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27 Nov 2013

Gravity Screen - On / Off

 Gravity Screen - On / Off - screenshot

 Gravity Screen - On / Off




Using your phone often? Tired of the On-Off switching?
This app turns automatically your screen off when you put your phone into your pocket or onto a table and turn the screen on when you take it out or up. No need to touch any button and you are ready to go. 

It monitors the orientation of the device through the gravity sensor. When your phone is pointing downward by its top, below a certain angle, it's likely to be out of use. In this situation the proximity sensor is activated to determine if it is covered. If yes, the screen turns off because probably you placed the phone into your pocket or onto a table.
To keep the battery usage low the program turns on the proximity sensor only when it's really necessary. Moreover, when it turns your screen off and the proximity sensor is covered it puts your phone into deep sleep state to save as much energy as possible.
- Pocket Sensor: Recognizes if your phone is in your pocket.
- Table Sensor: Detects your phone is lying on a table and turns the screen off.
- Turn Screen On by Motion: If the screen is off and it's facing up the device can be woken up by any movements, for example lift up by hand.
- Keep Screen On by Motion: It's a Screebl like feature but it's relying on the small movements you are doing by your hand while holding the phone. If small motions are detected while the screen is facing up the feature keeps the screen on because it can be suspected that the phone is held and probably you are reading something. If the phone is steady the normal screen timeout will apply in any position you leave your device.
- Exclude Apps option: The app pauses itself anytime if selected app is running, it'll resume when you close the app. Useful when playing games etc.
- Tasker, Llama, Locale supported by plug-in.

It should be not significant. I experienced about 6 per cent extra consumption on the test device. However it can be much higher by often using the Turn Screen On by Motion feature. Thus, keep your phone face down if you want to save energy.
On some devices (e.g. HTC One) the alarm clock is switched off by the app after it had gone off! Please check if it's the case for you. If, yes, use a third party app, for example:
- The app was not widely tested. Hopefully it will work fine for you. But, if you experience any issue or just have a question, please email me.
In the Pro version the screen can be turned on by motion up to 16 hours instead of 15 minutes. Also, in the Pro version the Table sensor is more accurate. Unlock version has everything what Pro has plus it can be paused if any app running from the Exclude app list.
Q: The screen not always turns off when I put my phone into my pocket, why?
A:The proximity sensor not always accurate. It can fail recognizing some materials specially if they are very close to it. If it happens to you often, you can activate the False Turn-On Protection feature which effectively reduces the number of accidental wake-ups.
Q: I'm experiencing high battery usage, why?
A: The app should use about 6 percent extra energy per day if you are not using too much the Turn Screen On by Motion feature, for example keeping your phone face down when it's on a table. Moreover, please, keep in mind that the android en-built battery consumption measurement can show much higher results if it's based on a short period of time.

download this for ur phone


 Gravity Screen - On / Off - screenshot        Gravity Screen - On / Off - screenshot

4 Nov 2013

New Optical Disc

New Optical Disc Can Store Information “for a billion years” 




If you’ve been worried about how to preserve your digital records, you may soon be able to purchase a new optical disk that could store data for up to a billion years. To some this may seem hubristic, to others definitely not.
According to the latest gizmag report, a researcher at the University of Twente in the Netherlands has developed a new optical memory device made out of tungsten and silicon nitride that could store data for extremely long periods of time—up to a billion years.

Hard drives are very susceptible to external magnetic fields and mechanical failures, with a normal lifespan not much longer than 10 years; similarly CDs, DVDs and flash drives each have their own Achilles’ heel.
University of Twente researcher Jeroen de Vries set out to solve this problem by designing his own data storing device. For the materials he chose tungsten, which can withstand very high temperatures, encapsulated in silicon nitride, which is highly resistant to fracture and deforms very little when exposed to high levels of heat.
The disc, de Vries claims, is so sturdy that it could be used to store important data on the human race and retain it well past its extinction, for the benefit of whoever is left (of course, that’s assuming that the aliens, robots, or mutants will somehow know exactly how to decode the information on the disk in the first place)

From left to right: the QR codes after fabrication, after two hours at 613 K, and after two hours at 763 K (Image: de Vries/University of Twente)

Inside the device, information is stored by etching QR codes in tungsten – which can be easily decoded by today’s smartphones. This method is very resilient because the information is still preserved even when up to seven percent of the data has been compromised. Each pixel of the code also has within it a second set of much smaller QR codes, with pixels of only a few microns in size.
To find out how long the device could retain information, de Vries relied on the Arrhenius model, which simulates extended periods of time by exposing the device to predetermined levels of heat for a set amount of time.
The researcher heated the storage device to a temperature of 200 °C (400 °F) for one hour and noted no visible degradation, which according to the model simulates one million years of usage. The device only showed some signs of degradation once it was heated to much higher temperatures, around 440 °C (820 °F) – but even then, the tungsten was not harmed and the data was still readable.
Though the mathematical model used for testing was limited to exposure to high temperatures (and, as the researcher admits, may not be entirely accurate), de Vries says that if they can find a place that is very stable to store the device, such as a nuclear storage facility, then the disc and the data it contains still has all the requisites to last for extremely long periods of time, on the order of millions of years.


13 Oct 2013

Want to become a Web Developer?

Want to become a Web Developer? – Take a Start

Do you want to be a web developer because you love computers, laptops and websites so much. Then this is great according to me because it’s just a creative world. Being a web developer is good because you can easily translate your ideas to the world in the shape of a website. Being a web developer feels a kind of satisfaction to those who get some reward out of this developing in shape of people praising their work. Most of the schools miss this part of web developing but the future certainly is about computer programming. I am writing this basic post to help you that how can you take a start.

Be A Web Developer with these easy pre-requisites:

Just keep on reading, fulfill the objectives and take the first step to be a web developer.

Starting with being a perfect computer user:

If you want to be  good developer at your own then you should know that how to use a computer. Chances are that you already know how to use software and know every thing about them without any course by just experimenting with them. It can seem time consuming to you but keep in mind that the thing which you learn at your own is never forgotten so easily. You learn the things which you find amazing so you never get bored of this computer thingy. If you know how to deal with computers and how to deal with software along with social networking sites then you can start with developing the stuff too. At least you should be able to be a master user of the computer. You should be able to understand what computer is saying to you and what you should do. Since most people never read the computer message because they don’t understand it so they ignore, but you shouldn’t be like this you should understand that what computer is about to let you know.

Start With Google – The Ultimate Master to Guide you!

After you are a good internet user as well as computer one, now you can think to be a web developer. You can take a lot of help from the Google to learn how to code. You should know how to search things, For this you just need to go to Google and then put the keywords of the things which you want to search. After that you can get million of sites related to that in a matter of seconds. Like if you want to search about how to use microsoft word then just search for “How to use Microsoft word or else using Microsoft word tutorials” simple! Thus, after making up mind to learn about web developing take help from Google where ever you get stuck.

Start with the most easy language to be learnt – HTML

Want to be a developer and understand the complicated languages? Then this is the start you should be able to master over the static content sites, you should be able to know that behind every site visible at the internet their is a code running behind the site which tells the browser how to display the site over all. If you want to look at the soure code of the site then open the website and right click on that. After that click on “View page source” the code which you will see is in mostly HTML and you can see that how the HTML can make the front visual look of the page. Actually it’s the browser like Mozilla and chrome which make the visual look of the website from the source code.
To learn HTML you can make use of Google Search but I will recommend you a website where you can take HTML lessons daily:
Learn HTML from W3Schools here by reading one lesson daily and by practicing it you will be able to learn HTML in a week or two. Depends on how sharp are you! What ever you learn you should practice also I previously posted that how can you convert your PC into a server and install wordpress on it. You can easily use the same software to view your pages which you code using the HTML language. Grab a good editor like notepad++which will highlight the starting and closing tags of HTML and then save it to your xampp folder. Access that using the browser and look at your hardwork. Yes! I described all this long task in a matter of few lines but if you are sharp enough and know how to use computers and software then you can grab my point.

After Learning HTML Move on to styling the Pages Using CSS:

After you have learnt the HTML now you need to style the pages so that they may look colorful. You can easily change the following things with CSS , actually CSS is a language which can change the visual look of your HTML code output.
  • The Background of the page
  • The Font Color of the Page
  • The Specific Area Color and Background Color
  • Border of Specific Area
  • To Put shadow around a font
And Much More! Thus it’s CSS which makes the web page look like  web page. CSS is abbreviation of Cascading Style Sheets If I am not wrong. You can easily learn CSS from here: Learn CSS from w3schools
After you have learnt HTML and CSS. You can easily take a start with your developing skills.

Be Experimental – Key to Everything:

You need to be experimental if you want to learn developing and also you need to be persistent with things too. If you stuck at something then you should Google that. You should never think that you are the only one who got stuck at this point search about the question and in every case the question has been pre asked at many sites and a working solution is present there. You can also drop comment here below this post to ask for any major help I will be also in contact with you soon. You should not stop on HTML and CSS rather the next step should be that you should experiment with photoshop. Photoshop a very amazing tool to create the graphics needs nothing but a fresh mind. I know it can seem hard to you but don’t worry time will tell you many things, you just need to look at every tool in the Photoshop and try to sort out the use of that tool. The hover bar which shows when you hover over any button also helps a lot as it happens in most of software. So just be experimental. It works and you learn thing with experiments and Google now look that at the end of the day you know how to take a start to be a developer. The things needed are:
  • When
  • Where
  • How
I will post more tutorials about developing soon so stay in touch and subscribe to news letter to get amazing deals.

Electronic color code

Electronic color code

The electronic color code is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables.
The electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062
Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing construction costs. However, there were drawbacks, especially for color blind people. Overheating of a component, or dirt accumulation, may make it impossible to distinguish brown from red from orange. Advances in printing technology have made printed numbers practical for small components, which are often found in modern electronics.

Resistor color-coding

One decade of the E12 series (there are twelve preferred values per decade of values) shown with their electronic color codes on resistors.
A 100 kΩ, 5% through-hole resistor.
A 0Ω resistor, marked with a single black band.
A diagram of a resistor, with four color bands A, B, C, D from left to right A diagram of a 2.7 MΩ color-coded resistor.
A 2260 ohm, 1% precision resistor with 5 color bands (E96 series), from top 2-2-6-1-1; the last two brown bands indicate the multiplier (x10), and the 1% tolerance. The larger gap before the tolerance band is somewhat difficult to distinguish.
To distinguish left from right there is a gap between the C and D bands.
  • band A is first significant figure of component value (left side)
  • band B is the second significant figure (Some precision resistors have a third significant figure, and thus five bands.)
  • band C is the decimal multiplier
  • band D if present, indicates tolerance of value in percent (no band means 20%)
For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.
Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details.
Tight tolerance resistors may have three bands for significant figures rather than two, or an additional band indicating temperature coefficient, in units of ppm/K.
All coded components will have at least two value bands and a multiplier; other bands are optional.
The standard color code per EN 60062:2005 is as follows:

Color Significant
Multiplier Tolerance Temp. Coefficient (ppm/K)
Black 0 ×100 250 U
Brown 1 ×101 ±1% F 100 S
Red 2 ×102 ±2% G 50 R
Orange 3 ×103 15 P
Yellow 4 ×104 (±5%) 25 Q
Green 5 ×105 ±0.5% D 20 Z
Blue 6 ×106 ±0.25% C 10 Z
Violet 7 ×107 ±0.1% B 5 M
Gray 8 ×108 ±0.05% (±10%) A 1 K
White 9 ×109
Gold ×10-1 ±5% J
Silver ×10-2 ±10% K
None ±20% M

  1. Any temperature coefficent not assigned its own letter shall be marked "Z", and the coefficient found in other documentation.
  2. For more information, see EN 60062.
  3. Yellow and Gray are used in high-voltage resistors to avoid metal particles in the lacquer.
Resistors use preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude: 6.8, 68, 680, and so forth. In the E24 series the values are related by the 24th root of 10, while E12 series are related by the 12th root of 10, and E6 series by the 6th root of 10. The tolerance of device values is arranged so that every value corresponds to a preferred number, within the required tolerance.
Zero ohm resistors are made as lengths of wire wrapped in a resistor-shaped body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a single black band.
The 'body-end-dot' or 'body-tip-spot' system was used for radial-lead (and other cylindrical) composition resistors sometimes still found in very old equipment; the first band was given by the body color, the second band by the color of the end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was colored gold or silver to give the tolerance, otherwise it was 20%.

Capacitor color-coding

Capacitors may be marked with 4 or more colored bands or dots. The colors encode the first and second most significant digits of the value, and the third color the decimal multiplier in picofarads. Additional bands have meanings which may vary from one type to another. Low-tolerance capacitors may begin with the first 3 (rather than 2) digits of the value. It is usually, but not always, possible to work out what scheme is used by the particular colors used. Cylindrical capacitors marked with bands may look like resistors.
Color Significant digits Multiplier Capacitance tolerance Characteristic DC working voltage Operating temperature EIA/vibration
  Black 0 1 ±20% −55 °C to +70 °C 10 to 55 Hz

Brown 1 10 ±1% B 100

Red 2 100 ±2% C −55 °C to +85 °C

Orange 3 1000 D 300

Yellow 4 10000 E −55 °C to +125 °C 10 to 2000 Hz

Green 5 ±0.5% F 500

Blue 6 −55 °C to +150 °C

Violet 7

Grey 8

White 9 EIA

Gold ±5%* 1000

Silver ±10%

*or ±0.5 pF, whichever is greater.
Extra bands on ceramic capacitors will identify the voltage rating class and temperature coefficient characteristics. A broad black band was applied to some tubular paper capacitors to indicate the end that had the outer electrode; this allowed this end to be connected to chassis ground to provide some shielding against hum and noise pickup.
Polyester film and "gum drop" tantalum electrolytic capacitors are also color-coded to give the value, working voltage and tolerance.

Diode part number

The part number for diodes was sometimes also encoded as colored rings around the diode, using the same numerals as for other parts. The JEDEC "1N" prefix was assumed, and the balance of the part number was given by three or four rings.

Postage stamp capacitors and war standard coding

Capacitors of the rectangular 'postage stamp" form made for military use during World War II used American War Standard (AWS) or Joint Army Navy (JAN) coding in six dots stamped on the capacitor. An arrow on the top row of dots pointed to the right, indicating the reading order. From left to right the top dots were: either black, indicating JAN mica, or silver, indicating AWS paper; first significant digit; and second significant digit. The bottom three dots indicated temperature characteristic, tolerance, and decimal multiplier. The characteristic was black for ±1000 ppm/°C, brown for ±500, red for ±200, orange for ±100, yellow for −20 to +100 ppm/°C, and green for 0 to +70 ppm/°C. A similar six-dot code by EIA had the top row as first, second and third significant digits and the bottom row as voltage rating (in hundreds of volts; no color indicated 500 volts), tolerance, and multiplier. A three-dot EIA code was used for 500 volt 20% tolerance capacitors, and the dots signified first and second significant digits and the multiplier. Such capacitors were common in vacuum tube equipment and in surplus for a generation after the war but are unavailable now.
Postage-stamp mica capacitors marked with the EIA 3-dot and 6-dot color codes, giving capacitance value, tolerance, working voltage, and temperature characteristic. This style of capacitor was used in vacuum-tube equipment.


A useful mnemonic matches the first letter of the color code, by order of increasing magnitude. Here is one that includes tolerance codes gold, silver, and none:
  • Bad beer rots our young guts but vodka goes well – get some now.
The colors are sorted in the order of the visible light spectrum: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.


Color-coded resistors
From top to bottom:
  • Green-Blue-Black-Brown
    • 56 ohms ± 1%
  • Red-Red-Orange-Gold
    • 22,000 ohms ± 5%
  • Yellow-Violet-Brown-Gold
    • 470 ohms ± 5%
  • Blue-Gray-Black-Gold
    • 68 ohms ± 5%
  • violet-red-orange-no band
    • 72,000 ohms ± 20%
The physical size of a resistor is indicative of the power it can dissipate, not of its resistance.

Printed numbers

0Ω and 27Ω (27×100) surface-mount resistors.
Color-coding of this form is becoming rarer. In newer equipment, most passive components come in surface mount packages. Many of these packages are unlabeled, and those that are labeled normally use alphanumeric codes, not colors.
In one popular marking method, the manufacturer prints 3 digits on components: 2 value digits followed by the power of ten multiplier. Thus the value of a resistor marked 472 is 4,700 Ω, a capacitor marked 104 is 100 nF (10x104 pF), and an inductor marked 475 is 4.7 H (4,700,000 µH). This can be confusing; a resistor marked 270 might seem to be a 270 Ω unit, when the value is actually 27 Ω (27×100). A similar method is used to code precision surface mount resistors by using a 4-digit code which has 3 significant figures and a power of ten multiplier. Using the same example as above, 4701 would represent a 470x101=4700 Ω, 1% resistor. Another way is to use the "kilo-" or "mega-" prefixes in place of the decimal point:
1K2 = 1.2 kΩ = 1,200 Ω
M47 = 0.47 MΩ = 470,000 Ω
68R = 68 Ω
For some 1% resistors, a three-digit alphanumeric code is used, which is not obviously related to the value but can be derived from a table of 1% values. For instance, a resistor marked 68C is 499(68) × 100(C) = 49,900 Ω. In this case the value 499 is the 68th entry of the E96 series of preferred 1% values. The multiplier letters are as follows:
EIA E96 SMD alphanumeric code
Letter Multiplier Decimal
Z 10−3 0.001
Y or R 10−2 0.01
X or S 10−1 0.1
A 100 1
B or H 101 10
C 102 100
D 103 1000
E 104 10000
F 105 100000

SMT jumpers, marked "0" or "000", are sometimes called "Zero-ohm links" or "0-ohm resistors" although technically they are not resistors.

Transformer wiring color codes

Power transformers used in North American vacuum-tube equipment often were color-coded to identify the leads. Black was the primary connection, red secondary for the B+ (plate voltage), red with a yellow tracer was the center tap for the B+ full-wave rectifier winding, green or brown was the heater voltage for all tubes, yellow was the filament voltage for the rectifier tube (often a different voltage than other tube heaters). Two wires of each color were provided for each circuit, and phasing was not identified by the color code.
Audio transformers for vacuum tube equipment were coded blue for the finishing lead of the primary, red for the B+ lead of the primary, brown for a primary center tap, green for the finishing lead of the secondary, black for grid lead of the secondary, and yellow for a tapped secondary. Each lead had a different color since relative polarity or phase was more important for these transformers. Intermediate-frequency tuned transformers were coded blue and red for the primary and green and black for the secondary.


8 Oct 2013

Diode logic

Diode logic

Diode logic (DL) or diode-resistor logic constructs Boolean logic gates from diodes acting as electrically operated switches. While diode logic has the advantage of simplicity, the lack of an amplifying stage in each gate limits its application. Not all logical functions can be implemented in diode logic alone; only the non-inverting logical AND and logical OR functions can be realized by diode gates. If several diode logic gates are cascaded, the voltage levels at each stage are significantly changed, so one-stage applications are used.

Diode logic gate versions

In logic gates, logical functions are performed by parallel or series connected switches controlled by input logical variables. In diode logic, electrically operated switches are implemented by diodes: when forward biased, a diode switch is closed; when backward biased, the switch is open. There are two kinds of diode logic gates - OR and AND. It is not possible to construct NOT diode gate. The explanations below are true for positive logic (high voltage represents logical 1 and low voltage represents logical 0).

OR logic gate

In a diode OR gate, the output voltage is high if at least one input voltage is high. The output voltage is low if all the input voltages are low.
OR logic gates are implemented by parallel connected normally open switches. So, in diode OR logic gates, the input voltage sources are connected to diode anodes. Diode cathodes are joined to the output (node 1 in the figure), which is connected through the pull-down resistor R1 to ground.
Input logical one. If the voltage of a particular input voltage source is high (input logical 1), the according diode is forward biased and this diode switch is closed. The input source passes current through the diode and creates high voltage drop across the resistor R1 (output logical 1). The rest of diodes connected to low input voltage (input logical 0s) are backward biased and their input sources (grounds) are disconnected from the output.
Input logical zeros. If all the input voltages are low (input logical 0), the voltage drops across the diodes are zero. These diode switches are open and the input sources (grounds) are disconnected from the output. No current flows through the resistor. The output voltage is low (output logical 0) and the output resistance is R1.
If two diode OR logic gates are cascaded, they behave as current-sourcing logic gates: if the first gate produces high output voltage, the second gate consumes current from the first one. If the first gate produces low output voltage, the second gate does not inject current into the output of the first one. A diode OR gate does not use its own power supply. The input sources with high voltage (logical 1) supply the load through the forward-biased diodes.

AND logic gate

Basic idea

AND logic gates are implemented by series connected normally open switches. So, diode AND logic gates should be implemented by series connected diode switches (like an NMOS AND gate that is implemented by series connected transistor switches). However, in contrast to transistors, diodes are two-terminal switching elements, in which the input and output are not separated but they are the same. As a result, series connected diode switches cannot be driven by grounded input voltage sources. To solve this problem, diode AND gates are constructed in the same manner as OR diode gates - by parallel connected diode switches. However, to obtain AND instead of OR function according to De Morgan's laws, the input and output logical variables are inverted:
Y = NOT (NOT (X1) OR NOT (X2)) = NOT (NOT (X1 AND X2)) = X1 AND X2,
where X1 and X2 are the two input logical variables; Y is the output variable.
Therefore, the diode AND logic gate is a modified diode OR logic gate: the diode AND gate is actually a diode OR gate with inverted inputs and output.


In a diode AND gate, the output voltage is high if all the input voltages are high. The output voltage is low if at least one of the input voltage is low.
To realize the basic idea, the diodes are reverse connected and forward biased by an additional voltage source +V (a power supply) through the pull-up resistor R1. The input voltage sources are connected in opposite direction to the supplying voltage source (traveling along the loop +V - R1 - D - Vin). To invert the output voltage and to get a grounded output, the complementary voltage drop (+V - VR1) between the output and ground is taken as an output instead the floating voltage drop VR1 across the resistor.
Input logical ones. When all the input voltages are high, they "neutralize" the biasing supply voltage +V. The voltage drops across the diodes are zero and these diode switches are open. The output voltage is high (output logical 1) since no current flows through the resistor and there is no voltage drop across it. The output resistance is R1. Hence, the behavior of the diode switches is reversed - whereas in diode OR logic gates diodes act as normally open switches, in diode AND logic gates diodes act as normally closed switches.
Input logical zero. If the voltage of some input voltage source is low (input logical 0), the power supply passes current through the resistor, diode and the input source. The diode is forward biased (the diode switch is closed) and the output voltage drop across the diode is low (output logical 0). The output resistance is low and is determined by the input source. The rest of diodes connected to high input voltages (input logical 1s) are backward biased and their input sources are disconnected from the output Node 1.
If two diode AND logic gates are cascaded, they behave as current-sinking logic gates: if the first gate produces high output voltage, the second gate does not consume current from the first one; if the first gate produces low output voltage, the second gate injects current into the output of the first one. A diode AND gate uses its own power supply to drive the load through the pull-up resistor.


Non-restoring logic

In cascaded AND-OR diode gates, the high voltage level is decreased more than two times.
Digital logic implemented by active elements is characterized by signal restoration. True and false or 1 and 0 are represented by two specific voltage levels. If the inputs to a digital logic gate is close to their respective levels, the output will be closer or exactly equal to its desired level. Active logic gates may be integrated in large numbers because each gate tends to remove noise at its input. Diode logic gates are implemented by passive elements; so, they have two restoration problems.
Forward voltage drop. The first restoration problem of diode logic is that there is a voltage drop VF about 0.6 V across the forward-biased diode. This voltage is added to or subtracted from the input of every gate so that it accumulates when identical diode gates are cascaded. In an OR gate, VF decreases the high voltage level (the logical 1) while in an AND gate, it increases the low voltage level (the logical 0). The feasible number of logic stages thus depends on the difference between the high and low voltages.
Source resistance. Another problem of diode logic is the internal resistance of the input voltage sources. Together with the gate resistor, it constitutes a voltage divider that worsens the voltage levels. In an OR gate, the source resistance decreases the high voltage level (the logical 1) while in an AND gate, it increases the low voltage level (the logical 0). In the cascaded AND-OR diode gates in the picture on the right, the AND high output voltages are decreased because of the internal voltage drops across the AND pull-up resistances.

Non-inverting logic

Diode logic is non-inverting in both the OR and AND configurations: a diode OR gate is true non-inverting (Y = X in the case of one-input OR gate) while a diode AND gate is non-inverting since it is double inverting (Y = NOT (NOT (X)) = X in the case of one-input AND gate - see the considerations above). Diode AND gate would be inverting if the voltage drop across the resistor is taken as an output but the load would be not grounded in this case.


Diode logic gates are used to build diode–transistor logic (DTL) gates as integrated circuits.
The outputs of conventional ICs (with complementary output stages) must never be directly connected together since they act as voltage sources. However, diodes can be used to combine two or more digital (high/low) outputs from an IC such as a counter. This wired logic connection can be a useful way of producing simple logic functions without using additional logic gates

Diode matrix

Diode matrix

A diode matrix is a two-dimensional grid of wires: each "intersection" wherein one row crosses over another has either a diode connecting them, or the wires are isolated from each other.
It is one of the most popular techniques for implementing a read-only memory. A diode matrix is used as the control store or microprogram in many early computers. A logically equivalent transistor matrix is still used as the control store or microprogram or 'decode ROM' in many modern microprocessors.
At any one instant, a single row of the diode matrix (or transistor matrix) is activated. Charge flows through each diode connected to that row. That activates the column corresponding to each row. The only activated control signals during that instant were those whose corresponding column wire was connected with a diode to that row.



A diode matrix ROM was used in many computers in the 1960s and 70s, as well as electronic desk calculators and keyboard encoders for computer terminals.
The microsequencer of many early computers, perhaps starting with the Whirlwind (computer), simply activated each row of the diode matrix in sequence, and after the last row was activated, started over again with the first row.
The technique of microprogramming as first described by Maurice Wilkes in terms of a second diode matrix added to a diode matrix control store. Later computers used a variety of alternative implementations of the control store, but eventually returned to a diode matrix or transistor matrix. A person would microprogram the control store on such early computers by manually attaching diodes to selected intersections of the word lines and bit lines. In schematic diagrams, the word lines are usually horizontal and the bit lines are usually vertical.
The control store on some minicomputers was one or more programmable logic array chips. The "blank" PLA from the chip manufacturer came with a diode matrix or transistor matrix with a diode (or transistor) at every intersection. A person would microprogram the control store on these computers by destroying the unwanted connections at selected intersections.
Some modern microprocessors and application-specific integrated circuits (ASICs) use a diode matrix or transistor matrix control store. Typically a blank grid is designed with a diode (or transistor) at every intersection, and then a mask is prepared that leaves out the unwanted connections at selected intersections. When reverse engineering integrated circuits that include such a mask-programmed decode ROM, one of the key steps is to take photographs of that ROM with enough resolution to separate each intersection site and enough color depth to distinguish between the "connected" and "not connected" intersections.
Since the control store is in the critical path of computer execution, a fast control store is an important part of a fast computer. For a while the control store was many times faster than program memory, allowing a long, complicated sequence of steps through the control store per instruction fetch, leading to what is now called complex instruction set computing. Later techniques for fast instruction cache sped that cache up to the point that the control store was only a few times faster than instruction cache, leading to fewer and eventually only one step through the control store per instruction fetch in reduced instruction set computing.
A keyboard matrix circuit has a very similar grid of diodes, but is used differently.

28 Sept 2013



An OLED (organic light-emitting diode) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound (an organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon) which emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes. Generally, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld games consoles and PDAs. A major area of research is the development of white OLED devices for use in solid-state lighting applications. 

There are two main families of OLED: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell or LEC, which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes.
A typical OLED is composed of a layer of organic materials situated between two electrodes, the anode and cathode, all deposited on a substrate. The organic molecules are electrically conductive as a result of delocalization of pi electrons caused by conjugation over all or part of the molecule. These materials have conductivity levels ranging from insulators to conductors, and therefore are considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors.
Originally, the most basic polymer OLEDs consisted of a single organic layer. One example was the first light-emitting device synthesised by J. H. Burroughes et al., which involved a single layer of poly(p-phenylene vinylene). However multilayer OLEDs can be fabricated with two or more layers in order to improve device efficiency. As well as conductive properties, different materials may be chosen to aid charge injection at electrodes by providing a more gradual electronic profile,or block a charge from reaching the opposite electrode and being wasted. Many modern OLEDs incorporate a simple bilayer structure, consisting of a conductive layer and an emissive layer. More recent developments in OLED architecture improves quantum efficiency (up to 19%) by using a graded heterojunction. In the graded heterojunction architecture, the composition of hole and electron-transport materials varies continuously within the emissive layer with a dopant emitter. The graded heterojunction architecture combines the benefits of both conventional architectures by improving charge injection while simultaneously balancing charge transport within the emissive region

During operation, a voltage is applied across the OLED such that the anode is positive with respect to the cathode. Anodes are picked based upon the fact of how good their optical transparency, electrical conductivity, and chemical stability are. A current of electrons flows through the device from cathode to anode, as electrons are injected into the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode. This latter process may also be described as the injection of electron holes into the HOMO. Electrostatic forces bring the electrons and the holes towards each other and they recombine forming an exciton, a bound state of the electron and hole. This happens closer to the emissive layer, because in organic semiconductors holes are generally more mobile than electrons. The decay of this excited state results in a relaxation of the energy levels of the electron, accompanied by emission of radiation whose frequency is in the visible region. The frequency of this radiation depends on the band gap of the material, in this case the difference in energy between the HOMO and LUMO.
As electrons and holes are fermions with half integer spin, an exciton may either be in a singlet state or a triplet state depending on how the spins of the electron and hole have been combined. Statistically three triplet excitons will be formed for each singlet exciton. Decay from triplet states (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light-emitting diodes make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet states, thus obtaining emission from both singlet and triplet states and improving the internal efficiency.

Indium tin oxide (ITO) is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the HOMO level of the organic layer. A typical conductive layer may consist of PEDOT:PSS as the HOMO level of this material generally lies between the workfunction of ITO and the HOMO of other commonly used polymers, reducing the energy barriers for hole injection. Metals such as barium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the LUMO of the organic layer. Such metals are reactive, so they require a capping layer of aluminium to avoid degradation.
Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface adhesion, increase electrical resistance, and allow for more frequent formation of non-emissive dark spots in the OLED material adversely affecting lifetime. Mechanisms to decrease anode roughness for ITO/glass substrates include the use of thin films and self-assembled monolayers. Also, alternative substrates and anode materials are being considered to increase OLED performance and lifetime. Possible examples include single crystal sapphire substrates treated with gold (Au) film anodes yielding lower work functions, operating voltages, electrical resistance values, and increasing lifetime of OLEDs.
Single carrier devices are typically used to study the kinetics and charge transport mechanisms of an organic material and can be useful when trying to study energy transfer processes. As current through the device is composed of only one type of charge carrier, either electrons or holes, recombination does not occur and no light is emitted. For example, electron only devices can be obtained by replacing ITO with a lower work function metal which increases the energy barrier of hole injection. Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection.


15 Aug 2013

Google kills the Messenger in latest Google+ Android update

Google kills the Messenger in latest Google+ Android update

Google will shut down its Messenger group chatting service as part of an update to its Google+ app for Android-based devices, the company announced. Google also will ditch the service on iOS devices.
Google Hangouts, which performs similar messaging and video calling functions, will act as a replacement for Messenger, said Google software engineer Virgil Dobjanschi, in a Wednesday blog post. Google Messenger was a service for mobile devices designed for group conversations with text, photos, and face-to-face video chat.
Because Hangouts provides messaging and video calls across Android, iOS, and the Web, “we’re moving Messenger from the Google+ mobile apps, first on Android, then on iOS,” Dobjanschi said. Messenger will be shut down Wednesday for Android-based devices. A Google spokeswoman declined to comment further on when the service will be removed on iOS.
Users will be able to download all of their Messenger conversations, including text and photos, from Google’s Takeout data export service later on Wednesday, Dobjanschi said.


The offer of a transition to Hangouts, however, does not guarantee that users will stay, because the product occupies an increasingly crowded market of other group chat and messaging services. Competitors include Facebook’s Messenger service, WhatsApp, Rounds, and Imo messenger.
A Google Hangout
Google also faces pressure to distinguish its Google+ social network from large rivals like Twitter and Facebook. To make Google+ more attractive to users, the company announced more than 40 new featuresat its annual I/O conference for developers in May. Some of those enhancements included an improved interface and ongoing chat and photo improvements.
Google+ has roughly 190 million active users, the company reported in May. More than 390 million people are active across Google, which includes liking content in the Google Play Store, making video calls in Gmail and sharing YouTube videos.
Facebook, meanwhile, has more than 1 billion monthly active users, and Twitter has just over 200 million.
Google has recently shut down some other services in the process of updating its apps. Last month the company scrapped its Latitude and check-ins products as part of an update to its Maps app. Google Latitude provided a way for people to see the approximate locations of friends and others who have shared that information.

New features

Several new features are coming to the Google+ Android app that will be rolling out over the next few days, the company said on Wednesday.
While some of the location-sharing features might now be absent from Google Maps, there are additional tools in this area within the Google+ Android app.
With the new version of the app, location sharing includes more controls, so people can share their pinpoint or city-level location with others, and on a circle-by-circle basis, if they want, Google said. In other words, users can share their pinpoint location with family, and their city-level location with co-workers, according to the company.
The update also lets Google+ for Android interact more with Google’s Drive cloud storage service. If users are sharing photos or videos in Google Drive, they now have the option to view and share them from Google+ on Android and on the Web, Google said. Google’s photo auto-enhancement feature, which was first rolled out at the I/O conference, will be applied here as well.
A pull-to-refresh feature, which commonly lets people see the latest content within an app by pulling down on the screen, also is on the way for the app, Google said.
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10 Jul 2013



Gather information on your system

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CPU-Z is a freeware that gathers information on some of the main devices of your system.

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PC Cleaner software safely cleans the windows registry, corrects DLL file issues, removes unwanted start-up applications resulting in a faster, cleaner PC.
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