Remote control of light and fans basics

Introduction:- Home automation is very interesting project idea  now a days in electronics. To control any light or fan by remote control we have to use relays in addition to switch. The light can be control by relay only or relay and switch depends on wiring of relay/switch. To control light with both switch and relay we need two way switch and a relay with change over contact.

Basics of remote control:- There are mainly two parts first is hand held remote control unit and other is receiver unit. These remote works for a distance of 10 feet's normally. remote control has a set of push buttons to give on off commands. The signal from remote is sent to receiver by radio waves/ infrared waves or blue tooth system. TV remote uses infrared signals. Small toys car/drones uses radio waves. DTMF signal is also used in some system where more items (channel) are controlled. In case of blue tooth control we can use mobile phone as a remote control with some remote apps. So on the basis of medium of signal sending remote control can be of following types

1. Infrared remote control:-  uses infra red rays as medium.
2. Radio frequency remote control:- it uses radio frequency as carrier for signal. Blue tooth also uses radio frequency. 27 MHz trans receiver modules are also available for remote control.
3. Mobile SMS based:- this system uses a GSM mobile module with a sim card. With mobile phone SMS is sent to Gsm module. This message is decoded by arduino microcontroller and operate different relays to control appliances.

Main steps in working

1. Push buttons / switches:- we can use single button/switch to on/off a light or two button separately for on and off operation. To control 4 light we need 4 button in first system and need 8 button in second system.

2.  Coding button signal:- The 5v signal from button goes to coding IC which generate a digital signal corresponding to that button.

3. Oscillator circuit:- this circuit generate a high frequency carrier wave.

4 Modulation:- the digital signal received from IC is mixed with this carrier wave. This modulated signal is amplified and given to small loop aerial.

5. Receiver unit:- the signal received by receiver unit is amplified and demodulated to separate the digital signal sent by remote control. This digital signal is decoded in decoder IC, which gives output on a corresponding pin. This signal is used to picks up a relay. The contact of relay is closes and makes light on. The remote control has same number of relays as number of channel to control.

Note above is a general description but different remote control may use some what different logics for control.




main-sections-of-lcd-tv

Megger construction and working

Introduction:- Megger is used for measuring insulation resistance (IR) value of motors, cables, and panel mounted components and bus bar etc. Megger are available for different voltage range like  50 volt, 500 volt, 1000 volt, 2500 volt(2.5kv), 5 kv . IR value measurement is very important in electrical work to ensure safety of working personnel's and equipment.

Construction and working:- it consist of a permanent magnet cross coil dynamo meter type indicating instrument and a hand operated DC generator. There is permanent magnet as shown in fig. Two moving coil are placed within the magnetic field of magnet supported by pivots. The two coil are placed at 90 degree to each other. First coil is known as pressure coil connected in parallel to output voltage of generator. it provide torque to spindle in anti clock wise direction hence moves the pointer towards infinity. The second coil is connected in series with testing resistance, it produce torque in opposite direction which  moves pointer towards 0 ohms. So when Megger is used for measuring resistance , Megger pointer indicates the ratio of V/I that is R of the circuit.

Hand operated generator:- it is very small generator with permanent magnet field. armature is rotated with the the help of handle and gear system. A clutch is provided so that handle start slipping after the 120 rpm. So when handle is rotated with full speed the armature speed is limited to 120 rpm and the output voltage remains constant.

Uses:- LT motor are Meggered with 1000  volt Megger. HT motors are meggered with 2.5 kV Megger. Minimum IR value should not be less than voltage rating of machine into 1000 ohms that means 1000 ohms per volt of machine rating. In HT motors and HT cables R15/R60 ratio is also considered. R15 and R60 is meggering values at 15 seconds and 60 seconds respectively. R60 value must be 1.3 to 1.5 times higher than R15 value.

Main sections of LCD TV

Main sections of LCD TV

Power supply section:- power supply gives 12volt or 5 volt DC output. This 12/5 volt is given to 3.3 volt regulator IC which gives 3.3 volt DC . this 3.3 volt is given to mother board main ic , bios IC , reset button and IR sendser. This 3.3 volt supply is known as 3.3 v SB (stand by). Power supply also gives 24 volt DC for inverter board in LCD TV.

Mother board:- It consist of main microcontroller IC , bios ROM,  flash  IC RAM. A crystal of 24 MHz is used to generate clock pulses. Main IC receives audio video signals from A/V input, HDMI input, RF Signal from tuner and MPEG files from USB. Input signal is selected by mother board throught signal switching circuit. This signal is processed and sound signal is seperated, amplified and sent to speaker. Video signal is sent to analog to digital converter. It gives out red, blue, green, sync  and clock signals in the form of LVDS (low voltage differential signal) signal. LVDS signal is sent to timing controller IC (Tcon IC) on Tcon board through LVDS cable. Mother board sents Back light on/off  control  signal is to back light inverter/ driver board.

Tcon board:- It has normally four section
1- DC to DC IC :- Tcon board receives  vcc supply generally 12 volts  from LVDS connector is given to this Ic . It produce 3.3 volt supply which is given to Tcon IC. A 1.2 volt regulator is also used to supply core voltage to Tcon IC . One more regulator IC is used to supply 3.5/1.8/1.5/1.2 volt to RAM depending on  version of RAM (DDR1 3.5 volt, DDR2  1.8 volt, DDR3 1.5volt, DDR4 1.2 volt). When Tcon IC receives all input voltages and signals, it starts working and gives an enable signal to DC to DC IC . After receiving enable signal DC to DC IC start producing AVDD, HVDD, VGH and VGL voltages. In some cases enable signal is directly given to DC to DC ic. HVDD and VDD voltages are also given to gama IC.

2- Tcon IC :- It receives working voltage VDD 3.3 volt, 1.2 volt for core and 1.8 volt for RAM. It receives Signal 0-, 0+ (red color signal data), 1-,1+ (green color signal data), 2-,2+(blue color signal and horizontal and vertical sync signal data), 3-,3+(clk+, clk-),  4-,4+(RGB signal data) from LVDS connector. This IC process all signals and gives output as mini LVDS 0-, 0+, 1-,1+, 2-,2+, clk-,clk+, 3-,3+, to panel through COF flex strip and EN, CPV1 CPV2, STV signal to scan driver ic.

3- Scan driver or level shifter:- It receives 3.3 volt, VGH, VGL from DC to DC IC and , CPV1, CPV2, STV, and EN (enable signals) from Tcon IC. It gives CKV1, CKV2 for scan clk odd and CKVB1, CKVB2 for scan clk even to panel source COF.

4- Gama IC :- HVDD voltage are given to this IC. With the help of voltage divider circuit Vref and Vcom voltage is produced. And all gama voltages are produced with the help of voltages divider circuit. Some programmed IC are also uses in which voltage divider circuit is not used. Gama voltage start from 1.5 volt to AVDD voltage with increasing gradually in steps. Gama voltages are given through source COF for gama correction.

Chip on flex IC (COF):- This IC receives all voltage through flex strip and produces driving signal voltage to drive all TFT in the panel. Main voltages received by COF IC are VDD 3.3 volt, AVDD (16 volt), HVDD (8volt), VGH (27 volt), VGL (-8 to -10volt), CKV1, CKV2, CKVB1, CKVB2, VCOM and Gama voltages and all signal voltages from Tcon through mini LVDS.

Panel or screen:- All working voltage to panel is received through COF connector flexible strip cable. The light for screen working is given by back light ccfl/led. Main part of panel are
1 light source
2 horizontal poloizor
3 TFT screen:- Thin film transistorscreen:-  complete screen is filled with matrix of TFT. each pixel need three TFT. Each transtor three points are connected to source, commen and gate circuit of panel and controlled separately by multiplexing mathod.
4 vertical polorizor

Back light:- cold cathode florocent light (CCFL) are used in LCD panel for back light. LED Strips are used in Led TV panel. In LCD TV back light is given supply with a inverter board, where as in led TV led drivers are used to give supply to led strips. Back light on/off signal is received from mother board.

Control button panel:- all control button are placed in this panel to control TV locally. Otherwise remote control is used in which all control signals are received by IR senser and sent to mother board.

In this article  I have sum up my information regarding LCD/led TV. If any person like to give more information pls share in commect so I can add more information. Thanks for reading.


effects-of-low-power-factor

functional-block-diagram-of-television

Bi Stable Multi Vibrator or Set Reset Flip Flop

Bi Stable Multi Vibrator or Set Reset Flip Flop

Introduction:- Bi stable multi vibrator has two stable states that is its output can be set to 1 with set pulse or can be set to 0 with reset pulse. It is also known as set reset flip flop or SR flip flop. It is the basic unit of electronic solid state memory. It stores one bit of data that is 0 or 1.To store 8 bits data set of 8 flip flop are used. Register also uses the flip flops for storing data. Additional logic circuitry is also used to write read data.

Basically in all digital circuit supply voltage used is 5 volt dc. So in this set reset flip flop working voltage 5 volt is given to Vcc and - ve to ground. There are two input points set and reset. When a positive pulse is given to set input the output of flip flop changes to state 1. This state remains constant until a reset pulse is given to reset input. Again when we want to reset a reset pulse is given to reset input, the output reset to 0 state and remain in 0 state until set pulse is given to set input.
this property of SR flip flop make it suitable for digital bit storage. According to data bits all flip flop of eight bit storage locations are set to their corresponding bit. In simple electronics this flip flop can be used to make latching relay circuit.

Circuit Working:- When set switch is pressed positive voltage goes to the base of transistor T1 make it conducting. So the collector voltage of transistor T1 becomes 0 so biasing of transistor T2 base through R3 resistance reduce to 0 volt and T2 gets cutoff. Due to cutoff of  transistor T2 collector voltage of transistor T2 becomes 5 volt which start providing biasing to base of  transistor T1  through resistance R4 this makes T1 to remain in saturation level even after set button is depressed.
Same process is repeated when reset button is pressed. Transistor T2 start conducting so the collector voltage of T2 becomes 0 volt so biasing of T1 base trough resistance R4 reduced to 0 volt and T1 gets cutoff. Due to cutoff of transistor T1 the collector voltage of T1 becomes 5 volt which start providing biasing to base of transistor T2 trough resistance R3 this makes transistor T2 to remain in saturation level even after reset button is depressed.


https://vijayelectronicsforu.blogspot.com/2018/07/uses-of-transistor-as-amplifier.html

https://vijayelectronicsforu.blogspot.com/2018/07/dc-motor-direction-control-by-two-relay.html

Simple Arduino program, blinking a LED for beginners

A Simple Arduino program, blinking a LED for beginners

Introduction:- Arduino  board is a complete board for learning use of micro controller.It uses micro controller IC ATMega328 16 Mega Hertz. It is 8 bit micro controller with 32 kb of program memory. It has inbuilt programmer to upload program through USB port. Input dc supply jack is provided for giving input dc supply 8-12 volt. Inbuilt voltage regulator are used to provide 5 volt and 3.3 volt regulated power supply for internal use. 13 numbers digital input / output pins are provided for external devices connection. one LED is internally connected to pin number 13. Analog I/O pins, PWM pin and serial transfer Rx Tx pins are also provided.

Micro controller is a very small computer on a single chip. It consist of inbuilt CPU, storage memory, input output ports. Arduino board has every thing required for use of micro controller. It needs to upload a program and run. In this post I am writing a very small program to explain program structure and syntax use for Arduino programming. It used open source integrated environment development software for arduino. Screen shot of arduino IDE for windows is as shown below. Software can be downloaded from net.

When you open this arduino IDE in PC you will see this screen. Open blink example from menu bar
file  examples//basic/ blink . you will see screen open with above code. now please see the code it is similar to c++ programming language. this is very first and small program for beginners. first part of program is void setup() in this function we write the code which has to executed  only once. To use any digital input/output pin we have to configure the pin as input or output with a line of code like pinMode(pin number, OUTPUT/INPUT). Here we are using function pinMode to declare LED_BUILTIN (pin 13) as a output pin.

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

Second part of program is loop function it runs continuously till the program is not stopped.
In loop function   digitalWrite(LED_BUILTIN, HIGH);  is use to write (give) a high value to  LED_BUILTIN (pin  13). when high value is given to pin 13 led connected to this pin gets on. Function   delay(1000);   Provides a delay of 1000 mili  seconds. This keeps pin 13 high for 1000 ms. Then the function digitalWrite(LED_BUILTIN, LOW);  is use to write low on  LED_BUILTIN (pin  13). When low value is given to pin 13 led connected to this pin gets off. Again function delay(1000); is used to give 1000 ms off time for pin 13 led. this complete code is repeated continuously as it is in loop function. Code for loop function is as given below.

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

After writing the program code in editor window it need to compile. in editor. Below menu bar there is a tool bar. In tool bar there are tab buttons for compile and upload the program.there is tool tip on each button. so by clicking on compile button program will compile and a message of successfully compiled or some error will display in output window.if your program is written correctly it will compile successfully.after compile we have to upload the program in Arduino board. For this we have to connect our board to computer with the help of USB cable which comes with board. The USB cable serves two purpose first it gives the power supply to the board and second it upload the hex code to the board. As soon as code upload is completed a message is displayed on IDE that upload is completed. Now micro controller runs this program and you will see that led connected to pin 13 starts blinking at the rate  of 1 second off and 1 second on. To blink a led can be done by any electronic circuit. but to change on/ ff duration will required to change components. With micro controller we have to change delay time in our program and upload. you can experiment by changing time period. any other output pin can also be use to control other led. We can also use 5 volt miniature relay in place of led and control any device from relay. Maximum output current of any output pin is max 50 ma. so we should be care full to connect load to pin that current should be in safe limit. Arduino is very vast can not be cover in such a small post. so for any doubt please ask in comment or take some help from net.
This program as well as many programs are given in  examples of arduino IDE that can be used for further learning. I hope this post will help full to you. your valuable suggestion and comments are welcome for improvement.



https://vijayelectronicsforu.blogspot.com/2018/06/transformer-introduction-and.html

https://vijayelectronicsforu.blogspot.com/2018/06/dc-motor-construction-and-working.html

http://vijayelectronicsforu.blogspot.com/2018/07/radio-receiver-block-diagram.html

Functional block diagram of Television with explaination

Functional block diagram of Television with explanation

Different stages of television: - The main stages of black and white television are as follows.

Power supply stage:- Here 230 volt power supply is converted to 110 volt and 12 volt DC supply required for different sections (stages) of TV. Following type of power supply are used in TVs and many other electronics items.

1 Transformer power supply:- Consist of a step down transformer with 110 volt 12 volt and 6.3 volt secondary windings. Bridge rectifier and filter capacitor is used to produce 110 volt DC and 12 v DC. 110 volt DC is used in EHT section and 12 volt DC is used in sound section.

2 Scr based power supply:- scr (silicon controlled rectifier also known as thyristor is used to make 110 volt DC regulated supply. 110 volt DC is given to EHT section. All other supply are produced from the EHT section.

3 SMPS POWER SUPPLY :-Now a days all TVs uses smps (switch mode power supply)  power supply. More are less are electronic item uses smps power supply. Nearly 30 percent problems of TVs are due power supply and can be fixed by repairing power supply.

Tuner section :- This is the first section of TV. It has three sub section ie RF amplifier section, local oscillator section and a mixer section. It generates local oscillator frequency as per the requirement of receiving RF signal frequency. TV signal received from antenna is given to RF amplifier section with matching transformer known as balloon. The antenna output impedance is 300 ohms to be matched with tuner input impedance of 75 ohms. Balloon is used with input impedance 300 ohms and output impedance 75 ohms as impedance matching transformer between antenna and tuner. The RF signal is amplified in RF amplifier section. Then local oscillator signal and RF signal is mixed in mixer stage. The mixer stage output signal is known as video IF signal which is then sent as input signal to video IF section. AGC (Automatic gain control signal) voltage is received from VIF Section to tuner section for RF Amplifier gain control .12 V DC power supply is given to tuner for its working. In old TVs 12 channel tuner were used in which channel was changed with knob manually. Now a days all TVs are using electronic tuner in which band selection and tuning is done electronically from front panel or remote control. In electronic tuner 33 volt supply is also given as tuning voltage. In electronic tuner varactor diode is used in oscillator circuit to control the oscillator frequency by changing tuning voltage applied to varactor diode. Varactor diode capacitance is changes with reversed bais  applied voltage changes.

VIF Section:- This section has a 3 stage video IF amplifier, keyed AGC generator and demodulator built in a single IC . The video IF signal received from tuner is amplified. After amplification VIF signal is demodulated, After demodulation composite video signal is sent to video amplifier and sync separator stage. Sound IF signal is sent to sound IF section.To produce keyed AGC  VIF section receive's fly back pulses  from EHT section.

Sound IF amplifier:- In  this section sound IF signal is amplified in two stages and the signal is demodulated  to produce sound or audio signal. Audio signal a sent to audio amplifier stage through volume control.

Sound amplifier :- This section consist of four stages of  audio amplification ie first audio  amplifier, second audio amplifier, driver  stage and. Power amplification stage. All stages of audio  amplifier are built  in a single IC known as sound/audio amplifier IC. The speaker is connected to output of audio amplifier and convert amplified audio signal to sound.

Picture tube:- The function of picture tube is to produce picture. It has a cathode which is heated by filament. When cathode is heated electrons emits from cathode. With the help of control grid focusing anode, first accelerating anode and final accelerating anode an electron beam is produced and focused at the center of screen. The screen has phosphor coating in side when this electron  beam strikes on screen a light spot is produced on screen. With the help of vertical deflection coil and horizontal deflection coil this spot is deflected in sequentially way to create raster. And hence complete screen gets illuminated with a single point of light running very fast on screen . Due to persistence of vision our eyes feels continuous presence of light. The picture formation and raster details will be covered in other article.The video signal from video amplifier is given to cathode of picture tube. It is known as cathode modulation. It control the intensity of spot on screen. The movement of spot created by electron gun is synchronized with the scanning gun of camera so the position of spot and intensity of spot is exactly the same as the camera so same image is formed on the  screen. Such 25 images (50 frames) per second is produced by picture tube so that we see a movie picture on screen.

Video amplifier :- The video signal received after demodulation is amplified in video amplifier stage. The output signal is given to cathode of picture tube from the collector of video amplifier transistor. Vertical blanking pulses are also added in this stage for blanking of vertical retrace lines. In color TV video amplifier stage has a chroma IC which processes the composite video signal and produces 3 signal for red, green and blue color. These color signal are amplified in three amplifier transistors and given to red gun (red cathode), green gun and blue gun of color picture tube.

Horizontal oscillator stage:- In this stage horizontal oscillator signal of 15625 hz is generated. A sync separator circuit in side IC separates vertical sync pulses and horizontal sync pulses from composite video signal received from VIF section. A AFC circuit synchronized the horizontal oscillator with horizontal sync pulses. Vertical sync pulses are sent to vertical oscillator for synchronization.

Horizontal driver :- horizontal oscillator signal is amplified in driver stage. A driver transformer is used. The signal from secondary of driver transformer is given to base of horizontal output transistor. The collector supply to the output transistor is received from primary winding of EHT transformer. horizontal deflection Coils are connected to output of horizontal output section.

Horizontal output section:- It uses a power transistor (BU205, BU208), A EHT transformer and horizontal deflection coil placed in yoke which is mounted on picture tube neck. EHT transformer has few more winding which are used to generate 50 volt supply for vertical stage. 6.3 volt winding for picture tube(CRT) filament. Different EHT have some difference in auxiliary supply voltages.

Vertical stage:- This stage has in built vertical oscillator and vertical amplifier in a single IC. Vertical oscillator generate 50 hz saw tooth wave signal. After amplification this voltage is given to vertical deflection coil placed in yoke. The vertical oscillator uses vertical sync pulses received from sync separator to get synchronised with composite video signal. Vertical stage has two presets to adjust vertical hold of picture and vertical linearity of picture respectively.

Some common faults.
No light no sound :- problem of power supply.
Horizontal line:- problem in vertical stage.
No picture no sound but raster (light) is present :- fault is in VIF stage or in tuner stage.
Picture coming sound is not coming:- problem is in sound IF stage or audio amplifier stage.
Sound is OK but only plain light on screen :- problem in video amplifier stage.
Sound OK but no light : problem may be in horizontal oscillator or EHT section.

It is a very brief discription of black and white TV. Interested reader need to go for more details. Any question are welcome in comment. Thanks for reading.

three-phase-welding-rectifier circuit diagram with working principle

main-sections-of-lcd-tv/ LCD TV block diagram

Variable frequency variable voltage VVVF

Variable frequency variable voltage VVVF

Introduction :- The motor used in any machine need to be operate at variable speed.Earlier DC motor was used for applicatios where speed control is requred. The speed of ac motor is considered as fixed speed because the speed is depend upon number of pole and frquency of supply. But now a day with invent of VVVF drive it becomes easy to control speed of motor by producing variable voltage variable frequency supply for motor.
Working:-

In VVVF drive three phase voltage is converted in to dc voltage generally 500  v dc. Then three phase inverter circuit is used to produce 3 phase ac supply of  varable frequency and variable voltage. Voltage to frequency ratio remains constant.It uses digital control system for firing control of IGBT and inverter parameter setting. All the data of motor (such as voltage current rpm)  and operational requirements are  stored in parameters of drive.  VVVF drive has a display and key pad which are used for parameter setting. During running of motor running data load current and fault candition is also displayed on display. Drive key pad has buttons for start stop local remote forward reverse etc. In addition to this external push buttons can also be connected in control terminal block for start stop speed increase decrease etc. drive has three power terminal nuetral terminal and earth terminal for input connection. similarly three power terminal and one earth terminal for motor connection.

different makes of drive has some difference in control terminal block connection but basically all are same. With the help of instruction manual given with drive and following all instructions care fully it is easy to use VVVF drive for speed control of ac motor application. please see my blog for more articles. your comment and suggestions are welcome.