Showing posts with label works. Show all posts
Showing posts with label works. Show all posts
Monday, March 27, 2017
How Google Drive Works
How Google Drive Works
Google drive is a place where you can share your files and folders with yourself or public . It lets you to store your cool stuff online , and access that content from any part of the world. Now say bye to uploading email attachments and share all files at once with your friends by uploading it to Google drive. Generally , Google Drive offers up to 5 GB storage capacity and beyond that storage capacity they charge you a genuine price.
So simply share whatever you want , if you dont have a Google drive for your PC simply get it by Signing In to your Google account & visiting this link
https://drive.google.com
Google drive provides a powerful cloud storage online & has various advantages
- Free Cloud Storage Upto 5GB .
- Share files with your friends with a single click .
- Create spreadsheets, documents & share with people that you want.
- More Secure - Just hide your cool stuff from the unwanted people.
- Share the files right from your desktop.
Operating System Supported:
There are many operating system that works as a charm with google drive.
Windows : Windows 95/98/XP/NT/2000/7/8
Linux : Ubuntu , Fedora , Debian etc.
Macintosh : Mountain Loin , Snow Leopard etc.
How It Works ?
Now before starting , lets have a brief introduction to Google drive . Lets see the full exploration of Google drive.
Now before starting , lets have a brief introduction to Google drive . Lets see the full exploration of Google drive.
Simply , Google drive works on the concept of cloud computing which follows pay as you go procedure but it offers free storage up to 5 GB.
Now when you upload specific file on the Google drive right from your desktop with internet connection , it tries to maintain a synchronization with the drive by examining "Is any new files and folders are available on your google drive ".Once sync is maintained , the file will get uploaded to your account. Now Its depends upon you what you want.
a.) File or folder with yourself only.
b.) File or folder with friends.
c.) File or folder with everyone (Public).
If you are accessing google drive without internet connection , then that very particular file or folder get uploaded to your drive but visible on your desktop only , whenever a necessary internet connection is made available then your stuff ( Files or folders ) got uploaded to your online google drive account.
Google drive always keep in touch with your computer by ensuring that files and folders available on the drive is up to date.
If you have any further suggestions or queries , leave a comment below !
a.) File or folder with yourself only.
b.) File or folder with friends.
c.) File or folder with everyone (Public).
If you are accessing google drive without internet connection , then that very particular file or folder get uploaded to your drive but visible on your desktop only , whenever a necessary internet connection is made available then your stuff ( Files or folders ) got uploaded to your online google drive account.
Google drive always keep in touch with your computer by ensuring that files and folders available on the drive is up to date.
If you have any further suggestions or queries , leave a comment below !
Available link for download
Sunday, January 29, 2017
What is 555 Timer How it Works
What is 555 Timer How it Works
555 Timer
Timers
Timers are those circuits, which provide periodic signals to a digital system which change the state of that system. In other words, those circuits, which work on the base of multivibrator changes or a device, which can be used as multivibrator is called Timer. (We will discuss Multivibrator in detail in next coming posts)
555 Timer
555 Timer is a digital monolithic integrated circuit which may be used as a clock generator. In other words, 555 Timer is a circuit which may be connected as a stable or monostable multivibrator.
555 Timer is a versatile and most usable device in the electronics circuits and designs which work for both stable and monostable states. It may provide time delay from microseconds up to many hours.
Below is the pin diagram of DIP (Dual inline Package) 555 timer with 8 pins.
555 timer is a very cheap IC which works for wide range of potential difference (typically, from 4.5 to 15V DC) and the different provided input voltages do not affect the timer output.
555 Timer is a linear device and it can be directly connected to the CMOS or TTL (Transistor – Transistor Logic) digital circuits due to its compatibility but, interfacing is must to use 555 timer with other digital circuits.
555 Timer Construction
There are lots of manufacturers who manufacture 555 timer which included the number 555 e.g. NE555, CA555, SE555, MC14 555 etc. typically, two 555 timers sandwiched inside a single chip which is called 556. Nowadays, chips are available with four 555 timers in it. These devices are available in circular IC with eight (8), DIP (Dual inline Package) with 8 pins or DIP with 14 pins.
Here is the simple explanation of the 8 pins of 555 Timer.
1. Ground (GND)
It’s the common ground point of the circuit. The ground terminal of external circuit as well as power supply (Vcc) ground terminal is connected with this i.e. GND (Ground) terminal of 555 timer.
2. Trigger
When Trigger terminal gets one –third (1/3) of the supply voltage i.e. Vcc/3 equal amplitude’s negative trigger pulse, then the circuit output changes form Low to High.
3. Output
This terminal is used for getting output and connected with load. At any instant, its value is low or high.
4. Reset
Without taking into account the previous state of output, by providing a trigger pulse to this terminal resets the device. I.e. Its output becomes low.
5. Control Voltage
There are two third positive voltages of the total Supply voltages (Vcc) at control voltage terminal. Thus, it becomes a part of the comparator circuit. Generally, a capacitor is connected between ground and voltage control terminals.
6. Threshold Voltage
Threshold voltage and control voltage is the two inputs of comparator circuit. The circuit compares the available voltage at threshold voltage terminal to the available reference voltage at control terminal.
If the available voltage at threshold terminal (Pin 6) is greater than the control voltage i.e. two-third of Vcc, then the output would be low, otherwise, it would be high.
7. Discharge
When output is low, then Discharge terminal provides a low resistance discharge path to the externally connected capacitor. However, it acts an open circuit, when output is high.
8. +Vcc (Supply Voltage Terminal)
Supply voltage is provided at this terminal for timer operation.
A simple 555 timer circuit is shown below in fig _ which shows the internal construction of 555 timer. According to the fig, the timer contains on two comparators, an RS flip flop, an Output stitch (output buffer) and a Discharge Transistor Q1.
In addition, there are three 5k? resistors are connected in series with 5k? resistor which first end is connected with Vcc (Pin 8 = Supply voltage) and the other end is connected with ground (GND = Pin 1).
Good to Know: due to the three 5k? series connected resistors, this IC timer chip is called 555 Timer J.
Working Principle of 555 Timer
In the 555 Timer block or functional diagram, comparators are those devices which output is high, when their positive input voltage is greater than their negative input voltage and vise versa.
The voltage divider in the circuit (which contains on three series connected 5k? resistors), which provides the trigger level of one-third of Vcc (Vcc/3) and two-third (2/3) of threshold voltage. To understand this point, suppose the input value is 15V. In this case, the value of trigger level would be 5V as (Vcc/3 = 15V/3 = 5V). And the value of threshold level would be 10V as (Vcc x 2/3 = 15V x (2/3)) = 10V.
When needed, the trigger level and threshold can be adjusted by using the Control Voltage terminal (Pin 5) i.e. by changing the control voltage at Pin 5, we may change the trigger level and threshold voltage according to the required specification. However, in this case, the value of trigger and threshold would be remain equal to 1/3 Vcc and 2/3 Vcc respectively.
When the normal high trigger input value instantaneously reduce then the 1/3 Vcc, Then the output of Comparator B becomes High from Low, as a result, RS latch or RS Flip flop goes to “set”. When flip flop goes to set, then Output (at Point 3) becomes high. Simultaneously, the discharge transistor Q1 gets off and The output remains high until the value of normally low threshold input does not increase then the 2/3 Vcc.
As soon as the threshold input increase than the 2/3Vcc, then the output of comparator A becomes Low, as a result, RS flip flop get reset (because the output of comparator is directly connected to the RS flip flop’s input R as shown in the fig). When flip flop gets reset, output becomes low and discharge transistor Q1 goes to on.
The flip flop can be reset by applying external input reset without threshold circuit. Note that, the trigger and threshold inputs (Pin 2 and Pin 6) are controlled by externally components and the 555 timer can be used for Available link for download
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Monday, January 2, 2017
What is TRIAC How it Works
What is TRIAC How it Works
For DC switching circuits this “one-way” switching characteristic may be acceptable as once triggered all the DC power is delivered straight to the load. But in Sinusoidal AC Switching Circuits this unidirectional switching may be a problem as it only conducts during one half of the cycle (like a half-wave rectifier) when the Anode is positive irrespective of whatever the Gate signal is doing. Then for AC operation only half the power is delivered to the load by a thyristor.
In order to obtain full-wave power control we could connect a single thyristor inside a full-wave bridge rectifier which triggers on each positive half-wave, or to connect two thyristors together in inverse parallel (back-to-back) as shown below but this increases both the complexity and number of components used in the switching circuit.
Thyristor Configurations
There is however, another type of semiconductor device called a “Triode AC Switch” or Triac for short which is also a member of the thyristor family that be used as a solid state power switching device but more importantly it is a “bidirectional” device. In other words, a Triac can be triggered into conduction by both positive and negative voltages applied to its Anode and with both positive and negative trigger pulses applied to its Gate terminal making it a two-quadrant switching Gate controlled device.
A Triac behaves just like two conventional thyristors connected together in inverse parallel (back-to-back) with respect to each other and because of this arrangement the two thyristors share a common Gate terminal all within a single three-terminal package.
Since a triac conducts in both directions of a sinusoidal waveform, the concept of an Anode terminal and a Cathode terminal used to identify the main power terminals of a thyristor are replaced with identifications of: MT1, for Main Terminal 1 and MT2 for Main Terminal 2 with the Gate terminal G referenced the same.
In most AC switching applications, the triac gate terminal is associated with the MT1 terminal, similar to the gate-cathode relationship of the thyristor or the base-emitter relationship of the transistor. The construction, P-N doping and schematic symbol used to represent a Triac is given below.
Triac Symbol and Construction
We now know that a “triac” is a 4-layer, PNPN in the positive direction and a NPNP in the negative direction, three-terminal bidirectional device that blocks current in its “OFF” state acting like an open-circuit switch, but unlike a conventional thyristor, the triac can conduct current in either direction when triggered by a single gate pulse. Then a triac has four possible triggering modes of operation as follows.
- ? + Mode = MT2 current positive (+ve), Gate current positive (+ve)
- ? – Mode = MT2 current positive (+ve), Gate current negative (-ve)
- ??? + Mode = MT2 current negative (-ve), Gate current positive (+ve)
- ??? – Mode = MT2 current negative (-ve), Gate current negative (-ve)
And these four modes in which a triac can be operated are shown using the triacs I-V characteristics curves.
Triac I-V Characteristics Curves
In Quadrant ?, the triac is usually triggered into conduction by a positive gate current, labelled above as mode ?+. But it can also be triggered by a negative gate current, mode ?–. Similarly, in Quadrant ???, triggering with a negative gate current, –?G is also common, mode ???– along with mode ???+. Modes ?– and ???+ are, however, less sensitive configurations requiring a greater gate current to cause triggering than the more common triac triggering modes of ?+ and ???–.
Also, just like silicon controlled rectifiers (SCR’s), triac’s also require a minimum holding current IH to maintain conduction at the waveforms cross over point. Then even though the two thyristors are combined into one single triac device, they still exhibit individual electrical characteristics such as different breakdown voltages, holding currents and trigger voltage levels exactly the same as we would expect from a single SCR device.
Triac Applications
The Triac is most commonly used semiconductor device for switching and power control of AC systems as the triac can be switched “ON” by either a positive or negative Gate pulse, regardless of the polarity of the AC supply at that time. This makes the triac ideal to control a lamp or AC motor load with a very basic triac switching circuit given below.
Triac Switching Circuit
The circuit above shows a simple DC triggered triac power switching circuit. With switch SW1 open, no current flows into the Gate of the triac and the lamp is therefore “OFF”. When SW1 is closed, Gate current is applied to the triac from the battery supply VG via resistor R and the triac is driven into full conduction acting like a closed switch and full power is drawn by the lamp from the sinusoidal supply.
As the battery supplies a positive Gate current to the triac whenever switch SW1 is closed, the triac is therefore continually gated in modes ?+ and ???+ regardless of the polarity of terminal MT2.
Of course, the problem with this simple triac switching circuit is that we would require an additional positive or negative Gate supply to trigger the triac into conduction. But we can also trigger the triac using the actual AC supply voltage itself as the gate triggering voltage. Consider the circuit below.
Triac Switching Circuit
The circuit shows a triac used as a simple static AC power switch providing an “ON”-“OFF” function similar in operation to the previous DC circuit. When switch SW1 is open, the triac acts as an open switch and the lamp passes zero current. When SW1 is closed the triac is gated “ON” via current limiting resistor R and self-latches shortly after the start of each half-cycle, thus switching full power to the lamp load.
As the supply is sinusoidal AC, the triac automatically unlatches at the end of each AC half-cycle as the instantaneous supply voltage and thus the load current briefly falls to zero but re-latches again using the opposite thyristor half on the next half cycle as long as the switch remains closed. This type of switching control is generally called full-wave control due to the fact that both halves of the sine wave are being controlled.
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Tuesday, November 15, 2016
What is IGBT How it Works
What is IGBT How it Works
Insulated Gate Bipolar Transistor
The Insulated Gate Bipolar Transistor also called an IGBT for short, is something of a cross between a conventional Bipolar Junction Transistor, (BJT) and a Field Effect Transistor, (MOSFET) making it ideal as a semiconductor switching device.
The IGBT transistor takes the best parts of these two types of transistors, the high input impedance and high switching speeds of a MOSFET with the low saturation voltage of a bipolar transistor, and combines them together to produce another type of transistor switching device that is capable of handling large collector-emitter currents with virtually zero gate current drive.
Typical IGBT
The Insulated Gate Bipolar Transistor, (IGBT) uses the insulated gate (hence the first part of its name) technology of the MOSFET with the output performance characteristics of a conventional bipolar transistor, (hence the second part of its name). The result of this hybrid combination is that the “IGBT Transistor” has the output switching and conduction characteristics of a bipolar transistor but is voltage-controlled like a MOSFET.
IGBTs are mainly used in power electronics applications, such as inverters, converters and power supplies, were the demands of the solid state switching device are not fully met by power bipolars and power MOSFETs. High-current and high-voltage bipolars are available, but their switching speeds are slow, while power MOSFETs may have high switching speeds, but high-voltage and high-current devices are expensive and hard to achieve.
The advantage gained by the insulated gate bipolar transistor device over a BJT or MOSFET is that it offers greater power gain than the bipolar type together with the higher voltage operation and lower input losses of the MOSFET. In effect it is an FET integrated with a bipolar transistor in a form of Darlington configuration as shown.
Insulated Gate Bipolar Transistor
We can see that the insulated gate bipolar transistor is a three terminal, transconductance device that combines an insulated gate N-channel MOSFET input with a PNP bipolar transistor output connected in a type of Darlington configuration. As a result the terminals are labelled as: Collector,Emitter and Gate. Two of its terminals (C-E) are associated with a conductance path and the third terminal (G) associated with its control.
The amount of amplification achieved by the insulated gate bipolar transistor is a ratio between its output signal and its input signal. For a conventional bipolar junction transistor, (BJT) the amount of gain is approximately equal to the ratio of the output current to the input current, called Beta.
For a metal oxide semiconductor field effect transistor or MOSFET, there is no input current as the gate is isolated from the main current carrying channel. Therefore, an FET’s gain is equal to the ratio of output current change to input voltage change, making it a transconductance device and this is also true of the IGBT. Then we can treat the IGBT as a power BJT whose base current is provided by a MOSFET.
The Insulated Gate Bipolar Transistor can be used in small signal amplifier circuits in much the same way as the BJT or MOSFET type transistors. But as the IGBT combines the low conduction loss of a BJT with the high switching speed of a power MOSFET an optimal solid state switch exists which is ideal for use in power electronics applications.
Also, the IGBT has a much lower “on-state” resistance, RON than an equivalent MOSFET. This means that the I2R drop across the bipolar output structure for a given switching current is much lower. The forward blocking operation of the IGBT transistor is identical to a power MOSFET.
When used as static controlled switch, the insulated gate bipolar transistor has voltage and current ratings similar to that of the bipolar transistor. However, the presence of an isolated gate in an IGBT makes it a lot simpler to drive than the BJT as much less drive power is needed.
An insulated gate bipolar transistor is simply turned “ON” or “OFF” by activating and deactivating its Gate terminal. A constant positive voltage input signal across the Gate and the Emitter will keep the device in its “ON” state, while removal of the input signal will cause it to turn “OFF” in much the same way as a bipolar transistor or MOSFET.
IGBT Characteristics
Because the IGBT is a voltage-controlled device, it only requires a small voltage on the Gate to maintain conduction through the device unlike BJT’s which require that the Base current is continuously supplied in a sufficient enough quantity to maintain saturation.
Also the IGBT is a unidirectional device, meaning it can only switch current in the “forward direction”, that is from Collector to Emitter unlike MOSFET’s which have bi-directional current switching capabilities (controlled in the forward direction and uncontrolled in the reverse direction).
The principal of operation and Gate drive circuits for the insulated gate bipolar transistor are very similar to that of the N-channel power MOSFET. The basic difference is that the resistance offered by the main conducting channel when current flows through the device in its “ON” state is very much smaller in the IGBT. Because of this, the current ratings are much higher when compared with an equivalent power MOSFET.
The main advantages of using the Insulated Gate Bipolar Transistor over other types of transistor devices are its high voltage capability, low ON-resistance, ease of drive, relatively fast switching speeds and combined with zero gate drive current makes it a good choice for moderate speed, high voltage applications such as in pulse-width modulated (PWM), variable speed control, switch-mode power supplies or solar powered DC-AC inverter and frequency converter applications operating in the hundreds of kilohertz range.
A general comparison between BJT’s, MOSFET’s and IGBT’s is given in the following table.
IGBT Comparison Table
| Device Characteristic | Power Bipolar | Power MOSFET | IGBT |
| Voltage Rating | High <1kV | High <1kV | Very High >1kV |
| Current Rating | High <500A | Low <200A | High >500A |
| Input Drive | Current 20-200 hFE | Voltage VGS 3-10V | Voltage VGE 4-8V |
| Input Impedance | Low | High | High |
| Output Impedance | Low | Medium | Low |
| Switching Speed | Slow (uS) | Fast (nS) | Medium |
| Cost | Low | Medium | High |
We have seen that the Insulated Gate Bipolar Transistor is semiconductor switching device that has the output characteristics of a bipolar junction transistor, BJT, but is controlled like a metal oxide field effect transistor, MOSFET.
One of the main advantages of the IGBT transistor is the simplicity by which it can be driven ON or OFF or in its linear active region as a power amplifier. With its lower on-state conduction losses and its ability to switch high voltages without damage makes this transistor ideal for driving inductive loads such as coil windings, electromagnets and DC motors.
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