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1. A Background on Technology

Bob Dukish1 

(1)

Canfield, Ohio, USA

 

The Difference Between Science and Technology

The two words science and technology are used interchangeably in the everyday world, but the fields are distinguishably different. As a technologist, one should have a profound appreciation of science; however, it is imperative that a technologist not only appreciate and understand general scientific concepts, but also be able to apply them to the everyday world. Essentially, science can be thought of as a body of knowledge with technology being the practical application of that knowledge. To be an effective electrical engineer or technician, for example, it helps to have an understanding of the actual physical theory of materials and electricity, but many times we will take a simplified approach to solve specific problems. To gain an understanding of the reasoning for simplification in problem solving, please refer to Figure 1-1, a drawing of the copper atom.

Figure 1-1

The Bohr model of the copper atom

The copper atom is composed of 29 protons, each having a positive charge, and located at the center of the atom. Surrounding the protons and uncharged neutrons in the nucleus are 29 negatively charged electrons in several thin spherical clouds located at distances from the center. The location of each cloud is dependent on the energy level of the electrons it contains. Electrons with higher energy levels are located farther away from the center. Like charges repel and unlike charges attract in an inverse square relationship to the distance between charges. In the element copper, there is a single electron called the valance electron in the highest energy level, and that electron is loosely bound to the atom because of its distance from the nucleus. The basic original theory of charge, and even the name electron, comes about from the work of early Greek scholars more than 2,500 years ago, who theorized about electrostatic interactions between cloth and the substance known as amber . More recently, physicists in the early 1900s helped to refine our basic understanding of the structure of matter. Through studies of the nature of electricity, it is known that in a conductive wire, such as one made of copper, if given an amount of external energy from a power source such as a battery, the electron farthest away from the nucleus can become free, and escape the atom to flow with an organized electric current through the wire, eventually joining an atom farther down the line that has a vacancy, called a hole , from the loss of its highest energy electron. Although the movement of each electron, called drift,takes a slight amount of time, the effective signal speed through the entire wire occurs at roughly three-fourths the speed of light.

With the preceding explanation, it is possible to have a very good working knowledge of how a conductor works. Please note that materials at the atomic level are actually much more complicated due to recently discovered quantum theory, but we do not need to discuss the subatomic quarks to understand the essential mechanics for electric current flow. Our technological discussion, therefore, relies mainly on the educated guesses of ancient Greek scholars 2,500 years ago, and through the groundbreaking, but now outdated, explanation of the construction of atoms by physicist Niels Bohr in the 1920s, which is enough to give us a simplified working model of matter as it relates to current flow through a conductor. Now, let us go back in time about 200 years, to the days of one of America’s greatest scientists, Ben Franklin, who was without an understanding of the atomic theory, for which Bohr was awarded the Nobel Prize in 1922. Ben Franklin used intuition and common sense, and hypothesized that electric flow most probably flowed like water, from a high level, to one that is lower. He felt that, like gravity, the electric force pulled down toward a low point of charge. We now typically refer to this low point as either ground, neutral, or return.

Many college courses in electrical engineering still use Ben Franklin’s conventional current theory to evaluate circuits like the one shown in Figure 1-2, even though Franklin’s flow, called conventional, is completely backward! Thanks to the work of Bohr and other scientists of the 20th century, we now know that the negative electrons are the current carrier, as the proton is more massive and locked within the nucleus, but we can simplify the thought process for problem solving by using the conventional flow theory of Ben Franklin. The conventional idea is that the flow of current starts at the positive terminal of the battery (red wire) and proceeds around the loop, until it ends up at the battery’s negative terminal (black wire). The reason that current flows is because the battery is providing an electric force to the circuit through chemical means, and a path for the current flow exists through the components that are in series in the loop of wiring connected between the battery terminals. Theoretically we know the electrons are jumping from atom to atom toward the positive battery terminal, but it is more helpful to us, for problem solving, to use the analogy of water flowing through a pipe when thinking about the process of electric current flow in a wire.

Figure 1-2

An LED circuit

The symbols used in our circuit drawing might look a little like ancient Egyptian hieroglyphics, but they actually make sense once we have a little background information. We call the symbols and diagrams schematics. The battery in the circuit is shown on the left, and the symbol is how a car battery looks inside, as seen from above with the water fill caps removed. The battery is comprised of a system of plates of metal surrounded by a sulfuric acid solution. One plate loses electrons, and the other gains them. This chemical action is responsible for setting up a positive charge on the one outside terminal of the battery, and a negative charge on the other. In our light-emitting diode (LED) circuit, the positive terminal is shown on the top. Because our circuit has a complete path of components and wiring, it is called a closed series circuit, which allows the battery’s stored electric charge to flow as current through the components and wire around the loop. The first component that the conventional current flow encounters is shown as a squiggly line, which is the schematic symbol for a resistor. A resistor is used to restrict current flow. Again, the symbol is drawn to make sense, and can best be understood if you think of electric current flow being similar to water flow, and then thinking about how a stream or river zigzagging from side to side would tend to restrict, or resist, the free flow of water. The next component in the circuit that the current encounters is the LED, shown wired just underneath the resistor. It is a schematic symbol drawn as an arrow, because diodes only allow current flow in one direction. The positive and negative sides of the diode must connect toward their respective terminals of the battery or it will not light. The diode has polarization, whereas the resistor does not. The LED negative side can be identified as having the shorter lead, and also is represented by the side of the plastic component that is slightly flattened. Diodes work with electric current flow somewhat similarly to how valves work with water flow. In fact, in the very early days in the development of electronic diodes when they were vacuum tubes, they actually were called valves. Diodes have many purposes in electronics; when they are used to turn alternating current (AC) into direct current (DC) they are called rectifier diodes; diodes used to keep a voltage constant are called regulators or Zener diodes; and diodes used to oscillate at microwave frequencies and produce radio signals are called tunnel diodes. The LED is a diode that has the enhanced function to give off light as current flows through the polarized junction. The small unconnected arrows shown at an angle from the component in our schematic signify that it is an LED, with the arrows representing the light that is emitted from the device.

In the circuit, we have a 5-volt source, as this is the operating voltage of an Arduino Uno, and also the voltage it sends as a high level to its output ports (a port is a connection to the outside world). The unit of resistance is the Ohm, and resistors with higher Ohm values tend to restrict current flow more. The symbol for the Ohm is the horseshoe Ω, which actually is the uppercase Greek character Omega. So as to not overload the controller output, the value of 220 Ω will be used to limit current flow in many of our later Arduino projects. The resistor value does not need to be precise to illuminate a typical LED; one with a value in the 100 to 400 Ohm range will work fine. It’s usually best to try to limit current flow as much as possible.

Using Ben Franklin’s conventional current flow theory, the circuit operation is as follows: The positive charge on the high side of the battery terminal flows into the wire connected to the resistor. The resistor limits the current flow and drops the voltage. The LED that is connected between the resistor and the negative terminal of the battery lights with an intensity corresponding to the amount of current flow, as limited by the resistor. The LED will produce a voltage drop as well. When we talk about voltage drops, they occur across a component. When talking about voltage drops of more than one component, we add them together. Normally, the negative battery terminal is directly connected to ground, or the chassis, as it is in a vehicle. The symbol below the battery in our LED circuit represents earth ground. In residential house wiring, there is actually a long copper rod, 8 feet or longer, that is driven into the ground to establish the earth ground connection. Soil is somewhat conductive because of moisture and the salts and minerals it contains. Inserting the copper rod deeply into the earth provides much surface area contact with the soil and enables a good electrical connection. In automotive wiring, the same concept is used; however, in residential wiring the use of ground is primarily for safety concerns, whereas in a vehicle, the entire metal chassis is used as a return for the current to reach the negative terminal of the battery. The vehicle chassis is one half of the circuit path, so there is no need to run long lengths of wire to the negative terminal of the battery.

Now with all this background in electric current flow we can see why simplification is important to achieve a working knowledge of technology. Going back to the Bohr model of the atom and Figure 1-1showing a copper atom, we know that the electron is charged negatively, and that when energy produced by a battery is connected to a closed circuit that current will flow. We were able to explain the operation of the LED circuit using Ben Franklin’s conventional flow, and it makes sense because water runs downhill from a high level to one that is lower. Electrons actually flow uphill, though, because the negatively charged electrons are the carriers and move through the wires from a more negative, or low point, to a higher positive point where there is a deficiency of electrons. Thinking about water flowing uphill is hard to imagine, and the simplistic explanation of using conventional flow is incorrect, but it works and makes sense! A good analogy is that if you had one gallon of water per second flowing down a stream, or up a stream, either way you would have one gallon of water per second flowing in the stream. The numbers work out, and simplification keeps us from having nightmares about electrons jumping uphill, from atom to atom.

Ohm’s Law

Just because a theory is old does not necessarily make it outdated or incorrect. The law we are about to look at was first published in 1827, and it remains in use to this day. Georg Ohm was a physicist who studied the relationship between the amounts of voltage, resistance, and current in electrical circuits. In science, there is a difference between a relationship and a law. A relationship signifies a linkage between values. A quantity might tend to increase or decrease as another quantity varies. If both values tend to rise together, then we can say that there is a direct relationship. If, however, one quantity increases as the other decreases, we would refer to the relationship as being inverse. In the last section, we mentioned that with a steady voltage, a larger value of resistance (measured in Ohms, Ω) would cause a decrease in current flow, and likened it to a zigzagging stream obstructing the path of water. The relationship between resistance and current is thus inverse. With constant voltage, you can look at this relationship in two ways:

1. 1.
   As resistance goes up, current goes down.
    
2. 2.
   As current goes down, resistance goes up.
    

The math symbol for proportionality resembles a fish (α). Usually in science, proportional relationships are found and then a constant of proportionality is used to make an equation that can then be solved for a numerical result. Just as in everyday life, relationships start out easy and get more complicated as stronger links are made. Luckily, Ohm’s Law is not messy at all, and the relationships between voltage, resistance, and current turn right into equations without the need for a constant of proportionality. Ohm found the following simple equations to explain electricity (using V for volts, R for Ohms of resistance, and I for amps of current intensity):

Figure 1-2, the schematic from the previous section, has been redrawn and is now shown as Figure 1-3, with the LED and resistor flip-flopped. The position of the components in a series circuit is irrelevant. The reason is because a series circuit is one loop, and all the current must pass through the wire and through every component in the path, regardless of the component’s location within the loop. It makes the explanation a little clearer to design the circuit with the LED on top, because due to the internal construction of an LED, regardless of other circuit parameters, they tend to always drop approximately 2 volts. The reason there is a drop of voltage between the positive and negative sides of an LED is because a barrier junction is formed between the two sides that requires about 2 volts of force to push current through the device. The amount of voltage drop will vary with color; red has a little less drop and blue a little more, and the drop will increase slightly as current increases. Typical LEDs need about 20 milliamps (mA), which is two hundredths (0.020) of an amp of current to properly illuminate; some need a little less and some need a little more current to achieve proper brightness. In a circuit we will later build later, 120 Ω resistors are used. The nice thing about a hand grenade, nuclear war, and electronics design is that you do not have to be exact, just close. Now using Ohm’s Law to calculate current in our circuit, first subtract the 2-volt drop across the LED internal junction, write the proper formula, and plug the numbers into a calculator.

Figure 1-3

Revised LED circuit

5 – 2 = 3 volts across the resistor

I = .014 amps

The current rounds off to about 14 mA, which is fourteen thousandths (0.014) of an amp. Because this is in series with the LED, it is also the LED current. Although this is only about three-quarters of the amount needed to bring the LED to full brightness, it will be visible. This will be a good Ohm value for our projects, as we will be connecting many LEDs to Arduino ports and need to keep currents to a minimum, so as not to overload the controller’s maximum output.

Some people find it easy to have a graphical method to aid in finding the proper Ohm’s Law formula to use with a given problem. The procedure for using the wheel shown in Figure 1-4 is to cover the unknown quantity, and the other two variables appear in the proper position to write the formula.

Figure 1-4

Ohm’s Law wheel

It is interesting to note that if one were to graph a series of results with one independent variable held constant, and the other were to vary in the Ohm’s Law formula for current:

We find that with R held steady as V varies, a graph of a linear equation results because it is of the form y = x.

We also find that with V held steady as R varies, a graph of a hyperbola results because it is of the form 1/x.

Along with the first quadrant graph, as shown for the linear equation, one could graph negative results located in the third quadrant, dependent on the frame of reference; however, there is not a true negative current, other than that as being referenced to its direction of flow. The hyperbola could also have a similar graph located in the fourth quadrant if the frame of reference of the fixed voltage was negative, which then caused current flow in a negatively referenced direction. Interestingly, both asymptotes of the hyperbola could never touch either on the axis because both continue to approach infinity, and the curve could never touch the origin, as there is no perfectly zero resistance.

Engineering Notation

In the last section, we said that LEDs typically require approximately two hundredths (0.020) of an amp of current for full brightness. Although the current requirement will vary greatly depending on the size, color, and lumens of output brightness, it will normally be in a range from 0.010 to 0.040 amps for common LEDs. Expressing quantities such as this in tenths, hundredths, or thousandths is very cumbersome, so in engineering the way of expressing large and small quantities is in a slightly different format than is used in scientific notation. To make things simple, engineering notation requires numbers to be in groups of three. Each group of three numbers is given a word prefix, so that they can easily be understood. When we discuss the large amounts of voltage and power the energy companies generate, we use two of the word prefixes, kilo and mega, attached to the units. For power, we have the names kilowatts for thousands of watts, and megawatts for millions of watts. The following is a list of engineering prefixes for both large and small numbers used frequently in electronics:

For large numbers:

Trillion = Tera = x 1012

Billion = Giga = x 109

Million = Mega = x 106

Thousand = Kilo = x 103

The exponent × 100 is assigned to the first group of three numbers, ending in 999, which are just units with no engineering prefix used. The following prefixes are for fractionally small numbers between 0.999 of a unit and 0.000000000001 of a unit:

Thousandth = milli = x 10-3

Millionth = micro = x 10-6

Billionth = nano = x 10-9

Trillionth = pico = x 10-12

In our LED circuit design problem in the last section (see Figure 1-3), we would say in engineering terms that the current in the circuit is calculated to be 14 milliamps (mA).

REVIEW QUESTIONS

1. 1.
   LED voltage drop will vary with color. (True/False)
    
2. 2.
   One Meg-Ohm represents what value resistor in Ohms?

   1. a.
      1,000 Ohms
       
   2. b.
      10,000 Ohms
       
   3. c.
      100,000 Ohms
       
   4. d.
      1,000,000 Ohms
       
    
3. 3.
   In Ohm’s Law, resistance and current are:

   1. a.
      directly related.
       
   2. b.
      proportionally related.
       
   3. c.
      inversely related.
       
   4. d.
      the product of sums.
       
    
4. 4.
   A diode that is used to turn AC voltage into DC voltage is called a __________________ diode.
    
5. 5.
   The unit of current is the ______________ and the unit of power is the ________________.
    
6. 6.
   Conventional current flow goes around a closed path starting at the ________________ terminal of a battery and ending at the ________________ terminal.
    
7. 7.
   Fifteen thousandths of an amp would be called what in engineering notation?

   1. a.
      1.5 milliamps
       
   2. b.
      15 milliamps
       
   3. c.
      1.5 microamps
       
   4. d.
      15 microamps
       
    
8. 8.
   Explain the difference between science and technology.
    
9. 9.
   The particle that carries current through a conductor is a(n)

   1. a.
      electron.
       
   2. b.
      mooseon.
       
   3. c.
      proton.
       
   4. d.
      nucleus.
       
    
10. 10.
    A coefficient turns a mathematical relationship into a(n) _____________ that can be solved.
     

PROJECT 1

Figure 1-5

A voltage divider

Problem

Using Figure 1-5, find the current flowing through the wire.

Solution

One solution is that because it is given that 2.5 volts is dropped across the top resistor in the circuit, you can find the current flowing through it by using Ohm’s Law. (You have V and R, so solve for current I.) Because this is a series circuit, the current is the same everywhere in the loop so the current through the top resistor will be of equal value to the current flowing through the bottom resistor, and also through the wire.

(Answers to the review questions and problems can be found in the Appendix of this book.)

Continuous Delivery in Java

Essential Tools and Best Practices for Deploying Code to Production

Daniel Bryant

Brendan Eich

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Brendan Eich
Brendan Eich, foto oficial de Mozilla Foundation, 21 agosto de 2012
Información personal
Nacimiento	1961 Pittsburgh, Pensilvania
Nacionalidad	Estadounidense
Educación
Educado en	University of Illinois at Urbana–Champaign
Información profesional
Ocupación	CEO de Brave Software
Conocido por	JavaScript
Cargos ocupados	Director de tecnología de Corporación Mozilla (2005–2014) Director ejecutivo de Corporación Mozilla (2014) Director ejecutivo de Brave Software (desde 2015)
Empleador	Corporación Mozilla
Obras notables	JavaScript
Web
Sitio web	brendaneich.com
[editar datos en Wikidata]

Brendan Eich es un programador estadounidense conocido por inventar el lenguaje de programación JavaScript.

Biografía[editar]

Brendan Eich recibió su licenciatura en matemáticas y ciencias de la computación en la Universidad de Santa Clara. Recibió su maestría en 1986 de la Universidad de Illinois en Urbana-Champaign.

Eich comenzó su carrera en Silicon Graphics, trabajando por siete años en el sistema operativo y código de la red. Luego trabajó por tres años en MicroUnity Systems Engineering escribiendo el micronúcleo y el código de DSP, y en hacer el primer port de GCC para la MIPS R4000.

Tras trabajar en Silicon Graphics, pasó por varias empresas hasta llegar a Netscape Communications Corporation en abril de 1995, trabajando en el desarrollo del lenguaje JavaScript (originalmente llamado Mocha, luego denominado LiveScript) para el navegador web Netscape Navigator. A principios de 1998 ayudó a fundar la Fundación Mozilla, sirviendo como principal arquitecto. Cuando AOL cerró la unidad del navegador Netscape en julio de 2003, Eich ayudó a hacer girar a la Fundación Mozilla.

El 24 de marzo de 2014 Eich fue ascendido a CEO de la Corporación Mozilla.¹​ Gary Kovacs, John Lilly y Ellen Siminoffdimitieron de la junta directiva de Mozilla por la elección,²​ expresando desacuerdos con la estrategia de Eich y su deseo de tener un CEO con experiencia en la industria del móvil.³​⁴​ Algunos empleados de la Fundación Mozilla (una organización separada de la Corporación) tuitearon que debía dimitir, haciendo referencia a las donaciones de Eich por valor de 1000 dólares estadounidenses a la Proposición 8 de California, que prohibía el matrimonio entre personas del mismo sexo,⁵​⁶​ antes de ser derogada en 2013, cuando fue declarada inconstitucional y pudieron reanudarse los casamientos.⁷​ Eich se reafirmó en su decisión de financiar la campaña, pero escribió en su blog que lamentaba haber "causado daño" y se comprometía a promover la igualdad en Mozilla.²​⁸​ El sitio de citas online OkCupid automáticamente reprodujo un mensaje a las personas usuarias de Firefox con información sobre la donación de Eich y sugería que utilizaran otro navegador (aunque les permitía continuar con Firefox si así lo deseaban).⁹​¹⁰​¹¹​ El 3 de abril de 2014 Eich dimitió como CEO de Mozilla y abandonó la organización, citando su incapacidad para "ser un líder efectivo en las presentes circunstancias".¹²​¹³​ Desde finales de 2015 es el CEO de Brave Software.¹⁴​