Modern Instruments and Communication System(EB) : Chapter 6

     CH-6.   CONSUMER ELECTRONIC APPLIANCES         Marks: 10(15)

LCD TV (Principle):

1. LCD TV is a television display technology based on liquid crystal display. LCD TV consumes less power because it works on principle of blocking light rather than emitting it. 

2. An LCD display uses passive matrix or active matrix display. An active matrix LCD is called thin film transistor (TFT) display. 

3. The passive matrix LCD has a grid of conductors. Pixels are located at each intersection of the grid. An active matrix has a transistor located at each pixel.

4. LCD televisions produce a colored image by selectively filtering light produced by a backlight.  The light is provided by a series of cold cathode fluorescent lamps (CCFLs). But now typically by white or colored LEDs are used as backlighting.  

5. Millions of individual LCD shutters, arranged in a grid, open and close to allow a amount of the white light through. 

6. Each shutter is paired with a colored filter to remove all but the red, green or blue (RGB) portion of the light from the original white source. Each shutter–filter pair forms a single sub-pixel. 

7. The sub-pixels are so small that when the display is viewed from even a short distance, the individual colors blend together to produce a single spot of color, a pixel. 

Advantages of an LCD TVs over conventional CRT TVs:

1. LCD TV consumes less amount of power compared to CRT TV.

2. LCD TVs are very compact and light in weight.

3. LCD panels are much thinner than CRTs.

4. LCD screen size may be very large (65 inch). But large size displays using CRT are not possible.

5. LCD TVs are thinner and lighter when compared to CRT TVs.

6. LCD screen has little emission of electromagnetic radiation.

Disadvantages of an LCD’s:

1. Require additional light sources

2. LCD screen has limiting viewing angle.

3. Range of temperature is limited for operation

4. Cost is more as compared to CRT TV.

5. Speed is very low

6. In sun light LCD screen shows poor displays.

LED TV:

1. LED TV is a type of LCD television that uses light-emitting diodes (LEDs) to backlight the display instead of the cold cathode fluorescent lights (CCFLs) used in standard LCD televisions. 

2. LED TVs are more formally known as LED-backlight LCD television. An LED TV illuminates its LCD panel with light-emitting diodes. 

3. An LED screen is actually an LCD screen, but instead of having a normal CCFL backlight, it uses light-emitting diodes (LEDs) as a source of light behind the screen. 

4. An LED is more energy efficient and a lot smaller than a CCFL, enabling a thinner television screen.

Merits:

1. Power consumption is less at it produces less heat.

2. Display is brighter and sharp.

3. Contrast is better.

4. More life span than LCD TV.

5. More reliable.

Demerits:

1. Expensive as compared to LCD TV

Plasma TV:

1. An ionized neon-xenon gas mixture is placed between two glass plates with electrons. Such state of matter is called plasma. 

2. There are many tiny cells consisting of this mixture. When voltage is applied to cells, ionization takes place. 

3. There is collision of ions with electrons resulting emission of light. Each pixel (cell) is subdivided into three subpixels to glow red, green and blue light.

4. Plasma displays can be made upto large sizes like 150 inches diagonal. Plasma screens operate at higher temperature and consume more power than LCD screen of same size. 

5. They have high viewing angel and high contrast. Now a days plasma screen TVs are no longer in production.

3-D TV:

1. 3D TV is a television that 3D perception of the picture to viewer. It uses stereoscopic display technique. Stereoscopy involves capturing stereo pairs in a two view set ups. 

2. It uses two cameras mounted side by side separated by the same distance as is between a person’s eyes.

Smart TV:

1. A smart TV is a television set with integrated Internet capabilities. Besides email and word processing, a smart TV is a lot like a computer. 

2. It enables to browse the web, watch YouTube and catch up on social networking. Some of the TVs support a better web browsing experience. 

3. In smart TVs, the operating system is preloaded or is available through the set-top box.

4. The software applications or "apps" can be preloaded into the device, an app store similar as modern smart phones.

DTH (Direct To Home) Technology:

1. Direct to home technology refers to the satellite television broadcasting process which is actually intended for home reception. DTH refers to the reception of satellite signals on a TV with a personal dish in an individual home. 

2. The satellites that are used for this purpose is geostationary satellites. The satellites compress the signals digitally, encrypt them and then are beamed from high powered geostationary satellites. 

3. They are received by dishes that are given to the DTH consumers by DTH providers. Set top box is necessary for DTH technology.

4. The main advantage is that this technology is equally beneficial to everyone. As the process is wireless, this system can be used in all remote or urban areas.

5. High quality audio and video are cost effective due to absence of mediators.

6. With a single DTH service you will be able to use digital quality audio, video and also high speed broadband.

Introduction to iPod:

1. An iPod is a portable digital audio player. It is designed and marketed by Apple Computer. 

2. An iPod is used for storing and playing audio files encoded by MP3.  iPod can store 100 to 0,000 songs. It is easily available in the market with storage capacity of 1GB, 2GB, 4GB etc.

3. The smallest member of the iPod family is the Shuffle. Shuffle uses a type of memory known as flash.

MP3 music player:

1. MP3 is an abbreviation of MPEG audio layer 3. MPEG means Moving Picture Experts Group. MP3 is a compression system for music. 

2. This compression method helps to reduce the space required to store song on CD. The goal of the MP3 format is to compress a CD quality song by a factor of 10 to 14, without losing the CD sound quality. 

3. This allows one MP3 CD to store 100 to 150 songs compared to 10-15 songs on an audio CD.

4. This is the same group who has developed compression system for video data. VCD and DVD use MPEG compression to fit video and movie data into CDs.

P.A. System (Public address system):

Principle: 

1. The intensity of sound decreases with distance. Hence when a large gathering is to be addressed, sound needs to be amplified. 

2. So that people at a distance from the rostrum or stage may receive good intensity of sound for comfortable listening. The system which fulfils this function is called Public address system or simply ‘PA’ system. 

3. It is used in sports, meets, public meetings, auditoriums, concerts, functions etc. It is also used to convey information to isolated locations as at railway stations, airports, hospitals, factories etc.

Block diagram of public address system:

.

Mixer-Juicer:

1. A mixer grinder along with a juicer has become necessary appliances in almost every Indian household today. It can do variety of tasks like pureeing, mincing and grating the ingredients. Juicer A juicer is an appliance which helps extract juices from fruits and vegetables.

2. It uses medium sized universal motor housed in the base. The motor housing ensures vibration free running. For two or more speeds, the tapping is taken out from field winding. 

3. Safety features such as overload trip, jar mounting lock and proper lid closing are included. The jar contains the cutting knives. 

4. The mixer power rating ranges from 100W to 650W. The revolution is 3000 to 14000 rpm. The desired blending speed is selected on the control switch.

 

Microwave Oven:

Principle:

1. A microwave oven uses microwaves, which are basically radio waves, to cook food. The commonly used frequency is roughly 2,500 MHz (2.5 GHz). 

2. Radio waves in this frequency range are absorbed by water, fats and sugars. When absorbed, they are converted directly into heat. 

3. The radio waves penetrate the food and excite water and fat molecules. In a microwave oven, there is heat everywhere all at once because the molecules are all excited together.

4. Microwaves are not absorbed by plastic, glass or ceramics. Hence the food containers to be kept for microwave cooking are made of ceramics, glass and suitable plastics. Metal containers cannot be used, as metals reflect microwaves and cause sparks.

Working:

1. The microwaves bounce back and forth off the reflective metal walls of the food compartment. 

2. When the microwaves reach the food itself, they don't simply bounce off. Microwaves penetrate inside the food. As they travel through it, they make the molecules inside it vibrate more quickly.

3. Vibrating molecules have heat so, the faster the molecules vibrate, the hotter the food becomes. Thus the microwaves pass their energy onto the molecules in the food, rapidly heating it up.

 

Advantages:

1. Cooking time is short.

2. Destruction of nutrients is less.

3. No physical change of foods.

4. Melting process is easy.

Types of microwave ovens:

1. Solo microwave oven: It has a magnetron inside to produce micro waves. It can do heating and boiling, but not roasting and baking operations.

2. Grill Microwave oven: It is provided with heating coils. When we use the grill function, microwave function is in off function.

3. Convection microwave oven: It has microwave function, the coils for grilling and heaters with blower to bake food. We can use all these functions independently or in combination to suit cooking needs.

 

Washing machine:

1. A machine used to clean the laundry as clothes, towels, sheets etc., without having to do hard labor. It helps to wash clothes easier.

2. The performance of these machines is based on the rotation of the clothes inside a tub while they mixed with water and some kind of detergent. 

Types of Washing Machines:

Semi-automatic:

It has separate tub for wash and dry. The clothes are first washed in wash tub and then transferred to spin tub for rinse.

Fully automatic- top loading machine:

It has single tub operation. It consists of wash programs and manual setting. The auto program completes the entire operation without any human intervention. A running water source is required.

Fully automatic- front loading machine:

It has single tub operation. Wash action is tumble. It consists a set of wash programs and manual setting. The auto program completes the entire operation without any human intervention. A running water source is required. The operation is more efficient and closest to the hand wash.

 

Parts of washing machine:

1) Water inlet control valve: Near the water inlet point of the washing there is water inlet control valve. When you load the clothes in washing machine, this valve gets opened automatically and it closes automatically depending on the total quantity of the water required. The water control valve is actually the solenoid valve.

2) Water pump: The water pump circulates water through the washing machine. It works in two directions, re-circulating the water during wash cycle and draining the water during the spin cycle.

 

3) Tub: There are two types of tubs in the washing machine: inner and outer. The clothes are loaded in the inner tub, where the clothes are washed, rinsed and dried. The inner tub has small holes for draining the water. The external tub covers the inner tub and supports it during various cycles of clothes washing.

4) Agitator or rotating disc: The agitator is located inside the tub of the washing machine. It is the important part of the washing machine that actually performs the cleaning operation of the clothes. During the wash cycle the agitator rotates continuously and produces strong rotating currents within the water due to which the clothes also rotate inside the tub. 

5) Motor of the washing machine: The motor is coupled to the agitator or the disc and produces it rotator motion. These are multispeed motors, whose speed can be changed as per the requirement. In the fully automatic washing machine the speed of the motor i.e. the agitator changes automatically as per the load on the washing machine.

6) Timer: The timer helps setting the wash time for the clothes manually. In the automatic mode the time is set automatically depending upon the number of clothes inside the washing machine.

7) Printed circuit board (PCB): The PCB comprises of the various electronic components and circuits, which are programmed to perform in unique ways depending on the load conditions

8) Drain pipe: The drain pipe enables removing the dirty water from the washing that has been used for the washing purpose.

 

 

Method/working:

1. Put clothes in the machine and detergent in machine or in a tray.

2. Switch on supply and set the program according to clothes.

3. Inlet water valve opens and water is taken as per requirement.

4. Program makes the drum to rotate back and forth the clothes through soapy water.

5. After set time, program opens outlet ware valve to drain the water from drum.

6. Clean water is taken by opening inlet water valve.

7. Inner drum rotates to and fro to rinse the clothes. 

8. Water is removed and process is repeated.

9. After rinse process, drum rotates at high speed. 

10. The clothes flung against the outside edge of inner drum. It has tiny holes through which water from clothes pass to outer drum. Wash cycle comes to end.

11. Clothes are taken out for drying.

 

Air conditioner (AC):

Air conditioning is the process of removing heat from a confined space, thus cooling the air and removing humidity.

Parts of an air conditioner:

Air conditioner installations mainly come in two types: window systems and split systems. In everyday language, these are commonly referred to as window ACs and split ACs.

1. Evaporator: An evaporator is basically a heat exchanger coil that’s responsible for collecting heat from inside a room through a refrigerant gas. This component is known as the evaporator.

2. Compressor: As the name clearly signifies, this is where compression of the gaseous refrigerant occurs. It’s located in the outside unit, i.e., the part that’s installed outside the house.

3. Condenser: The condenser receives the vaporized refrigerant from the compressor, converts it back to liquid and expels the heat outside. Needless to say, it’s also located on the outside unit of the split AC.

4. Expansion valve: Also referred to as the throttling device, the expansion valve is located between the evaporator and condenser coils. 

 

Some of the most common refrigerant gases used in air conditioning systems include hydrofluorocarbons (HFCs),  hydrochlorofluorocarbons (HCFCs) and Freon.

 

Refrigeration cycle (Working):

1. Every air conditioner has got a compressor inside it. It works to compress and pump the refrigerant gas. Compression of refrigerant produces heat.

2. To dissipate this heat, compressed refrigerant is pumped to the condenser coils where a fan blows the heat out to outer atmosphere. During this process, refrigerant takes the liquid form. 

3. This liquid refrigerant is pumped towards expansion valve. Expansion valve releases the appropriate amount of refrigerant to evaporator (cooling coils) 

4. In evaporator, liquefied refrigerant takes gaseous form. Conversion from liquid to gaseous state due to expansion causes cooling because energy is absorbed from the surrounding. 

5. Air when passes through fins (attached to coils) gets cooled and blown to the room. 

6. The gaseous refrigerant in cooling coils then enters the compressor and gets compressed once again. The cycle continues unless the compressor is shut down.

 

 

Electronic Bell:

Working:

Figure shows the electronic bell using IC555. In this circuit two timer ICs are used. When switch S1 is pressed, IC1 is triggered. It acts as a monostable multivibrator. Its output at pin 3 goes high for a time period previously set by pot R4. When output IC1 goes high it resets IC2. IC2 acts as astable multivibrator. It generates square wave signal in audio range. Its frequency can varied with the help of pot R5 and different audio musical tones can be generated. It is given to loudspeaker. 

 

Electronic fan regulator:

Working:

1. Before giving the power supply to this simple fan regulator circuit, keep the variable resistor or potentiometer in maximum resistance position so that no triggering is applied to TRIAC and hence the TRIAC will be in cutoff mode.

2. Turn ON the power supply of the circuit and observe whether the fan is in standstill condition or not. Vary the potentiometer position slowly so that the capacitor starts charging at the time constant determined by the values of R1 and R2.

3. Once the voltage across the capacitor is more than the break over voltage of the DIAC, DIAC starts conducting. Thus, the capacitor starts discharging towards the gate terminal of TRIAC through DIAC.

4. Therefore, TRIAC starts conducting and hence the main current starts flowing into the fan through the closed path formed by TRIAC.

5. By varying the potentiometer R1, the rate at which capacitor is going to be charged get varied this means that if the resistance is less, the capacitor will charge at a faster rate so the earlier will be the conduction of TRIAC.

6. As the potentiometer resistance gradually increases, the conduction angle of TRIAC will be reduced. Hence the average power across the load will be varied.

7. Due to the bidirectional control capability of both TRIAC and DIAC, it is possible to control the firing angle of the TRIAC in both positive and negative peaks of the input.

Questions

Marks wise Questions: 1M(2),  3M(1), 4M(1), 6M(1)

1. Fill in the blanks.

1. A food mixer uses a ----------- motor.

2. In microwave oven frequencies in the range of---------- are used.

3. iPOD is a ---------player.

4. --------- is used to store music files.

5. To crush solid particles ----------part of mixer is used.

6. -----------is used to generate electromagnetic radiation in microwave oven.

7. -------------is used in washing machine.

8. ----------is required for DTH system.

9. ----- is used in electronic fan regulator.

Answers.: 1. Universal 2. 2500MHz. 3. Portable media 4. MP3 system

5. Grinder 6. Magnetron 7. Agitator 8. St top box 9. Triac

 

2. Answer the following 

1. Write a short note on (a) LCD TV (b) LED TV (c) Plasma TV (d) Smart TV.

2. State advantages and disadvantages of LCD TV.

3. Write a short note on (a) IPod (b) MP3 player (c) DTH technology

4. With block diagram explain working of PA system.

5. Explain working of mixer juicer. Write names of its parts.

6. Explain the principle of microwave oven.

7. With diagram explain working of microwave oven.

8. Name the types washing machines.

9. Write the parts of washing machine.

10. Explain the method to wash clothes in washing machine.

11. Name the parts of air conditioner. Explain each.

12. With diagram explain refrigeration cycle in air conditioner. OR Explain working of air conditioner.

13. With circuit diagram explain working of electronic door bell.

14. With circuit diagram explain working of electronic fan regulator.