How to make IP68 enclosures

IP 68 sealing is important for military computers and other units.

The usage of right type of gaskets and sealants are required.

The important aspect is how to water seal the cable glands and connectors.

there are hermitically sea;led connectors available.

How to wire VME backplanes

Rear wiring of VME back plane is a tricky business.

We can use one out of the following:

1. Berg connectors
2. 5 row connectors
3. wire wrap
4. Sandwich PCB with edge connectors.

Any other technique available please let me know.

Avionic racks

How to design a avinic rack?
The main feature required are weight and accoustic proofing.
Can we use 6061 alloy inplace of 2024 alloy?

What are the design creiteria to be adhered?

C4I consoles

How do we design C4I consoles?
C4I stations or commad consoles are a tricky design requirement. Each customer has diffrent view on the platform.
Dual monitor single monitor or even triple monitor.

The I/O devices oalso come with multiple choices.

Mil Std 1472 F is one standard which gives some design inputs.

Fiber Optic Communication

The new trend is to convert the Copper channel to optical links for all the advantages known to the users.
The usage of Fiber links in defense network is catching up across the world. Presently the method is to add converters for each of the links.
Say RS422/232, LAN and other Analog signals.
Analog RF upto 4.2GHz signals also can be easily converted to optical mode easily now.

We can use CWDM method to reduce the cost of the fiber. In a single fiber we can send all these data with wavelength division multiplexing.

The connectors are available in 38999 shells and more reliable ones are expanded beam circular ones.
If any more inputs into this are available please mail me this to sdshenoy@gmail.com

Acoustic proofing

How to reduce the sound noise from an electronic rack?

Will using composite enclosure reduce noise?

CAn we use any sound absorbing pads?

What is the most irritating noise?

Will fans create lot of noise?

What is the effect electronic IC on sound leves?

Military DC DC power supplies

Aerospace and Military power supplies have always been subjected to stringent requirements including transients, spikes, EMI, hold-up, monitoring specifications. As a result majority of power supplies have been designed specifically with discrete components.
Since the beginning of the 90’s with the introduction of the COTS (Commercial Off-The-Shelf) philosophy in US and modular power architecture the use of standard modules has become of more importance to design complex power supplies.
The standard input voltages in Aerospace and Military applications are 24, 28 VDC or 115 VAC within a permanent variation of 16-40 VDC or 70-180 VAC to meet worldwide standards. Drop out down to 0VDC and transients have also to be covered. EMI compliance is of primarly importance and are described in the widely used MIL-STD-461 or DO-160 standard.
To cope with these particular requirements, DC DC Converter proposes typical Off-The-Shelf modular power architecture :
• Qualified front filters to allow compliance with the MIL-STD-461D or DO-160D, ..., EMI requirements
• Essential functions such as drop-out voltage recovery, transient and spike protections as per MIL STD-704A, MIL-STD-1275 or DO-160D are handled by standard "Pre-Regulator" front-end product :
• Power factor corrected 115VAC to 28VDC converters allow easy board intermediate bus configurations.
• Monitoring and hold-up functions are provided by DC DC Converter hold-up module to sustain bus losses together with fault and advisory signals :
• For the heart of the power system, DC DC Converter proposes a complete series of low profile, cost-effective and high performance DC/DC modules that come in multiple combinations of input voltages, output possibilities and power ratings :
Whatever your power system´s need, DC DC Converter has a modular architecture using standard products to provide an instant solution to a wide range of applicationsfrom on-board computers, man-machine interface, communication systems, ...

Display for Military applications

We touch up on the display requirement for the Military vehicles.
Since these are rugged vehicles we need a rugged flat panel display.
The operating and storage temperature, IP rating,Shock and vibration, EMI,humidity and other issues are more important than the display features.
Ther may be requirement for video mixing also.

All these are very much different requirement from the generally available LCD panels.

Baytek,Barco and IRTS are the main manufactureres of flat panel displays for the military field.

C4I - Command Console Designs

C4I consoles for command,communication,control,intellegence plays an important role in the military applications.
There are typically 3 to 4 types of consoles, namely twin displays or single displays. MIL hand book 1472 F gives a good picture of the design features for the console design. Generally consoles will have some 19" rack space at the bottom of the console for the display compute nodes.
The selectio of view angle,accesibilty and easy to operate are the main design criteria we need to take care in a console design.

AluminiumAlloy

The aluminim alloy used for electronics enclosures are as follows:

6061
6082
2024

T4 or T6

VME CARD DETAILS

Three basic VMEbus card [Dimensions] sizes are shown above, which include 9U, 6U, and 3U. Two 6U card sizes are depicted.The VME64 spec added the P0 connector between P1 and P2 on the 6U size card (not shown).IEEE 1101.1 Base Document for Mechanics ~ Defines 3U/6U/9U (high) x 100/160/220/280/340/400mm (Long) cardsIEEE 1101.10 Mechanics for VME Boards and SubracksIEEE 1101.11 Mechanics for Rear Transition ModulesThree card heights are allowed with VME; 3U, 6U, or 9U; a single slot card is 6T wide. Length is either 160mm or 340mm (Norm)Height is given in 'U' [1U = 43.60mm], Length is given in 'mm', Width is given in 'T' or HP [1HP = 5.08mm [HP: Horizontal Pitch];Card sizes listed below are one slot or 6T wideA size CCA dimensions = 3U x 160mm. A 3U Printed Wiring Board [PWB] is 100mm high.B size CCA dimensions = 6U x 160mm. A 6U Printed Wiring Board [PWB] is 233mm high.C size CCA dimensions = 6U x 340mm, ... {H x L x W {@ width=6T}D size CCA dimensions = 9U x 340mm. A 9U Printed Wiring Board [PWB] is 360mm high.A, B, C, and D are VXI terms. VME normally only references 3U or 6U [dimensions] by a length.The board thickness for VME cards is 0.063 +/- 0.008 inchs [1.6mm +/- 0.2mm] Thicker or thinner CCAs may not fit in the card guides correctly.How ever an 0.90 board may work if you mill down the top and bottom [2.5mm] of the card to 0.63 so it fits in the card guides.A, B, C, and D are VXI terms. VME normally only references 3U or 6U by a length, but the 9U was added a few years ago.The VMEbus PWB Dimensions [size] or form factor is also called the Euro-card form factor.
Back to the main VMEbus page for additional details including connector types, bus pin outs, and electronic equipment manufacturers and component manufacturers. OEM VME Card Vendors, and products listing is found on the VME Board manufacturers page. {This Web Site}
The Diagram above provides a number of VMEbus connectors, including 3 x 32 pins 5 rows x 32 pins and a number of P2 Split Pin Coax types.There are a number of different types:P1 and P2 are 96 pin DIN (41612, Type C) 3 rows x 32 pins [Pitch 2.54mm (.100")] @ IEEE 1014-1987P1 and P2 are 160 pin DIN (41612, Type C Expanded) 5 rows x 32 pins [Pitch 2.54mm (.100")] @ ANSI/VITA 1-1994P2 is a Split DIN / RF Coax (DIN 41612 Type M) DIN + Coax @ 78 + 2, 60 + 4, 42 + 6, 24 + 8P0 is a 95 pin 2mm 5 rows x 19 pins (IEC 1076-4-101), PCI Style @ VITA 1.1-1997The class of connectors determines the number of insertions it's designed to handle per DIN 41612 [Mechanical Endurance]. DIN connectors may be purchased in one of three classes:Class 1: 500 mating cyclesClass 2: 400 mating cyclesClass 3: 50 mating cycles

Rugged Cooling fans

If we think of a convection cooled electronic enclosure, be it standatrd 19" rack unit, ATR or desk top version, the cooling fan comes as the most important component.
The generally available fans are:

EBM NADI
PAPST
COMAIR ROTRON
SUNON
STRONGFIELD TECHNOLOGIS
do we have any choice other than this?

compact PCI Power supplies

Most of the Miltary chassis require modular power supplies.
One way of getting this is cPCI power supplies.
Which are available in 3U and 6U sizes.

Thermal Analysis Software tools

Flowtherm and Ice pak are the well known thermal analysis tools.

VME/cPCI boards

The new age military computing nodes are of the following form factor:

VME 64x
VPX
VXS
cPCI
The I/O cards are configured using PMC and IP modules.

The euro pins make these form fits very rugged while operating in harsh environments.

EMI/EMC design

EMI gaskets
Honey comb filters
Power inline filters
Optical conductive filters

MIL-STD-461E

Air Transport Rack - Thermal Design

Case Study: ATR Design Tackles Thermal Hurdles


Tasked to improve upon the power dissipation capabilities of a standard ATR chassis, a design team puts thermal modeling to good use.
In publication since 1974, the ATR ARINC 404A specification spells out a tried and true airborne chassis design. So when the engineers set out to craft a system to meet this specification they didn’t want to re-invent the wheel. Their challenge was to implement an ATR ARINC 404A system with improved resistance to environmental conditions, while still adhering to the strict guidelines of the spec.
With that in mind, the engineers embarked on a conduction-cooled 3/4 ATR (Air Transport Rack) short chassis design that could dissipate enough power at the harsh ambient temperatures of up to 70°C. The other design goals included flexibility for customization of input and I/O connections, switches and monitoring. The 3/4 chassis would also need to suit the needs of not only industry standard VME, but also VME 64X and CompactPCI structures. It was established that the chassis needed to be versatile and adaptable to as many configurations as possible.
Get the Heat Out
The thermal side of the team’s design goal was straightforward: gets as much heat out of the chassis as possible in order to raise the maximum power dissipation at an elevated ambient temperature. The first step was to design a conduction-cooled, high-power, efficient power supply that would have an operational maximum base plate temperature of 85°C. That called for using highly efficient power modules for +5V, +12V, -12V and 3.3V. The supply was designed and built to deliver 500W of total power in the 6U x 0.80 configurations. De-rating the supply to more than half its available power increases its reliability and efficiency. Moreover, the supply was designed to sink all heat losses to the base plate of the case.
Before the chassis design and thermal models were created, the team established a goal of dissipating 135W at 50°C ambient. The design temperature of -55°C to 70°C would cause de-rating above ambient of 50°C. Figure 1 graphs the maximum power supply temps for various power ratings and temperatures. The total surface area of the 3/4 ATR short chassis of 1300 square inches plays a critical role in a cooler design.

Thermal modeling of the chassis played a key role in the design process. Using Fluent’s IcePak software, the design team began to look for ways to increase chassis surface to ambient air interface. IcePak is an object-based thermal
management software tool that handles systems, components, heat sinks and packages. With IcePak software the engineers were able to increase and modify the calculations, until they came up with an optimized fin size and pattern that would cool the chassis. The surface area was increased by the use of multi-fin heat dispersion sidewalls and rear panel.
That approach boosted the chassis’ surface area by 15 percent. The thermal models also showed the engineers some interesting results they’d not expected. The mechanical layout in Figure 2 shows eight standard conduction-cooled slots in a front to rear configuration. That configuration meant that the distribution of heat had to pass through the two card retainer plates.

By modeling the rear card plate to combine with the rear fin plate of the brazed chassis, the designers found a direct air-cooling effect. Further study of the thermal results showed that the heat generated by the cards in slots one and eight was creating intense hot spots in the sidewalls of the ATR in the areas where the card retainers were brazed to the sidewalls.
Heat Transfer Tricks
Taking advantage of cooler areas that were non-heat saturated already proved to be a challenge. The power supply the team had designed was modified by creating a heat-spreading wedge-lock base that takes the heat from the power supply and, instead of directing it to the card edge, transfers it directly to the sidewall (Figure 3). The heat from the power supply transfers to the centrally located non-heat saturated area of the sidewall. The unique reverse direction wedge-lock card guide forces the power supply in the opposite direction from the other cards, engaging its base plate to the sidewall of the ATR chassis.

sidewall and showed a marked decrease in temperature at the all important junctions of the cards to the card guides. The base plate temperature also showed a marked drop, therefore allowing more power dissipation at higher temps.
Table 1 lists “per card” power rating boundary conditions that became the guidelines for the design. As the table shows, the goal ambient temperature of 50ºC and a rated power of 140W corresponds to 20.0 Watts per slot and a heat loss of 35W at the supply board. Again, Figure 1 shows the maximum power supply base plate temperature as the cutoff for maximum power rating for various ambient temperatures. To simplify the process, the lowest ambient tested was 20ºC. Lower temperatures of operation result in much higher power dissipation ratings. That’s based on the ability for cooler ambient air to assist cooling of the fins on the chassis. Reviewing Figure 1 shows that at 20ºC ambient the power supply base temperature will remain below the cutoff of 85°C all the way to 225W.
With the guideline boundary conditions in mind, the power supply can deliver up to 500W. At the extreme limit of 70ºC ambient temperature the supply will deliver near 80W. That’s a reasonable cutoff anyway, given that most conduction-cooled boards have maximum junction temperatures of 70-75°C. Figure 4 graphs the decrease in available power consumption based on ambient operating temperatures. The values in the graph are maximums based on power supply operating temperatures of 85°C.
After adding the heat spreading wedge-lock base, new thermal models showed an increase in heat dispersion along the

Heat Sink on SBC Too
While developing the chassis, the CG Mupac design team saw a chance to apply the same principle to the single board computer that would reside in the opposite side of the chassis. With that in mind, they set out to design a heat sink for the heat generating components on the ruggedized simple board computer and wedge lock that to the sidewall. This removes more of the heat away from the card retainer plates and ensures better cooling for slots two through seven. The heat sink on the SBC takes the heat directly to the non-heat saturated center portion of the right sidewall.
It was important for the chassis design to incorporate as much flexibility as possible to make it a “one design meets all options” solution. With that in mind, the card cage configuration accepts up to seven slots including the system slot, and can accept VME 64, VME 64X as well as CompactPCI conduction-cooled boards per IEEE std 1101.2. Each backplane, regardless of the type, is designed to permit easily accessible top side I/O connectors. The I/O can then be routed to a fully removable factory customizable front I/O panel.
Because the front of the chassis is a removable panel, it can be changed to accommodate any custom design including AC/DC input connection, I/O connectors, reset, LEDs and monitoring. Monitoring can include voltage monitoring at the supply and temperature monitoring of various surfaces throughout the chassis. The chassis is designed to operate under the temperatures described previously, but the optional cooling methods that have been added to the ATR specification can be simply added to the chassis. The flange mounts and cold plate base can easily be used in the design.
Because the chassis does not require access to the bottom, a cold plate can be added, distributing heat from the sides, rear and card retainer plates to the base plate and transferring to the cold plate. There is an optional version of the ATR chassis that uses internal fin sidewalls with rear fan assistance. There is a front to rear air flow path that takes air in through the front sides; the rear fan pulls air through the specially designed heat sink fin sidewalls and exhausts out the rear bottom. That option is only available in long versions.

For more details: sales@aayurtech.com/www.aayurtech.com

THERMAL CALCULATIONS


Tool : Airflow and pressure loss calculations, EBM PAPST PLC.


POWER SUPPLY SELECTION MATRIX

No. of Slots : 06 x 6U Compact PCI

Wattage per slot : 50 watts Max.

Total Power required : (50 x 6) + 50 W for accessories 350 W

Power supply wattage : 600 W

Max. Load with 75% eff. : 450 W

Please refer to the above matrix the power supply requirement has been selected with enough back up as far as the wattage needs are considered.

The air flow needs of the enclosure are calculated considering the delta in temperature between the ambient and internal to the enclosure. Please find below various matrices for different delta T’s. Delta T is the difference in temperature between the ambient air outside the system and the maximum permissible operating temperature within the system. For example some applications have a permissible temperature rise of 10 degrees within the system. The maximum temperature could be governed by a particular component rating. For various iterations we are considering the Delta T from 3 degree C onwards.
After entering the values in the two fields press CALCULATE. Two figures (M3/sec and CFM) will then appear that represent the airflow required to eradicate the level of waste heat.
Having calculated the airflow needed it is then necessary to establish what back pressure the fan needs to overcome to deliver the required flow rate.
In a large number of applications air is either blown into a cabinet or enclosure or extracted from it. This may occur through a large singular square slot or round hole, or alternatively, a series of slots and holes in varying arrangements. For example if a large square aperture has a series of slots punched out in the metal work in a grid like arrangement. Unless the openings be they square or round are singular, the design reduces the open area available for air to move through and increases the back pressure the fan has to work against.
The second stage of the tool therefore calculates the overall smallest available "open" area for air to pass through and culminates in a figure for back pressure in PASCAL’s. By clicking on either the SQUARE SLOT tab you will automatically select the input fields for the relevant design.
Using the square slot as an example, first enter the number of slots; this may be one entire slot or more usually a number of slots. Then enter the length and breadth (mm) of the slots. By pressing CALCULATE the result will be shown in meters2 and is the total available open area for air to travel through. The very last data field will now also show the Pressure loss the fan needs to overcome to deliver the required airflow.
This will now provide you with two measurements
1) Airflow in CFM needed to remove the waste heat form the system. This has been calculated based on the inputted data of Power (watts) and the permissible temperature rise (DELTA-T) within the system.
2) Pressure in PASCAL’s that the fan needs to overcome to deliver the calculated required airflow.
These values can now be used to help determine the correct fan or fans needed to cool your application by matching up your pressure and airflow results to the fan performance curves available under the data sheet section of our website. You may also use the Airflow result as one of the specifying criteria for our interactive fan selector
Even if you have a large singular slot or hole creating minimal back pressure there will most likely be a requirement for you to fit a protective finger guard (s) to the system that will have an effect on flow rate. Depending on the type of guard metal or plastic, the open area for air to flow through will be typically decreased by 7-10%. In this design the air entry opening is 120mm x 60 mm. So typically for pressure loss calculations we need to consider only 10% less for practical calculations. So an effective honeycomb opening of 110mm x 55mm will result in a pressure loss of 14.848 pa.
The design tool will give good approximations for the required airflow and the back pressure the fan(s) have to overcome to deliver it. However due to the wide variation in system design, particularly component layout, architecture and densities, the tool has to assume an unpopulated system.
Therefore once the pressure drop figure in PASCAL’s is obtained, it is possible to increase the accuracy of the results by factoring in the effects of the system being full of electronics.
For example: if it is estimated that the system will be 80% full of components, simply take the pressure loss result and add 80% of it again. This will not account for the particular configuration of the system in terms of how and where components are located and the airs' flow path, but will help to account for increased overall density.
In Project Code #0900412001 the above example holds good, so for the fan selection the select a pressure drop of 14.848 plus 80%. i.e. 26.73 pa.

For detailed calculator please log on to http://www.papstplc.com/tools/calculators/calculators


The general data fed into the calculator for the air flow and the pressure drop is as follows:

Power(watts) : 450
No. of slots : 06
Length(mm) : 60
Breadth(mm) : 120

i) When Delta T is 3 deg C
1. The air flow requirement in CFM is 277.513
2. The pressure drop in pa is . 26.73

ii) When Delta T is 4 deg C
1. The air flow requirement in CFM is 208.135
2. The pressure drop in pa is . 26.73

iii) When Delta T is 5 deg C
1. The air flow requirement in CFM is 166.508
2. The pressure drop in pa is . 26.73

iv) When Delta T is 6 deg C
1. The air flow requirement in CFM is 138.757
2. The pressure drop in pa is . 26.73

v) When Delta T is 7 deg C
1. The air flow requirement in CFM is 118.934
2. The pressure drop in pa is . 26.73

vi) When Delta T is 9 deg C
1. The air flow requirement in CFM is 92.504
2. The pressure drop in pa is . 26.73
vii) When Delta T is 8 deg C
1. The air flow requirement in CFM is 104.067
2. The pressure drop in pa is . 26.73

viii) When Delta T is 10 deg C
1. The air flow requirement in CFM is 83.254
2. The pressure drop in pa is . 26.73

Figure 1: fan selection Matrix

Figure 2: Flow rate vs. Pressure loss



Considering the above chart one fan P/N 5112N each for suction and exhaust is considered enough to keep the Delta T within the admissible limits. The fan selected is of 147 CFM and the pressure drop is about 26.73 Pascal. Both criteria are met as per the chart above. More over we proposed to use one fan for forced air ventilation at the sides and two similar fans for suction one each for the electronics and the power supply unit.

Compare Touch screen technologies

1. Introduction 2
2. Comparing CRT and Flat Panel Displays 3
3. Touch Panel Technology 5
4. Applications of Touch screen 7
5. Different Technologies 8
6. Comparing Different Technologies 10
7. Benefits of Touch screen interface 12



1.INTRODUCTION

The use of a touch screen interface for the control and input of a given computer system is becoming more popular on the plant floor and other hazardous environments. At one point keyboards were the only means of interfacing with a PC until the development of a "pointing device" i.e., the mouse. Since then other pointing devices have gained favor such as joysticks and track-balls. Today, virtually all software applications require the use of a pointing device such as a mouse.
Another such "pointing device" is a touch screen which is the most direct form of operator interface since the operator is touching the actual area of the screen they want activated. It also serves as an intuitive tool for operators that are not as familiar with basic computer pointing devices. Touch screens have found their way onto the plant floor for a number of reasons. One of these reasons is to eliminate the need for a keyboard or traditional mouse and provide operators with graphical icons that represent the specific task at hand. This serves to keep operators focused on the application and can be used by virtually all operators of regardless of their level of computer knowledge.
Another consideration for touch screen technology in lieu of a traditional mouse/keyboard is the fact it is more industrial grade and resilient to the elements found on the traditional plant floor. Most touch screen technologies can also be used with a gloved hand eliminating the need for the operator to remove their gloves prior to operating the computer system.
Touch is one of the simplest, most instinctive, and universal human actions. There are several reasons to use touch technologies, which include limiting an end-user's access to a computer in kiosk-type applications as well as harsh environments where data entry needs to be balanced against sealing and protecting the computer. Touch technologies allow both of these applications to be retrofitted to computers utilizing one of several technologies currently available. A touch screen is the simplest, most direct way for a person to interact with a computer. Though it is a relatively new technology - two of the larger touch screen manufacturers claim to have started their operations in the 70s - the basic way users interact with a touch screen is age old: you point to what you want. It's intuitive for virtually every child and adult in the world. Companies in a broad cross-section of industries have successfully harnessed the power of a touch screen for a wide variety of applications. Airlines use them to simulate aircraft cockpits and train their pilots to fly. Realtors use them to put full-color images of homes for sale a fingertip away from homebuyers. Greeting card companies use them to let customers create their own one-of-a-kind cards. Restaurants use them to simplify their point-of-sale terminals. Medical schools use them to teach student nurses how to respond to crisis situations.



2.COMPARING CRT AND FLAT PANEL DISPLAYS

The two most common types of monitors that are being used today are CRT (Cathode Ray Tube) monitors and LCD (Liquid Crystal Display) monitors. CRT type monitors are the traditional monitors that we have been using for years. LCD type monitors are based on a newer technology and are becoming very popular, mainly because they have great space and energy saving advantages over CRT monitors. CRT and LCD monitors are based on completely different technologies, and thus have quite different display characteristics

Physical Size
One of the biggest advantages of LCD monitors is that they are compact and lightweight. An LCD monitor is based upon a very thin screen as opposed to the bulky tube of a CRT monitor. This means that not only do they take up less of your desktop space; they can also be used in many places where a larger CRT monitor cannot fit. A 12.1" LCD monitor with a stand takes up only about one-third of the desk space of a typical 14" CRT monitor.

Display Size
Thanks to advances in LCD technology, color flat panel LCD monitors are now available that are comparable in screen size to traditional CRT monitors. A 12.1" LCD display has only a slightly smaller viewing area than a typical 14" CRT monitor. Newer, larger LCD monitors are also appearing that have 15", 17", and even larger screen sizes that are comparable to the largest CRT monitors. One thing to note is that LCD monitors are typically sized by their actual viewable diagonal measurement, but CRTs typically are not. For example, the viewable area on a 17" LCD monitor will typically measure 17" diagonally, but the viewable area on a CRT monitor will typically only measure 16" diagonally.
Colors
Most CRT monitors are capable of displaying unlimited colors. Some LCD monitors are only capable of hundreds or thousands of colors, but many of the newer LCD's are capable of unlimited colors.
Resolution
An important issue with LCD monitors is resolution. CRT monitors are usually capable of displaying multiple video resolutions, each with the same quality. LCD monitors, however, usually has what is called a Native resolution, or the resolution that it displays best. The native resolution is generally the highest resolution that the LCD can display and this is the display resolution that will appear the crispest/sharpest.

Brightness
Typically, brightness is not a concern with CRT monitors. LCD monitors are backlit and have different levels of brightness. The brightness rating for an LCD monitor is commonly referred to as 'nits', and commonly ranges from 70 to 250 nits. The higher the nits, the brighter the display
Viewing Angle
Another issue with the LCD monitor is the viewing angle. A CRT screen can be looked at from a very wide angle, practically from the side, but an LCD monitor typically has a smaller viewing angle, needing to be viewed more directly from the front. From the side, the image on an LCD screen can seem to disappear, or invert colors. Newer displays that are coming out have wider viewing angles so this is not as much of an issue as it has been in the past.
Power Consumption and Radiation Emission

Besides being compact and space saving, LCD displays offer several other benefits. For one, LCD monitors consume much less energy than CRT monitors. This makes the LCD great for laptop and portable computers. Secondly, CRT monitors are known to emit harmful radiation, whereas LCD monitors do not.

Price

CRT monitors are generally more affordable than LCD monitors. In the past LCD monitors have been very expensive but their costs have come down quite a bit in the last 1-2 years. One thing to consider is the up-front cost versus the long-term cost. A CRT monitor will cost less up front but will use more energy than a flat panel monitor. An LCD monitor will cost more up front but will conserve energy in the long run. The energy savings may not be much for an individual user, but if you are looking at a corporate office where 50 displays are in use, the energy savings might be more of an issue



3.Touch Panel Technology

How it works?
Most of the technologies discussed here operate on the principle of dividing the screen image area into a predetermined grid (dependent upon screen size and resolution capabilities). Touching one of the quadrants of the menu selection causes a subroutine to execute in the same manner as typing the command at the prompt line or you would with a mouse. The first touch screen was created by adding a transparent surface to a touch-sensitive graphics digitizer and sizing it to fit a computer monitor. The purpose was to increase the speed data that could be entered into a computer. Today, the touch screen has been transformed into a more user-friendly and environmentally robust replacement for the computer keyboard and mouse. Because of that, touch is changing the world. With a touch screen, people with little or no computer experience can instantly work with complex software programs, without even being aware they're doing it. And computers can go to work in places where a keyboard or mouse would too cumbersome, fragile, or impractical.

A basic touch screen has three main components: a touch sensor, a controller, and a software driver. The touch screen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.










1. Touch Sensor
A touch screen sensor is a clear glass panel with a touch responsive surface. The touch sensor/panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen. There are several different touch sensor technologies on the market today, each using a different method to detect touch input. The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen.




2. Controller
The controller is a small PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand. The controller is usually installed inside the monitor for integrated monitors or it is housed in a plastic case for external touch add-ons/overlays. The controller determines what type of interface/connection you will need on the PC. Integrated touch monitors will have an extra cable connection on the back for the touch screen. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port (PC or Macintosh). Specialized controllers are also available that work with DVD players and other devices. 3. Software Driver
The driver is a software update for the PC system that allows the touch screen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent from the controller. Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen the same as clicking your mouse at the same location on the screen. This allows the touch screen to work with existing software and allows new applications to be developed without the need for touch screen specific programming. Some equipment such as thin client terminals, DVD players, and specialized computer systems either do not use software drivers or they have their own built-in touch screen driver.
So it is clear that the touch sensor and the software are the important links for any touch screen panels. There are different kinds of Sensor technologies available. Each technology has its on merits and drawbacks depending on the application and the environment.





4.APPLICATIONS OF TOUCH SCREENS

Regardless of the industry or application, the essential benefits touch screen technology provides remain unchanged:
§ Touch screens enable people to use computers instantly, without any training whatsoever
§ Touch screens virtually eliminate operator errors because users select from clearly defined menus 
§ Touch screens eliminate keyboards and mice, which many find intimidating and cumbersome to use
§ Touch screens are rugged enough to stand up to harsh environments where keyboards and mice often get damaged
§ Touch screens provide fast access to any and all types of digital media, with no text-bound interface getting in the way
§ Touch screens ensure that no space - on the desktop or elsewhere - is wasted, as the input device is completely integrated into the monitors
§ Simplifies the User/MPC interface
§ Durable in harsh conditions
§ Suitable for all environments
§ Greater accuracy
§ Smaller footprint

Where is Touch Used?

§ In Military command and control applications
§ In Kiosks
§ In industrial environments for control and automation
§ In hospitals
§ In retail locations
§ At tourist destinations
§ In schools for computer based training
§ Assistive technology



5.DIFFERENT TECHNOLOGIES

1. Resistive Technology





A thin glass substrate is "sandwiched" in between two layers of a plastic overlay. On the surface of the glass substrate is a tin oxide coating onto which a slight electrical current is constantly applied. The plastic overlay and the glass substrate are separated by hundreds of microscopic dot separators. When pressure is applied to the outside of the plastic overlay the two currents touch and a ground occurs. The X and Y coordinates of the touch are then detected by the touch screen controller card that is installed in the PC.

2. Capacitive Technology

A glass substrate with a tin oxide coating is charged with a slight electrical current. When the human hand touches the surface it causes a current draw at that point. The X and Y coordinates can then be determined from that point. It is a durable technology that is used in a wide range of applications including point-of-sale systems, industrial controls, and public information kiosks. It has a higher clarity than resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus.













3.Surface Acoustical Wave (SAW) Technology




A set of transducers emits a mechanical "wave" across the horizontal axis and vertical axis via reflective arrays. Receivers on the other side pick up the flow of these waves. If the surface of the screen is touched then a disruption in the wave occurs and the software determines the X and Y coordinates. . The SAW screen is a good choice for applications where image clarity is important, but it may not perform well in extremely dirty or dusty environments. Responds to finger or soft rubber tipped pointers.

4.Pen touch Capacitive Technology

Pen Touch Capacitive touch screen technology screen combines durable capacitive technology with a tethered pen stylus. The screen can be set to respond to finger input only, pen input only, or both. The pen stylus is a good choice for signature capture, on-screen annotations, or for applications requiring precise input.

5. Near Field Imaging technology

Near Field Imaging touch screen technology as one of the custom LCD touch monitor solutions it is an extremely durable screen that is suited for use in industrial control systems and other harsh environments. This rugged screen type is not affected by most surface contaminants, scratches, or vibration. Responds to finger or gloved hand

6. Infrared Technology

Infrared touch screen technology with the Plasma display solutions this is the only type of touch technology that we have available for large displays such as 42-inch Plasma screens. It is a durable technology that offers high image clarity. Responds to any input device or stylus.




6.Comparing Different Technologies.


§ 4-Wire Resistive Touch screens

Advantages

High touch resolution
Pressure sensitive, works with any stylus
Not affected by dirt, dust, water, or light
Affordable touch screen technology
Disadvantages
75 % clarity
Resistive layers can be damaged by a sharp object
Less durable then 5-Wire Resistive technology

§ Capacitive Touch screens
Advantages
o High touch resolution
o High image clarity
o Resistant to scratching
o Not affected by dirt, grease, moisture



Disadvantages
o Must be touched by finger, will not work with any non- conductive inputs, Cannot be used with gloves.
§ Infrared Technology
Advantages
o Good clarity
o Can be used with gloved hands
Disadvantages
o Not suitable for direct wash down
o Subject to activation by flying objects

§ Surface Acoustical Wave (SAW) Technology
Advantages
o Good clarity
o Can be used with gloved hands
High transmissivity - >92%
High resolution - 900 x 900, smooth mouse tracking and small target activation
Low parallax with spherical screen that conforms to CRT faceplate
Impervious to scratching by all but the hardest materials
Only technology with Z axis control

Disadvantages
o Pressure hosedown may cause unwanted target selection
o Dust, oil or grease on surface of touch screen may cause malfunction or unwanted target selection


WHICH TECHNOLOGY IS BEST?
Once the decision to use a touch screen has been made the next decision is which touch screen technology is best. This can easily be determined by looking at the application, where the touch screen will be used and the environment it will be operating in. There is four touch screen technologies that are generally used: Resistive, Infrared, Capacitive and Surface Acoustical Wave (SAW). They all have their pros and cons as outlined below. Capacitive for example cannot be used with gloves but can be washed down whereas Infrared can be used with gloves but should not be washed down.

In India capacitive touch technology or SAW is recommended for all application because of its ability to perform in contaminated environments. Contaminants such as grease, liquid and dust do not interfere with the touch screen's operation. It is the most durable and robust touch screen available today and to maintain watertight seal, can be set off by wash down

7.Benefits of Touch Interface

Many years ago, touch screens were an exotic, expensive interface for demanding applications like air-traffic and nuclear power-plant control. Not anymore! Companies across a broad spectrum of industries have successfully harnessed the power of touch for a wide variety of applications. Yet the essential benefits provided by touch technology remain unchanged
Fast, faster, fastest
Touch screens provide fast access to any and all types of digital media, with no text-bound interface getting in the way. It takes time for the user to grab a mouse or use a keyboard or trackball and coordinate it with what needs to be activated on the display. Faster input can mean better customer service in restaurants, hotels, movie theaters, and retail stores, which results in increased customer loyalty. In other cases, such as in-vehicle control or security equipment, being even one second faster can make all the difference.
Touch makes everyone an expert
Reaching out for what you want is an instinctive gesture. Using touch is just as simple: you simply point at what you want. Although some people still shy away from computer keyboards, mice, or trackballs, there is no hesitation when they can just touch a screen. Users feel comfortable that they cannot "do anything wrong"; they instinctively understand how to use the interface. Touch screen systems make everyone an "expert user" from the first touch—whether it’s a person consulting a kiosk, a worker controlling an industrial process, a nurse entering a patient’s information, or a waiter entering an order
Reduced costs
Using a touch interface can effectively increase operator accuracy, reduce training time, and improve overall operational efficiencies, thus keeping costs down. In the retail environment, for example, a properly designed touch interface can improve each operator’s accuracy, while maintaining optimum checkout speeds. Users can respond quickly without making significant errors. Also, touch-based point-of-sale (POS) systems streamline the returns and refunds process by reducing the time it takes a customer to return merchandise; they also improve loss-prevention management. In addition, compared to traditional training methods, using touch screens can drastically reduce training time, since touch technology is intuitive and requires no special skills to learn. Moreover, the flexibility of touch technology can significantly contribute to cost reductions: it creates operational efficiencies by simplifying procedures and reduces the need for additional capital investment.
Compact and Handy
Space is valuable, so you want to use it as efficiently as possible. Touch monitors ensure that no space—on the desktop or elsewhere—is wasted, since the input device is completely integrated into the display. Flat LCD touches monitors help save even more space. And there are no keyboard or mouse cords in front of the monitor to get tangled or damaged, or to gather dust
Durable and Easy to Clean
A touch screen is made of glass or a similar hard-coated surface. So it’s easy to clean and therefore extremely well suited for the typical environments found in restaurants, hospitals, and the food and pharmaceutical industries. Most of the touch screens can be used with gloves, which is great for applications where hygiene is particularly important or where temperature or workplace safety rules require the use of gloves. We offer touch screen systems that are not affected by dirt, dust, grease, or liquid droplets. They are even rugged enough to stand up to harsh environments where keyboards and mice often get damaged

When ease of use is required
Touch screen-based systems virtually eliminate errors because users select from clearly defined menus. The information on each screen is limited in number and options, thus providing step-by-step, fail-safe sequences to guide the user through complex procedures. This greatly simplifies medical diagnostics applications—for example, where voluminous databases must be accessed quickly and easily. Touch screens are also useful in simplifying process-control applications involving many buttons or switches, and for applications where system contents require protection from unauthorized entry.

Making COTS electronics to work for extended temperature

My point is to make the commercially available of the shelf elctronics boards to use in tndustrial and military environment with externally hardening the electronics.

The concerens are as follows:

1. Temperature
2. Shock
3. Vibration
4. Humidity
5. EMI/EMC

Out of the above we shall explain the temperature hardening in this article.

Earlier days the computing electronics were required to be operated in the controlled environment. So air conditioning e\was a necessary. These days all the electronics components are tropicalised and they operate at a very wide temoerature range. SO selecting the right componet and the cooling techniques are very important in extending the the temperature range of the COTS item.

If that is also not possible www.aayurtech.com has developed a temperature controlled enclosure to heat and cool the electronics. Heting is asimple mechanism. But for cooling we can use either peltier TEC chips or liquid cooling for only for the targeted electronics.

Coming chapters will deal with other aspects of ruggediastion.