VGA Connector

VGA connectors are sub miniature D type graphic connectors which are primarily used for connecting CPUs to monitors. The shape of the metal shield of these connectors resembles a “D”, hence the name “D” type connectors.

Since their invention in the year 1987, these graphic connectors have come a long way. From interfacing desktop computers to light weight tablet computers, VGA connectors serve as one of the most inexpensive video interfaces for smart computing devices. It is quite interesting to note that even though these connectors were developed by IBM PC, it was their counter rivals Apple Inc. who preferred these connectors for iPad. An interesting history with a mass applicative scenario, VGA connectors get demystified in this Insight.

                                                                                Image 01: Pin-outs

Pin Outs: A 15 pin VGA connector is seen in Image 01 above. The pins, in three rows of five as shown in the image, are placed in a plastic molding which is surrounded by a metal casing.

The pin-outs are:

                                                              Image 02: Output Pins

Output Pins: Corresponding to the 15 pins that interface with the device are the pins on the opposite side that are soldered to wire.

                                                           Image 03: Plastic Moldings

Plastic MoIdings: In Image 03, the metal casing is opened to show the placement of pins in the plastic molding.
                                                                      Image 04: VGA Connector Pins

VGA Connector Pins: Pins of the connector are not sturdy enough and get bent on application of slightest force. This is why they are sheathed by a protective metal casing. Once the casing is removed, the pins are plucked out from the plastic moldings.

                                                                       Image 05: Pin Structure
Pin Structure: Image 05 provides a clear picture of the structure of the pin. The e

Pin	Name	Type	Description
1	RED	Output	Red Video (75 ohm, 0.7 V p-p)
2	GREEN	Output	Green Video (75 ohm, 0.7 V p-p)
3	BLUE	Output	Blue Video (75 ohm, 0.7 V p-p)
4	ID2	Input	Monitor ID Bit 2
5	GND	-	Ground
6	RGND	-	Red Ground
7	GGND	-	Green Ground
8	BGND	-	Blue Ground
9	KEY	-	Key (No pin)
10	SGND	-	Sync Ground
11	ID0	Input	Monitor ID Bit 0 GND=Color; NC=Mono
12	ID1 or SDA	Input	Monitor ID Bit 1 NC=Color; GND=Mono Some systems only uses ID0 for monitor ID
13	HSYNC or CSYNC	Output	Horizontal Sync (or Composite Sync)
14	VSYNC	Output	Vertical Sync
15	ID3 or SCL	Input	Monitor ID Bit 3

How to create your own calculator using DOS commands

 

Batch files are text files that contain a sequence of commands generally used in system command prompt to perform various computer operations like starting programs or running system utilities, etc. In DOS and Windows, batch files are intended to be executed by the command interpreter. There are numerous computer operations that can be performed by using these .bat files. Through this short article we will know how we can create our own calculator by writing a few commands.

Open a notepad (or any other text editor) file and paste the following code in it:

@ECHO OFF
color 2a
title My Calculator
pause
ECHO ---------------------------------------- -------
ECHO * = MULTIPLY
ECHO + = ADD
ECHO - = SUBTRACT
ECHO / =DIVIDE
ECHO ---------------------------------------- -------
pause

:loop
echo.
echo ---------------------------------------- -------
SET /p UDefine=
SET /a UDefine=%UDefine%
ECHO =
ECHO %UDefine%
ECHO.
goto loop

 

Save the notepad file with a name say “calc.bat” where .bat is extension for batch files. Now click on the batch file icon and there opens your own calculator in command prompt window. You can also create an .exe file as well. Download a .bat to .exe converter to do this; one can be found here - http://www.f2ko.de/programs.php?lang=en&pid=b2e

 

How Gas Sensor Works

How Gas Sensor Works

In current technology scenario, monitoring of gases produced is very important. From home appliances such as air conditioners to electric chimneys and safety systems at industries monitoring of gases is very crucial. Gas sensors are very important part of such systems.  Small like a nose, gas sensors spontaneously react to the gas present, thus keeping the system updated about any alterations that occur in the concentration of molecules at gaseous state.   

Gas sensors are available in wide specifications depending on the sensitivity levels, type of gas to be sensed, physical dimensions and numerous other factors. This Insight covers a methane gas sensor that can sense gases such as ammonia which might get produced from methane. When a gas interacts with this sensor, it is first ionized into its constituents and is then adsorbed by the sensing element. This adsorption creates a potential difference on the element which is conveyed to the processor unit through output pins in form of current. What is this sensing element? Is it kept in some chamber or is kept exposed? How does it get current and how it is taken out? Let’s find out in this Insight!!!

The sensor module consists of a steel exoskeleton under which a sensing element is housed. This sensing element is subjected to current through connecting leads. This current is known as heating current through it, the gases coming close to the sensing element get ionized and are absorbed by the sensing element. This changes the resistance of the sensing element which alters the value of the current going out of it.

Image01

Image 01 shows externals of a standard gas sensor module: a steel mesh, copper clamping ring and connecting leads. The top part is a stainless steel mesh which takes care of the following:

1 Filtering out the suspended particles so that only gaseous elements are able to pass to insides of the sensor.  

2 Protecting the insides of the sensor.

3 Exhibits an anti explosion network that keeps the sensor module intact at high temperatures and gas pressures.In order to manage above listed functions efficiently, the steel mesh is made into two layers. The mesh is bound to rest of the body via a copper plated clamping ring.

Image2

The connecting leads of the sensor are thick so that sensor can be connected firmly to the circuit and sufficient amount of heat gets conducted to the inside part. They are casted from copper and have tin plating over them. Four of the six leads (A, B, C, D) are for signal fetching while two (1,2) are used to provide sufficient heat to the sensing element.

The pins are placed on a Bakelite base which is a good insulator and provides firm gripping to the connecting leads of the sensor. 

Image3

The top of the sensor is removed off to see the internals parts of the sensor: sensing element and connection wiring. The hexapod structure is constituted by the sensing element and six connecting legs that extend beyond the Bakelite base.

Image4

Image4 shows the hollow sensing element which is made up from Aluminum Oxide based ceramic and has a coating of tin oxide. Using a ceramic substrate increases the heating efficiency and tin oxide, being sensitive towards adsorbing desired gas’ components (in this case methane and its products) suffices as sensing coating.

The leads responsible for heating the sensing element are connected through Nickel-Chromium, well known conductive alloy. Leads responsible for output signals are connected using platinum wires which convey small changes in the current that passes through the sensing element.  The platinum wires are connected to the body of the sensing element while Nickel-Chromium wires pass through its hollow structure.

Image5

While other wires are attached to the outer body of the element, Nickel-Chromium wires are placed inside the element in a spring shaped. Image 5 shows coiled part of the wire which is placed on the inside of the hollow ceramic.

 Image6

Image06 shows the ceramic with tin dioxide on the top coating that has good adsorbing property. Any gas to be monitored has specific temperature at which it ionizes. The task of the sensor is to work at the desired temperature so that gas molecules get ionized. Through Nickel-chromium wire, the ceramic region of the sensing element is subjected to heating current. The heat is radiated by the element in the nearby region where gases interact with it and get ionized. Once, ionized, they are absorbed by the tin dioxide. Adsorbed molecules change the resistance of the tin dioxide layer. This changes the current flowing through the sensing element and is conveyed through the output leads to the unit that controls the working of the sensor.

How Network Resistor (Pull up resistor ) Works

How Network Resistor Works

https://docs.google.com/file/d/0B9dFd9Q1TrK3UWpFbmwtNnRnV2s/edit?usp=sharing 

How Adaptor Works

 How Adaptor Works 


https://docs.google.com/file/d/0B9dFd9Q1TrK3dHVBVUVoUkhGZ1U/edit?usp=sharing 

Insight - How LED Light Bulb works

LED bulbs are the future of lighting. Be it automobiles, industries, household or any hobbyist requirement, LEDs form the best solutions in terms of long-term cost savings and power efficiency. Not only are these devices more efficient than traditional lighting devices, they are built to outlast any of their lighting predecessor. Click to know more about LED lighting. The internals of a typical LED bulb will be explored here.

Externally, a LED bulb might look similar to a conventional incandescent lamp, but the two are quite different. The chassis of the bulb is made of ceramic and houses the electronic ballast. Ceramic is used for its insulating and heat dissipative properties. The LED bulb is housed inside a phosphor coated glass dome. In order to provide output over a constant wavelength and enhance Light output, LED lamps use Remote Phosphor (RP) Technology for coating purposes. This also enables the LED to emit only a single colored light throughout its lifetime while also reducing glare at the same time.

 

he LED structures become visible once the glass is removed.  LED lights are placed in a COB (CHIP ON BOARD) LED structure. This structure is covered by a plastic disc which once removed, reveals the COB LED Structure as shown in the image above.

The LEDs are mounted on a disc shaped Aluminum substrate that functions as a heat sink for the LEDs. The size of the substrate is kept quite large as compared to the size of the LEDs, as high amount of heat has to be dissipated when the bulb is in operation

These Light Emitting Diodes are made from suitable extrinsic semiconductor materials like Gallium Arsenide or Gallium Arsenide Phosphate. Bulbs made of these diodes consume very less energy and have a longer life than a conventional bulb or a CFL.

The LED structure is covered in a dome shaped silicone or epoxy resin layer. This dome or bubble defines the light distribution angle of the LED, which may vary from a narrow beam to a wide angle. Inside the epoxy, LED semiconductor is in form of a die placed on thermally conductive adhesive.  It is connected to the thermal pad through gold or platinum bond wires whose thickness is in the order of micrometers. These elements are excellent heat conductors and will efficiently help dissipate all the heat generated during LED operation.  There can be multiple dies in a single dome too. In this case there are two domed structures housing individual LEDs. The use of COB LEDs technology, and Gold (Au) and/or Platinum (Pt) bonding wires is the main reason behind the relatively higher cost of LEDs as compared to their other lighting counterparts such as CFL and the incandescent bulb.

The wires on the periphery of the Aluminum disc are connected to the internal circuitry.

 

  

 

Lateral view of the LED bulb reveals the insulation layer which separates the LED from rest of the circuitry. Also, adhesives that hold the aluminum substrate to the ceramic chassis are visible.

The internal circuitry is mounted on a double side printed PCB housed in the rear part of the chassis.

 

 

The images above show both sides of the electronic ballast driver circuit used inside the LED bulb. The use of electronic ballast makes the structure light and power efficient. The electronic ballast driver circuit is a constant current provider that operates at high frequencies and provides current limiting functionality to protect the LEDs.  Moreover, this ballast is very stable at high temperatures and can work for longer durations.

The bottom metallic cap of the LED can either be a Bayonet base or Edison base.  Image below shows the internal structure of the Edison base. The red wire connects the power source to the electronic ballast, while the black one provides the grounding.

LEDs are commercially available in both types of the bases so that they can be readily plugged into the holder as replacement to the lesser efficient la

 

 

 

SMPS Working-------------Inside View

SMPS Working-------------Inside View

A computer is an assembly of several essential and optional electronic parts such CD drive, motherboard, hard disk etc. . Every peripheral has its own power requirement and to serve the same regulated power supplies such as linear power supplies, ferro resonant power supplies and switched mode power supplies, are used.

Switched mode power supplies are unanimously preferred as computer power supply units for their small size and high efficiency.  SMPS units dissipate less power by employing a transformer that regulates input voltage and provides constant current to the peripherals attached to the computer.

The input voltage is chopped to different levels or is switched through different levels using a chopping process. This is done at very high frequency which enhances the efficiency of the circuit.  A normal linear voltage supply can works at 30% efficiency, while an SMPS based power supply unit can provide 70-80% of efficiency. Also, using a high switching frequency usage makes the process quicker. An SMPS also has the features of being light-weight and economical as comparedto other power supplies. Also, the circuit topology of it can be varied depending upon the power requirements of the device to which it is attached.

Introduced in 1960s with the Apple-II, SMPS are a light weight, economic and power efficient solution in regulating power supply to a computer. This insight will detail with the internal parts, their working and wiring of SMPS.

Various types of SMPS architectures are popular on the basis of their power handling capacities and applications. The one used in computer is push-pull type which can handle input voltage of more than 200V.

The image above shows a conventional 450W computer SMPS. From the outer casing, the SMPS fan and the power input plug can be seen. The purpose of installing a fan is to remove the heat produced by the SMPS. The outer casing is made from light weight metal casing, usually aluminum, so as to protect the internal structure. The casing is made by screwing upper and lower section and has segments cut to allow heat dissipation during the time a computer is in use.

 

The image shows a grilled metal casing which provides better ventilation to the heat generated in the power supply unit.

As the power supply unit is responsible to fulfill electrical requirements of multiple devices, an SMPS can have various types of connectors. Depending on the connections, there can be AT (Advanced Technology) and ATX (Advanced Technology extended) power supplies. The one shown in the images is an ATX one.  In ATX power supplies, user can switch on and off the peripheral through software commands that are conveyed to the device by motherboard. On the other hand, in AT supplies, the user has to manually switch on and off the peripherals.

Wiring in both types of power supply units is also quite different as ATX doesn’t has a -5V biasing voltage but features efficient remote sensing 3.3V voltage and a few more connector wires which have been discussed later in this insight. Various versions of ATX based connectors are also widely popular as there have been phenomenal developments in the hardware of computer system too.

 

On unscrewing the metal casing we can see the PCB which forms the core of the SMPS. From regulating power for all the devices to powering the exhaust fan, PCB manages all the major and minor power needs of the computer. It can be divided into various sections on the basis of the function that each performs.

  

The image above shows the filter, rectifier and heat sink regions of the SMPS. This section gets the input power supply, which is in AC form, converts and rectifies it into DC. A fuse is added to the PCB so that sudden high current impulses don’t harm and the circuit.

The fuse in the SMPS unit aids in forming a crowbar circuit. A crowbar circuit compares the input voltage value to the standard voltage requirements of the respective circuit. If the input values match the output ones, then only it allows it to flow to the circuit (SMPS in this case), otherwise, it stops the power supply. Crowbar circuit makes sure that the components of the circuit don’t get damaged as it is very difficult to remove or repair the components on a PCB.

 

The central section of the SMPS houses an array of transformers which drop down the input voltage to match the requirements of peripherals attached.These transformers are designed to work at high frequencies as the input is a high frequency DC voltage. The transformer cores are made of ferrite and are lighter and small so that they can function at high frequencies.

 In order to accommodate the feature of high frequencies, precautions are taken so as to reduce the electromagnetic interference. Hence, shape and design of the PCB becomes a critical factor too.

Apart from the voltage down transformers, a power MOSFET forms one of the most important parts of the SMPS. This MOSFET works as a switch, taking the unregulated voltage from the voltage down transformers and chopping it down to control the output voltage level.

The control logic to the chopper is sent via a PWM modulation circuitry, which, in this SMPS has been done by IC 2958.It generates a high frequency feedback pulse which is sent to MOSFET so that width of output DC pulses can match the requirement of theperipheral.

It can also be said that IC regulates the duty cycle of the MOSFET switch. Duty cycle can be defined as the ratio time for whichthe MOSFET switch is ON to the total time it is under consideration.

The MOSFET switch works at very high frequency, thus providing highest of efficiency levels to the SMPS.  Compared to the frequency of input AC level of 50 or 60Hz, the MOSFET chops at a rate of 50KHz or more, which is at least 1000times of the input levels. The feature of high efficiency provided by the MOSFET makes SMPS an in-demand regulated power supply. Operation at high frequency increases the noise produced by the whole system.

 

Output power supply voltages

An SMPS delivers medium output voltages such as 3.3V, 5V, 12V and biasing voltages like -12V.

To ease the process of mounting peripherals through combination of different wires, the wiring is followed by a color coding. The standard for color coding in a SMPS is as follows:

·         Orange wire represents  3.3 volt 

·         Yellow wire represents+12 volt 

·         Red wire represents +5 volt 

·         Blue wire represents -12 volt 

·         Black wire denotes ground 

·         Gray wire is a 5V supply that checks whether the peripheral is in working condition or not. It is of foremost importance that this wire signals correct, otherwise the supply to that peripheral would be reset until it receives a genuine signal.

·          Green wire serves for power.

A few connectors that formed by the combination of wires include SATA hard disk connector, DVD drive connector, motherboard connector.

As the hardware configurations of computers are increasing, power supplies are being asked to deliver more and more power. SMPS have now elevated from 450W levels to 650W levels and more. Constant changes in the PCB are taking place in order to reduce the heat produced or exhaust it off. Some SMPS even include a feature for an extra fan.  With usage of better switching circuitry, the EMI reduces and output is more refined.