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Sunday 24 April 2011

PCB Designing Tips And Tricks


Placing Components
Generally, it is best to place parts only on the top side of the board.
When placing components, make sure that the snap-to-grid is turned on. Usually, a value of 0.050" for the snap grid is best for this job.
First place all the components that need to be in specific locations. This includes connectors, switches, LEDs, mounting holes, heat sinks or any other item that mounts to an external location.
Give careful thought when placing component to minimize trace lengths. Put parts next to each other that connect to each other. Doing a good job here will make laying the traces much easier.
Arrange ICs in only one or two orientations: up or down, and, right or left. Align each IC so that pin one is in the same place for each orientation, usually on the top or left sides.
Position polarized parts (i.e. diodes, and electrolytic caps) with the positive leads all having the same orientation. Also use a square pad to mark the positive leads of these components.
You will save a lot of time by leaving generous space between ICs for traces. Frequently the beginner runs out of room when routing traces. Leave 0.350" - 0.500" between ICs, for large ICs allow even more.
Parts not found in the component library can be made by placing a series of individual pads and then grouping them together. Place one pad for each lead of the component. It is very important to measure the pin spacing and pin diameters as accurately as possible. Typically, dial or digital calipers are used for this job.
After placing all the components, print out a copy of the layout. Place each component on top of the layout. Check to insure that you have allowed enough space for every part to rest without touching each other.


Placing Power and Ground Traces
After the components are placed, the next step is to lay the power and ground traces. It is essential when working with ICs to have solid power and ground lines, using wide traces that connect to common rails for each supply. It is very important to avoid snaking or daisy chaining the power lines from part-to-part.
One common configuration is shown below. The bottom layer of the PC board includes a "filled" ground plane. Large traces feeding from a single rail are used for the positive supply.

Placing Signal Traces
When placing traces, it is always a good practice to make them as short and direct as possible.
Use vias (also called feed-through holes) to move signals from one layer to the other. A via is a pad with a plated-through hole.
Generally, the best strategy is to lay out a board with vertical traces on one side and horizontal traces on the other. Add via where needed to connect a horizontal trace to a vertical trace on the opposite side.
A good trace width for low current digital and analog signals is 0.010".
Traces that carry significant current should be wider than signal traces. The table below gives rough guidelines of how wide to make a trace for a given amount of current.
0.010" 0.3 Amps
0.015" 0.4 Amps
0.020" 0.7 Amps
0.025" 1.0 Amps
0.050" 2.0 Amps
0.100" 4.0 Amps
0.150" 6.0 Amps
When placing a trace, it is very important to think about the space between the trace and any adjacent traces or pads. You want to make sure that there is a minimum gap of 0.007" between items, 0.010" is better. Leaving less blank space runs the risk of a short developing in the board manufacturing process. It is also necessary to leave larger gaps when working with high voltage.
When routing traces, it is best to have the snap-to-grid turned on. Setting the snap grid spacing to 0.050" often works well. Changing to a value of 0.025" can be helpful when trying to work as densely as possible. Turning off the snap feature may be necessary when connecting to parts that have unusual pin spacing.
It is a common practice to restrict the direction that traces run to horizontal, vertical, or 45 degree angles.
When placing narrow traces, 0.012" or less, avoid sharp right angle turns. The problem here is that in the board manufacturing process, the outside corner can be etched a little more narrow. The solution is to use two 45 degree bends with a short leg in between.
It is a good idea to place text on the top layer of your board, such as a product or company name. Text on the top layer can be helpful to insure that there is no confusion as to which layer is which when the board is manufactured.

Checking Your Work
After all the traces are placed, it is best to double check the routing of every signal to verify that nothing is missing or incorrectly wired. Do this by running through your schematic, one wire at a time. Carefully follow the path of each trace on your PC layout to verify that it is the same as on your schematic. After each trace is confirmed, mark that signal on the schematic with a yellow highlighter.
Inspect your layout, both top and bottom, to insure that the gap between every item (pad to pad, pad to trace, trace to trace) is 0.007" or greater. Use the Pad Information tool to determine the diameters of pads that make up a component.
Check for missing vias. ExpressPCB will automatically insert a via when changing layers as a series of traces are placed. Users often forget that via are not automatically inserted otherwise. For example, when beginning a new trace, a via is never inserted. An easy way to check for missing via is to first print the top layer, then print the bottom. Visually inspect each side for traces that don't connect to anything. When a missing via is found, insert one. Do this by clicking on the Pad in the side toolbar; select a via (0.056" round via is often a good choice) from the drop down listbox, and click on the layout where the via is missing.
Check for traces that cross each other. This is easily done by inspecting a printout of each layer.
Metal components such as heat sinks, crystals, switches, batteries and connectors can cause shorts if they are placed over traces on the top layer. Inspect for these shorts by placing all the metal components on a printout of the top layer. Then look for traces that run below the metal components.

Wednesday 20 April 2011

Cisco Packet Tracer 5.3

Packet Tracer is a Cisco router emulator that can be utilized in training and education, but also in research for simple computer network simulations. The tool is created by Cisco Systems and provided for free distribution to faculty, students, and alumni who are or have participated in the Cisco Academy program. The purpose of Packet Tracer is to offer students and teachers a tool to learn the principles of networking as well as develop Cisco Technology specific skills.

Cisco Networking Academy is pleased to announce the release of Cisco Packet Tracer version 5.3, a minor release that includes the following new protocol support and enhanced functionality:

* Improved Linksys models, added WEP wireless security algorithm, Cable and DSL enhancements
* Call Manager Express (VOIP support)
* FTP server and routers/switches – server and client
* Email system (SMTP and POP3) – server and client
* Border Gateway Protocol (BGP) – limited implementation that allows for a more realistic representation of the Internet for scenarios
* Generic IP end devices – to create more versatility in device creation
* Activity Wizard Initial Tree enhancements – more scenario variations

The new protocol support and activity wizard enhancements in version 5.3 will enable instructors to teach concepts in CCNA Discovery, CCNA Exploration, and CCNP courses more effectively, including the following:
CCNA Discovery

* Networking for Home and Small Businesses: Improved Linksys models and wireless security protocols and algorithms, generic IP end devices
* Working at a Small-to-Medium Business or ISP: Better DNS, improved DHCP, wireless security, new FTP, SMTP, POP3
* Introducing Routing and Switching in the Enterprise: Improved multi-area OSPF, EIGRP, BGP
* Designing and Supporting Computer Networks: New VOIP, Call Manager Express

CCNA Exploration

* Network Fundamentals: Improved HTTP, DNS, DHCP; new FTP, SMTP, POP3
* Routing Protocols and Concepts: Improved multi-area OSPF, EIGRP, new BGP
* LAN Switching and Wireless: Improved Linksys models, wireless security algorithms, 802.11
* Accessing the WAN: New PPPoE, enhanced IPSec, Cable and DSL enhancements

CCNP

* Improved multiarea OSPF, EIGRP, new BGP

We recommend upgrading to the new version to take advantage of the many improvements included in this release. To learn more about how Packet Tracer can be used in each Networking Academy course, please view this new Packet Tracer 5.3 Curricula Support chart.
Packet Tracer 5.3 is currently available for download from the Packet Tracer resource pageon Academy Connection. To access this page, log in to Academy Connection and click the Cisco Packet Tracer graphic on the left of the page, select Software Downloads, then select the appropriate download package for your needs. The previous version of Packet Tracer, version 5.2.1.8, will continue to be available for download.
Packet Tracer 5.3 supports activities authored in Packet Tracer 5.0, 5.1, and 5.2.x. All activities included in IT Essentials: PC Hardware and Software, CCNA Discovery, CCNA Exploration, and CCNA Security are also fully compatible with Packet Tracer 5.3. Please note that activities authored or saved with Packet Tracer 5.3 can only be used with the version 5.3 software.

For more information, please review the Packet Tracer 5.3 FAQs and the updated resources available on the Packet Tracer resource page on Academy Connection.

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The Microsoft Macro Assembler (MASM)

The Microsoft Macro Assembler (MASM) is an x86 assembler for MS-DOS and Microsoft Windows. It supports a wide variety of macro facilities and structured programming idioms, including high-level functions for looping and procedures. Later versions added the capability of producing programs for Windows. MASM is one of the few Microsoft development tools that target 16-bit, 32-bit and is supplied as a 64 bit version ML64.EXE for 64-bit platforms. Versions 5.0 and earlier were MS-DOSapplications. Versions 5.1 and 6.0 were available as both MS-DOS and OS/2 applications.Versions 6.12 to 6.14 were implemented as patches for version 6.11 which converted them from 16 bit MZ executables to 32 bit PE executable files. All later versions have been 32 bit PE executable files built as Win32 console mode applications.


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Monday 18 April 2011

DB-25 Parallel Port Interfacing Circuit Diagram


Masm Emulator For Windows 7

Easy Code for MASM is the visual assembly programming environment made to build 32-bit Windows applications. The interface for Easy Code for MASM looks like Visual Basic and will allow you to program a Windows assembler application in an easy way as was never possible before.

Easy Code for MASM is distributed with a setup program and includes the source code of a nice CD player, a complete and fast text editor in a dll file (to be able to program your own editor), a complete and excellent text editor ready to use, a file shredder, a MIDI player and many other applications.



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Sunday 17 April 2011

Electronic Repairing Article

The Four Senses



Sight, sound, smell and touch can solve a lot of electronic problems. They are the most important tools and can give you a strong clue as to the source of the problem. When the unit is opened, it must be inspected closely with the four senses; otherwise you may spend countless hours trying to find the culprit which is caused by a leaky electrolytic capacitor (oil leak) which you’ve missed out during troubleshooting.


Sight - You can see a cracked printed circuit board, a burnt resistor, blown

electrolytic capacitor, arcing from Flyback transformer, lightning damage, cracked diode, oil leak from capacitors, poor board connection, melted plastic of the Flyback transformer, cracked CRT neck and many more.


Sound - You can hear a tic-tic and high pitch sound from the Flyback

Transformer, arc over in the neck of CRT, capacitor bursting while the unit is operating, high voltage shutdown and arcing at the Flyback Transformer.


electronic repair


Smell - The oil from a leaky electrolytic capacitor can generate a powerful smell,

a burnt resistor also produces a smell and ozone smell from the Flyback Transformer.


Touch - You can use your finger to make a quick “touch test” of components in a

suspected faulty circuit. Overheated components in the printed circuit board are always a source of trouble. Always turn off the equipment before you begin to touch on the suspected components like IC’s, transistor and diode. Before you touch any components, be careful to ground yourself by touching the case of the equipment for a moment. If you don’t do this, you can accumulate a static charge, which can damage delicate CMOS ICs. Some components are hot even when they’re operating normally. If a transistor is attached to a large metal plate (a heat sink), you can expect the plate to be quite hot. A transistor with a smaller heat sink should be proportionally cooler.


touch on electronic


Use of the sight, sound, smell and touch senses will reveal the untold story of the faulty circuit and may provide helpful clues.






Friday 15 April 2011

Berry B.Brey E-Book



































This fourth edition text is written for the student in a course of study that requires a thorough
knowledge of programming and interfacing of the Intel family of microprocessors. It is a very
practical reference text for anyone interested in all programming and interfacing aspects of this
important microprocessor family. Today, anyone functioning or striving to function in a field of
study that uses computers must understand assembly language programming and interfacing.
Intel microprocessors have gained wide applications in many areas of electronics, communications, control systems, and particularly in desktop computer systems.
ORGANIZATION AND COVERAGE
In order to cultivate a comprehensive approach to learning, each chapter of the text begins with
a set of. objectives that briefly define the contents of the chapter. This is followed by the body of
the chapter, which includes many programming applications that illustrate the main topics of the
chapter. At the end of each chapter, a numerical summary, which doubles as a study guide, re
views the information presented in the chapter. Finally, questions and problems are provided to
promote practice and mental exercise with the concepts presented in the chapter.
This text contains many example programs, using the Microsoft MACRO assembler pro
gram, to provide an opportunity to learn how to program the Intel family of microprocessors.
Operation of the programming environment includes the linker, library, macros, DOS function,
and BIOS functions.
Also provided is a thorough description of each family member, memory systems, and various I/O systems that include disk memory, ADC and DAC, 16550 UART, PIAs, timers, key
board/display controllers, arithmetic coprocessors, and video display systems. Also discussed
are the personal computer system buses (ISA, VESA, and PCI). Through these systems, a practical approach to microprocessor interfacing is learned.

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Wednesday 13 April 2011

Various Video Amplifiers


555 simple VCO



















The VCO has output range from 1500 Hz at Vin =1V to 300Hz at Vin=5V, R1 or C1 can be varied to change this range. U2 provides a symmetrical square-Wave output of half of the timer frequency



Restricted range oscillator
















It is a Restricted range oscillator, from 60 Hz to 1.4Khz

Voltage Controlled Oscillator VCO


Headphone Hack! Noise Eliminating Headphones!

Mint tin speaker/amp

Weekend Project: Mint Tin Amp

Amazing Car Remote Mod!

Boost the Range of any Remote!

World's Loudest Alarm Clock!

Laser Guided Slingshot!

Tuesday 12 April 2011

Regulator / Current Source

























The circuit powers the load via the regulator’s input instead of its output. Because the regulator’s
output sees constant dummy load R1, it tries to consume a constant amount of current, no matter what
the voltage across the actual load really is. Hence, the regulator’s input serves as a constant-current
source for the actual load. Power the circuit with any one of the commonly available ± 15- or ± 12-V sup
plies. The voltage dropped across the regulator and dummy load decreased the total compliance voltage of
the circuit. You set the load’s current with R1. The current equals 1.25 A /ohms  x R1.

















Simple Power Supply






















This power supply delivers plus and minus 9 V
to replace two 9-V batteries. The rectifier circuit is
actually two separate full-wave rectifiers fed from
the secondary of the transformer. One full-wave
rectifier is composed of diodes Dl and D2, which
develop +9 V, and the other is composed of D3 and
4, which develop —9 V.
Each diode from every pair rectifies 6.3 Vac, half the secondary voltage, and charges the associated
 filter capacitor to the peak value of the ac
waveform, 6.3 x 1 Á14 = 8.9 V. Each diode should
have a PIV, Peak Inverse Voltage, rating that is at
least twice the peak voltage from the transformer,
2x8.9=18 V. The 1N4001 has a PIV of 50V.















Universal Battery Charger























When power is applied to the circuit, SCR1 is off so there is no bias-current path to ground;
thus, LM317 acts as a current regulator. The LM317 is connected to the battery through steering
 diode D1, limiting resistor R1, and bias resistor R2. The steering  diode prevents the battery
from discharging through the LED and the SCR when power is removed from the circuit. As the
battery charges, the voltage across trip-point potentiometer
R5 rises, and at some point, turns on the SCR.
Then, current from the regulator can flow to
ground, so the regulator now functions in the volt
age mode. When the SCR turns on, it also provides
LED1 with a path to ground through R3. So. when
LED1 is on, the circuit is in the voltage-regulating
mode; when LED1 is off, the circuit is in the cur
rent-regulating mode.




12V Battery Charger


















This circuit ¡s a high-performance charger for gelled-electrolyte lead-acid batteries. This charger
quickly recharges the battery and shuts off at full charge. Initially, charging current is limited to 2 A. As the
battery voltage rises, current to the battery decreases, and when the current has decreased to 150 mA,
the charger switches to a lower float voltage, which prevents overcharge. When the start switch is pushed,
the output of the charger goes to 14.5 V. As the battery approaches full charge, the charging current
decreases and the output voltage is reduced from 14.5 V to about 12.5 V, terminating the charging. Transistor Q1 then lights the LED as a visual indication of full charge.

Robokits Line Follower Robot

How to program the AVR microcontroller Pt 1

Secret Hidden RC Hard-Drive

Fire-fighting Robot

Metal Detector













Using an oscillator running at 455 kHz, the metal-detector circuit produces an indication on the meter
Ml. When the oscillator frequency changes because of metal in the field of Li, the change will show as an
increase or decrease in frequency, which produces a charge iii the meter reading. The ceramic filter FILT1
produces a selective band pass that yields this effect. Li can be a 4” diameter coil wound on a suitable
plastic form. About 10 turns of #26 wire are required. Use a frequency counter to adjust Li and verify that
Q1 is operating on or near 455 kHz.

Automatic Garage Door Circuitry by Faizan and Taabish

Thermal Operated Direction Detector















A heat-sensitive sensor can be used to construct a direction detector. Such a sensor reacts to all animal heat. The one used in this design has a sensitive surface that has been divided into two. It, therefore,
makes a difference, whether the heat approaches from the left or the right. The indication for cold objects
is, of course, exactly the opposite.
Circuit IC1B forms a symmetric supply. Terminal s of the sensor is its output. The signal at s is amplified in IC1A by a factor of about 70 before it is available at the output of the detector.
To obtain good directivity, it is best to place the sensor behind a single narrow slit, rather than behind
the usual raster of a multifaceted mirror. The circuit draws a current of only a few mA from a 5-V supply.


Door Buzzer















When SI is depressed, an initial positive voltage is placed on C2 and the non iinvertirig terminal of U1.
The circuit oscillates at a low frequency. As C2 charges up through R3, a rapid increase in frequency of
oscillation results, producing (at SPKRI) a rapidly rising pitched sound. This sound is easily recognized
over ambient noise.

Actel's nanopower and nanosize FPGAs



Actel has introduced nano versions of its IGLOO and ProASIC 3 FPGAs. The new devices reduce power consumption to as low as 2 mW in standby mode with package sizes as small as 3x3  mm.

IGLOO nano FPGAs provide 10k to 250k system gates and support 1.2-V to 1.5-V core and I/O operations, ultra-low-power Flash*Freeze mode with bus hold capability, and advanced I/O features such as hot swapping and Schmitt trigger inputs.

Support for IGLOO and ProASIC3 nano FPGAs is available now in Actel's Libero Integrated Design Environment (IDE) v8.4. This power-optimized development environment enables power-driven layout, battery estimation and advanced power analysis.

For immediate prototyping and programming, designers can leverage the Actel IGLOO Icicle Kit immediately available for USD 99. It features the ultra low-power attributes, flexible implementation options and battery-saving advantages of the company's standard low-power IGLOO FPGA for portable applications. The kit also enables designers to easily and rapidly program, evaluate and modify their IGLOO-based portable designs.

In November, Actel plans to offer a low-cost nano starter kit, priced at USD 50 and fitted with an IGLOO AGLN250 in a VQG100 package. With multiple voltage levels provided, this board will allow quick prototyping and access to all I/O pins and can demonstrate Flash*Freeze mode control and enable battery operation.



Monday 11 April 2011

Fluid Detector


The National LM1830 fluid detector detects the presence,
 absence, or level of a polar liquid, such as water. The LM1830 is a
linear bipolar integrated circuit that operates from a wide range
of operating voltages. The fluid detector shown in Fig. 3-6 deter
mines the presence of a fluid by comparing the resistance of the
fluid between the probes and the internal resistance of the IC. An
ac signal is used to overcome the plating problems associated
with a dc voltage source. Provisions are available for connecting
an external resistance in applications where the fluid impedance
is of a different magnitude than an internal resistor in the IC. As
the probe resistance increases above a preset value, the internal
capacitor produces a signal.



















The internal oscillator is coupled to the base of an open col
lector transistor so that the output signal can drive an LED, a
speaker, or low-current relay. A O.OO1-JÅ.F timing capacitor be
tween pins I and 7 produces a 6-kHz signal on pin 5 of the fluid
detector. A filter capacitor on pin 9 enables the fluid detector to
operate at a constant output. Removing this filter allows a 50%
duty cycle. When used with a speaker, the output will cycle on
and off.
Although the LM1830 detector was primarily designed for
sensing conductive liquids, it can also be used in the direct-
coupled mode. A variable resistance sensing device, such as a light-
dependent resistor or a thermistor, could be used as the sensing
device, as shown in Fig. 3-7. The fluid detector is a complete, low-
cost level-detector system that can be used in many different
 sensing applications. The detector can drive a low-current relay as a
local alarm. The relay contacts could be wired to other sensors,
and the multiple sensors could activate a central alarm panel.