards used in computers system.

Introduction

An expansion card (also expansion board, adapter card or accessory card) in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard to add additional functionality to a computer system. One edge of the expansion card holds the contacts that fit exactly into the slot. They establish the electrical contact between the electronics (mostly integrated circuits) on the card and on the motherboard. Connectors mounted on the bracket allow the connection of external devices to the card. Depending on the form factor of the motherboard and case, around one to seven expansion cards can be added to a computer system. There are also other factors involved in expansion card capacity. For example, some expansion cards need two slots like some NVIDIA GeForce FX and newer GeForce graphics cards and there is often a space left to aid cooling on some high-end cards.

History of the expansion card

The first microcomputer to feature a slot-type expansion card bus was the Altair 8800, developed 1974-1975. Initially, implementations of this bus were proprietary (such as the Apple II and Macintosh), but by 1982 manufacturers of Intel 8080/Zilog Z80-based computers running CP/M had settled around the S-100 standard. IBM introduced the XT bus with the first IBM PC in 1983. XT was replaced with ISA in 1984. IBM's MCA bus, developed for the PS/2 in 1987, was a competitor to ISA, but fell out of favor due to the latter's industry-wide acceptance. EISA, the 16-bit extended version of ISA, was common on PC motherboards until 1997, when Microsoft declared it as "legacy" subsystem in the PC 97 industry white-paper. VESA Local Bus, an early expansion bus that was inherently tied to the 80486 CPU, became obsolete (along with the processor) when Intel launched the Pentium processor in 1993.

The PCI bus was introduced in 1991 as replacement for ISA. The standard (now at version 3.0) is still found on PC motherboards to this day. Intel introduced the AGP bus in 1997 as a dedicated video acceleration solution. Though termed a bus, AGP supports only a single card at a time. From 2005 PCI-Express has replaced both of these buses. This standard, approved in 2004, implements the logical PCI protocol over serial communication interface.

Expansion slot standards

AGP PCI ISA MCA

VLB PCI Express Card Bus/PC card/PCMCIA (for notebook computers) Compact flash (for handheld computers)

Expansion card types

Graphics cards :- A video card, (also referred to as a graphics accelerator card, display adapter, graphics card), and numerous other terms), is an item of personal computer hardware whose function is to generate and output images to a display. The term is usually used to refer to a separate, dedicated expansion card that is plugged into a slot on the computer's motherboard, as opposed to a graphics controller integrated into the motherboard chipset. Some video cards offer added functionalities, such as video capture, TV tuner adapter, MPEG-2 and MPEG-4 decoding or even FireWire, mouse, light pen or joystick connectors. Video cards are not used exclusively in Intel-based PCs; they have been used in devices such as Commodore Amiga (connected by the slots Zorro II and Zorro III), Apple II, Apple Macintosh, Spectra video SVI-328, MSX and, obviously, in video game consoles.

Sound cards :- A 'sound card is a computer expansion card that can input and output sound under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment (games). Many computers have sound capabilities built in, while others require these expansion cards if audio capability is desired. A typical sound card includes a sound chip, usually featuring a digital-to-analog converter, that converts recorded or generated digital waveforms of sound into an analog format. This signal is led to a (typically 1/8-inch earphone-type) connector where an amplifier, headphones, or similar sound destination can be plugged in. More advanced designs usually include more than one sound chip to separate duties between digital sound production and synthesized sounds (usually for real-time generation of music and sound effects utilizing little data and CPU time).

Graphics card

Sound card Network cards :- A network card, network adapter or NIC (network interface

controller) is a piece of computer hardware designed to allow computers to communicate over a computer network. It is both an OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly. Every network card has a unique 48-bit serial number called a MAC address, which is stored in ROM carried on the card. Every computer on a network must have a card with a unique MAC address. No two cards ever manufactured share the same address. This is accomplished by the Institute of Electrical and Electronics Engineers (IEEE), which is responsible for assigning unique MAC addresses to the vendors of network interface controllers. The card implements the electronic circuitry required to communicate using a specific physical layer and data link layer standard such as Ethernet or token ring. This provides a base for a full network protocol stack, allowing communication among small groups of computers on the same LAN and large-scale network communications through routable protocols, such as IP.

There are four techniques used to transfer data, the NIC may use one or more of these techniques.

Polling is where the microprocessor examines the status of the peripheral under program control.

Programmed I/O is where the microprocessor alerts the designated peripheral by applying its address to the system's address bus.

Interrupt-driven I/O is where the peripheral alerts the microprocessor that it's ready to transfer data.

DMA is where an intelligent peripheral assumes control of the system bus to access memory directly. This removes load from the CPU but requires a separate processor on the card.

A network card typically has a RJ45, BNC socket where the network cable is connected, and a few LEDs to inform the user of whether the network is active, and whether or not there is data being transmitted on it. Network cards are typically available in 10/100/1000 Mbit/s varieties. This means they can support a notional maximum transfer rate of 10, 100 or 1000 Megabits per second.

TV tuner cards :- A TV tuner card is a computer component that allows television signals to be received by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard drive. While typically a PCI-bus expansion card, they can also be a USB device. Some video cards double as TV tuners, notably the ATI All-In-Wonder series.

The card contains a receiver, tuner, demodulator, and a analog-to-digital converter for analog TV. Like TV sets, each version is designed for the radio frequencies and video formats used in each country. However, many TV tuners used in computers use DSP, so a firmware upgrade is often all that's necessary to change the supported video format. Many newer TV tuners have flash memory big enough to hold the firmwares for decoding several different video formats, making it possible to use the tuner in many countries without having to flash the firmware. In addition to the frequency tuner, many include a composite video input. Many TV tuners can function as FM radios: this is because the FM radio spectrum lies between television channels 6 and 7, and the DSP can be easily programmed to decode FM.

NIC CARD

TV Tuner card

Modems :- Modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio. Experiments have even been performed in the use of modems over the medium of two cans connected by a string

Host Adapter card MODEM

Host adapters :- Such as SCSI and RAID controllers. In computer hardware, a host adapter or host bus adapter (HBA) connects a host system (the computer) to other network and storage devices. The terms are primarily used to refer to devices for connecting Fibre Channel, eSATA, and SCSI devices (see SCSI host adapter), but devices for connecting to ESCON, Ethernet, and other systems may also be called host adapters. Recently, the advent of iSCSI has brought about Ethernet HBAs, some including TCP Offload Engines.

POST cards :- In computing, a POST card is a card that reports error codes produced by a POST. They are easy to use, by simply inserting one into an available expansion slot. Postcards are available in ISA, parallel port, PCI and AGP variants. The card reports either a number, consisting of two hexadecimal digits or an equivalent pattern of LEDs. The code depends on the manufacturer of the BIOS of the motherboard. A book of reference tables usually accompany the card and can tell what is wrong. These can cover a large range of motherboard manufacturers, as different BIOSes use different codes. Postcards are often used by technicians to troubleshoot computers that refuse to boot. Some motherboards come with a built in display to diagnose hardware problems.

Physics cards :- Only recently became commercially available. : A physics card is an expansion card for computers, similar to a graphics card but which is used to process physics interactions as opposed to graphics. By taking over the processing of these effects, the CPU can use more of its power for other tasks. A physics card is centered around a physics processing unit, similar to the graphics processing unit on a graphics card, and also contains RAM for use in its processes. The first physics card created was the PhysX by AGEIA, released in 2006.

Video processing cards:- A Video processing expansion card is a computer expansion card that allows a computer to receive television signals, record video, and/or playback video content

Experiment No. - 9

Aim:- To Study the components of Hard disk.

The first hard disk drive was the IBM 350 Disk File, invented by Reynolds Johnson and introduced in 1955 with the IBM 305 computers. This drive had fifty 24 inch platters, with a total capacity of five million characters. A single head was used for access to all the platters, making the average access time very slow. The IBM 1301 Disk Storage Unit Control System Megan cal International System, announced in 1961, introduced the usage of a separate head for each data surface. 

The first disk drive to use removable media was the IBM 1311 drive, which used the IBM 1316 disk pack to store two million characters. In 1973, IBM introduced the 3340 "Winchester" disk system, the first to use a sealed head/disk assembly (HDA). Almost all modern disk drives now use this technology, and the term "Winchester" became a common description for all hard disks, though generally falling out of use during the 1990s. Project head designer/lead designer Kenneth Haughton named it after the Winchester 30-30 rifle after the developers called it the "30-30" because of its two 30 MB spindles. For many years, hard disks were large, cumbersome devices, more suited to use in the protected environment of a data center or large office than in a harsh industrial environment (due to their delicacy), or small office or home (due to their size and power consumption). Before the early 1980s, most hard disks had 8-inch (20 cm) or 14-inch (35 cm) platters, required an equipment rack or a large amount of floor space (especially the large removable-media drives, which were often referred to as "washing machines"), and in many cases needed high-amperage or even three-phase power hookups due to the large motors they used. Because of this, hard disks were not commonly used with microcomputers until after 1980, when Seagate Technology introduced the ST-506, the first 5.25-inch hard drive, with a capacity of 5 megabytes. In fact, in its factory configuration the original IBM PC (IBM 5150) was not equipped with a hard drive. 

While internal drives became the system of choice on PCs, external hard drives remained popular for much longer on the Apple Macintosh and other platforms. Every Mac made between 1986 and 1998 has a SCSI port on the back, making external expansion easy; also, "toaster" Macs did not have easily accessible hard drive bays (or, in the case of the Mac Plus, any hard drive bay at all), so on those models, external SCSI disks were the only reasonable option. External SCSI drives were also popular with older microcomputers such as the Apple II series, and were also used extensively in Servers, a usage which is still popular today. The appearance in the late 1990s of high-speed external interfaces such as USB and FireWire has made external disk systems popular among regular users once again, especially for users who move large amounts of data between two or more locations, and most hard disk makers now make their disks available in external cases. The capacity of hard drives has grown exponentially over time. With early personal computers, a drive with a 20 megabyte capacity was considered large. In the latter half of the 1990s, hard drives with capacities of 1 gigabyte and greater became available. The "smallest" desktop hard disk still in production has a capacity of 40 gigabytes, while the largest-capacity internal drives are a 3/4 terabyte (750 gigabytesNearly every desktop computer and server in use today contains one or more hard-disk drives. Every mainframe and supercomputer is normally connected to hundreds of them. You can even find VCR-type devices and camcorders that use hard disks instead of tape. These billions of hard disks do one thing well -- they store changing digital information in a relatively permanent form. They give computers the ability to remember things when the power goes out.

Hard Disk BasicsHard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes. They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disks." Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.  At the simplest level, a hard disk is not that different from a cassette tape. Both hard disks and cassette tapes use the same magnetic recording techniques described in How Tape Recorders Work. Hard disks and cassette tapes also share the major benefits of magnetic storage -- the magnetic medium can be easily erased and rewritten, and it will "remember" the magnetic flux patterns stored onto the medium for many years. 

Cassette Tape vs. Hard DiskLet's look at the big differences between cassette tapes and hard disks:

The magnetic recording material on a cassette tape is coated onto a thin plastic strip. In a hard disk, the magnetic recording material is layered onto a high-precision aluminum or glass disk. The hard-disk platter is then polished to mirror-type smoothness. With a tape, you have to fast-forward or reverse to get to any particular point on the tape. This can take several minutes with a long tape. On a hard disk, you can move to any point on the surface of the disk almost instantly.  

In a cassette-tape deck, the read/write head touches the tape directly. In a hard disk, the read/write head "flies" over the disk, never actually touching it. The tape in a cassette-tape deck moves over the head at about 2 inches (about 5.08 cm) per second. A hard-disk platter can spin underneath its head at speeds up to 3,000 inches per second (about 170 mph or 272 kph)! The information on a hard disk is stored in extremely small magnetic domains compared to a cassette tapes. The size of these domains is made possible by the precision of the platter and the speed of the medium. Because of these differences, a modern hard disk is able to store an amazing amount of information in a small space. A hard disk can also access any of its information in a fraction of a second. 

Capacity and PerformanceA typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files. A file is simply a named collection of bytes. The bytes might be the ASCII codes for the characters of a text file, or they could be the instructions of a software application for the computer to execute, or they could be the records of a data base, or they could be the pixel colors for a GIF image. No matter what it contains, however, a file is simply a string of bytes.

 

There are two ways to measure the performance of a hard disk: Data rate - The data rate is the number of bytes per second that the drive can deliver to the CPU. Rates between 5 and 40 megabytes per second are common.

Seek time - The seek time is the amount of time between when the CPU requests a file and when the first byte of the file is sent to the CPU. Times between 10 and 20 milliseconds are common. The other important parameter is the capacity of the drive, which is the number of bytes it can hold. 

Platters and HeadsIn order to increase the amount of information the drive can store, most hard disks have multiple platters. This drive has three platters and six read/write heads:   

 The mechanism that moves the arms on a hard disk has to be incredibly fast and precise. It can be constructed using a high-speed linear motor.  Many drives use a "voice coil" approach -- the same technique used to move the cone of a speaker on your stereo is used to move the arm. 

Underneath the board are the connections for the motor that spins the platters, as well as a highly-filtered vent hole that lets internal and external air pressures equalize:Removing the cover from the drive reveals an extremely simple but very precise interior:The platters - These typically spin at 3,600 or 7,200 rpm when the drive is operating. These platters are manufactured to amazing tolerances and are mirror-smooth (as you can see in this interesting self-portrait of the author... no easy way to avoid that!). The arm - This holds the read/write heads and is controlled by the mechanism in the upper-left corner. The arm is able to move the heads from the hub to the edge of the drive. The arm and its movement mechanism are extremely light and fast. The arm on a typical hard-disk drive can move from hub to edge and back up to 50 times per second -- it is an amazing thing to watch! 

Electronics BoardThe best way to understand how a hard disk works is to take a look inside. (Note that OPENING A HARD DISK RUINS IT, so this is not something to try at home unless you have a defend structure. It is a sealed aluminum box with controller electronics attached to one side. The electronics control the read/write mechanism and the motor that spins the platters. The electronics also assemble the magnetic domains on the drive into bytes (reading) and turn bytes into magnetic domains (writing). The electronics are all contained on a small board that detaches from the rest of the drive: 

Storing the DataData is stored on the surface of a platter in sectors and tracks. Tracks are concentric circles, and sectors are pie-shaped wedges on a track, like this:    

A sector contains a fixed number of bytes -- for example, 256 or 512. Either at the drive or the operating system level, sectors is often grouped together into clusters. The process of low-level formatting a drive establishes the tracks and sectors on the platter. The starting and ending points of each sector are written onto the platter. This process prepares the drive to hold blocks of bytes. High-level formatting then writes the file-storage structures, like the file-allocation table, into the sectors. This process prepares the drive to hold files.

Experiment No. - 10

Aim:- To study Floppy Drive and how to install it.

History of the Floppy Disk DriveThe floppy disk drive (FDD) was invented at IBM by Alan Shugart in 1967. The first floppy drives used an 8-inch disk (later called a "diskette" as it got smaller), which evolved into the 5.25-inch disk that was used on the first IBM Personal Computer in August 1981. The 5.25-inch disk held 360 kilobytes compared to the 1.44 megabyte capacity of today's 3.5-inch diskette.

The 5.25-inch disks were dubbed "floppy" because the diskette packaging was a very flexible plastic envelope, unlike the rigid case used to hold today's 3.5-inch diskettes.

By the mid-1980s, the improved designs of the read/write heads, along with improvements in the magnetic recording media, led to the less-flexible, 3.5-inch, 1.44-megabyte (MB) capacity FDD in use today. For a few years, computers had both FDD sizes (3.5-inch and 5.25-inch). But by the mid-1990s, the 5.25-inch version had fallen out of popularity, partly because the diskette's recording surface could easily become contaminated by fingerprints through the open access area.

Parts of a Floppy Disk Drive

Disk

A floppy disk is a lot like a cassette tape:

Both use a thin plastic base material coated with iron oxide. This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it is permanently magnetized by the field.

Both can record information instantly. Both can be erased and reused many times. Both are very inexpensive and easy to use.

If you have ever used an audio cassette, you know that it has one big disadvantage -- it is a sequential device. The tape has a beginning and an end, and to move the tape to another song later in the sequence of songs on the tape you have to use the fast forward and rewind buttons to find the start of the song, since the tape heads are stationary. For a

long audio cassette tape it can take a minute or two to rewind the whole tape, making it hard to find a song in the middle of the tape.

A floppy disk, like a cassette tape, is made from a thin piece of plastic coated with a magnetic material on both sides. However, it is shaped like a disk rather than a long thin ribbon. The tracks are arranged in concentric rings so that the software can jump from "file 1" to "file 19" without having to fast forward through files 2-18. The diskette spins like a record and the heads move to the correct track, providing what is known as direct access storage.

In the illustration above, you can see how the disk is divided into tracks (brown) and sectors (Grey)

The Drive

The major parts of a FDD include:

Read/Write Heads: Located on both sides of a diskette, they move together on the same assembly. The heads are not directly opposite each other in an effort to prevent interaction between write operations on each of the two media surfaces. The same head is used for reading and writing, while a second, wider head is used for erasing a track just prior to it being written. This allows the data to be written on a wider "clean slate," without interfering with the analog data on an adjacent track.

Drive Motor: A very small spindle motor engages the metal hub at the center of the diskette, spinning it at either 300 or 360 rotations per minute (RPM).

Stepper Motor: This motor makes a precise number of stepped revolutions to move the read/write head assembly to the proper track position. The read/write head assembly is fastened to the stepper motor shaft.

Mechanical Frame: A system of levers that opens the little protective window on the diskette to allow the read/write heads to touch the dual-sided

diskette media. An external button allows the diskette to be ejected, at which point the spring-loaded protective window on the diskette closes.

Circuit Board: Contains all of the electronics to handle the data read from or written to the diskette. It also controls the stepper-motor control circuits used to move the read/write heads to each track, as well as the movement of the read/write heads toward the diskette surface.

The read/write heads do not touch the diskette media when the heads are traveling between tracks. Electronic optics check for the presence of an opening in the lower corner of a 3.5-inch diskette (or a notch in the side of a 5.25-inch diskette) to see if the user wants to prevent data from being written on it.

Read/write heads for each side of the diskette

Writing Data on a Floppy Disk

GEOMETRY/STRUCTURE

Position of Read Head Relative to Disk Track

Read Write Element Used To Read A Floppy Disk

Top View of Disk Reading Mechanism

The following is an overview of how a floppy disk drive writes data to a floppy disk. Reading data is very similar. Here's what happens:

The computer program passes an instruction to the computer hardware to write a data file on a floppy disk, which is very similar to a single platter in a hard disk drive except that it is spinning much slower, with far less capacity and slower access time.

The computer hardware and the floppy-disk-drive controller start the motor in the diskette drive to spin the floppy disk. The disk has many concentric tracks on each side. Each track is divided into smaller segments called sectors, like slices of a pie.

A second motor, called a stepper motor, rotates a worm-gear shaft (a miniature version of the worm gear in a bench-top vise) in minute increments that match the spacing between tracks. The time it takes to get to the correct track is called "access time." This stepping action (partial revolutions) of the stepper motor moves the read/write heads like the jaws of a bench-top vise. The floppy-disk-drive electronics know how many steps the motor has to turn to move the read/write heads to the correct track.

The read/write heads stop at the track. The read head checks the prewritten address on the formatted diskette to be sure it is using the correct side of the diskette and is at the proper track. This operation is very similar to the way a record player automatically goes to a certain groove on a vinyl record.

Before the data from the program is written to the diskette, an erase coil (on the same read/write head assembly) is energized to "clear" a wide, "clean slate" sector prior to writing the sector data with the write head. The erased sector is wider than the written sector -- this way, no signals from sectors in adjacent tracks will interfere with the sector in the track being written.

The energized write head puts data on the diskette by magnetizing minute, iron, bar-magnet particles embedded in the diskette surface, very similar to the technology used in the mag stripe on the back of a credit card. The magnetized

particles have their north and south poles oriented in such a way that their pattern may be detected and read on a subsequent read operation.

The diskette stops spinning. The floppy disk drive waits for the next command. On a typical floppy disk drive, the small indicator light stays on during all of the above operations.

Installing a Floppy Disk Drive

Installing a floppy disk drive in all but the newest systems is straightforward. Note, however, that some cases designed to accept FlexATX motherboards have only one externally accessible 5.25" drive bay, intended to accept a CD or DVD drive. This is because FlexATX systems are intended to boot from CD and so eliminate "legacy" connectors, including the FDD. That means if you intend to install an FDD in a FlexATX system, you'll need a case with two or more externally accessible drive bays (assuming you also want to install an optical drive and/or tape drive in the system), and you'll need to buy a separate PCI card that provides an FDD interface, because FlexATX and other "legacy-reduced" and "legacy-free" motherboards do not provide an embedded FDD interface.

FlexATX motherboards also fit standard ATX cases, so installing the FlexATX motherboard in a standard ATX case eliminates the drive bay problem, although not the lack of an FDD interface. If you really need an FDD in a system, we recommend using a motherboard that provides an embedded FDD interface.

Use the following rules when installing FDDs:

To install one FDD in a system, standard practice is to jumper that drives as the second drive (DS1/DS2) and connect it to the end connector. Alternatively, you can jumper the drive as the first drive (DS0/DS1) and connect it to the middle connector. Either method allows the system to see that drive as A:. If your drive cable has only two connectors, jumper the drive as the second drives (DS1/DS2). Note that most current 3.5" FDDs are set permanently as the second drive, and have no jumper to allow changing that assignment. Such drives work properly with a 2-connector data cable, and should be connected to the end connector on a 3-position data cable.

To install two FDDs in a system, jumper both drives as the second drive (DS1/DS2). Connect the A: drive to the end connector and the B: drive to the middle connector. (Note that the chipsets used in many recent systems support only one FDD.)

Sometimes, cable constraints (length or available connector types) make it impossible to configure the drives as you want them. If this happens, check BIOS Setup to see if it allows you to exchange A: and B:, overriding the drive designations made by DS jumper settings and cable position.

To install the floppy diskette drive, take the following steps:

Before you start, examine the drive to verify the location of pin 1 on the data connector, because it may be impossible to determine which is pin 1 once the drive is installed in the computer. Most drives use an enshrouded and unkeyed connector, many of which are very poorly labeled. Some do not label pin 1 at all. On all such drives we have seen, pin 1 is located nearest the power connector. Better drives use a shrouded and/or keyed connector like that shown in Figure A, and are a better choice.

Figure A. This NEC 3.5" FDD uses a shrouded cable connector rather than the typical bare pins (note the missing pin at lower left, which keys the connector)

Once you have located pin 1 on the drive, connect the FDD data cable to the drive, aligning pin 1 on the cable (the side with the red stripe) with pin 1 on the drive. Do these before you install the FDD in the drive bay, particularly if you are using a drive with an enshrouded data connector? Otherwise, it's very easy to install the data cable offset by a column or row of pins. We know, because we've done it frequently. Be very careful when installing the cable, because it's quite easy to bend pins on an enshrouded connector. Once you're sure the cable is aligned properly with the connector, place your thumb in the middle of the cable connector, as shown in Figure B, and push gently on the cable connector until it seats fully.

Figure B. Connect the cable to the FDD, with pin 1 oriented properly and all pins aligned

In most cases, the FDD installs from the front, but in some cases it installs from the rear. If the drive bay requires installing from the front, slide the FDD into the bay, using your free hand to feed the cable through without kinking it, as shown in Figure C. In most cases, you must leave the FDD projecting half an inch or so in front of the metal chassis so that the FDD bezel will align properly with the case bezel once it is installed. Most 3.5" FDD bays have round screw holes positioned properly to ensure that everything aligns once the case bezel is replaced. Some, however, have elongated slots rather than round holes. On these cases, you may have to align the FDD by trial and error.

Figure C. Slide the FDD into the drive bay, making sure the cable feeds smoothly into the case interior

Once you have properly aligned the screw holes in the drive bay with those in the drive, insert the screws and tighten them until they are fully seated. Do not over torque the screws. The number of screws required and their positions depend upon the particular FDD and case. Most FDDs and cases allow you to install as many as eight screws—two in front and two in back on each of the two sides. That's complete overkill. We generally use four screws, top-front and bottom-

back on each side. Some cases make it very difficult to install screws to support the right side of the FDD (as you face the front of the case). In such cases, we generally install screws in all four positions on the left side of the drive and leave the right side unsupported. If your case is one that requires trial-and-error alignment to get the front of the FDD lined up with the front of the case, insert only two screws initially and tighten them down only enough to allow the FDD to slide in or out with some resistance. Then, replace the front system bezel, get the FDD aligned just right, tighten down the two screws you already installed, and then install the remaining screws. If you're a belt-and-suspenders person, place a small dab of nail polish on each screw head to prevent it from vibrating loose.

With the drive securely fastened to the chassis, connect the power cable to the drive, as shown in Figure D. The power cable and connector are keyed, and so can fit only in the proper orientation. But be careful to align everything properly before you press the connector into place. Some drives use fragile pins on the power connector, and we've bent more than one set when attempting to connect power to an FDD in an awkward situation, such as working under a desk in near darkness.

Figure D. Connect the power cable to the FDD, making sure the connector is aligned properly with the pins

The BIOS of all modern systems recognizes standard FDDs automatically, so no configuration is required.

Floppy Disk Drive FactsHere are some interesting things to note about FDDs:

Two floppy disks do not get corrupted if they are stored together, due to the low level of magnetism in each one.

In your PC, there is a twist in the FDD data-ribbon cable -- this twist tells the computer whether the drive is an A-drive or a B-drive.

Like many household appliances, there are really no serviceable parts in today's FDDs. This is because the cost of a new drive is considerably less than the hourly rate typically charged to disassemble and repair a drive.

If you wish to redisplay the data on a diskette drive after changing a diskette, you can simply tap the F5 key (in most Windows applications).

In the corner of every 3.5-inch diskette, there is a small slider. If you uncover the hole by moving the slider, you have protected the data on the diskette from being written over or erased.

Floppy disks, while rarely used to distribute software (as in the past), are still used in these applications:

in some Sony digital cameras for software recovery after a system crash or a virus attack when data from one computer is needed on a second computer and

the two computers are not networked in bootable diskettes used for updating the BIOS on a personal

computer in high-density form, used in the popular Zip drive

Experiment No. - 11

Aim:- To Study the compact disk drives.

Introduction:- A CD-ROM (Compact Disk Read Only Memory) is a drive which reads aluminum-coated round plastic discs, however does not write to the discs. Invented in the United States on 1972, the CD-ROM standard was officially introduced in 1982 when Philips and Sony agreed on the 4.72-inch size format we now use today. Later, as Phillips and Sony continued cooperation in the 1980s, additional specifications were announced concerning the use of CD technology for computer data which evolved into computer CD-ROM drives used today.

The CD-ROM diskettes are 12 x 12 cm with a width of .1cm, as shown in the above picture. The disc is made of a polycarbonate wafer and is coated with a metallic film, usually an aluminum alloy. This aluminum film is the portion of the disc that the CD-ROM drive reads for information. The aluminum film (strata) is then covered by a plastic polycarbonate coating that protects the underlying data. A label will usually be placed on the top of the disc and data is read from the bottom of the CD.

CD-ROM INTERFACES

SCSI (Small Computer System Interface):- These require a SCSI Host adapter card connected into the system. These cards may be ISA, VLB or even PCI bus cards. It is highly recommended to get a card that matches the CD-ROM drive as some of the earlier drives had proprietary SCSI interfaces. Otherwise, a SCSI-2 card is recommended

IDE (Integrated Device Electronics):- These CD-ROM drives connect to an IDE port on the motherboard or hard drive interface card. Usually, the IDE controller on the hard

drive is set as master and the CD-ROM drive is set to slave. IDE is commonly used for CD-ROMs in standard computers today.

Parallel:- Parallel port CD-ROM drives come with special drivers to help communicate through a PC system's parallel port. The transfer rate tends to be slower than other interfacing methods. Biggest advantage is the portability between systems including notebooks.

PCMCIA (PC Card):- Interface now exists for connecting an external CD-ROM drive through the system's PCMCIA port. This is good for portability and provides faster access than the Parallel port.

The CD-ROM uses a controller to "talk" to the PC. The Interface is the actual connection from the drive to the expansion slot. CDROM drives are available in the SCSI, the IDE and Parallel-Port interfaces.

Here are the components and how they work together to allow the drive to communicate to the computer system.

Inside The CDROM Drive

The Laser Diode emits a low-level beam toward the reflection mirror. A servo motor is activated by a microprocessor onto the tracks on the disc. This is done by moving the reflecting mirror. When the beam hits the disc, refracted lights is then focused through the first lens under the disc. It is then bounced off the mirror, and directed to the beam splitter. The beam splitter sends returning laser light to the next focusing lens. And the last lens sends the beam to a photo detector, which converts the light into electric pulses.The microprocessor then decodes these electric pulses and sends them to the computer through the data cable and the controller.

Components outside the CDROM Drive

When you look inside your computer you will notice that the CDROM Drive is mounted at the top in all tower units and may be mounted in an assembly at the front of the Desktop PC.As with the Hard and the Floppy Drives, the CDROM Drive processes data with the help of the Controller which may be mounted in an expansion slot but in most cases it will be mounted directly unto the motherboard. The drive and controller are connected by the Ribbon Cable which allows the data to flow back and forth as needed.

At the rear of the CDROM Drive you will see a Jumper which is used to assign the drive as the Master drive or the Slave drive. Since the CDROM is can be used to play music on compact disks, the Sound Card is connected at the rear of the cdrom drive. At the other end of this connection you will see the Power Supply connector. Take the time to remove the cover of your PC and get to know each and every component. Study the location of your CDROM drive and how its mounted in the System Unit. By doing so you will become more confident about understanding your computer system.

Experiment No. - 12

Aim:- To Study, Remove And Replace Keyboard.

Keyboard Basics

A keyboard's primary function is to act as an input device. Using a keyboard, a person can type a document, use keystroke shortcuts, access menus, play games and perform a variety of other tasks. Keyboards can have different keys depending on the manufacturer, the operating system they're designed for, and whether they are attached to a desktop computer or part of a laptop. But for the most part, these keys, also called keycaps, are the same size and shape from keyboard to keyboard. Most keyboards have between 80 and 110 keys, including: Typing keys, A numeric keypad, Function keys, Control keys etc.The typing keys include the letters of the alphabet, generally laid out in the same pattern used for typewriters. According to legend, this layout, known as QWERTY for its first six letters, helped keep mechanical typewriters' metal arms from colliding and jamming as people typed. Some people question this story – whether it’s true or not, the QWERTY pattern had long been a standard by the time computer keyboards came around.

The numeric keypad is a more recent addition to the computer keyboard. As the use of computers in business environments increased, so did the need for speedy data entry. Since a large part of the data was numbers, a set of 17 keys, arranged in the same configuration found on adding machines and calculators, was added to the keyboard.

Inside the Keyboard

A keyboard is a lot like a miniature computer. It has its own processor and circuitry that carries information to and from that processor. A large part of this circuitry makes up the key matrix.

The microprocessor and controller circuitry of a keyboard

The key matrix is a grid of circuits underneath the keys. In all keyboards (except for capacitive models, which we'll discuss in the next section), each circuit is broken at a point below each key. When you press a key, it presses a switch, completing the circuit and allowing a tiny amount of current to flow through. The mechanical action of the switch causes some vibration, called bounce, which the processor filters out. If you press and hold a key, the processor recognizes it as the equivalent of pressing a key repeatedly.

When the processor finds a circuit that is closed, it compares the location of that circuit on the key matrix to the character map in its read-only memory (ROM). A character map is basically a comparison chart or lookup table. It tells the processor the position of each key in the matrix and what each keystroke or combination of keystrokes represents. For example, the character map lets the processor know that pressing the a key by itself corresponds to a small letter "a," but the Shift and a keys pressed together correspond to a capital "A."

The key matrix

A computer can also use separate character maps, overriding the one found in the keyboard. This can be useful if a person is typing in a language that uses letters that don't have English equivalents on a keyboard with English letters. People can also set their computers to interpret their keystrokes as though they were typing on a Dvorak keyboard even though their actual keys are arranged in a QWERTY layout. In addition, operating

systems and applications have keyboard accessibility settings that let people change their keyboard's behavior to adapt to disabilities.

Keyboard Switches

Keyboards use a variety of switch technologies. Capacitive switches are considered to be non-mechanical because they do not physically complete a circuit like most other keyboard technologies. Instead, current constantly flows through all parts of the key matrix. Each key is spring-loaded and has a tiny plate attached to the bottom of it. When you press a key, it moves this plate closer to the plate below it. As the two plates move closer together, the amount of current flows through the matrix changes. The processor detects the change and interprets it as a key press for that location. Capacitive switch keyboards are expensive, but they have a longer life than any other keyboard. Also, they do not have problems with bounce since the two surfaces never come into actual contact.

All of the other types of switches used in keyboards are mechanical in nature. Each provides a different level of audible and tactile response -- the sounds and sensations that typing creates. Mechanical key switches include:-

Rubber dome Membrane Metal contact Foam element

Rubber dome switches are very common. They use small, flexible rubber domes, each with a hard carbon center. When you press a key, a plunger on the bottom of the key pushes down against the dome, and the carbon center presses against a hard, flat surface beneath the key matrix. As long as the key is held, the carbon center completes the circuit. When the key is released, the rubber dome springs back to its original shape, forcing the key back up to its at-rest position. Rubber dome switch keyboards are inexpensive, have pretty good tactile response and are fairly resistant to spills and corrosion because of the rubber layer covering the key matrix.

Metal contact and foam element keyboards are increasingly less common. Metal contact switches simply have a spring-loaded key with a strip of metal on the bottom of the plunger. When the key is pressed, the metal strip connects the two parts of the circuit. The foam element switch is basically the same design but with a small piece of spongy foam between the bottom of the plunger and the metal strip, providing a better tactile response. Both technologies have good tactile response, make satisfyingly audible "clicks," and are inexpensive to produce. The problem is that the contacts tend to wear out or corrode faster than on keyboards that use other technologies. Also, there is no barrier that prevents dust or liquids from coming in direct contact with the circuitry of the key matrix.

From the Keyboard to the Computer

As you type, the processor in the keyboard analyzes the key matrix and determines what characters to send to the computer. It maintains these characters in its memory buffer and then sends the data. A PS/2 type keyboard connector. Many keyboards connect to the computer through a cable with a PS/2 or USB (Universal Serial Bus) connector. Laptops use internal connectors. Regardless of which type of connector is used, the cable must carry power to the keyboard, and it must carry signals from the keyboard back to the computer.

Experiment No. - 13

Aim: To Study, Remove And Replace Mouse.

Evolution

It is amazing how simple and effective a mouse is, and it is also amazing how long it took mice to become a part of everyday life. Given that people naturally point at things -- usually before they speak -- it is surprising that it took so long for a good pointing device to develop. Although originally conceived in the 1960s, a couple of decades passed before mice became mainstream.

 

Optical mice are characterized by the integration of a very small camera capable to take 1,500 pictures per second while the LED light bounces light off that surface onto a CMOS sensor, which sends the images to the digital signal processor. The processor, having an operating speed of 18 million instructions per second, detects image patterns changes and establishes the distance the mouse has moved since the last change. The coordinates are sent to the computer, which translates the information into the cursor movement.

Inside a Mechanical Mouse

The main goal of any mouse is to translate the motion of your hand into signals that the computer can use. Let's take a look inside a track-ball mouse to see how it works:- 

A ball inside the mouse touches the desktop and rolls when the mouse moves.  

Two rollers inside the mouse touch the ball. One of the rollers is oriented so that it detects motion in the X direction, and the other is oriented 90 degrees to the first roller so it detects motion in the Y direction. When the ball rotates, one or both of these rollers rotate as well. The following image shows the two white rollers on this mouse: 

The rollers each connect to a shaft, and the shaft spins a disk with holes in it. When a roller rolls, its shaft and disk spin. The following image shows the disk

On either side of the disk there is an infrared LED and an infrared sensor. The holes in the disk break the beam of light coming from the LED so that the infrared sensor sees pulses of light. The rate of the pulsing is directly related to the speed of the mouse and the distance it travels. 

An on-board processor chip reads the pulses from the infrared sensors and turns them into binary data that the computer can understand. The chip sends the binary data to the computer through the mouse's cord.  

In this opt mechanical arrangement, the disk moves mechanically, and an optical system counts pulses of light. On this mouse, the ball is 21 mm in diameter. The roller is 7 mm in diameter. The encoding disk has 36 holes. So if the mouse moves 25.4 mm (1 inch), the encoder chip detects 41 pulses of light.  You might have noticed that each encoder disk has two infrared LEDs and two infrared sensors, one on each side of the disk (so there are four LED/sensor pairs inside a mouse). This arrangement allows the processor to detect the disk's direction of rotation.  Data InterfaceMost mice on the market today use a USB connector to attach to your computer. USB is a standard way to connect all kinds of peripherals to your computer, including printers, digital cameras, keyboards and mice. See How USB Ports Work for more information about this technology.  

 

Some older mice, many of which are still in use today, have a PS/2 type connector.