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PCBs Fabrication Methods

Printed Circuit Board (PCB) is a mechanical assembly consisting of layers of fiberglass sheet laminated with etched copper patterns. It is used to mount electronic parts in a rigid manner suitable for packaging. Also known as a Printed Wiring Board (PWB). A schematic diagram must be made available that shows the connection of the parts on the board. Each part on the schematic should have a reference designator that matches the one shown on the Bill of Materials (BOM). Many schematic layout programs will allow automatic generation of the BOM. The parts to be mounted on the PCB should be…

Bohr’s tall story

Some time ago I received a call from a colleague who asked if I would be the referee on the grading of an examination question. He was about to give a student a zero for his answer to a physics question, while the student claimed he should receive a perfect score and would if the system were not set up against the student: The instructor and the student agreed to submit this to an impartial arbiter, and I was selected.   I went to my colleague’s office and read the examination question: “Show how it is possible to determine the…

What would happen if oxygen were to disappear for 5 seconds?

All Oxygen? A few things..   Everyone at the beach would get sunburns. Ozone is molecular oxygen, and blocks the majority of UV light. Without it we are toast. The day-time sky would get darker. With fewer particles in the atmosphere to scatter blue light, the sky would get a bit less blue and a bit more black. Every internal combustion engine would stall. This means that every airplane taking off from a runway would likely crash to the ground, while planes in flight could glide for some time. All pieces of untreated metal would instantly spot weld to each…

Logical puzzles & answers – For Interviews, Placement, Competitive and Entrance Examinations

Question: Three friends divided some bullets equally. After all of them shot 4 bullets the total number of bullets remaining is equal to the bullets each had after division. Find the original number divided? Answer : 18. Assume that initial there were 3*X bullets. So they got X bullets each after division. All of them shot 4 bullets. So now they have (X – 4) bullets each. But it is given that,after they shot 4 bullets each, total number of bullets remaining is equal to the bullets each had after division i.e. X Therefore, the equation is 3 * (X…

Why is Stainless Steel Stainless?

What Is Stainless Steel and Why Is it Stainless? In 1913, English metallurgist Harry Brearly, working on a project to improve rifle barrels, accidentally discovered that adding chromium to low carbon steel gives it stain resistance. In addition to iron, carbon, and chromium, modern stainless steel may also contain other elements, such as nickel, niobium, molybdenum, and titanium. Nickel, molybdenum, niobium, and chromium enhance the corrosion resistance of stainless steel. It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, or stain ‘less’ than other types of steel. The chromium in the steel combines…

What’s a servo

A Servo is a small device that has an output shaft. This shaft can be positioned to specific angular positions by sending the servo a coded signal. As long as the coded signal exists on the input line, the servo will maintain the angular position of the shaft. As the coded signal changes, the angular position of the shaft changes. In practice, servos are used in radio controlled airplanes to position control surfaces like the elevators and rudders. They are also used in radio controlled cars, puppets, and of course, robots. A Futaba S-148 Servo Servos are extremely useful in…

WHY A BLUE LED IS WORTH A NOBEL PRIZE?

Three scientists have jointly earned the Nobel Prize in physics for their work on blue LEDs, or light-emitting diodes. Why blue in particular? Well, blue was the last — and most difficult — advance required to create white LED light. And with white LED light, companies are able to create smartphone and computer screens, as well as light bulbs that last longer and use less electricity than any bulb invented before.   LEDs are basically semiconductors that have been built so they emit light when they’re activated. Different chemicals give different LEDs their colors. Engineers made the first LEDs in…

Advantages of CMOS logic family over TTL

Negligible power dissipation The main advantage of CMOS logic family is their extremely low power consumption. This is because there is no direct conducting path from Vdd to ground in either of input conditions. So there is practically zero power dissipation in STATIC conditioms.There is only dynamic power dissipation, i.e. power is dissipated only during the switching of MOSFETs.   High fan out For TTL logic family the maximum fan out is found to be around 10.Whereas for CMOS logic family fan out rating rating may exceed 50. Hence a larger no of gates can be driven by the output…

A Guide to Understanding Battery Specifications

A battery is a device that converts chemical energy into electrical energy and vice versa. This summary provides an introduction to the terminology used to describe, classify, and compare batteries for hybrid, plug-in hybrid, and electric vehicles. It provides a basic background, defines the variables used to characterize battery operating conditions, and describes the manufacturer specifications used to characterize battery nominal and maximum characteristics.   Battery Basics Cell, modules, and packs– Hybrid and electric vehicles have a high voltage battery pack that consists of individual modules and cells organized in series and parallel. A cell is the smallest, packaged form…

8051 Tutorial 4

The tutorial for the LCD screen will use the basic 1602 type from Hitachi!! This has been cloned to death… Everyone has a copy of this chip set down to mimicking its every function..   I use “Displaytech” and “Fordata” mainly because of the cost… I’m certainly not advertising them.. Use whatever you have… But they have served me well over the past few years…   To use these devices you have to set them up before you can use them…. The chip set can use a variety of sizes, the main ones being 16 character by 2 line, 20…

8051 Tutorial 3

The next tutorial I want to look at a stepping motor… To step a stepper motor we need to sequence the coil windings… The windings are arranged so applying current to the coils in a certain sequence we can turn the motor in small steps.     The sequence shown in the diagram will step the motor in full steps 0AH, 09H, 05H, 06H..The connections are as follows…     To half step the motor then just add a single excitation in between the steps .. As A1 and A2 are on in the first sequence moving to A1 to…

8051 Tutorial 2

Ok… Back on track.   The next tutorial we need to read a 4 x 3 ( 12 key ) keypad…   If we attach a keypad to port 0 and place some resistors as external pull up’s we can read can read the 12 possible on the keypad on only 7 pins… 4 pins as columns and 3 pins as rows.. Here is the connection I used… I have included a 7 segment LED as a simple visual response…     The pinout is shown above… We don’t have enough power to sink the current so I used a…

8051 Tutorial 1

The 8051 micro has been on the scene for a number of years now since the early 80’s.   There are literally hundreds of derivatives.. Ti, Silicon, Atmel, Microchip, Cypress and many many more have come up with several products using this core….. I used Phillips personally. These chips came with a tight boot-loader… With a free program called “Flash Magic” you could simply write a program, compile or assemble to a hex file and flash magic puts it on the device through the serial port.   Boot-loading isn’t a new thing, many devices out today employ a boot-loader… The…

Sensors Demystified

What Is a Sensor? A sensor is a device for detecting and signalling a changing condition. And what is this “changing condition”? Often this is simply the presence or absence of an object or material (discrete sensing). It can also be a measurable quantity like a change in distance, size or color (analog sensing). This information, or the sensor’s output, is the basis for the monitoring and control of a manufacturing process.   Contact vs. Non-Contact Technologies Contact sensors are electromechanical devices that detect change through direct physical contact with the target object. Contact sensors: Typically do not require power…

Who is Lena Soderberg?

Lenna or Lena is the name given to a standard test image widely used in the field of image processing since 1973. It is a picture of Lena Söderberg, shot by photographer Dwight Hooker, cropped from the centerfold of the November 1972 issue of Playboy magazine. Given the nature of the image and its source, several academics have criticized its continued use in scientific publications and higher education as both sexist and unprofessional. Model for Playboy became a superstar within the computer vision community as her picture became one of the most widely used standard test images for compression algorithms….

Why do resistors have color coding when printing the value over the resistor would have been more convenient to the users?

Ever wondered how to see the circuit if you can not *remove* any resistors from their own position from a circuit? Something like this : Question then, how you propose to write the value, where? How can one ensure that the folks who adds those resistors to the circuit, actually takes care of the printed value showing UP so that other people can read the rating? Clearly one can not. There is no way to ensure that. Thus, color coding is mandatory – so that any way, in any configuration one can *read* the values. Why do resistors have color…

Pulse Width Modulation (PWM) – Basics

In layman language, PWM is a technique in which you vary the ratio of HIGH time to LOW time of a pulse. One of the applications is simulation of an analogue signal using digital TTL signals. What if you want to supply 2.5 Volts to a component? You can use a voltage divider circuit using R1=R2 and then supply the output across any one of these resistors to your component of interest. Simple enough? But what you are overlooking is the fact that this circuit is highly inefficient as there is always going to be power dissipation across the resistors….

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