Transistor test

How can we say that a transistor which we are using is good or faulty ? 

we can test it by simply using multi-meter. We all know that three junction are in transistor, which are Emitter, Base ,Collector. 

Base-Emitter junction is always forward bias. 

Base-Collector junction is always reverse bias.

Therefore Base-Emitter junction should have low resistance,and Base-Collector junction should have high resistance.

we simply check it by using multi meter. we set multi-meter on Ohms value.

(i) We connect one Emitter to negative terminal and Base to positive terminal of the transistor.

Typically ohmmeter displays value 100 to 1 K . So forward side resistance is low, now we have to check on output side which is Collector Base side.

(ii) When we connect positive terminal to Base and negative terminal to Collector if it shows 100K or higher ohms, So it is good transistor.

If multi-meter  displays any other value like forward side high and reverse side low than transistor is faulty.

above example is for NPN transistor, but you can apply for PNP only polarity is reversed.

Samsung Galaxy S7

Network- Technology GSM/HSPA/LTE
Body  Dimensions 142.4 x 69.6 x 7.9 mm
           Weight-       152 gram
           Build-          Corning Gorilla glass 4 back panel
           SIM-           Single Sim (Nano SIM) or Dual SIM (Nano SIM)

Display  Type - Super AMOLED capactive touchscreen, 16 M colors

               Resolution-1440 x 2560 pixels

               Multi touch- Yes 

Plateform  OS- Anroid OS v6.0

                   Chipset- Qualcomm MSM8996 Snapddragon 820

                   CPU- Dual core 2.15 GHz kryo & dual core 1.6 GHz kryo

                   GPU- Adreno 530

Memory  Card slot- microSD up to 200 GB -single SIM model

                                   microSD up to 200 GB -dual SIM model

                 Internal-    32/64 GB , 4 GB  RAM

Camera Primary- 12 MP,26 mm  Led flash 

               Features- 1/2.6" sensor size, 1.4 micro m pixel size, geo- tagging, simultaneous 4K video     and 9MP image recording, touch focus, face/smile detection, Auto HDR, panorama.

               Video - 2160p@30 fps, 1080p@60 fps, 720p@240fps, HDR,dual video record 

               Secondary- 5 MP, f/1.7 ,22mm ,dual video call, Auto HDR 

Cheapest smart phone costs Rs. 251 Book now !!!

world's cheapest smart phone in the world in India is now available .

To book it now open below link
Freedom 251


Specifications

      Display

• Screen Size - 4.00 inch
• Resolution - 540 x 960 pixels

     Hardware

• Processor -             1.3 GHz quad core
• RAM -                   1 GB
• Internal Memory - 8 GB
• Expand. Memory- 32GB

   Camera 

• Rear  - 3.2 Mega Pixel
• Front - 0.3 Mega Pixel

   Operating System 

• OS - Android 5.1 

    Other Features 

• Wi fi  -         Yes 
• Bluetooth -   Yes
• FM  -            Yes
• GSM-           Yes 
• 3G -              Yes 

Its name is FREEDOM 251  
here are some of picture of it!

The freedom 251 is complies government's make in India program. its price is Rs 251 (approx 4$)
worlds chepest.

 Its design completely looks similar to i6s (apple).

Freedom 251 has 4 inch IPS display. It is powered by a quad core SoC clocked at 1.3 GHz, coupled with 1 GB RAM.

Download videos from FB using 3 easy steps!!!

we show so many videos in facebook, some of them are very nice and if you wish to download that videos for your collections than here are simple steps by following them you can download them.

Follow 3 easy steps for downloading videos from facbook

1.Open video - 

First open a video which you like to download. 

GIF

We show many times in some of social networking sites mainly in Face book that one picture where in center it is written GIF in middle of picture like below :

its full name is Graphic Interchange Format (GIF)
The main question is how to make it :


We can make GIF online and offline .

Online process is very easy , there are so many websites available like

make gif

gif creator.


ezgif.com

these are some of them and so other many are available .
 In such websites you have to just upload photos and resize them make in sequence as you needed and then create it . you can directly share it on any of social networking sites if you wishes.


Offline process is also good one .

But  you needed to download software for it .

1. using video converter tool


2. Easy GIF maker

3.Giffing Tool



By using this tools and websites you can make your own GIF .

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RRB announce vacancies for  following posts for more than 18000 posts across India.

Filling up online form start on  26/12/2015 to 25/01/2016 only through below link

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3. Enquiry cum reservation clerk (ECRC) -127 Posts
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6. Senior clerk cum typist (SCT) - 869 Posts
7. Assistance Station Master (ASM) - 5942 Posts 
8. Traffic Assistance (TA) - 166 Posts
9. Senior Time Keeper (STK)- 04 Posts

Education details - Any graduates can apply .(T&C apply)

Exam details:

• Exam is objective paper 
• 100 Questions 
• 90 minutes
• 1/3 negative marks

General Knowledge

• Current Affairs  india and international 
• World general science 
• Indian economy 
• Indian culture
• Science technology

Arithmetic Ability 

• Percentage
• Time & Work
• Boats & Steams
• Time & Distance
• Interest 
• Profit & Loss
• Averages
• Problems on Age

General Intelligence 

• Analogies
• Similarities 
• Problem solving
• Relationship concepts
• Decision making
• Judgement 
• Visual memory discrimination 

General Science 

• Physics
• Environmental Studies
• Chemistry
• Biology

LiFi technology

What is LiFi ?

LiFi is a wireless optical networking technology that uses light emitting diodes (LEDs) for data  transmission.

LiFi is designed to use LED light bulbs similar to those currently in use in many energy conscious homes and offices. However , LiFi bulbs are outfitted with chip that modulates the light imperceptibly for optical data transmission . LiFi data is transmitted by the LED bulbs and received by photoreceptors.


LiFi early developmental models were capable of 150 Mbps. Some commercial kits enabling that speed have been released . In the lab with stronger LEDs and different technology , researchers have enabled 10 gigabits per second which is faster than 802.11ad.

Base of Digital electronics

1. AND Gate


2. OR Gate


3. NOT Gate


4. NAND Gate


5 NOR Gate


6. EX-OR Gate


7. EX-NOR Gate

EX-NOR Gate

The Exclusive NOR Gate function is a digital logic gate that is the reverse or complementary form of the EX-OR function. Basically the EX-NOR is a combination of EX-OR Gate and NOT Gate but has a truth table similar to the standard NOR Gate in that it has an output that is normally at logic level "1" and goes LOW to logic level "0"  when any of its inputs are at logic level "1".

Above is how EX-OR Gate  form using other Gates .

EX-OR Gate

There are two other types of digital logic gates which although they are not a basic gate in their own right as they are constructed by combining together other logic gates, their output boolean function is important enough to be considered as complete logic gates. These two logic gates called Exclusive-OR (EX-OR) Gate and its complement the Exclusive NOR Gate.

Above shows EX-OR Gate and its truth table.

By using basic gates and Universal gate we make EX OR Gate

OR Gate

In this gate any of the input is 1 so output is 1. This is basic function of this gate. Basically it will add all the input and gives output. figure below is 2 input OR gate.

Truth table of 2 input OR gate

Basically how it will work like a parallel circuit

NOT Gate

This gate is basically a inverse gate . It have only one input and one output. It just inverse the input
Given below symbol and truth table.

Transistor circuit of NOT gate.

IN this circuit NOT gate in IC . generally 6 gates are included in one IC, it is more than AND & OR gate because it has only one input and one output.





Other Gates
AND Gate

OR Gate

NAND Gate

NOR Gate

AND Gate

1. AND Gate

Symbol of AND gate

Above the basic operation for 2 input AND gate.(multiply system)

If both  A &  B are true than answer will be TRUE 

Above is the 2 and 3 input AND gate.

NOR Gate

The logic NOR gate is a combination of the digital logic OR gate with that of an inverter NOT gate connected togather in series.

" If both A & B are Not true , than Q is true."

NAND Gate

The NAND function is a combination of two separate gates  function AND & NOT .
NAND function is a series combination of series AND gate and NOT gate.
The logic function of NAND gate in Boolean algebra is   A.B.

Above figure is for symbol of NAND gate.

Above figure is how we get output of NAND gate .

Truth table for NAND Gate.

Other  Gates

AND Gate

OR Gate

NOT Gate

NOR Gate

Automatic night light using 555 timer

Description 
A cheap and simple  automatic night light using few transistors and NE555 timer is shown here . The circuit will automatically switch on the AC lamp when night falls and the lamp will automatically switched off after a preset time.


The working of this night light circuit very simple. An LDR is used as the sensor here. At day time the resistance of the LDR will be low and so do the voltage drop across it, the transistor Q1 will be in conducting mode . When darkness falls the resistance of LDR increases and so do the voltage across it. This makes the transistor Q1 OFF.  Base of Q2 is connected to the emitter of Q1 and so Q2 is biased on which in turn power IC1.



NE 555 is wired as monostable multivibrator that is automatically triggered at power ON . This automatically triggering is achieved with the help of capacitor C2. The  output of IC1 remains high for   a time determined by resistor R5 and capacitor C4 . When output of IC1 goes high transistor Q3 is switched ON which triggers triac T1 and the lamp glows . A 9V battery is included in the circuit in the order to power the timer circuit during power failures . Resistor R1 and diode D1 , capacitor C1 and Zener D3 forms the power supply section of the circuit . R7 and R8 are current limiting resistors.



Notes:

• The circuit can be assembled on a very board.
• Preset R2 can used to adjust sensitivity of the circuit.
• Preset R5 can be used to adjust the ON time of the lamp.
• The wattage of L1 must nor exceed 200W
• Heat sink is recommended for BT136.

for more information about 555 timer IC

more information about 555 IC

Silicon Controlled Rectifier

What is SCR ?

It is Silicon Controlled Rectifier , use in power electronic device. It use as a switching devices in many high voltages area and high temperature .

figure shows physical diagram and symbol of SCR.
SCR is well known member of thyristor family, although there are many different members are available in thyristor family but SCR are so widely used that as if thyristor and SCR become synonymous.


If we see from the constructional and operation point of view , it is a four layer (PNPN) three terminals (anode,cathode, gate) semiconductor device. This device has two states ON and OFF. We can turn it ON by sending gate current signal between second P layer and cathode. But we cannot turn OFF by control signal. That means we have control upon its turn ON, once it goes to conduction mode , we lose control over it.

It can block both forward and reverse voltage but can conduct only in one direction.It use in high power application like AC -DC converter etc.

SCR V-I Characteristic 

Images electronics figure, circuit diagram chart

Mobile  to Smart phone of popular companies 

Apple

Samsung

Nokia

Lumia series 

old nokia

TV from 1970 to 2015

In 1970

In 1980

In 1990

In 2001

In 2005