Monday, November 19, 2018

Earthing

Types of Earthing

1). Plate Earthing:

2). Pipe Earthing:

3). Rod Earthing

4). Earthing through the Waterman

5). Strip or Wire Earthing

What is Grounding or Earthing?

To connect the metallic (conductive) Parts of an Electric appliance or installations to the earth (ground) is called Earthing or Grounding.

In other words, to connect the metallic parts of electric machinery and devices to the earth plate or earth electrode (which is buried in the moisture earth) through a thick conductor wire (which has very low resistance) for safety purpose is known as Earthing or grounding.

To earth or earthing rather, means to connect the part of electrical apparatus such as metallic covering of metals, earth terminal of socket cables, stay wires that do not carry current to the earth. Earthing can be said as the connection of the neutral point of a power supply system to the earth so as to avoid or minimize danger during discharge of electrical energy.

Difference between Earthing, Grounding and Bonding.

Let me clear the confusion among earhing, grounding and bonding.

Earthing and Grounding is the same terms used for earthing. Grounding is the commonly word used for earthing in the North American standards like IEEE, NEC, ANSI and UL etc while, Earthing is used in European, Common wealth countries and Britain standards like IS and IEC etc.

The word Bonding used for jointing two wires (as well as conductors, pipes or appliances together. Bonding is known as connecting the metallic parts of different machines which is not considered to be carrying electric current during normal operation of the machines to bring them at the same level of electric potential.

Need of Earthing or Grounding. Why Earthing is Important?

The primary purpose of earthing is to avoid or minimize the danger of electrocution, fire due to earth leakage of current through undesired path and to ensure that the potential of a current carrying conductor does not rise with respect to the earth than its designed insulation.

When the metallic part of electrical appliances (parts that can conduct or allow passage of electric current) comes in contact with a live wire, maybe due to failure of installations or failure in cable insulation, the metal become charged and static charge accumulates on it. If a person touches such a charged metal, the result is a severe shock.

To avoid such instances, the power supply systems and parts of appliances have to be earthed so as to transfer the charge directly to the earth.

Below are the basic needs of Earthing.

To protect human lives as well as provide safety to electrical devices and appliances from leakage current.
To keep voltage as constant in the healthy phase (If fault occurs on any one phase).
To Protect Electric system and buildings form lighting.
To serve as a return conductor in electric traction system and communication.
To avoid the risk of fire in electrical installation systems.
Different Terms used in Electrical Earthing

Earth: The proper connection between electrical installation systems via conductor to the buried plate in the earth is known as Earth.
Earthed: When an electrical device, appliance or wiring system connected to the earth through earth electrode, it is known as earthed device or simple “Earthed”.
Solidly Earthed: When an electric device, appliance or electrical installation is connected to the earth electrode without a fuse, circuit breaker or resistance/Impedance, It is called “solidly earthed”.
Earth Electrode: When a conductor (or conductive plate) buried in the earth for electrical earthing system. It is known to be Earth Electrode. Earth electrodes are in different shapes like, conductive plate, conductive rod, metal water pipe or any other conductor with low resistance.
Earthing Lead: The conductor wire or conductive strip connected between Earth electrode and Electrical installation system and devices in called Earthing lead.
Earth Continuity Conductor: The conductor wire, which is connected among different electrical devices and appliances like, distribution board, different plugs and appliances etc. in other words, the wire between earthing lead and electrical device or appliance is called earth continuity conductor. It may be in the shape of metal pipe (fully or partial), or cable metallic sheath or flexible wire.
Sub Main Earthing Conductor: A wire connected between switch board and distribution board i.e. that conductor is related to sub main circuits.
Earth Resistance: This is the total resistance between earth electrode and earth in Ω (Ohms). Earth resistance is the algebraic sum of the resistances of earth continuity conductor, earthing lead, earth electrode and earth.
POINTS TO BE EARTHED

    Earthing is not done anyhow. According to IE rules and IEE (Institute of Electrical Engineers) regulations,

Earth pin of 3-pin lighting plug sockets and 4-pin power plug should be efficiently and permanently earthed.
All metal casing or metallic coverings containing or protecting any electric supply line or apparatus such as GI pipes and conduits enclosing VIR or PVC cables, iron clad switches, iron clad distribution fuse boards etc should be earthed (connected to earth).
The frame of every generator, stationary motors and metallic parts of all transformers used for controlling energy should be earthed by two separate and yet distinct connections with the earth.
In a dc 3-wire system, the middle conductors should be earthed at the generating station.
Stay wires that are for overhead lines should be connected to earth by connecting at least one strand to the earth wires.
Components of Earthing System

A complete electrical earthing system consists on the following basic components.

Earth Continuity Conductor
Earthing Lead
Earth Electrode

Earth Continuity Conductor or Earth Wire

That part of the earthing system which interconnects the overall metallic parts of electrical installation e.g. conduit, ducts, boxes, metallic shells of the switches, distribution boards, Switches, fuses, Regulating and controlling devices, metallic parts of electrical machines such as, motors, generators, transformers and the metallic framework where electrical devices and components are installed is known as earth wire or earth continuity conductor as shown in the above fig.

The resistance of the earth continuity conductor is very low. According to IEEE rules, resistance between consumer earth terminal and earth Continuity conductor (at the end) should not be increased than 1Ω. In simple words, resistance of earth wire should be less than 1Ω.

Size of the Earth Continuity Conductor or Earth Wire depends on the cable size used in the wiring circuit.

Size of Earth Continuity Conductor

The cross sectional area of the Earth Continuity Conductor should not be less than the half of the cross sectional area of the thickest wire used in the electrical wiring installation.

Generally, the size of the bare copper wire used as earth continuity conductor is 3SWG. But keep in mind that, don’t use less than 14SWG as earth wire. Copper strip is also can be used as earth continuity conductor instead of bare copper wire but don’t go for it until manufacture recommend it.

Earthing Lead or Earthing Joint

The conductor wire connected between earth continuity conductor and earth electrode or earth plate is called earthing joint or “Earthing lead”. The point where earth continuity conductor and earth electrode meet is known as “connecting point” as shown in the above fig.

Earthing lead is the final part of the earthing system which is connected to the earth electrode (which is underground) through earth connecting point.

There should be minimum joints in earthing lead as well as lower in size and straight in the direction.

Generally, copper wire can be used as earthing lead but, copper strip is also used for high installation and it can handle the high fault current because of wider area than the copper wire.

A hard drawn bare copper wire is also used as an earthing lead. In this method, all earth conductors connected to a common (one or more) connecting points and then, earthing lead is used to connect earth electrode (earth plat) to the connecting point.

To increase the safety factor of installation, two copper wires are used as earthing lead to connect the device metallic body to the earth electrode or earth plate. I.e. if we use two earth electrodes or earth plats, there would be four earthing leads. It should not be considered that the two earth leads are used as parallel paths to flow the fault currents but both paths should work properly to carry the fault current because it is important for better safety.


Size of the Earthing Lead

The size or area of earthing lead should not be less than the half of the thickest wire used in the installation.

The largest size for earthing lead is 3SWG and the minimum size should not be less than 8SWG. If 37/.083 wire is used or the load current is 200A from the supply voltage, then it is recommended to use copper strip





Monday, June 12, 2017

555 Timer IC


The 555 timer is a very popular IC used in electronic industry which is reliable, easy to use and cheaper in cost. It was invented in 1971 by American company signets. It is an integrated circuit (chip) used in variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, as a flip-flop element, temperature measurement,monostable and astable multivibrator.It operates basically in one of the two modes either as a monostable multivibrator or as an astable multivibrator.The name 555 timer has come from the three resistor of 5k each within the timer circuits.
                                                                                           Figure 1: 555 Timer
Pin configuration
Pin1: Grounded terminal
All voltage is measured with respect to this terminal.
Pin 2: Trigger terminal
It is an inverting input to a comparator that is responsible of flip flop from set to reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin.
Pin 3: output terminal
There are two ways in which load can be connected to the output terminal either between pin 3 and ground or between Pin 3 and Pin 8 and is usually called a load and normally off load respectively.
Pin 4: Reset terminal
To disable or reset the timer a negative pulse is applied to this pin due to which it is referred to as reset terminal. When this pin is not to be used for reset purpose, it should be connected to Vcc to avoid any possibility of false triggering.


Pin5: Control voltage terminal
Its function is to control the threshold and trigger level. Thus either the external voltage or a pot connected to this pin determines the pulse width of the output waveform. The external voltage applied to this pin can also be used to modulate the output waveform. When this pin is not used it should be connected to ground through a 0.01uF capacitor to avoid any noise pollution.
Pin 6: Threshold terminal
This is non inverting input terminal of comparator , which compares the voltage applied to this terminal with a reference voltage of +2/3 v. the amplitude of voltage applied to this terminal is responsible for the set state of flip flop.
Pin 7: Discharge terminal
This pin is connected internally to the collector of transistor and mostly a capacitor is connected between this terminal and ground. It is called discharge terminal because when transistor is at saturation capacitor discharge through the transistor. When the transistor is at cut off, the capacitor changes at a rate determined by external resistor and capacitor.
Circuit Operation










·        The voltage divider consisting of 5k resistors provides a trigger level of 1/3 VCC and a threshold level of 2/3 VCC.
·        The control voltage input (pin 5) can be used to externally adjust the trigger and threshold levels to other values of necessary.
·        When the trigger input (at +5v) momentarily goes below 1/3 VCC the output of comparator B switches from 0 to 5v and sets the S-R latch, causing the output pin3 to go +5v and turning the discharge transistor Q1 OFF.
·        The output will stay at +5V until the threshold input (at 0V) goes above 2/3 VCC and causes the output of comparator A to switch from 0 to +5 V.
·        This resets the latch causing the output to go back to 0Vand turning the discharge transistor ON  the external reset input can be used to reset the latch independent of the threshold input the trigger threshold inputs (pin 2 and 6) are controlled by external components connected to produce either monostable or astable action.
Monostable operation of 555 timer
A monostable vibrator is often called a one shot multivibrator.In such vibrator one state of output is stable while the other is unstable.It makes use of external resistor(R) and a capacitor(C).The pulse width of the output is given by
                         tp = 1.1 R1 C1      
Before a trigger pulse is applied, the output is 0V.When a negative (0V) pulse is applied to the trigger input (pin2), the internal comparator detects the input and sets the state of flip-flop.At 2/3 VCC, the comparators output goes high and resets the flip-flop.Monostable 555 Timer circuit triggers on a negative going pulse applied to pin 2. Once triggered, the 555 monostable will remain in this HIGH unstable output state until the time period set up by the R, XC.




Figure 2: Monostable Multivibrator

Astable Operation
                                                          Figure 3: Astable Multivibrator
It is often called as a free-running multivibrator which is used to generate rectangular wave. It does not require external trigger to change the state of the output. It can be produced by adding two resistors and a capacitor to the basic timer IC.The output is either high or low and is determined by the two resistors and capacitors.
Pin 1 is grounded, Pins 4 and 8 are shorted and then tied to supply +vcc, Output is taken from pin3, Pin 2 and 6 are shorted and then connected to ground through a capacitor (C).Pin 7 is connected to supply +Vcc through a resistor RA and between pins 6 and 7 are resistor RB is connected.At pin 5 either a bypass capacitor of 0.01 uF s connected or Modulation input is applied.
Circuit operation
·        When the power is turned ON, the capacitor is uncharged and thus the trigger voltage (pin2) is at 0v.
·        The output of comparator b is at +5v and the output of comparator A to be at 0v forcing the output of the latch and the base of Q1 to be at 0v.As a result the transistor Q1 is OFF, c1 is charging through R1 and R2.
·        When the capacitor voltage reaches 1/3 Vcc, comparator B switches to its 0 output state and when the capacitor reaches 2/3Vcc, comparator A switches to its +5V state.
·        This resets the latch causing the base of Q1 to go +5V. As a result Q1 turns ON. This sequence creates a discharge path for the capacitor through R2.
·        The capacitor now begins to discharge causing comparator A to go to 5V at the point where the capacitor discharges down to 1/3 Vcc, comparator B switches to +0V level.
·        This sets the latch, making the base of Q1 to go down to 0V.
·         As a result Q1 turns OFF. Another charging cycle begins and the entire process repeats.
·        This produce a rectangular wave output whose duty cycle depends on the values of R1 and R2.
·        The frequency of oscillator of a 555 timer in astable mode is given by the expression,
F=1.44/(R1 + 2R2) C1
·        By selecting R1 and R2, the duty cycle of the output can be adjusted since C1 charges through R1+R2 and discharges only through R2, a duty cycle approaching 50% can be achieved of R2>>R1 so that charging and discharging times are approximately equal.


Sunday, June 11, 2017

RAM and ROM

Read-only memory, or ROM, is a form of data storage in computers and other electronic devices that can not be easily altered or reprogrammed. RAM is referred to as volatile memory and is lost when the power is turned off whereas ROM in non-volatile and the contents are retained even after the power is switched off.
Random-access memory, or RAM, is a form of data storage that can be accessed randomly at any time, in any order and from any physical location in contrast to other storage devices, such as hard drives, where the physical location of the data determines the time taken to retrieve it. RAM is measured in megabytes and the speed is measured in nanoseconds and RAM chips can read data faster than ROM.

Comparison chart

RAM versus ROM comparison chart
RAMROM
DefinitionRandom Access Memory or RAM is a form of data storage that can be accessed randomly at any time, in any order and from any physical location., allowing quick access and manipulation.Read-only memory or ROM is also a form of data storage that can not be easily altered or reprogrammed.Stores instuctions that are not nescesary for re-booting up to make the computer operate when it is switched off.They are hardwired.
Stands forRandom Access MemoryRead-only memory
UseRAM allows the computer to read data quickly to run applications. It allows reading and writing.ROM stores the program required to initially boot the computer. It only allows reading.
VolatilityRAM is volatile i.e. its contents are lost when the device is powered off.It is non-volatile i.e. its contents are retained even when the device is powered off.
TypesThe two main types of RAM are static RAM and dynamic RAM.The types of ROM include PROM, EPROM and EEPROM.
SOURCE; Google

Monday, May 8, 2017

Managerial Skills

Managerial Skills

Primary Skills
• Conceptual Skill
• Technical Skill
• Human Skill

Secondary Skills
• Design Skill
• Communication Skills
• Leadership Skill

Human or interpersonal skills:
• How should I understand myself to
understand others and achieved the
common goals and objectives of the
organization? Also focus on how
something is done?
• This includes the ability to
understand other people and
interact effectively with them. The
human skills are also important in
creation of an environment in which
people feel secure and free to
express their opinions.
• In short it is the ability to work with
other people in teams

Design skill:
These skills enable a manager to
handle and solve any kind of
unforeseen or actual problems, that
may crop up in the organization. Such
problems could arise due to internal
factors or external factors and/or
both.
In short it is the problem solving skill

Conceptual skill:
What should be the right thing
and focus on why something is
done?
• This refers to the ability to
think and conceptualize
abstract situations. These
abilities are required for
making complex decisions.
• In short it is the mental
capacity to develop plans,
strategies and vision

Technical Skills
How can we do better and focus
on what is done?
These skills include the
knowledge, abilities of and
proficiency in activities involving
methods, processes and
procedures in the relevant fields as
accounting, engineering,
manufacturing etc.
In short it is the ability to use the
knowledge or techniques of a
particular discipline to attain ends.

Communicational skill
The abilities of exchanging
ideas and information
effectively.
To understand others and let
others understand
comprehensively.

Leadership Skills
The abilities to influence
other people to achieve the
common goal. �


Sunday, May 7, 2017

Kuensel retrieved

Library developed and functional

July 1, 2016 News 1 Comment 992 Views

Council: The government has developed an e-Library portal and e-Library studio.

This was revealed in its responses to the National Council (NC).

The government also stated that the installation and commissioning of the entire network will be completed by August end.

“The e-Library would be a collection of digital objects that will include text, visuals, video, audio among others stored as standardised and customised electronic media along with means for organising, storing, and retrieving the contents from the e-library repository,” the government states in its response which is available on the NC’s website.

The response also stated that the Centre for Development of Advanced Computing (CDAC) assigned with the project has developed e-library portal and is functional now. It can be viewed by visiting: http://14.139.61.149/elib/.

The syllabus for all classes from preprimary to higher secondary along with textbooks is available.

As of June 2016, the CDAC project engineer stationed in Thimphu visited 49 schools and identified 40 schools for site readiness to implement the project.

The project engineer also discussed with the Royal University of Bhutan and education ministry on 12 schools and three colleges where the project could be launched.The education ministry is currently processing custom clearances for the equipment to be used for the e-Library.

Once the e-Library is established, training on its use and management will be conducted in September. Content creation for Bhutanese would be initiated from October this year.

Each of the 49 schools will be provisioned with three computers connected through local servers so local content can be accessed and stored.

A central repository is proposed to be located at a data centre in the country, preferably the Thimphu Tech Park, to host the e-Library portal.

In places with poor Internet connectivity, the contents of the local server will be periodically updated with the use of a movable media such as hard drives. The contents will also be accessible by users on their own devices outside the e-Library section using Wi-Fi facility.

The e-Libraries will also be facilitated with televisions so that content can be broadcasted to students. While each schools would be given three computer, each of the 12 tertiary institutes will be provided with five computers.

The e-Library will also have a studio to create digital content for digitalising books, documents and audio-video, which will also be connected to central repository to upload contents to the library’s portal either with use of internet or movable data.

Meanwhile, the purchase order for supply, installation and commissioning of IT hardware for the central repository, colleges, schools and studio has been placed. The vendor is processing to dispatch hardware from India and Singapore. Delivery and distribution of IT hardware to all locations in Bhutan would be done between June-July this year.

Tempa Wangdi

Wednesday, May 3, 2017

Digital game

1. Educational Game

Educational games are games explicitly designed with educational purposes, or which have incidental or secondary educational value. All types of games may be used in an educational environment. Educational games are games that are designed to help people to learn about certain subjects, expand concepts, reinforce development, understand a historical event or culture, or assist them in learning a skill as they play. Game types include boardcard, and video games. An educational game is a game designed to teach humans about a specific subject and to teach them a skill. As educators, governments, and parents realize the psychological need and benefits of gaming have on learning, this educational tool has become mainstream. Games are interactive play that teach us goals, rules, adaptation, problem solving, interaction, all represented as a story. They satisfy our fundamental need to learn by providing enjoyment, passionate involvement, structure, motivation, ego gratification, adrenaline, creativity, social interaction and emotion in the game itself while the learning takes place.

2. Action Games

The action game is a video game genre that emphasizes physical challenges, including hand–eye coordination and reaction-time. The genre includes diverse subgenres such as fighting gamesshooter games and platform games which are widely considered the most important action games, though multiplayer online battle arena and some real-time strategy games are also considered to be action games.

In an action game, the player typically controls the protagonist or avatar. The avatar must navigate a level, collecting objects, avoiding obstacles, and battling enemies with various attacks. At the end of a level or group of levels, the player must often defeat a boss enemy that is more challenging and often larger than other enemies. Enemy attacks and obstacles deplete the avatar's health and lives, and the player receives a Game over when they run out of lives. Alternatively, the player wins the game by finishing a sequence of levels. But some action games, usually arcade games, are unbeatable and have an indefinite number of levels; and the player's only goal is to maximize their score by collecting objects and defeating enemies.

3. Excergaming

Fitness ,[1] exergaming or exer-gaming (a portmanteau of "exercise" and "gaming"), or gamercising[2][3] is a term used for video games that are also a form of exercise.[4] Exergaming relies on technology that tracks body movement or reaction. The genre has been credited with upending the stereotype of gaming as a sedentary activity, and promoting an active lifestyle.[5][6] Research indicates that exergames can produce real improvements in fitness.[7] Exergames are seen as evolving from technology changes aimed at making video games more fun.[8]

4. Racing Game

The racing video game genre is the genre of video games, either in the first-person or third-person perspective, in which the player partakes in a racing competition with any type of land, water, air or space vehicles. They may be based on anything from real-world racing leagues to entirely fantastical settings. In general, they can be distributed along a spectrum anywhere between hardcore simulations, and simpler arcade racing games. Racing games may also fall under the category of sports games.


Digital game

1. Educational Game
Educational games are games explicitly designed with educational purposes, or which have incidental or secondary educational value. All types of games may be used in an educational environment. Educational games are games that are designed to help people to learn about certain subjects, expand concepts, reinforce development, understand a historical event or culture, or assist them in learning a skill as they play. Game types include boardcard, and video games. An educational game is a game designed to teach humans about a specific subject and to teach them a skill. As educators, governments, and parents realize the psychological need and benefits of gaming have on learning, this educational tool has become mainstream. Games are interactive play that teach us goals, rules, adaptation, problem solving, interaction, all represented as a story. They satisfy our fundamental need to learn by providing enjoyment, passionate involvement, structure, motivation, ego gratification, adrenaline, creativity, social interaction and emotion in the game itself while the learning takes place.
2. Action Games
The action game is a video game genre that emphasizes physical challenges, including hand–eye coordination and reaction-time. The genre includes diverse subgenres such as fighting gamesshooter games and platform games which are widely considered the most important action games, though multiplayer online battle arena and some real-time strategy games are also considered to be action games.
In an action game, the player typically controls the protagonist or avatar. The avatar must navigate a level, collecting objects, avoiding obstacles, and battling enemies with various attacks. At the end of a level or group of levels, the player must often defeat a boss enemy that is more challenging and often larger than other enemies. Enemy attacks and obstacles deplete the avatar's health and lives, and the player receives a Game over when they run out of lives. Alternatively, the player wins the game by finishing a sequence of levels. But some action games, usually arcade games, are unbeatable and have an indefinite number of levels; and the player's only goal is to maximize their score by collecting objects and defeating enemies.
3. Excergaming
Fitness ,[1] exergaming or exer-gaming (a portmanteau of "exercise" and "gaming"), or gamercising[2][3] is a term used for video games that are also a form of exercise.[4] Exergaming relies on technology that tracks body movement or reaction. The genre has been credited with upending the stereotype of gaming as a sedentary activity, and promoting an active lifestyle.[5][6] Research indicates that exergames can produce real improvements in fitness.[7] Exergames are seen as evolving from technology changes aimed at making video games more fun.[8]

4. Racing Game

The racing video game genre is the genre of video games, either in the first-person or third-person perspective, in which the player partakes in a racing competition with any type of land, water, air or space vehicles. They may be based on anything from real-world racing leagues to entirely fantastical settings. In general, they can be distributed along a spectrum anywhere between hardcore simulations, and simpler arcade racing games. Racing games may also fall under the category of sports games.



Earthing

Types of Earthing 1). Plate Earthing: 2). Pipe Earthing: 3). Rod Earthing 4). Earthing through the Waterman 5). Strip or Wire Earthing ...