Computer Devices

The case and the power supply unit Casing
The PC consists of a central unit (referred to as the computer) and various peripherals. The computer is a box, which contains most of the working electronics. It is connected with cables to the peripherals.
Casing is the outer look of the CPU box. Selecting the case unit is mostly a matter of deciding for a style. In board terms there are two types of cases: i) Desktop Model (flat) ii) Tower Models Both types of cases vary by size and profile. Whereas the desktop case sits (as the name implies) on the desktop, the tower case is designed to stand upright and can be much larger.
Before choosing the case we should think about our location requirements for computer. If we need a simple office machine then we might decide for a desktop style. If, however, we want to keep our options open for upgrading the computer at a later stage, maybe by adding more hard drives or other devices, then we might consider a tower with more room for add-ons.

Power Supply :
A power supply is the heart of the computer system. The computer’s components would no be able to operate without power. A computer needs a well regulated 5-volt to 12 volt DC power supply for the proper functioning of its various parts.

SMPS :- Switch Mode Power Supply

The power from the mains is 220 volts AC current, with a lot of interference, so, it cannot be directly fed to the computer. A SMPS is used in between the computer and the mains to convert the 220 V AC current to a well regulated 12 volt and 5 volt DC current [+5 volts DC(red wire), -5 volts DC (ground, Black wire), +12 volts DC (Yellow wire), and -12 volts DC (ground, black wire)]. Usually, the electronic components and circuits in the system (motherboard, adapter cards and disk drives, logic boards etc) use the 5 volt power and the motors in the disk drives use the 12 volt power. The power supply of the computer must ensure a proper, good and steady supply of both types of current to the system, so that the complete computer system can operate properly.
Whichever case you buy, it will most likely include a power supply to produce a regulated source of electricity. The electrical connectors supply the motherboard and all other devices with +5V, -5V and +12V, -12V. a power supply is rated by the number of watts of power it can deliver to all connected devices. Although today’s computer components are more energy efficient than a few years ago it is always a good idea to look for a power supply that is a little bit stronger that actually needed to ensure a safety margin in the event of having to supply for additional devices. Standard power supplies normally rate between for 200w to 300w, which is enough for any normal computer. But if you intend to build a machine with multiple hard drives and lots of others internal devices, try to get a 300w supply. Better too much than too little. Some ATX systems don’t come with a power supply unit of that strength as the most power consuming component of the PC now plugs directly into the power outlet: the monitor. Today’s monitors don’t like to be switched off any more but rather switch themselves off when the computer sends the signal to do so.
Another important factor is the cooling fan, which normally comes with the power supply. Because today’s computers produce much more heat than in earlier years (especially the processors), it is important to ensure that the case has no unnecessary open slots as those will affect the efficiency in which the heat is removed from within the case. Always make sure that you get a working cooling fan with the power supply as excessive heat can cause premature failure of the components. This is another good reason for buying a larger case; a bigger case means less heat. If you are going for a larger system you might even think about a second fan. If you do decide for a second fan, make sure it supports the airflow within the case and blows in the same direction as the power supply fan.
A power supply has three types of connectors used to power the various devices within the computer. These are :
i) Floppy drive power connectors (berg connector)
ii) Molex connector (hard disk, optical disks) &
iii) System Connector [p8&p9 (6+6 pins); for the motherboard power supply. Make sure that all the black wires from both p8 and p9 are at the centre facing each other.]

The back of power supply (SMPS) contains three things. They are :
i) The computer’s power supply
ii) The monitor’s power connector
iii) The exhaust fan port

Uninterruptible Power Supply (UPS):
We know that, computer is an electronic device so electricity is compulsory requirement to operate it. Each and every components of computer can sustain a fixed current capacity so; fluctuation of voltage may damage these components. That’s why; we have to use UPS, Volt Guard, and Stabilizer etc. to maintain the voltage fluctuation.
UPS is a device that stores the electricity and supply to the computer automatically incase of electricity failure. It is used in computer to prevent the loss of data and damage of computer parts caused due to electricity failure.