Task Objective
The main objective of this knowledge task is to educate people about various electronics related material including: the basics of electronics and electricity and what is the difference between each one, the different electronic components, what is successive approximation, and why do different-sized batteries have the same voltage?
Introduction to Electronics and Basic Terminology
They store your money. They monitor your heartbeat. They carry the sound of your voice into other people's homes. They bring airplanes into land and guide cars safely to their destination—they even fire off the airbags if we get into trouble. It's amazing to think just how many things "they" actually do. However, the question is who are "they"?
"They" are electrons: tiny particles within atoms that march around defined paths known as circuits carrying electrical energy. One of the greatest things people learned to do in the 20th century was to use electrons to control machines and process information. The electronics revolution, as this is known, accelerated the computer revolution and both these things have transformed many areas of our lives. But how exactly do nanoscopically small particles, far too small to see, achieve things that are so big and dramatic? Let's take a closer look and find out one of the most crucial technologies utilized in digital fabrication, but first we need to know and define exactly what is Electronics?
Electronics by Definition
Electronics is the branch of science that deals with the study of flow and control of electrons (electricity) and the study of their behavior and effects in vacuums, gases, semiconductors, and with devices using such electrons. This control of electrons is accomplished by devices that resist, carry, select, steer, switch, store, manipulate, and exploit the electron.
In order to clarify things more, lets discuss the difference between electricity and electronics.
What is the difference between electricity and electronics?
Electricity is a kind of energy, a very versatile kind of energy, that we can make in all sorts of ways and use in many more. Electricity is all about making electromagnetic energy flow around a circuit so that it will drive something like an electric motor or a heating element, powering appliances such as electric cars, kettles, toasters, and lamps. Generally, electrical appliances need a great deal of energy to make them work so they use quite large (and often quite dangerous) electric currents.
While electronics is considered a much more subtle kind of electricity in which tiny electric currents (and, in theory, single electrons) are carefully directed around much more complex circuits to process signals (such as those that carry radio and television programs) or store and process information. Think of something like a microwave oven and it's easy to see the difference between ordinary electricity and electronics. In a microwave, electricity provides the power that generates high-energy waves that cook your food; electronics controls the electrical circuit that does the cooking.
Some Important Terminology in Electronics
Here I will highlight some of the main and most important terminologies that are used whenever we deal with electronics, which include the following:
Electric Charge: Often just called "Charge" is the fundamental quantity of electricity. However, no one can tell you what charge is. They can only tell you how charges interact. The classical study of electricity is generally divided into three general areas:
Electrostatics: the study of the forces acting between charges.
Electric current: the study of the forms of energy associated with the flow of charge.
Electromagnetism: the study of the forces acting between charges in motion.
The electric charge comes in only two types: positive (+) and negative (−). The term neutral does not refer to a third type of charge, but to the presence in a region of positive and negative charges in equal amounts. The sum of identical positive and negative quantities is zero (0) and this is what it means to be electrically neutral. The assumed charge of all macroscopic objects is neutral unless otherwise indicated, although regions of space might be described as being "positive" or "negative" the universe as a whole is electrically neutral.
This brings us to the Principle of Conservation of Charge which states that one can't create a charge nor annihilate it. You can, however, neutralize it. Early workers observed experimentally that if they took equal amounts of positive and negative charge and combined them on some object, then that object neither exerted nor responded to electrical forces; effectively it had zero net charge. This experiment suggests that it might be possible to take uncharged, or neutral material and to separate somehow the latent positive and negative charges. If you have ever rubbed a balloon on wool to make it stick to the wall, you have separated charges using mechanical action.
The sign of a charge can only be determined by comparison to a charge with a charge whose sign is already known and the Rule of Action (the way to tell one type of charge from another), shown in the figure below, is that:
like charges repel. (+/+ or -/-)
opposite charges attract. (+/-)
The common symbol for charge is the uppercase letter Q. The standard unit is the Coulomb symbolized by C.
Voltage: is something described as a type of "pressure" that drives electrical charges through a circuit. Bodies with opposite charges attract, they exert a force on each other pulling them together. The magnitude of the force is proportional to the product of the charge on each mass and some electric constant called "Coulomb's Constant" which has a value approximately equal to (9 x 10^9) when the medium is air, while this force's magnitude is inversely proportional to the square of the distance between the charges as shown in the following figure. The rule for the electric force's magnitude is directly derived from Coulomb's Law which will be discussed later in this section.
The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage or Electromotive Force (emf) is symbolized by an uppercase italic letter V or E and the standard unit is the Volt (Joule/ Coulomb), symbolized also by V. One volt will drive one coulomb (6.24 x 1018) charge carriers, such as electrons, through a resistance of one ohm in one second. And here is a figure which may be helpful for your understanding.
Also, there is the term called "Voltage Drop" which is defined as the amount of voltage loss that occurs through all or part of a circuit due to impedance/ resistance. A common analogy used to explain voltage, current and voltage drop is a garden hose (similar to the idea in the figure shown below). Voltage is analogous to the water pressure supplied to the hose. Current is analogous to the water flowing through the hose. And the inherent resistance of the hose is determined by the type and size of the hose - just like the type and size of an electrical wire determines its resistance. Excessive voltage drop in a circuit can cause lights to flicker or burn dimly, heaters to heat poorly, and motors to run hotter than normal and burn out. This condition causes the load to work harder with less voltage pushing the current.
Current: is a "flow" of electrical charge carriers, usually electrons or electron-deficient atoms. The common symbol for current is the uppercase letter I. The standard unit is the Ampere (Coulomb/ second ), symbolized by A. One ampere of current represents one coulomb of electrical charge (6.24 x 1018 charge carriers) moving past a specific point in one second. Physicists consider current to flow from relatively positive points to relatively negative points; this is called conventional current or Franklin current. Electrons, the most common charge carriers, are negatively charged so in reality they flow from relatively negative points to relatively positive points.
Electric current can be either direct or alternating. Direct current (DC) flows in the same direction at all points in time, although the instantaneous magnitude of the current might vary. In an alternating current (AC), the flow of charge carriers reverses direction periodically. The number of complete AC cycles per second is the frequency, which is measured in hertz. An example of pure DC is the current produced by an electrochemical cell, while the output of common utility outlets is AC.
Current per unit cross-sectional area is known as current density. It is expressed in amperes per square meter, amperes per square centimeter, or amperes per square millimeter. In general, the greater the current in a conductor, the higher the current density.
Moreover, an electric current always produces a magnetic field (Theory of Electromagnetism). The stronger the current, the more intense the magnetic field. A pulsating DC, or an AC, characteristically produces an electromagnetic field. This is the principle by which wireless signal propagation occurs.
Resistance: is described as the "opposition" to the flow of current in an electric circuit; resistance converts electrical energy to thermal energy, and in this regard is similar to mechanical friction. Resistances are said to dissipate electrical energy as heat. The common symbol for resistance is the uppercase letter R. The standard unit is the ohm (Volt/ Ampere), symbolized by Ω. If we make an analogy to water flow in pipes, the resistance is bigger when the pipe is thinner, so the water flow is decreased as shown in the illustrative figure below.
The resistance of a conductor is the resistivity of the conductor's material times the conductor's length divided by the conductor's cross sectional area, represented by the rule shown in the following figure.
R is the resistance in ohms (Ω).
ρ is the resistivity in ohms-meter (Ω.m).
l is the length of the conductor in meter (m).
A is the cross sectional area of the conductor in square meters (m^2).
Again here, it is easy to understand this formula with water pipes analogy:
when the pipe is longer, the length is bigger and the resistance will increase.
when the pipe is wider, the cross sectional area is larger and the resistance will decrease.
Electric Power: is the "rate" at which the work is being done in an electrical circuit. In other words, the electric power is defined as the rate of energy transfer. The electric power is produced by the generator and can also be supplied by the electrical batteries. It gives a low entropy form of energy which is carried over long distance and also it is converted into various other forms of energy like motion, heat energy, etc. The standard unit for power is the Watt (Joule/second) or (Volt x Ampere), symbolized by W. Thus, the power consumed in an electrical circuit is said to one watt if one ampere current flows through the circuit when a potential difference of 1 volt is applied across it.The bigger unit of electrical power is the kilowatt (kW = 1000W), it is usually used in the power system.
The electric power is divided into two types, i.e., the AC power and the DC power. The classification of the electric power depends on the nature of the current. The electric power is sold regarding joule which is the product of the power in kilowatts and the running time of the machinery in hours. The utility of power is measured by the electric meter which records the total energy consumed by the powered devices. The electric power is given by the following equation shown below.
V is the voltage in Volts (V).
I is the current in Amperes (A).
R is the resistance offered by the powered devices in ohms (Ω).
T is the time in seconds (s).
P is the power measured in Watts (W).
Coulomb's Law: is a law of physics that describes the interaction between electrically charged objects and was essential to the development of the theory of electromagnetism. This law quantifies the amount of electrostatic force that two charged objects exert on each other whether an attraction or repulsion between them. It applies to point charges that are relatively small compared to the distance between them.
Ohm's Law: is a law that describes the relationship between Voltage, Current and Resistance in any DC electrical circuit that was firstly discovered by the German physicist Georg Ohm. He found that, at a constant temperature, the electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it, and also inversely proportional to the resistance. This relationship between the Voltage, Current and Resistance forms the basis of Ohms Law and is shown below.
By knowing any two values of the Voltage, Current or Resistance quantities we can use Ohms Law to find the third missing value. Ohms Law is used extensively in electronics formulas and calculations so it is “very important to understand and accurately remember these formulas”:
To find the Voltage, ( V )
[ V = I x R ] V (volts) = I (amps) x R (Ω)
To find the Current, ( I )
[ I = V ÷ R ] I (amps) = V (volts) ÷ R (Ω)
To find the Resistance, ( R )
[ R = V ÷ I ] R (Ω) = V (volts) ÷ I (amps)
It is sometimes easier to remember this Ohms law relationship by using pictures. Here the three quantities of V, I and R have been superimposed into a triangle (commonly called the Ohms Law Triangle) giving voltage at the top with current and resistance at the bottom as shown in the figure below. This arrangement represents the actual position of each quantity within the Ohms law formulas.
Transposing the standard Ohms Law equation above will give us the following combinations of the same equation shown in the following triangles:
Then by using Ohms Law we can see that a voltage of 1V applied to a resistor of 1Ω will cause a current of 1A to flow and the greater the resistance value, the less current that will flow for a given applied voltage. Any Electrical device or component that obeys “Ohms Law” that is, the current flowing through it is proportional to the voltage across it ( I α V ), such as resistors or cables, are said to be “Ohmic” in nature, and devices that do not, such as transistors or diodes, are said to be “Non-ohmic” devices.
Kirchhoff's Laws: are laws that allow us to solve complex circuit problems by defining a set of basic network laws and theorems for the voltages and currents around a circuit. Sometimes, in complex circuits such as bridge or T networks, we can not simply use Ohm’s Law alone to find the voltages or currents circulating within the circuit. For these types of calculations we need certain rules which allow us to obtain the circuit equations and for this we can use Kirchhoff's Circuit Law.
In 1845, a German physicist, Gustav Kirchhoff developed a pair or set of rules or laws which deal with the conservation of current and energy within electrical circuits. These two rules are commonly known as: Kirchhoff's Circuit Laws with one of Kirchhoff's laws dealing with the current flowing around a closed circuit, Kirchhoff's Current Law, (KCL) while the other law deals with the voltage sources present in a closed circuit, Kirchhoff's Voltage Law, (KVL).
Kirchhoff's First Law – The Current Law, (KCL)
Kirchhoff's Current Law or KCL, states that the “total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node“. In other words the algebraic sum of ALL the currents entering and leaving a node must be equal to zero, I(exiting) + I(entering) = 0. This idea by Kirchhoff is commonly known as the Conservation of Charge.
Here, the three currents entering the node, I1, I2, I3 are all positive in value and the two currents leaving the node, I4 and I5 are negative in value. Then this means we can also rewrite the equation as:
I1 + I2 + I3 – I4 – I5 = 0
The term Node in an electrical circuit generally refers to a connection or junction of two or more current carrying paths or elements such as cables and components. Also for current to flow either in or out of a node a closed circuit path must exist. We can use Kirchhoff’s current law when analyzing parallel circuits.
Kirchhoff's Second Law – The Voltage Law, (KVL)
Kirchhoff's Voltage Law or KVL, states that “in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop” which is also equal to zero. In other words the algebraic sum of all voltages within the loop must be equal to zero. This idea by Kirchhoff is known as the Conservation of Energy.
Starting at any point in the loop continue in the same direction noting the direction of all the voltage drops, either positive or negative, and returning back to the same starting point. It is important to maintain the same direction either clockwise or anti-clockwise or the final voltage sum will not be equal to zero. We can use Kirchhoff’s voltage law when analyzing series circuits.
When analyzing either DC circuits or AC circuits using Kirchhoff's Circuit Laws a number of definitions and terminologies are used to describe the parts of the circuit being analysed such as: node, paths, branches, loops and meshes. These terms are used frequently in circuit analysis so it is important to understand them.
Circuit: is a structure that directs and controls electric currents, presumably to perform some useful function. The very name "circuit" implies that the structure is closed, something like a loop.
Path: a single line of connecting elements or sources.
Node: is a junction, connection or terminal within a circuit were two or more circuit elements are connected or joined together giving a connection point between two or more branches. A node is indicated by a dot.
Branch: is a single or group of components such as resistors or a source which are connected between two nodes.
Loop: is a simple closed path in a circuit in which no circuit element or node is encountered more than once.
Mesh: is a single open loop that does not have a closed path. There are no components inside a mesh.
Here are some complementary videos that can help you further understand the main concept of electricity and most of the terminologies mentioned above:
What is Electricity ?
What is Voltage ?
What is Electrical Current ?
What is Coulomb's Law ?
Working with Electronics
Now that we can fully define what electronics is and know the basic and most important terminology in circuits, it's time to dive into the basic knowledge that we need to obtain about electronics and electronic components so that we can starting working with them and make our own unique circuits.
So let's get started with the basic equipment that we use when working with electronics:
Electronic Workbench
Before you get started, make sure your electronic workbench is properly set up. The work area doesn’t need to be fancy and you could even build your own electronic workbench as shown in the figure below.
Storage
Electronic components can be small and it’s a good idea to keep everything organized. The most popular option is to use clear plastic storage boxes for storing parts as shown below. In addition, you could use plastic storage bins that hang from a rack or fit on a shelf.
Tools
Now that you have a good work space set up, it’s time to stock it with the proper tools and equipment that can greatly help us while working with electronics. The list of tools given below is not entirely complete, however it does highlight most of the common items used in electronics which include the following:
Breadboard
Breadboards are an essential tool for prototyping and building temporary circuits. These boards contain holes for inserting wire and components. Because of their temporary nature, they allow you to create circuits without soldering. The holes in a breadboard are connected in rows both horizontally and vertically as shown below.
Jumper Wires
These wires are used with breadboard and development boards to make connections between electronic components lying on the board and are generally 22-28 AWG solid core wires. Jumper wires can have male or female ends depending on how they need to be used.
Digital Multimeter
A multimeter is a device that is used to measure electric current in (amps), voltage in (volts) and resistance in (ohms). It is a great for troubleshooting circuits and is capable of measuring both AC and DC voltage. You can check out this link for more information regarding how to use a multimeter. (Link: https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter)
Battery Holders
A battery holder is a plastic case that holds batteries from 9V to AA. Some holders are enclosed and may have an on/off switch built in. It is often used to easily connect a battery's terminals to a circuit.
Test Leads "Alligator Clips"
Test leads are great for connecting components together to test a circuit without the need for soldering.
Wire Cutters
Wire cutters are essential for efficiently stripping stranded and solid copper wires.
Precision Srewdrivers Set
Precision screwdrivers are also known as jeweler’s screwdrivers and usually come as a set. The advantage of these over normal screwdrivers is the precision tips of each driver. These are very handy when working with electronics that contain tiny screws.
Helping 3rd Hand
When working with electronics, it seems you never have enough hands to hold everything. This is where the helping hand (3rd hand) comes in. Great for holding circuit boards or wires when soldering or tinning.
Heat Gun
A heat gun is used to shrink plastic tubing known as heat shrink to help protect exposed wires. Heat shrink has been called the duct tape of electronics and comes in handy in a wide variety of applications.
Soldering Iron
When it is time to create a permanent circuit, you will want to solder the parts together. To do this, a soldering iron is the tool you would use. Of course a soldering iron isn’t any good unless you have solder to go with it. You can choose leaded or lead-free solder in a few diameters. I will discuss the topic of soldering more thoroughly in the next task which is focused on soldering a simple circuit on a printed circuit board (PCB).
Electronic Components
After going through the tools used in working with electronics, now it is time to talk about the different components that make your electronic projects come to life. Below is a detailed breakdown of the most commonly known components and the functions they each perform.
Switch
Switches can come in many forms such as pushbutton, rocker, momentary and others. Their basic function is to interrupt electric current by turning a circuit on or off.
Resistor
Resistors are used to resist the flow of current or to control the voltage in a circuit. The amount of resistance that a resistor offers is measured in Ohms. Most resistors have colored stripes on the outside and this code will tell you it’s value of resistance. You can use a multimeter or Digikey’s resistor color code calculator to determine the value of a resistor.
Variable Resistor (Potentiometer)
A variable resistor is also known as a potentiometer. These components can be found in devices such as a light dimmer or volume control for a radio. When you turn the shaft of a potentiometer the resistance changes in the circuit.
Capacitor
Capacitors store electricity and then discharges it back into the circuit when there is a drop in voltage. A capacitor is like a rechargeable battery and can be charged and then discharged. The value is measured in Farad (F), nano Farad (nF) or pico Farad (pF) range.
Diode
A diode allows electricity to flow in one direction and blocks it from flowing the opposite way. The diode’s primary role is to route electricity from taking an unwanted path within the circuit.
Light-Emitting Diode (LED)
A light-emitting diode is like a standard diode in the fact that electrical current only flows in one direction. The main difference is an LED will emit light when electricity flows through it. Inside an LED there is an anode and cathode. Current always flows from the anode (+) to the cathode (-) and never in the opposite direction. The longer leg of the LED is the positive (anode) side.
Transistor
Transistor are tiny switches that turn a current on or off when triggered by an electric signal. In addition to being a switch, it can also be used to amplify electronic signals. A transistor is similar to a relay except with no moving parts.
Relay
A relay is an electrically operated switch that opens or closes when power is applied. Inside a relay is an electromagnet which controls a mechanical switch.
Integrated Circuit (IC)
An integrated circuit is a circuit that’s been reduced in size to fit inside a tiny chip. This circuit contains electronic components like resistors and capacitors but on a much smaller scale. Integrated circuits come in different variations such as 555 timers, voltage regulators, microcontrollers and many more. Each pin on an IC is unique in terms of it’s function.
For more information and details about these electronic components and more, you can watch the following video:
What is Successive Approximation ?
Successive approximation ADC is the advanced version of Digital ramp type Analogue to Digital Conversion (ADC) which is designed to reduce the conversion and to increase speed of operation. The major draw of digital ramp ADC is the counter used to produce the digital output will be reset after every sampling interval. The normal counter starts counting from 0 and increments by one Least Significant Bit (LSB) in each count, this result in 2N clock pulses to reach its maximum value.
In successive approximation ADC the normal counter is replaced with successive approximation register as shown in below figure.
Operation of 3 bit Successive Approximation ADC
The output of Successive Approximation Register (SAR) is converted to analog out by the DAC and this analog output is compared with the input analog sampled value in the Opamp comparator. This Opamp provides an high or low clock pulse based on the difference through the logic circuit. In very first case the 3 bit SAR enables its MSB bit as high i.e. ‘1’ and the result will be “100”. This digital output is converted to analog value and compared with input sampled voltage (Vin). If the deference is positive i.e. if the sampled input is high then the SAR enables the next bit from MSB and result will be “110”. Now if the output is negative i.e. if the input sampled voltage is less than the SAR resets the last set bit and sets the next bit and resultant output in this case will be “101” which will definitely approximately equal to the input analog value. The counting sequence is explained by the following counter flow chat as shown in the figure below.
Conversion time of Successive Approximation ADC
By observing above 3 bit example it is illustrated for a 3 bit ADC the conversion time will be 3 clock pulses. Then:
N bit Successive Approximation ADC conversion time = 3T (T- clock pulse). So to avoid aliasing effect the next sample of input signal should be taken after 3 clock pulses.
Important Note on Successive Approximation ADC
In Counter type or digital ramp type ADC the time taken for conversion depends on the magnitude of the input, but in SAR the conversion time is independent of the magnitude of the input sampled value.
Advantages of Successive Approximation ADC
Speed is high compared to counter type ADC.
Good ratio of speed to power.
Compact design compared to Flash Type and it is inexpensive.
Disadvantages of Successive Approximation ADC
Cost is high because of SAR.
Complexity in design.
Applications
The SAR ADC will be used widely in data acquisition techniques at sampling rates higher than 10KHz.
Why batteries of different sizes have the same voltage?
A cell is a single electrochemical device, consisting of two plates and an electrolyte - the voltage of the cell is determined by the materials used. Every set of materials has a electrochemical voltage associated with it. The voltage is determined by the type of material, not the size or quantity.
A battery is made up of series connected cells and will have a voltage that is an integral multiple of the cell voltage.Thus single cell batteries such as AA, AAA, C, and D all have the same voltage. The amount of material inside affects the total charge available. So bigger lasts longer.Multi-cell batteries such as the 9V rectangular battery have 6 small cells inside, amounting to 9V. Its capacity is not very high due to the tiny cells crammed in there but the voltage is compensatingly higher which gives some advantage for things that require higher voltage.
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