Create your own operating system!

Nearly every true computer geek has, at some point, wanted to write an operating system. However, writing a custom kernel and other bits takes years of study, experience and patience. If you intend to keep your sanity, then the best course of action is to use someone else's code.

Cosmos, or C# open source managed operating system, is a pre-made kernel that provides you with "OS legos" that allow you to quickly and easily create your own operating system.

You will need:

• Microsoft Visual C# 2008.
• A knowledge of the C# programming language (don't worry if you don't have this, it's a pretty easy language).
• The Cosmos user kit (milestone 4).

Let's do a run down of the necessary software mentioned earlier.

Microsoft Visual C# can be downloaded free if you get the express edition. You can download it at http://www.microsoft.com/express/downloads/ You can also download the entire Visual Studio including visual basic and visual c++ as an ISO image (these can be tricky, see below for details on reading ISO images). Even on a blazing fast computer, downloading visual studio will take two hours at most, though.

WARNING: make sure that you get the 2008 edition and not 2010. This may seem backwards, but the Cosmos user kit has yet to support 2010.

The cosmos user kit is the platform that we will write our OS in. It's an all-in-one micro-kernel operating system that is written in 100% C#.You can download it at http://cosmos.codeplex.com/releases/view/58275

A note about ISO images:

If you opted to download the entire visual studio, then you're going to need to read the ISO image file. An ISO image is a map of a virtual DVD, using the same encoding as any other disk. You have two option: Use a program like nero or roxio to burn the image to a CD-ROM then insert that disk into your computer and download it (The latest Windows XP comes with Roxio, and Windows 7 comes with Nero pre-installed. Other than that, you will almost certainly find something on your computer that will burn a CD. Explore a bit), or you can use Daemon tools lite edition to read the file directly.

Daemon tools lite is free and can be found at http://www.daemon-tools.cc/eng/downloads.

Express users need to install the Visual Studio 2010 Integrated Shell run time. 

http://www.microsoft.com/download/en/details.aspx?id=115

Click on the Link below for further steps: 

http://www.instructables.com/id/Create-your-own-operating-system/step2/Creating-the-project/ 

Batch Files (Scripts) in Windows

By Vic Laurie

Batch files or scripts are small easy-to-write text files that carry out a series of commands. They can be simple enough that even the average home computer user can take advantage of them.

Systems administrators and power users are well aware of the utility of batch files but the average PC user is generally unacquainted with them or is intimidated by the notion of writing or even running a script. This is unfortunate since it means that many are foregoing the use of a powerful tool for carrying out routine or repetitive tasks. Although batch files can be quite sophisticated and used for complicated network and system administration, they can also be of the utmost simplicity and very brief. In this article, I will introduce the batch file and discuss some uncomplicated examples that make basic tasks easier.

What is a batch file?

These are simple text files containing some lines with commands that get executed in sequence, one after the other. These files have the special extension BAT or CMD. Files of this type are recognized and executed through an interface (sometimes called a shell) provided by a system file called the command interpreter. In Windows XP/ Vista the command interpreter is the file cmd.exe. The large assortment of versatile commands available in Windows XP/Vista/7 makes batch files a powerful tool.

To Learn More,

Link: http://commandwindows.com/batch.htm

The list of commands available in the command prompt for Windows 7 is similar to that for Windows Vista. Some commonly used commands and a brief explanation of their functions are given.

Link: http://commandwindows.com/windows7-commands.htm

Note: Here are some other links that could help you to understand the concept of Batch Programming,

Batch File Commands,

Link: http://academic.evergreen.edu/projects/biophysics/technotes/program/batch.htm

Batch Programming,

Link: http://www.infionline.net/~wtnewton/batch/

Windows Scripting,

Link: http://www.ericphelps.com/scripting/index.htm

DOS7 Batch Programming,

Link: http://www.ericphelps.com/batch/

How to Create Artificial Intelligence in Your Spare Time

One of the most popular futurist hobbyhorses is the idea that artificially intelligent machines will soon become ubiquitous and change the world forever. This is an old dream, which may have started with Isaac Asimov's idea that superintelligent computers would take over the geo-political management of Earth (see the final story in I, Robot) and create a more rational world. Early computer geeks like Alan Turing imagined that AI would simply be a perfected human brain, sentient but far more powerful and capable of solving problems humans can't. Most scientists and futurists agree that true AI has the potential to create a better world, but what can you put on your to-do list today that will help make AI a reality in fifty years? Actually, there's quite a lot.

To-Do List for Futurists: Creating A.I.

1. Today: Tag everything you can on the Web. Many A.I. theorists believe that the first steps to creating a sentient computer involve teaching it to recognize information in the same way humans recognize it. So, for example, if you tag images on photo-sharing site Flickr, you are building up a database for a future A.I. who can look at a picture of a car and say to itself, "90 percent of people called this a car, so it's most likely a car."
2. Today: Along the lines of the "tag everthing" task, you can also teach future A.I.s how to evaluate what they're seeing in a subjective way too. For instance, you can start generating data that will teach A.I.s to recognize the difference between science fiction and science by using services like StumbleUpon orDel.icio.us, where you have a chance to categorize and rate any Web page. Find an excerpt from a novel about computers by Neal Stephenson? Categorize it as "science fiction." Find a book about computers by journalist Steven Levy? Categorize it as "science." The richer our metadata is, the closer we come to creating machines that can evaluate images, text, and objects in a human-like way — simply because the machine will have so much data about how humans have already evaluated them.
3. This month: Tutor a kid in math or computer science. You may not be the next big genius who is going to invent the nice A.I. who does an anti-Skynet and stops all war through rationality. But the kid who lives in your neighborhood who doesn't have the cash to buy her own laptop? She might be. So help out by tutoring — you can often find opportunities via services like VolunteerMatch.
4. This month: Help make statistical machine translation of human languages as natural as possible. A few hours' worth of work with MIT's open source MOSES software project, and you can help A.I.s of the future gain a nuanced understanding of how to do idiomatic translations from one language to another. This will, of course, also help A.I.s to gain a feel for speaking in natural languages themselves. Basically, you upload "training data" to MOSES — usually two texts, one an original and one a translation — and then you give MOSES feedback on whether the translated phrases it has now learned work in all situations.
5.  This year: Many experts now believe that A.I.s will only evolve if we can place them inside robotic bodies, because sentience is so bound up with being able to move around in the world. (So say goodbye to the idea of an A.I. that just sits in a giant box.) Get educated about robotic intelligence by visiting a robot show (Robogames is a good one, and you can look for others like it in your local area). If you can't make it out to a robot show, try reading up on the future of robotics in a great book by MIT AI lab researcher Rodney Brooks called Flesh and Machines. It was written a couple of years ago, but it's still up-to-date in terms of what the most cutting-edge research is.

Make a Laser Ball

Laser Ball Specifications:

• Total optical power: ~70mW
• Current draw (max): ~300mA
• Operating voltage: 3.3V
• Battery life: ~2.5hrs (but its rechargeable!)

Steps and Timeline:

• 1.00 hr - Preparing and gathering materials/tools
• 0.25 hr - Thinking through the design
• 0.50 hr - Preparing the Teensy
• 0.75 hr - Cutting and installing diffraction gratings
• 0.50 hr - Drilling the tennis ball
• 0.50 hr - Installing lasers
• 1.00 hr - Soldering lasers, Teensy, and JST connector
• 0.50 hr - Squeezing components into tennis ball

Total time:

• 5.00 hrs

Materials:

• $42 - Red lasers (14) (Buy from Aixiz) (Buy from DealExtreme)
• $9 - Battery (Buy Li-Ion batteries from Sparkfun)
• $16 - Teensy microcontroller (Buy from PRJC)
• $5 - IR remote (Buy from Adafruit)
• $2 - IR receiver (Buy from Adafruit)
• $2 - Diffraction Grating (Buy from Edmund Scientific) (Buy from Ebay)
• $1 - JST connector (Buy from Sparkfun)
• $1 - Tennis Ball (your closet...)

Total cost:

• $78

Tools:

• Soldering iron
• Dremel
• Wire strippers/cutters
• Hobby knife
• Masking tape
• Marker
• Scissors
• Tweezers/Forceps
• Helping-hands/alligator clips

Link: http://www.instructables.com/id/Laser-Ball/?ALLSTEPS

DEFCON 19: Tracking the Trackers: How Our Browsing History Is Leaking into the Cloud

Speaker: Brian Kennish Founder of Disconnect

What companies and organizations are collecting our web-browsing activity? How complete is their data? Do they have personally-identifiable information? What do they do with the data? 

The speaker, an ex--Google and DoubleClick engineer, will answer these questions by detailing the research he did for The Wall Street Journal (http://j.mp/tttwsj) and CNN (http://j.mp/tttcnn), talking about the crawler he built to collect reverse-tracking data, and launching a tool you can use to do your own research.

DEFCON 19: Hacking and Forensicating an Oracle Database Server

Speaker: David Litchfield

David Litchfield is recognized as one of the world's leading authorities on database security. He is the author of Oracle Forensics, the Oracle Hacker's Handbook, the Database Hacker's Handbook and SQL Server Security and is the co-author of the Shellcoder's Handbook. He is a regular speaker at a number of coputer security conferences and has delivered lectures to the National Security Agency, the UK's Security Service, GCHQ and the Bundesamt f¸r Sicherheit in der Informationstechnik in Germany.

DEFCON 19: Economics of Password Cracking in the GPU Era

Speaker: Robert "Hackajar" Imhoff-Dousharm SanDisk Corporation

As this shift to "General Computing" and working in the cloud has accelerated in the last 4 years, so has the ability to take advantage of these technologies from an Information Security vantage point. This could not be more apparent than with the sudden uptick in GPU based password cracking technologies. In this presentation we will explore where the current GPU cracking technologies are, what their cost are to implement, and how to deploy and execute them (with demo). Most importantly, we will demonstrate the "brute force calculator" which can assist with getting your monies worth. Finally, we will explore where the future lays for this medium and what that means for safe passwords moving into the next decade.

DEFCON 19: Steganography and Cryptography 101

Speaker: eskimo

There are a lot of great ways to hide your data from prying eyes this talk will give a crash course in the technology and some tools that can be used to secure your data. Will also discuss hiding your files in plain site so an intruder will have no idea that hidden files even exist. These same techniques can also be employed by somebody wishing to transmit messages.

DEFCON 19: Three Generations of DoS Attacks

Speaker: Sam Bowne Instructor, City College San Francisco

Denial-of-service (DoS) attacks are very common. They are used for extortion, political protest, revenge, or just LULz. Most of them use old, inefficient methods like UDP Floods, which require thousands of attackers to bring down a Web server. The newer Layer 7 attacks like Slowloris and Rudy are more powerful, and can stop a Web server from a single attacker with incomplete Http requests. The newest and most powerful attack uses IPv6 multicasts, and can bring down all the Windows machines on an entire network from a single attacker.

I will explain and demonstrate these tools: Low Orbit Ion Cannon, OWASP Http DoS Tool, and flood_router6 from the thc-ipv6 attack suite. This deadly IPv6 Router Advertisement Flood attack is a zero-day attack--Microsoft has known about it since June 2010 but has not patched it yet (as of May 4, 2011).

Audience Participation: Bring a device to test for vulnerability to the Router Advertisement Flood! Some cell phones and game consoles have been reported to be vulnerable--let's find out! If your device crashes, please come to the Q&A room so we can video-record it and arrange disclosure to the vendor.

Assembly Language - Key to Electronics

This site provides you different tutorials and manuals for computer languages and programs. Anything and Everything that you need to know to master the Basic concepts of an Assembly Language..

Link: http://101.lv/learn/asm/index.htm

Here are the links to learn few other programming languages,

Java: http://101.lv/learn/Java/index.htm

Java Script: http://101.lv/learn/JSweek/index.htm

C:  http://dl.dropbox.com/u/10414458/cprogramming/movies.htm

C++: http://101.lv/learn/C++/index.htm

PHP: http://101.lv/learn/php3/manual.html

Delphi: http://101.lv/learn/delphi/index.htm

Visual Basic 5: http://101.lv/learn/Vbasic/index.htm

HTML 3.2: http://101.lv/learn/tyhtml/index.htm

Good Luck !!!

An Anemometer Circuit

Air Flow Differences:

Q1 has a Higher Collector to Emitter Voltage than Q2, Therefore a Greater Power Dissipation. Air Flow causes Cooling which causes the Collector to Emitter Voltage of Q1 to Change. This Results in Different Power Dissipations and Also a Different Voltage across R1, which is detected and amplified by A2. 

Thus the Air Flow MUST Pass over Both Transistor Equally.

Copyright 2004: Chemelec

Top 7 Reasons You Should Start a Small Business before Graduating College

By: Phil Novara (entrepreneurship)

Imagine if you started a $30 billion company by sophomore year? Would you think twice about graduation? Think differently about college all together?

In 2004, that’s exactly what Mark Zuckerberg did. He created “The Facebook” which evolved into the famous social platform we all know and love today. Of course it wasn’t always a billion dollar company, but Zuckerberg did build a very successful business in college, and you can too!

Most undergrads have no clue why they’re in college. The average freshmen changes majors 2-3 times before their sophomore year. Interests change. Life becomes a party and come to find out philosophy degrees aren’t applicable in the “real world.” Four years can happen fast. 

Now, I’m a realist, and I’m not convincing you to build “The Next Facebook.” I have an alternative solution: Start a small business. Even a funny t-shirt business will prepare you more than any college course. You don’t have to create the next Facebook - you just have to start something, now! 

Here are the top 10 reasons to start a small business before graduating college: 

1. Free Time

College is full of free-time. Young professionals quickly realize how much free time a “real job” eats up. The 40-50 hour work week really cuts into playing X-Box. 

Don’t waste that precious time, I know your young, but building wealth starts now. Start a small business and gain the knowledge to propel your future. You’ll be 10 steps ahead of the game. 

2. What do you Love?

Most undergrads are not free from their parents. That’s a bummer when you want to spend a summer partying, but it’s awesome when starting a small business. 

Your parents are covering your expenses. You’re not 40 years old supporting a family. That gives you freedom to work on what you love, even if it doesn’t make tons of cash. For example, do you love editing videos? Get really good at it. There are thousands of companies who need rock-star video editors. The experience is worth its weight in gold. 

3. Friends Will Work for Free

In college, your friends will work for free (well, most of them). The majority of students consider themselves “broke college students.” A shot at making money easily motivates young entrepreneurs. Once you graduate, people have bills to pay, and working for free is not an option. 

SIDE NOTE: Choose who you work with wisely, don’t pick your party animal roommate. 

4. Be a Rock Star in your First Interview

Do you really want to bore an interviewer about how you constructed a detailed SWOT analysis on Coca-Cola? Trust me, they don’t care.

What if you referred to a real world situation how you handled a customer demanding back money because you sold them an inferior funny t-shirt? How did you handle that situation? What could you have done better?

It’s a no brainer, real life experience trumps schooling every time. When you run a small business, you gain that experience. Business isn’t what you read in college books, it’s about the people you meet and how you handle situations. If you have that experience, you can “WOW” interviewers with your knowledge through stories. Be interesting and prepare.

5. “The Real World” isn’t yet Real

Think big. Like really big. The “real world” hasn’t yet warped your mind. You’re young. You haven’t been molded into the 9-5 cookie cutter caffeine addicts that the “real world” creates. Use that to your advantage, what have you got to lose? 

6. Networking Resources

It may not seem like it now, but college can provide you with tons of resources. There are tons of students there with successful parents. If you work at making a handful of friends, you can leverage their parents to help you launch a small company. 

Building a small business takes resources, and if you don’t have the resources already, you need to find the people that do and convince them of your business. College is crawling with students that have the resources and connections you need to succeed.

7. Extra Income

What happens if you make an extra $300/mo selling funny t-shirts? What could you do with that money? How much more time will that consume vs working at the campus library for minimum wage? College campuses are tight knit, it would be easy to set up shop on campus and sell funny shirts (I know, I’m beating the t-shirt business into the ground). Get going!

Seriously…what have you got to lose? If you fail, you’ll learn and that is experience nobody can take away from you. 

---------------------------------------------------------------------------------------------------------------------------------------------------

Phil Novara is a serial entrepreneur looking to break out into his next venture. He is currently building a funny video contest called Blooper Box which can be found at http://www.blooperbox.com

If you have any business questions, here is his contact info:

Email: [email protected]

Twitter: @pnovara

Touch Activated Light

The circuits below light a 20 watt lamp when the contacts are touched and the skin resistance is about 2 Megs or less. The circuit on the left uses a power MOSFET which turns on when the voltage between the source and gate is around 6 volts. The gate of the MOSFET draws no current so the voltage on the gate will be half the supply voltage or 6 volts when the resistance across the touch contacts is equal to the fixed resistance (2 Megs) between the source and gate.

The circuit on the right uses three bipolar transistors to accomplish the same result with the touch contact referenced to the negative or ground end of the supply. Since the base of a bipolar transistor draws current and the current gain is usually less than 200, three transistors are needed to raise the microamp current level through the touch contacts to a couple amps needed by the light. For additional current, the lamp could be replaced with a 12 volt relay and diode across the coil.

Copyright 2006: Bill Bowden

Game Show Indicator Lights (Who's First)

The circuit below turns on a light corresponding to the first of several buttons pressed in a "Who's First" game. Three stages are shown but the circuit can be extended to include any number of buttons and lamps.

Three SCRs (silicon controlled rectifiers) are connected with a common cathode resistor (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR. When all lamps are off, and a button is pressed, the corresponding SCR is triggered due to the voltage at the divider junction being higher than the cathode. Once triggered, the SCR will remain conducting until current is interrupted by the reset switch. Or, you can just turn the power off and back on.

A 50 ohm, 5 watt resistor was selected to produce a 10 volt drop at 200 mA when a single 25 watt lamp comes on. Higher wattage lamps would require a lower value resistor, and visa versa. For example to use 60 watt lamps and maintain the 10 volt drop, the peak current would be 60/160 = 375 mA and the resistance would be E/I = 10/.375 or about 27 ohms at 3.75 watts. The SCRs are "Sensitive Gate' types which trigger on about 200 uA and the gate current is around 1.5 mA when the first button is pressed. The 1N914 diodes in series with the buttons gates are used to prevent a reverse voltage on the gate when a button is pressed after an SCR is conducting. The two 51 ohm resistors will be fairly large in physical size (compared to a 1/4 watt size) and should be rated for 5 watts of power or more. Use caution and do not touch any components while the circuit is connected to the AC line.

Adding a Buzzer:

The relay shown in parallel with the 50 ohm cathode resistor can be used to momentarily power a buzzer with an external circuit through the contacts. The 1000 uF capacitor causes the relay to energize for about one second, longer times can be obtained with a larger capacitor.

Parts List:
Quantity Description Radio Shack Part Number
1 4 Amp/400 Volt Bridge Rectifier 276-1173
3 Silicon Controlled Rectifier (SCR) NTE5457
3 120 VAC/ 25 Watt incandescent lamp
1 50-100 microfarad/ 200 volt capacitor
1 1000 microfarad / 35 volt capacitor 272-1032
1 50 ohm resistor/ 5 or 10 Watt 271-133
3 Push Button Switch (normally open)
1 Push Button Switch (normally closed)
3 2K resistor, 1/4 watt 271-1325
4 1N914 Diode
1 51K resistor, 1 watt
1 2 Amp Fuse 270-1064
1 Relay (SPDT) 9 Volt DC, 500 ohm coil 275-005

Copyright 2006: Bill Bowden

Light Activated Relay

This is same circuit as above with the addition of a photo resistor to trigger the flip flop instead of a push button. The bias resistor in series with photo resistor was chosen so that sufficient voltage is present at the base of the 2N3904 to supply current to the circuit in ambient lighting conditions. The circuit should toggle when the photo resistor is hit by a flashlight beam or other fast changing light source. Slow changes in light intensity will have no effect unless the light gets too bright to maintain sufficient bias for the 2N3904.

Copyright 2006: Bill Bowden

JAVA Design Pattern

What is the design pattern?

If a problem occurs over and over again, a solution to that problem has been used effectively. That solution is described as a pattern. The design patterns are language-independent strategies for solving common object-oriented design problems. When you make a design, you should know the names of some common solutions. Learning design patterns is good for people to communicate each other effectively. In fact, you may have been familiar with some design patterns, you may not use well-known names to describe them.

Do I have to use the design pattern?

If you want to be a professional Java developer, you should know at least some popular solutions to coding problems. Such solutions have been proved efficient and effective by the experienced developers. These solutions are described as so-called design patterns. Learning design patterns speeds up your experience accumulation in OOA/OOD. Once you grasped them, you would be benefit from them for all your life and jump up yourselves to be a master of designing and developing. Furthermore, you will be able to use these terms to communicate with your fellows or assessors more effectively.

Many programmers with many years experience don't know design patterns, but as an Object-Oriented programmer, you have to know them well, especially for new Java programmers. Actually, when you solved a coding problem, you have used a design pattern. You may not use a popular name to describe it or may not choose an effective way to better intellectually control over what you built. Learning how the experienced developers to solve the coding problems and trying to use them in your project are a best way to earn your experience and certification.

Patterns: According to commonly known practices, there are 23 design patterns in Java. These patterns are grouped under three heads:

1. Creational Patterns

2. Structural Patterns

3. Behavioral Patterns

Link: http://www.allapplabs.com/java_design_patterns/java_design_patterns.htm

Android Developers

Developing applications for Android devices is facilitated by a group of tools that are provided with the SDK. You can access these tools through an Eclipse plugin called ADT (Android Development Tools) or from the command line. Developing with Eclipse is the preferred method because it can directly invoke the tools that you need while developing applications.

However, you may choose to develop with another IDE or a simple text editor and invoke the tools on the command line or with scripts. This is a less streamlined way to develop because you will sometimes have to call command line tools manually, but you will have access to the same number of features that you would have in Eclipse.

Note: 

Before you begin developing Android applications, make sure you have gone through all of the steps outlined in Installing the SDK.

The basic steps for developing applications with or without Eclipse are the same:

1.  Set up Android Virtual Devices or hardware devices.

• You need to create Android Virtual Devices (AVD) or connect hardware devices on which you will install your applications.See Managing Virtual Devices and Using Hardware Devices for more information.

2.  Create an Android project.

• An Android project contains all source code and resource files for your application. It is built into an .apk package that you can install on Android devices.

3.  Build and run your application.

• If you are using Eclipse, builds are generated each time you save changes and you can install your application on a device by clicking Run. If you're using another IDE, you can build your project using Ant and install it on a device using adb.

4.  Debug your application with the SDK debugging and logging tools.

• Debugging your application involves using a JDWP-compliant debugger along with the debugging and logging tools that are provided with the Android SDK. Eclipse already comes packaged with a compatible debugger.

5.  Test your application with the Testing and Instrumentation framework.

• The Android SDK provides a testing and instrumnetation framework to help you set up and run tests within an emulator or device.

For more visit: http://developer.android.com/guide/index.html

National Instruments

Engage students and reinforce circuit and electronic concepts with a hands-on dynamic learning environment that is a unique combination of software, hardware, courseware, and textbooks. From teaching circuit basics to facilitating upper-level projects, educators are adopting circuits teaching software such as NI Multisim tightly integrated with the NI Educational Laboratory Virtual Instrumentation Suite (NI ELVIS) design and prototyping hardware, and NI Lab VIEW graphical systems design software to prepare students for tomorrow’s engineering challenges.

Link: http://www.ni.com/academic/circuits.htm

Other Topics:
1.  Controls and Mechatronics

     http://www.ni.com/academic/controls.htm

2.  Signal and Image Processing
     http://www.ni.com/academic/signalprocessing.htm

3.  RF and Communications
     http://www.ni.com/academic/communication.htm

4.  Embedded System Design
     http://www.ni.com/academic/embedded.htm

Programmable Digital Code Lock

A programmable code lock can be used for numerous applications in which access to an article/gadget is to be restricted to a limited number of persons. Here is yet another circuit of a code lock employing mainly the CMOS ICs and thumbwheel switches (TWS) besides a few other components. It is rugged and capable of operation on voltages ranging between 6 and 15 volts. The supply current drain of CMOS ICs being quite low, the circuit may be operated even on battery.

The circuit uses two types of thumbwheel switches. switch numbers TWS1 through TWS8 are decimal-to-BCD converter type while switch numbers TWS9 through TWS16 are 10-input multiplexer type in which only one of the ten inputs may be connected to the output (pole). One thumbwheel switch of each of the two types is used in combination with IC CD4028B (BCD to decimal decoder) to provide one digital output.Eight such identical combinations of thumbwheel switches and IC CD4028 are used. The eight digital outputs obtained from these combinations are connected to the input of 8-input NAND gate CD4068.

For getting a logic high output, say at pole-1, it is essential that decimal numbers selected by switch pair TWS1 and TWS9 are identical, as only then the logic high output available at the Specific output pin of IC1 will get transferred to pole-1. Accordingly, when the thumbwheel pair of switches in each combination is individually matched, the outputs at pole-1 to pole-8 will be logic high.

This will cause output of 8-input NAND gate IC CD4068b to change over from logic high to logic low, thereby providing a high-to-low going clock pulse at clock input pin of 7-stage counter CD4024B, which is used here as a flip-flop (only Q0 output is used here).The output (Q0) of the flip-flop is connected to a relay driver circuit consisting of transistors T1 and T2. The relay will operate when Q0 output of flip-flop goes low. As a result transistor T1 cuts off and T2 gets forward biased to operate the relay.Switch S1 is provided to enable switching off (locking) and switching on (unlocking) of the relay as desired, once the correct code has been set.

With the code set correctly, the NAND gate output will stay low and flip-flop can be toggled any number of times, making it possible to switch on or switch off the relay, as desired. Suppose we are using the system for switching-on of a deck for which the power supply is routed via the contacts of the relay. The authorised person would select correct code which would cause the supply to become available to the deck.

After use he will operate switch S1 and then shuffle the thumbwheel switches TWS1 through TWS8 such that none of the switches produces a correct code. Once the code does not match, pressing of switch S1 has no effect on the output of the flip-flop.Switches TWS9 through TWS16 are concealed after setting the desired code. In place of thumbwheel switches TWS1 through TWS8 DIP switches can also be used.

Ultrasonic Switch

Circuit of a new type of remote control switch is described here. This circuit functions with inaudible (ultrasonic) sound. Sound of frequency up to 20 kHz is audible to human beings. The sound of frequency above 20 kHz is called ultrasonic sound. The circuit described generates (transmits) ultrasonic sound of frequency between 40 and 50 kHz. As with any other remote control system this cirucit too comprises a mini transmitter and a receiver circuit. Transmitter generates ultrasonic sound and the receiver senses ultrasonic sound from the transmitter and switches on a relay. The ultrasonic transmitter uses a 555 based astable multivibrator. It oscillates at a frequency of 40-50 kHz. An ultrasonic transmitter transducer is used here to transmit ultrasonic sound very effectively.

The transmitter is powered from a 9-volt PP3 single cell. The ultrasonic receiver circuit uses an ultrasonic receiver transducer to sense ultrasonic signals. It also uses a two-stage amplifier, a rectifier stage, and an operational amplifier in inverting mode. Output of op-amp is connected to a relay through a complimentary relay driver stage. A 9-volt battery eliminator can be used for receiver circuit, if required. When switch S1 of transmitter is pressed, it generates ultrasonic sound. The sound is received by ultrasonic receiver transducer. It converts it to electrical variations of the same frequency. These signals are amplified by transistors T3 and T4. The amplified signals are then rectified and filtered. 

The filtered DC voltage is given to inverting pin of op-amp IC2. The non- inverting pin of IC2 is connected to a variable DC voltage via preset VR2 which determines the threshold value of ultrasonic signal received by receiver for operation of relay RL1. The inverted output of IC2 is used to bias transistor T5. When transistor T5 conducts, it supplies base bias to transistor T6. When transistor T6 conducts, it actuates the relay. The relay can be used to control any electrical or electronic equipment.

 Important hints:

1. Frequency of ultrasonic sound generated can be varied from 40 to 50 kHz range by adjusting VR1. Adjust it for maximum performance.

2. Ultrasonic sounds are highly directional. So when you are operating the switch the ultrasonic transmitter transducer of transmitter should be placed towards ultrasonic receiver transducer of receiver circuit for proper functioning.

3. Use a 9-volt PP3 battery for transmitter. The receiver can be powered from a battery eliminator and is always kept in switched on position.

4. For latch facility use a DPDT relay if you want to switch on and switch off the load. A flip-flop can be inserted between IC2 and relay. If you want only an ‘ON-time delay’ use a 555 only at output of IC2. The relay will be energised for the required period determined by the timing components of 555 monostable multivibrator.

5. Ultrasonic waves are emitted by many natural sources. Therefore, sometimes, the circuit might get falsely triggered, espically when a flip-flop is used with the circuit, and there is no remedy for that.

Teach Yourself Graphic Design: A Self-Study Course Outline

Fortunately, it isn’t required to go to design school in order to be a graphic designer. A good foundation in graphic design history, theory, and practical application will help you hit the ground running. There are plenty of resources available in which you can learn graphic design on your own. Don’t set your expectations to high at first, as it will take enthusiastic study for years to become great. You can do it though!

If you would like to learn graphic design from the ground up, through self directed study, then this article lists some great resources that will get you started with your design education. Also, even if you do go to design school, at least three-fifths of your education will be through self directed study anyway. Let’s get to it!

Link: http://psd.tutsplus.com/articles/inspiration/teach-yourself-graphic-design-a-self-study-course-outline/

VTC Training CD for C Programming

Author - Mark Virtue

1. Introduction
2. A Basic C Program
3. Basic Elements of a C Program
4. Conditional Code
5. Loops
6. Arrays
7. Strings and Characters
8. Advanced Operators
9. The C Preprocessor
10. Functions
11. Structures
12. The Compilation Process
13. Basic Pointers
14. Scope
15. Dynamic Memory
16. The Standard C Function Library
17. Bitwise Operators
18. Advanced Pointers
19. Function Pointers

Link: http://dl.dropbox.com/u/10414458/cprogramming/movies.htm

The Gas Chamber Expriment : Written By Ankit Malasi

Story:

The biggest worry of a soldier on the battle field is of course the enemy. But when a soldier has been fighting for several days without any time to rest, then his biggest enemy is not a guy with a loaded rifle pointed to his head. But, it is his own body. Sleep, fatigue and pain may not kill you, but it will dull your senses and make you a easy target and a worthless soldier.

The military once tried to address this problem by commissioning a group of scientist to conduct an illegal experiment to develop a stimulant that could make such problems irreverent. These researchers kept 5 people alive for 15 days using an experimental gas based stimulant. They were kept in a sealed environment to carefully monitor their oxygen intake so that the gas didn’t kill them, since the gas was toxic in high concentrations. This was before closed circuit cameras so they had only microphones and 5 inch thick glass porthole sized window into the chamber to monitor them. The chamber contained books, cots to sleep on but no bedding, running water and a toilet, and enough dried food to last them for over a month.

The test subjects were Pakistani prisoners. Each of them had spent at least 5 years in the Indian jails. And, in all this time no one had come to claim them. So it was safe to say that no one would miss them if anything went wrong in the experiment.

Everything was fine for the first 5 days, the subjects hardly complained having been promised (falsely) that they would be freed if they submitted to the test and did not sleep for 30 days. Their conversations and activities were monitored and it was noted that they continued to talk about increasingly traumatic incidents of the past, and the general tone of their conversations took on a darker aspect after the 4 day mark.

After 5 days they started to complain about the circumstances and events that led them to where they were and started to demonstrate severe paranoia. They stopped talking to each other and began alternately whispering to the microphones and one way mirrored port holes. Oddly they all seemed to think that they could win the trust of the experimenters by turning over their comrades, the other subjects in the captivity with them. At first the researchers suspected that this was an effect of the gas itself…

After 9 days the first of them started screaming. He ran the length of the chamber repeatedly screaming at the top of his lungs for 3 hours straight, he continued attempting to scream but was only able to produce occasional squeaks. The researchers postulated that he had physically torn his vocal cords. The most surprising thing about this behavior is how the other captives reacted to it… or rather didn’t react to it. They continued whispering to the microphones until the second of the captives started to scream. The 2 non screaming captives took the books apart, smeared page after page with their own feces and pasted them calmly over the portholes. The screaming promptly stopped.

So did the whispering into the microphones.

After 3 more days passed, the researchers checked the microphones hourly to make sure they were working. Since they thought that it was impossible that no sound could be coming with 5 people inside. The oxygen consumption in the chamber indicated that all 5 must still be alive. In fact it was the amount of oxygen 5 people would consume at a very heavy level of exercise. On the morning of the 14th the researchers did something they said they would not do to get a reaction from the captives, they used the intercom inside the chamber, hoping to provoke any response from the captives they were afraid were either dead of unconscious.

They announced: “We are opening the chamber to test the microphones. Step away from the door and lie flat on the floor or you will be shot. Compliance will earn one of you your immediate freedom.

To their surprise, they heard a single line in a calm voice response: “We no longer want to be freed.”

Debate broke out among the researchers and the military forces funding the research. Unable to provoke any response using the intercom, it was finally decided to open the chamber at midnight on the 15th day.

The chamber was flushed of the stimulant gas and filled with fresh air and immediately voices from the microphone began to object. 3 different voices began begging, as if pleading for the life of loved ones to turn the gas back on. The chamber was opened and soldiers sent in to retrieve the test subjects. They began to scream louder than ever, and so did the soldiers when they saw what was inside. 4 of the 5 subjects’ were still alive, although no one could rightly call the state that they were in as ‘life’.

The food rations past day 5 had not been so much as touched. There were chunks of meat from the dead test subject’s thighs and chest stuffed into the drain at the centre of the chamber, blocking the drain and allowing 4 inches of water to accumulate on the floor. Precisely how much of the water on the floor was actually blood was never determined. All 4 ‘surviving’ test subjects had large portions of muscles and skin thrown away from their bodies. The destruction of flesh and the exposed bone on their finger tips indicate that the wounds were inflected by hand, not with teeth as the researchers initially thought. Closer examination of the positions’ and the angles of the wounds indicated that most if not all of them were self-inflicted.

The abdominal organs below the rib cage of all test subjects had been removed. While the heart, lung and diaphragm remained in place, the skin and most of the muscles attached to the ribs had been ripped off exposing the lungs through the rib cage. All blood vessels and organs remained intact, they had just been taken out and laid on the floor, fanning out around the still living bodies of the subjects. The digestive systems of all four could be seen to be working digesting food. It quickly became apparent what they were digesting was their own flesh that they had ripped off and eaten over the course of days.

Most of the soldiers were Indian special operatives at the facility, but still many refused to return to the chamber to remove the test subjects. They continued to scream to be left in the chamber and alternatively begged and demanded that the gas be turned back on least they fall asleep…

Optical Sensor

Electro-optical sensors are those which convert the light rays in to electronic signal very similar to the photo resistor, these are applied in emergency lamps such that when there is light it is made to switch off and when there is no light it automatically made to switch on. In aviation, electro-optical devices have been used as part of the avionics, in order to expand both range and vision at low ambient light levels.

Travel Touch Alarm

The Travel Touch Alarm can be used to provide a audible alarm when someone touches the door knob or handle of your hotel room. The door knob or handle must be made of metal for the circuit to work. The main chip in the circuit is a 555 timer which will be triggered if a hand comes close to or touches the door knob. The circuit attaches to the door knob at the end of the 1 meg ohm resistor. 

Once the timer is triggered the LED will light and the UJT will output a tone to the speaker. The timer will time out in 5 seconds. The sensitivity of the trigger can be changed by changing the 1 meg ohm resistor to another value. The 5 second time out can be adjusted by changing the value of the resistor connected between pin 8 and pin 7. The output tone can be changed by changing the RC values on the base of the UJT.

Loop Sensor

Many security systems use a closed loop of wires and switches arranged so that whenever a door or window is opened, the loop will be broken and the alarm will sound. An obvious problem is that someone can tamper with the system, short out the loop, and later on, come back and burglarize the premises without sounding the alarm. Hiding a known resistance in the loop can prevent this. That way, the alarm can distinguish a short circuit from a correctly functioning closed loop. 

The figure above shows a circuit that does the job. It's a somewhat unusual application of a National Semiconductor LM3915 IC, normally used to drive LED bargraph displays. That chip happens to contain the right combination of comparators and logic circuits to do what you need. 

Step 1 is to translate the loop resistance into a voltage; that's done by putting it into a voltage divider with resistors R1 and R2. Capacitor C2 protects the circuit against electromagnetic noise-important because burglar alarms use long wires, often running near heavy electrical equipment. 

Step 2 is to translate the voltage into a logic signal indicating whether it's in the correct range. That's where the LM3915 comes in. Normally, the LM3 9 15 would drive ten LEDs, one for each of ten small ranges of voltage. The figure below shows the states of outputs A, B, and C under different loop-resistance conditions. obtain logic-level outputs, we have it driving 1K resistors instead of LEDs. Since we only need to distinguish three situations, not ten, we tie some of the outputs together. The LM3915 has open-collector outputs that can be paralleled in that way. 

The truth table in Fig. 2 shows how the outputs work. Note that they use negative logic (OV for "yes", +5V for "no"), the opposite of ordinary logic circuits. You can use inverters such as the 74HC04 to produce positive logic signals if that's what you need. 

Finally, note that the circuit will actually work with any supply voltage from 3 to 25 volts. Of course, if the supply isn't 5 volts, the outputs will not be compatible with j-volt logic circuits.

Digital Electronic Lock

The digital lock shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance.

As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13. The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge. 

A second monostable, one shot circuit is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner). 

The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter. When a correct key is pressed, outputs will be present from both monostable circuits (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives.

The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse. The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key. The circuit can be extended with additional gates (one more CD4011) to accept up to a 8 digit code.

The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The circuit will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The circuit draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.

Copyright 2006: Bill Bowden

Part list:

1x CD4017 decade counter

1x CD4011

1x 74C14 

1x CD4068 

Misc: diodes, resistors, capacitors, etc.

Infrared Remote Control

This circuit will allow you to turn on any piece of equipment that operates on 115 volts ac. The receiver circuit is based on the Radio Shack infrared receiver module (MOD), part number 276-137. It is also available from some of the other sources listed on my Links page. The MOD accepts a 40khz IR signal that is modulated at 4 khz. When a signal is received the MOD will go low. The sensitivity of the MOD is set by different values for R1 and C1. The values for R1 may need to be as high as 10,000 ohms and for C1 40uf. This will prevent the unit from turning on under normal lighting conditions. You will need to experiment with the values that work best for you. The output of the 4013 chip a flip flop toggles on and off with the reception of a IR pulse. The output of the 4013 turns on the MOC optical coupler which in turn switches on the triac and supplies power to the AC load. 

Copyright 1998 Randy Linscott

FM Beacon Transmitter (88-108 MHz)

This circuit will transmit a continuous audio tone on the FM broadcast band (88-108 MHz) which could used for remote control or security purposes. Circuit draws about 30 mA from a 6-9 volt battery and can be received to about 100 yards. A 555 timer is used to produce the tone (about 600 Hz) which frequency modulates a Hartley oscillator. A second JFET transistor buffer stage is used to isolate the oscillator from the antenna so that the antenna position and length has less effect on the frequency.

Fine frequency adjustment can be made by adjusting the 200 ohm resistor in series with the battery. Oscillator frequency is set by a 5 turn tapped inductor and 13 pF capacitor. The inductor was wound around a #8 X 32 bolt (about 3/16 diameter) and then removed by unscrewing the bolt. The inductor was then stretched to about a 3/8 inch length and tapped near the center. The oscillator frequency should come out somewhere near the center of the band (98 MHz) and can be shifted higher or lower by slightly expanding or compressing the inductor.

A small signal diode (1N914 or 1N4148) is used as a varactor diode so that the total capacity in parallel with the inductor varies slightly at the audio rate thus causing the oscillator frequency to change at the audio rate (600 Hz). The ramping waveform at pins 2 and 6 of the timer is applied to the reversed biased diode through a large (1 Meg) resistor so that the capacitance of the diode changes as the ramping voltage changes thus altering the frequency of the tank circuit. Alternately, an audio signal could be applied to the 1 Meg resistor to modulate the oscillator but it may require an additional pullup resistor to reverse bias the diode. The N channel JFET transistors used should be high frequency VHF or UHF types (Radio Shack #276-2062 MPF102) or similar. 

Copyright 2006 Bill Bowden

Signal Tracer

The main part of this circuit is the LM386 amplifier chip. It also uses a transistor input to buffer the input signal and provide extra gain for the LM386. The little unit has helped me out on numerous occasions when trouble shooting any amplifier circuit like a stereo receiver, tv / vcr audio section, radios, cd players and car stereos. 

Copyright 1998 Randy Linscott

Triangle Waveform Generator

The Tri-Waveform Generator can be used for a number of different uses. The one that I use it for is a signal generator to test circuits. The frequency range is 20 to 20khz. and can be adjusted by R1. The duty cycle or the time that the waveform is high and the time that the waveform is low can be adjusted by R4. The purpose of R2 and R3 are to clean up any distortion on the sine wave output. To do this you must hook up the sine wave output to and oscilloscope and adjust R2 & R3 to make the sine wave as accurate as possible. 

Copyright 1999 Randy Linscott

Two Component Metal Detector

The circuit shown must represent the limits of simplicity for a metal detector. It uses a single 4093 quad Schmitt NAND IC and a search coil -- and of course a switch and batteries. A lead from IC1d pin 11 needs to be attached to a MW radio aerial, or should be wrapped around the radio. If the radio has a BFO switch, switch this ON. 

Since an inductor resists rapid changes in voltage (called reactance), any change in the logic level at IC1c pin 10 is delayed during transfer back to input pins 1 and 2. This is further delayed through propagation delays within the 4093 IC. This sets up a rapid oscillation (about 2 MHz), which is picked up by a MW radio. Any change to the inductance of L1 (through the presence of metal) brings about a change to the oscillator frequency. Although 2 MHz is out of range of the Medium Waves, a MW radio will clearly pick up harmonics of this frequency. 

The winding of the coil is by no means critical, and a great deal of latitude is permissible. The prototype used 50 turns of 22 awg/30 swg (0.315 mm) enamelled copper wire, wound on a 4.7"/120 mm former. This was then wrapped in insulation tape. The coil then requires a Faraday shield, which is connected to 0V. A Faraday shield is a wrapping of tin foil around the coil, leaving a small gap so that the foil does not complete the entire circumference of the coil. The Faraday shield is again wrapped in insulation tape. A connection may be made to the Faraday shield by wrapping a bare piece of stiff wire around it before adding the tape. Ideally, the seach coil will be wired to the circuit by means of twin-core or figure-8 microphone cable, with the screen being wired to the Faraday shield. 

The metal detector is set up by tuning the MW radio to pick up a whistle (a harmonic of 2 MHz). Note that not every such harmonic works best, and the most suitable one needs to be found. The presence of metal will then clearly change the tone of the whistle. The metal detector has excellent stability, and it should detect a large coin at 80 to 90 mm, which for a BFO detector is relatively good. It will also discriminate between ferrous and non-ferrous metals through a rise or fall in tone. 

Copyright Rev. Thomas Scarborough

Combinational Conjuring Trick

The simple circuit of Fig.1 emulates a similar conjuring trick which sells for hundreds of Pounds. The trick seems to do the almost-impossible from an electronic point of view, let alone from the point of view of common sense.

It consists of a bank of three on-off switches (S19-S21), which have three switch covers, each of a different colour. These switch a bank of three lightbulbs (LP1-LP3), each of a different colour. The colours of the lightbulbs correspond with the colours of the switch covers.

Now comes the interesting part. The switch covers may be exchanged at will, but still they switch the lightbulbs of corresponding colour. Similarly, the lightbulbs may be exchanged at will, but still they respond to the switches of corresponding colour. On the surface of it, there would seem to be 64 possible connections between switches and lighbulbs, and no possible way that the conjurer can manipulate them all.

However, add some sleight-of-hand, and things become a lot simpler. Each switch cover is symmetrical, in such a way that it looks the same whether facing N, E, or W. Further, each lightbulb is screwed into a circular base, which looks the same whether facing N, E, or W.

Let us consider just one of the switch covers (S19). Three reed switches (S10-S12) are positioned beneath the cover, at positions N, E, and W, and each of these activates a different lightbulb. Any one of the three reed switches may be closed by a single magnet positioned strategically under the switch cover. Depending on the orientation of the switch cover, therefore, the switch will activate any one of the three reed switches, and thus the selected lightbulb.

On discussing this with an accomplished magician, the author was told that this alone would be sufficient for the full effect described - reed switches S1-S9 may be omitted. Nevertheless, the lightbulbs may similarly be surrounded with three reed switches each, which are activated by the orientation of the circular base - a magnet being strategically positioned within it. These reed switches may thus reroute the power to the conjurer's selected lightbulb.

There is just one caveat from an electronic point of view. Carefully consider the voltage and power ratings of the reed switches and on-off switches, to match these with the chosen lightbulbs. Failing this, your trick may demonstrate how none of the switches will activate none of the lightbulbs.

Copyright Rev. Thomas Scarborough

[Contact the author of this article at [email protected]]

Magnetic Gun

Picured in Figure 1 is a miniature magnetic gun. When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally. 

IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1 to L4 in rapid sequence. 

Transformer T1 secondary is 18 volts 1 amp A.C. When rectified and smoothed, this provides 25.2 V D.C for electromagnets L1 to L4. Resistor R4 drops 12 V to obtain a supply voltage low enough for IC1 and IC2. 

The electromagnets are wound on a 25 cm long, 3 mm dia. copper tube (available at hobby shops). Two "stops" may be cut from tin for each electromagnet, and 500 turns of approx. 30 swg. enamelled copper wire wound between them. The electromagnets should be wound on a base of reversed sellotape, so that one may slide them on the copper tube. The slug (or "bullet") is a 3 cm long piece of 2 mm dia. galvanized wire, which should slide loosely inside the copper tube. 

Most crucial to the effectiveness of the gun are the setting of VR1 and the positions of electromagnets L1 to L4 on the copper tube (the values and measurements shown are merely a guide). Firstly, with L2 to L4 disconnected, VR1 should be tuned and L1 positioned for optimum effectiveness (place a wire inside the tube to feel how far the slug jumps with L1). Then L2 (now connected) should be positioned for optimum effectiveness (the slug will now exit the tube). Repeat with L3 and L4. 

Electromagnets L2 to L4 were each found to substantially increase the range of the gun. In a forthcoming edition of EPE, the author will describe how readers may land a small projectile on Mars. 

Copyright Rev. Thomas Scarborough 

[Contact the author of this article at [email protected]]

Decimal to BCD Convertor

This circuit will provide an output in Binary Coded Decimal from any of the input switches. The input switches may be expanded to 16 switches, providing a Hexadecimal to BCD conversion. 

Notes

When any particular key is pressed, its value will appear in BCD form at the outputs (A, B, C & D). It will remain there until another key is pressed. The 12 keys produce outputs up to "1011". Extended to 16 keys, the circuit will give the full HEX to BCD conversion. 

Memory Module

The above circuit produces an output ONLY while the input switch is depressed. To make a convertor with a latched output, the following modifications are made. Each CMOS 'AND' gate has its free input tied to Vcc, and by the action of R1 through R4 any 'hi input' will therefore cause the output to be latched. The circuit is shown in dec_bcd.png 

When any particular key is pressed, its value will appear in BCD form at the outputs (A, B, C & D). It will remain there until another key is pressed. The 12 keys produce outputs up to "1011". Extended to 16 keys, the circuit will give the full HEX to BCD conversion. 

The LEDs are a visual indication of the value. They are not necessary to the operation of the circuit. If you wish, you may leave them out; together with their associated resistors (R5, R6, R7). 

The circuit works at voltages from 5 to 15 vdc. Please note that A, B, C & D are connected directly to the outputs of the Cmos IC. You will need to regulate the load your application places on these outputs. 

Construction

Because the keypad may be used without the memory, the layouts are drawn separately. If you build them both on the same piece of stripboard, isolate them from one another. Cut all of the tracks except for the six that join the keypad terminals to the memory module. Always check carefully that the copper is cut all the way through. Sometimes a small strand of copper remains at the side of the cut and this will cause malfunction. If you don't have the proper track-cutting tool, then a 6 to 8mm drill-bit will do. Just use the drill-bit as a hand tool; there is no need for a drilling machine. 

Board Layout

Board layout for converter without memomry is shown in pad_lay.png. The layout with memory can be found in mem_lay.png 

For clarity, all the components are shown lying flat on the board. However, those connected between close or adjacent tracks are mounted standing upright. Using a socket reduces the chances of damaging the IC; and makes it easier to replace if necessary. The links are bare copper wire on the component side of the board. Two of them need to be fitted before the IC socket. You can make the links from telephone cable:- the single stranded variety used indoors to wire telephone sockets. Stretching the core slightly will straighten it; and also allow the insulation to slip off.