Electronics Technology. Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate.

Electronics Technology

Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate the basics of time, weight, distance and electrical units. - How to simplify, and round large numbers, recognize and use Scientific notation while using its proper name and symbol. - Be aware of the differences in a digital and analog multi-meter. Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate the basics of time, weight, distance and electrical units. - How to simplify, and round large numbers, recognize and use Scientific notation while using its proper name and symbol. - Be aware of the differences in a digital and analog multi-meter.

History of the discovery of Electricity  In popular literature Benjamin Franklin is often credited with the discovery of electricity.  However, it was known at least as early as 600 BC that amber (fossilized sap) would attract dust and other small particles after being rubbed with wool.  This property was called electricity after the Greek word for amber, elektron.

How Electricity flows in:  Conductors Elements that have fewer than four valence electrons are called metals. With fewer than four valence electrons it is relatively easy for atoms to exchange electrons. Copper, for example, has only one electron in its valence shell.  Insulators Elements with more than four valence electrons are called non- metals. The electrons in non-metals form tight bonds with electrons of nearby atoms, locking them in place in the mass of material. Therefore, non-metals are generally non-conductors. Actually, most non-metals are not well suited for use in electrical circuits since they are either liquid or gaseous at normal temperatures and pressures. Because of this, most insulators are made of compounds such as glass, ceramic or plastic.  Semiconductors Elements that have four valence electrons, the halfway point between conductors and insulators, are called semiconductors. They are basically insulators but can be doped with impurities that cause them to act as conductors.

Conductors and Insulators

Semiconductors Silicon Germanium

Direction of Electrical Flow  Electron Flow  Electron flow considers the actual flow of negatively charged electrons-from negative to positive-as current flow. It is more difficult to visualize than conventional flow because the current seems to flow from a low pressure (negative) to a high pressure (positive). In schematic diagrams the current flows against the arrows in semiconductor devices.  Conventional Flow  Conventional flow considers flow of an imaginary (positively-charged) fluid from positive to negative. It is easier to visualize than electron flow because the current flows from a high pressure (positive) to a low pressure (negative). In schematic diagrams the current flows in the direction of arrows in semiconductor devices

The Elements of Electricity  Voltage  Current  Resistance  Types of Current: AC and DC  Circuits  Closed  Open  Short

VOLTAGE  Because like charges repel and unlike charges attract, electrons will move from the negative source to the positive end.  The applied force that causes the electrons to flow is called voltage (after the scientist Alessandro Volta) or electromotive force (emf).  We give it the symbol or ℰ in equations. Voltage is measured with a voltmeter or multimeter and is the potential difference between two points in a circuit. The basic unit is the volt (V).

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, symbolized by A. ampere

RESISTANCE  Opposition of a circuit to the flow of electric current. Resistance is measured in Ohms.  Resistance is represented by the Greek symbol- Omega Ώ.

Forms of Current  There are 2 types of current  The form is determined by the directions the current flows through a conductor  Direct Current (DC)  Flows in only one direction from negative toward positive pole of source  Alternating Current (AC)  Flows back and forth because the poles of the source alternate between positive and negative

The Water Analogy  Resistance is a property that slows the flow of electrons.  Using the water analogy, Resistance is anything that would slow the flow of water through a pipe

Measuring Electricity  The scientific world uses the International System of Units (SI units) to measure things. The International System of Units starts with three basic units:  The kilogram, the meter and the second. Every other unit is derived from these three basic units.  For example:  To know what a volt is, we have to know what a watt is.  To know what a watt is, we have to know what a joule is.  To know what a joule is we have to know what a meter and a Newton are.  Finally, to know what a Newton is we have to know what a kilogram a meter and a second are.

Base Units  Kilogram (kg) - The kilogram is the unit of mass that is equal to the mass of the international prototype of the kilogram.  The kilogram is a particular cylinder of platinum-iridium alloy that is preserved in a vault at Sevres, France, by the International Bureau of Weights and Measures.

Base Units  Second (s) - The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two- hyperfine levels of the ground state of the cesium 133 atom.

Base Units  Meter (m) - The meter is the length of the path traveled by light in vacuum during a time interval of 1 / 299,792,458 of a second.  This speed is a definition, not a measurement.

Derived Non Electrical Units  Newton (N)  The Newton is that force which gives to a mass of 1 kilogram an acceleration of 1 meter per second per second (1m/s 2 ).  Joule (J)  The joule is the work done when the point of application of I Newton is displaced a distance of 1 meter in the direction of the force.

Derived Electrical Units  Ampere (A)  ampere (amp) is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2x10-7 Newton per meter of length.  Coulomb (C)  The coulomb is the quantity of electricity transported in 1 second by a current of 1 ampere.

Derived Electrical Units Cont’d  Watt (W)  The watt is the power which gives rise to the production of energy at the rate of 1 joule per second.  Volt (V)  The volt is the difference of electric potential (electromotive force) between two points of a conducting wire carrying a constant current of 1 ampere, when the power dissipated between these points is equal to 1 watt.

Derived Electrical Units (Cont’d)  Ohm()  ohm is the electric resistance between two points of a conductor when a constant difference of potential of 1 volt, applied between these two points, produces in this conductor a current of 1 ampere, this conductor not being the source of any electromotive force.  Farad (F)  The farad is the capacitance of a capacitor between the plates of which there appears a difference of potential of 1 volt when it is charged by a quantity of electricity equal to 1 coulomb.

Derived Electrical Units (Cont’d)  Henry (H)  The Henry is the inductance of a closed circuit in which an electromotive force of 1 volt is produced when the electric current in the circuit varies uniformly at a rate of 1 ampere per second.

SI Electrical Units Commonly Used with Electronics NameUnit Unit Unit Symb ol FormulaSymbol Electrical potential difference, electromotive force voltVE Electrical resistance ohmR Electrical conductance (1 / R, formerly known as mho) siemensSG Electrical current ampereAI Frequency hertzHzƒ Electrical charge, quantity of electricity coulombCq Capacitance faradFC Inductance HenryHL Impedance ohmZ

SI PREFIXES EXPLAINED  Working in electronics often requires working with very large and very small numbers, such as thousands of ohms or millionths of farads. To simplify writing these numbers, prefixes are use to represent multipliers. For example, 1,000 ohms is expressed as 1-kilo ohm, 1k ohm, or just 1k. A capacitance of.000001 farad is expressed as 1 microfarad, 1mF or just 1m.  Very large or very small numbers can be expressed in scientific notation. Scientific notation expresses the number as the three most significant digits (rounded) with a decimal point placed after the first digit followed by “X10” and an exponent (the exponent tells how many places to move the decimal point to get it back to its original place). For example, 1,000 is expressed in scientific notation as 1.00X103 (pronounced “one point zero zero times ten to the third”) and 1,258,432 is expressed as 1.26X106. Very small numbers are expressed with a negative exponent. For example, 0.001 is expressed as 1.00X10-3 and 0.000,001,258,432 is expressed as 1.26X10-6.

SI Prefixes Commonly used with Electronics SI Prefixes Commonly Used in Electronics NameSymbolMultiplier Scientific Notation TeraT x 1,000,000,000,000 1.00X10 12 GigaG x 1,000,000,000 1.00X10 9 MegaM x 1,000,000 1.00X10 6 kilok x 1,000 1.00X10 3 millim x.001 1.00X10 -3 micro x.000,001 1.00X10 -6 nanon x.000,000,001 1.00X10 -9 picop x.000,000,000,001 1.00X10 -12

How could we express 20,950? By using the prefix chart we could simply move the decimal in 20,950. over 3 places to the left and we end up with 20.95k. By using the prefix chart we could simply move the decimal in 20,950. over 3 places to the left and we end up with 20.95k.

Lets try a few more… 128M  =128,000,000 .0000052 =5.2µ 200G=200,000,000,000

Review of Section 1 Q.What constitutes a Conductor, Insulator, and a Semiconductor? A. A conductor less than 4 valence electrons, an insulator has more then 4 electrons and a semiconductor have exactly 4 electrons and can be manipulated to act as a conductor. Q.What is different between Electron flow and Conventional flow? A. Electron flow goes negative to positive for current flow, Conventional goes positive to negative. Q. What is Conductance? A. Conductance is the opposite of resistance: the measure of how easy is it for electrons to flow through something. Q. How do you calculate Conductance? A. 1/Resistance.

DC CIRCUITS

Section 2: Learning Objectives  Describe wire gauges and calculate color coded resistors.  Understand Kirchhoff’s Voltage law and Kirchhoff’s Current Law.  Determine resistor values by using color code.  Evaluate a basic circuit and determine wither it is series, or parallel or series- parallel.  Learn to apply Thevenins Theorem to series-parallel circuits.  Know and understand Ohm’s Law.

Resistors  The resistor is one of the basic components in electrical circuits. Resistors are used where the resistance of the circuit needs adjustment, typically for limiting the electrical current between two nodes. resistancecurrentresistancecurrent  The majority of resistors in a circuit have fixed resistance values, however potentiometers may be used to allow adjustment of the resistance. One typical application of potentiometers is volume control in audio players. potentiometers

Resistors  Function of resistors  The function of a resistor in a circuit is described by Ohm's law and depends upon three variables: Ohm's lawOhm's law 1. The resistance of the resistor, 2. The voltage difference between its poles voltage 3. The flow of electrons (current) through the resistor. If two of the three are known, the third can easily be calculated. electrons  Resistors are not polarized, meaning that they can be inserted into a circuit either way around.

Resistance Defined  Resistance is the impediment to the flow of electrons through a conductor  Resistance is Friction to moving electrons  Friction generates heat  All materials exhibit some resistance, even the best of conductors  Resistance is measured in Ohm(s)  From fractions of Ohms to millions of Ohms

Resistance Example  If you rub the palms of your hands together, you will realize that your hands do not move freely across each other. You will also note that while rubbing your hands back and forth, heat is generated. This heat is generated from the friction between your palm surfaces resisting the movement of your hands. Since your palms are resisting the kinetic energy from the movement of your hands, the resistance is converted to heat..  The same thing happens as electrons try to move through a conductor or other material. The electrons run into things as they move, and each collision causes the electron’s movement to be impeded in some way, and the resulting loss of kinetic energy is converted into heat. In the majority of cases in electronics, this heat is an undesired byproduct. In other cases, the heat is desirable as is the case with a stove top. In still other cases, the generated heat must be moved away from the electronic device to prevent damage to other components. A good example of this would be the fans in a computer.  In summary, resistance is friction toward moving electrons. All materials provide some level of resistance. The unit of resistance is the Ohm. Resistance measurements can be incredibly small to incredibly large.

Wire and Resistance  Wire is usually used to simply carry electricity from one point to another. Electrical wire is usually made of copper but aluminum and even silver and gold are sometimes used.  Notice that as the diameter of the wire increases the gauge number decreases. The electrical resistance decreases with larger diameter wire but increases with length.  The resistance also increases with temperature.  An ohmmeter is used to test the resistance or continuity of a wire.

Resistor Types  Fixed Value  Variable value  Composite resistive material  Wire-wound  Two parameters associated with resistors  Resistance value in Ohms  Power handling capabilities in watts

Resistor Types Defined  Fixed Value- A fixed-value resistor has a series of coloured bands around its body, which signifies the resistor's value and tolerance.  Variable- The resistance value of a variable resistor can be varied between an upper and lower limit.

Reading Resistor Color Codes

Ohm’s Law Ohms Law states that the direct current flowing in a conductor is directly proportional to the potential difference between its ends. Ohms Law is usually formulated as E = IR, where: E is the potential difference, or voltage, I is the current, and R is the resistance of the conductor.

Resistors in Circuits Series  Looking at the current path, if there is only one path, the components are in series.

Resistors in Circuits Series  The main distinction between series and parallel circuits is how many paths the current has available to complete the course from the negative pole of the power source to the positive pole.  In this diagram, all the current from the battery must pass through both resistors. Therefore this circuit a series circuit.  At this point you need to develop the concept of equivalent resistance. Equivalent resistance is what the total resistance would be if you substituted a single resistor the resistors that make up the circuit.  In this case, if the two resistors were to be combined and replaced with a single resistor that had the same resistance, that single resistor would be the equivalent resistor.

Calculating Resistors in Series  It is easy to calculate the equivalent resistance of resistors in series.  Total Resistance is simply the sum of all the resistances.  For example, if R1 is 400 ohms and R2 is 100 ohms, then the equivalent resistance would be 500 ohms.  Another example, if R1 is 50 ohms, R2 is 20k ohms (remember 20k ohms = 20,000 ohms), and R3 is 900 ohms, the equivalent resistance would be 20,950 ohms or 20.95k ohms.

Adding Resistors in Series  For the following exercise, use the series formula for finding total resistance R T = R 1 + R 2 + R 3 + R 4 …. R T = R 1 + R 2 + R 3 + R 4 …. Remember, Resistance is measured in Ohms and is represented by the Greek symbol Omega Ω.

Resistors in Circuits Parallel  If there is more than one way for the current to complete its path, the circuit is a parallel circuit.  In this case, there are two possible paths. The electrons can go through the left most resistor or the right most resistor.  Since there is more than one path option, this is a parallel circuit.

Resistors in Circuits Parallel  By the very nature of a parallel circuit, the equivalent resistance will be less than any of the single resistors that make up the circuit.  This property makes sense if you think about it. Referring back to the water analogy. If there is more than one hose for the water to flow through, each path has a relatively narrow hose (resistance).  Then what the water sees as it approached the hose openings is not the narrow opening of just one hose, but the sum of all the opening in the hose, which would make it appear that there is one large opening to go through.  That one large opening is like seeing one lower resistance path than the individual hose openings.

Total Resistance in Parallel Circuits R1R2 R1R1R1R1 R2R2R2R2 RT?RT?RT?RT? 100 Ω 200 Ω 420 Ω 500 Ω 210 Ω 610 Ω 360 Ω 25 Ω 12k Ω 2k Ω 15M Ω 12M Ω 20m Ω

Total Resistance in Parallel Circuits R1R2 R1R1R1R1 R2R2R2R2 RT?RT?RT?RT? 100 Ω 200 Ω 66.67 Ω 420 Ω 500 Ω 228.26Ω 210 Ω 610 Ω 156.21Ω 360 Ω 25 Ω 23.4Ω 12k Ω 2k Ω 1.7kΩ 15M Ω 12M Ω 6.7MΩ 20m Ω 10mΩ

Resistors in Circuits Combination Parallel and Series  If the path for the current in a portion of the circuit is a single path, and in another portion of the circuit has multiple routes, the circuit is a mix of series and parallel.

Resistors in Circuits Parallel and Combination  Let’s start with a relatively simple mixed circuit. Build this using:  R 1 = 330  R 2 = 4.7K  R 3 = 2.2K R1R1 R2R2 R3R3

Resistors in Circuits Combination  Take the parallel segment of the circuit and calculate the equivalent resistance: R1R1 R2R2 R3R3

Resistors in Circuits Combination  We now can look at the simplified circuit as shown here. The parallel resistors have been replaced by a single resistor with a value of 1498 ohms.  Calculate the resistance of this series circuit: R1R1 R 2,3 = 1498

Resistors in Circuits Combination  In this problem, divide the problem into sections, solve each section and then combine them all back into the whole.  R 1 = 330  R 2 = 1K  R 3 = 2.2K  R 4 = 4.7K R1R1 R2R2 R3R3 R4R4

Resistors in Circuits Combination  Looking at this portion of the circuit, the resistors are in series.  R 2 = 1k-ohm  R 3 = 2.2 k-ohm R2R2 R3R3

Resistors in Circuits Combination  Substituting the equivalent resistance just calculated, the circuit is simplified to this.  R 1 = 330 ohm  R 4 = 4.7 k-ohm  R 2,3 = 3.2 k-ohm  Now look at the parallel resistors R 2,3 and R 4. R1R1 R 2,3 R4R4

Resistors in Circuits Combination  Using the parallel formula for:  R E = 3.2 k- ohm  R 4 = 4.7 k- ohm RERE R4R4

Resistors in Circuits Combination  The final calculations involve R1 and the new R Total from the previous parallel calculation.  R 1 = 330  R E = 1.9K R1R1 R Total

Resistors in Circuits Combination R 1 = 330 ohm R 2 = 1 k-ohm R 3 = 2.2 k-ohm R 4 = 4.7 k-ohm R Total = 2,230 =

Thevenins Theorem Any circuit can be reduced to an equivalent circuit consisting of a single voltage source and a single resistor in series with the voltage source. Any circuit can be reduced to an equivalent circuit consisting of a single voltage source and a single resistor in series with the voltage source.

Power dissipation  Resistance generates heat and the component must be able to dissipate this heat to prevent damage.  Physical size (the surface area available to dissipate heat) is a good indicator of how much heat (power) a resistor can handle  Measured in watts  Common values ¼, ½, 1, 5, 10 etc.

Power dissipation Whenever electrical current flows through any resistance, power is consumed The following formulas are used to calculate power consumption in electrical circuits: P = EI or P = I 2 R or P = E 2 /R

Section 2: Review Q.A resistor that is Purple, Orange, and Red has what value? A. 7.3k with a 20% tolerance. Q. What is Kirchhoff’s current law? A. Kirchhoff’s current law states that the total current of a parallel circuit is equal to the sum of each leg of the circuit. Q. Why is current different on each leg of a circuit in a parallel circuit? A. Because with more paths for current to flow resistance effects current differently because current takes the path of least resistance. Q. Why is it important to understand Thevenins Theorem? A. It allows us to collapse the circuit to its basic series form.

Questions?

Section 3: Learning Objectives  Circuit analysis; finding resistance, current, voltage values, in a series circuit, parallel circuits and then series parallel.  Examine voltage dividers.  Determine the value of a unknown resistor.  How capacitors are constructed, their effects in series, and parallel circuits, and RC time constants.

Voltage Dividers The voltage at the junction of the two resistors is directly proportional to the ratio of the two resistors. In this example the ratio of the two resistors is 80:20. Therefore the 80k resistor (which is 80% of the total resistance) drops 80% of the total voltage. While the 20k resistor (which is 20% of the total resistance) drops 20% of the total voltage. (See Kirchhoff’s Voltage Law) Therefore the 80k resistor has 80 volts across it (80% of 100 volts) and the 20k resistor has 20 volts across it. Therefore the 80k resistor has 80 volts across it (80% of 100 volts) and the 20k resistor has 20 volts across it.

Find the mystery voltage  What is the voltage at the top of this voltage divider?  The ratio of resistances is 2:1 (200:100).

Find the mystery voltage  What is the voltage at the top of this voltage divider?  20V is dropped because of the 200K resistor, leaving 10V to be used elsewhere.

Find the mystery Resistor Value  For this exercise there are two resistors in series with a battery.  The value of one resistor is known and the other is unknown.  The potential of the battery and the current are known.  This exercise is useful for finding the internal resistance of a battery as well as other problems.

Mystery Resistor  Now it is clear that there are 60 mA flowing through the 50-ohm resistor.  Using Ohm’s law, the voltage across the resistor is calculated as 3 volts (0.06 amperes X 50 ohms).  Subtract 3 volts from the battery voltage of 4.5 volts and this leaves 1.5 volt across the mystery resistor ( Kirchhoff’s Voltage Law

Solution  Now it is clear that the mystery resistor has 60 mA flowing through it and 1.5 volts across it. Using Ohm’s law the resistance is calculated at 25 ohms (1.5 V ÷ 0.06 amperes).

Variable Resistors and Potentiometers (rheostats)  How variable resistors and potentiometers are constructed  Variable resistors (also called rheostats) are constructed with a resistive track (usually a carbon film) that is contacted by a wiper. There is usually a connection at each end of the resistive track and another to the wiper.  If a connection is made to the ends of the resistive track the potentiometer looks like a simple resistor. The wiper makes contact anywhere along the resistive track.

Variable Resistors and Potentiometers Variable Resistors and Potentiometers (rheostats) PotentiometerTrimpots Schematic symbols Potentiometer Potentiometer Variable Resistor Potentiometer as a Variable Resistor

Capacitors in DC Circuits  Capacitance is the ability to store energy as a volume of electricity and is measured in farads. A one-farad capacitor would be physically very large. Because of this, capacitors are usually specified in microfarads (mF) or even Pico farads (pF)  Sometimes, especially in material published before the mid 1960s, capacitors in the Pico farad range are specified in micro-microfarads (mmF). A micro-microfarad is the same as a Pico farad

The Capacitor  Capacitance defined  Physical construction  Types  How construction affects values  Power ratings  Capacitor performance with AC and DC currents  Capacitance values  Numbering system  Capacitors in circuits  Series  Parallel  Mixed

The Capacitor

The Capacitor Defined  A device that stores energy in electric field.  Two conductive plates separated by a non conductive material.  Electrons accumulate on one plate forcing electrons away from the other plate leaving a net positive charge.  Think of a capacitor as very small, temporary storage battery.

The Capacitor Physical Construction  Capacitors are rated by:  Amount of charge that can be held.  The voltage handling capabilities.  Insulating material between plates.

The Capacitor Capacitance Value  The unit of capacitance is the farad.  A single farad is a huge amount of capacitance.  Most electronic devices use capacitors that are a very tiny fraction of a farad.  Common capacitance ranges are:  Micro 10 -6  Nano 10 -9  Pico 10 -12

The Capacitor Capacitance Value  Capacitor identification depends on the capacitor type.  Could be color bands, dots, or numbers.  Wise to keep capacitors organized and identified to prevent a lot of work trying to re-identify the values.

The Capacitor Ability to Hold a Charge  Ability to hold a charge depends on:  Conductive plate surface area.  Space between plates.  Material between plates.

Charging a Capacitor

The Capacitor Behavior in DC  When connected to a DC source, the capacitor charges and holds the charge as long as the DC voltage is applied.  The capacitor essentially blocks DC current from passing through.

The Capacitor Behavior  A capacitor blocks the passage of DC current  A capacitor passes AC current

Capacitors in Series Circuits  Three physical factors affect capacitance values.  Plate spacing  Plate surface area  Dielectric material  In series, plates are far apart making capacitance less + - Charged plates far apart

Capacitors in Series Connecting capacitors in series has the effect of decreasing the total capacitance. This is the opposite of connecting resistors or inductors in series. Two capacitors of equal value connected in series essentially doubles the distance between the conducing plates. However, the plate area remains the same. The capacitors in series on the left essentially act like this capacitor. It has the same plate area as each of the capacitors on the left but the distance between the plates is twice the distance of each capacitor on the left. To calculate the total capacitance of capacitors connected in series use the same formula that is used for resistors in parallel.

Capacitors in Parallel Circuits  In parallel, the surface area of the plates add up to be greater.  This makes the total capacitance higher.  Add Capacitors in Parallel as you would resistors in series + -

Resistance With Capacitors With a compressed air system, if there is a restriction in the pipe leading to the storage tank, the airflow to the tank will be impeded and the tank will take longer to fill. Likewise, if a resistor is placed between a capacitor and the voltage source it will take longer for the capacitor to charge than if the resistor weren’t there. Therefore, the time it takes a capacitor to charge is a product not only of the capacitance but also of any resistance in the circuit.

RC TIME CONSTANTS  If you multiply the capacitance by the resistance you will get the number of seconds it takes for the capacitor to charge 63.2% of the source voltage.  This time is called a time constant and is represented by the Greek letter Tau (t).

RC TIME CONSTANTS  When discharging (assuming the capacitor is fully charged to the source voltage), the capacitor will discharge to 36.8% of the source voltage during one time constant.  In this case, instead of gaining 63.2% of the source voltage the capacitor loses 63.2% of the source voltage. (1 minus 0.632 equals 0.368). Similarly, the capacitor will lose 63.2% of the remaining voltage during each time constant

Calculating time constants of RC Circuits t = RC C = t / R R = t / C If you know the time constant, the capacitance or the resistance can be calculated by dividing the time constant by the other parameter.

RC Charge Curve

Discharging a Capacitor

RC Discharge Curve  The discharge curve will be the inverse of the charging curve above. The capacitor starts at the maximum voltage then discharges toward zero volts. After one time constant the capacitor loses 63.2% of the total voltage, leaving 36.8% of the total voltage across the capacitor.

Section 3: Review Q. A micro-microfarad is the same as a what? A. It is the same as a picofarad. Q. Capacitors are said to block what? A. Only allow a small amount of current thru when charging or discharging, or AC current. Q. In a parallel circuit capacitors are calculated how? A. Capacitors in parallel are calculated like resistors in series. Q. Each time constant is how many percent? A. 63.2%

Questions?

Section 4: Learning Objectives - Learn what an inductor does in a circuit and how it is calculated when it is placed into series, and parallel circuit. - How internal resistance affects a circuit. - Types of batteries. - Explain Metal Oxide Varistor (MOV), Thermocouples, and Thermistor.

The Inductor  Inductance defined  Physical construction  How construction affects values  Inductor performance with AC and DC currents

Inductors in DC Circuits Inductance is the ability of a conductor to store energy in a magnetic field while electric current is passing through the conductor. The unit of inductance is the Henry, named after the American scientist, Joseph Henry. Henry noticed that a spark would jump the gap between the contacts of a switch that operated an electromagnet.

The Inductor  There are two fundamental principles of electromagnetics: 1.Moving electrons create a magnetic field. 2.Moving or changing magnetic fields cause electrons to move.  An inductor is a coil of wire through which electrons move, and energy is stored in the resulting magnetic field.

The Inductor  Like capacitors, inductors temporarily store energy.  Unlike capacitors:  Inductors store energy in a magnetic field, not an electric field.  When the source of electrons is removed, the magnetic field collapses immediately.

The Inductor  Inductors are simply coils of wire.  Can be air wound (just air in the middle of the coil)  Can be wound around a permeable material (material that concentrates magnetic fields)  Can be wound around a circular form (toroid)

The Inductor  Inductance is measured in Henry(s).  A Henry is a measure of the intensity of the magnetic field that is produced.  Typical inductor values used in electronics are in the range of millihenry (1/1000 Henry) and micro Henry (1/1,000,000 Henry)

The Inductor  The amount of inductance is influenced by a number of factors:  Number of coil turns.  Diameter of coil.  Spacing between turns.  Size of the wire used.  Type of material inside the coil.

Inductor Performance With DC Currents  When a DC current is applied to an inductor, the increasing magnetic field opposes the current flow and the current flow is at a minimum.  Finally, the magnetic field is at its maximum and the current flows to maintain the field.  As soon as the current source is removed, the magnetic field begins to collapse and creates a rush of current in the other direction, sometimes at very high voltage.

Inductor in Series  Inductors in Series: Values add together just as resistors in series do.  Inductors in Parallel: Total inductance is divided as is the resistance in parallel.

R/L Time Constants An RL circuit has a time constant much like an RC circuit. In the case of RL circuits, the time constant is calculated by dividing the inductance by the resistance. t = L/R Whereas in RC circuits the formula is t = CR

Voltage and Current with Inductors  The time constant curves of an RL circuit are basically the opposite of the RC curves. If you look at the curves in Resistance with Capacitors above and simply label the voltage curve as “current” and the current curve as “voltage” and you will have the curves for an RL circuit. Event The Capacitor The Inductor The switch is first closed Looks like a short circuit Looks like an open circuit After one time constant Voltage is 63.2% of source voltage Current is 63.2% of maximum After several time constants Voltage equals the source voltage Current is at maximum The switch is opened Voltage reverses across the series resistor Voltage reverses across inductor After one time constant Voltage is 36.8% of source voltage Current at 36.8% of maximum After several time constants Current and voltage are at 0

Other Devices in DC circuits. Battery (Voltaic Cell) Long line is + Short line is -

How Batteries are Constructed

Internal Resistance Internal resistance is a theoretical limitation of the current sourcing capability of a battery. Internal resistance is calculated by dividing the open-circuit voltage by the closed-circuit current. Example: if a particular battery had an open-circuit potential of 1.58 volts (typical for an alkaline battery) and a closed-circuit current of 1 ampere, the internal resistance would be 1.58 ohms

EXERCISE Find the internal resistance: A battery rated at 1.58 Volts delivers 138ma through a load of 8 ohms. What is the internal resistance???

Solution Using Ohm’s law: Total resistance is calculated as 11.5 ohms (using the source voltage of 1.58 volts and the current of 138 milliamperes, i.e., (1.58V / 0.138A= 11.449 ohms). Subtract the load resistance (8 ohms) from the total resistance to find the unknown internal resistance of : 3.5 ohms (11.449 - 8 = 3.449).

Applications and Safety  Battery terminals should never be shorted for long periods  Never mix old and new batteries  Some batteries contain powerful acids  Never recharge non rechargeable batteries

Types of Batteries  Primary (Non rechargeable)  Carbon Zinc  Alkaline  Lithium  Mercury Oxide

Types of Batteries Cont’d  Secondary (Rechargeable)  Nickel Cadmium  Nickel-metal hydride  Lithium ion  Rechargeable Alkaline  Lead Acid

Fuses  Melt open when a certain current is exceeded  Will “blow” when the current reaches 1.5 times the labeled current rating  Installed in SERIES with the load Fuse schematic symbol

METAL OXIDE VARISTOR (MOV) Used for over voltage protection or “surge” protection. Connected in Parallel with the load. Once burned open, they no longer do their job and need to be replaced. Used in Surge protectors.

Thermocouple Thermocouples are very simple and durable temperature sensors. They are comprised of two different materials joined at one end and separated at the other. The separated ends are considered the output, and they generate voltage which is proportional to the heat they are measuring or monitoring.

Thermister  A thermistor changes resistance with temperature, like a normal resistor, except more pronounced. Thermistors, like thermocouples are used to measure temperature, but in less hostile environments.  Thermisters come in two types, those with positive temperature coefficients and those with negative coefficients. The resistance of a thermistor with a negative temperature coefficient will go down as the temperature rises. This is the opposite of most electronic devices. Thermistor schematic symbols

Section 4: Review Q. How does a\the number of turns of wire affect an inductor? A. Inductance increases with the number of turns. Q. How does a R/L time constant differ from an R/C time constant? A. t=RC; t=L/R Q. Metal Oxide Varistors protect what? A. Used for over voltage for surge protectors. Q. Thermocouple generate voltage how? A. Using 2 dissimilar metals bonded together creates milli-volts.

Questions?

Section 5: Learning Objectives - Alternating Current, how it differs from DC. - Be familiar with Alternators, Oscillators and four parameters of a Sine Wave. - Understand the difference between RMS voltage, Peak Voltage, and Peak to peak voltage. - Calculate capacitive reactance, inductive reactance, and impedance in series and parallel circuits.

Alternating Current  Alternating current simply means that the polarity of the voltage source alternates back and forth.  Alternating current can be generated with either an alternator (and alternating generator) or an oscillator

Show- AC - Verses -DC

Alternators  An alternator generates electricity by rotating coils of wire in a magnetic field. As the coils pass one way, current flows in one direction. As the coils pass the other way (on the second half of the rotation) current flows in the other direction. In an alternator a loop of wire rotates through a magnetic field and generates a sine wave on the oscilloscope.

How an oscillator works  Energy needs to move back and forth from one form to another for an oscillator to work. You can make a very simple oscillator by connecting a capacitor and an inductor together. If you've read How Capacitors Work and How Inductors Work, you know that both capacitors and inductors store energy. A capacitor stores energy in the form of an electrostatic field, while an inductor uses a magnetic field. Imagine the following circuit: capacitorinductorHow Capacitors WorkHow Inductors WorkcapacitorinductorHow Capacitors WorkHow Inductors Work  If you charge up the capacitor with a battery and then insert the inductor into the circuit, here's what will happen: battery  The capacitor will start to discharge through the inductor. As it does, the inductor will create a magnetic field.  Once the capacitor discharges, the inductor will try to keep the current in the circuit moving, so it will charge up the other plate of the capacitor.  Once the inductor's field collapses, the capacitor has been recharged (but with the opposite polarity), so it discharges again through the inductor.  This oscillation will continue until the circuit runs out of energy due to resistance in the wire. It will oscillate at a frequency that depends on the size of the inductor and the capacitor.

Oscillators  An oscillator is a circuit that produces an output that varies periodically. They are used as clocks for timing circuits, to drive digital circuits or as essential components of radio circuits.  The following are characteristics of oscillators  Positive feedback  An oscillator will often have a tuned circuit in the feedback loop.  Gain of 1 A Colpitts oscillator

Pierce Oscillator

Armstrong Tuned-Gate Oscillator

Hartley Oscillator

The Sine Wave The output of an alternator is a sine wave. A sine wave is the most pure waveform possible. In fact, any repetitive wave is made up of one or more sine waves. The output of an alternator is a sine wave. A sine wave is the most pure waveform possible. In fact, any repetitive wave is made up of one or more sine waves. The sine wave is closely related to a circle and parts of the wave are measured in degrees as a circle is.

Four parameters of a Sine Wave  Amplitude  Peak Voltage  RMS voltage  Phase Angle

Phase angle A sine wave is closely related to a circle. For phase measurements the wave is divided into 360 degrees, just as a circle is. A sine wave is closely related to a circle. For phase measurements the wave is divided into 360 degrees, just as a circle is. One cycle of a sine wave is measured in 360 degrees.

Frequency  Frequency is the number of times the wave completes one cycle in one second. It is measured in Hertz (Hz) where 1Hz equals one cycle per second, 20 Hz equals 20 cycles per second, etc The 60Hz sine wave on the left takes twice the time to complete one cycle as the 120Hz sine wave on the right (16.6 milliseconds compared to 8.33 milliseconds).

Period  The period of a wave is the time it takes to complete one cycle.  Mathematically it is the reciprocal of the frequency. For example, a 60Hz wave has a period of 16.6 ms (1 / 60 = 0.0166).

Other Waves  If a circuit does not have the necessary frequency response (bandwidth) to pass all components of a wave (harmonics), the wave will be distorted. Square Wave High-pass filter Distortion due to insufficient low frequency response.

Measurements  AC Voltmeter – Reads RMS Voltage which is 70.7% of peak voltage. Only accurate for measuring sine waves.

Oscilloscope  An oscilloscope is an analog voltmeter that measures voltage over time  Voltage is represented by vertical movement of the spot along the Y-axis. As the spot moves upward it represents more positive voltage. As it moves down it represents more negative voltage. The face of an oscilloscope showing a sine wave. The spot moves along the horizontal X-axis over a given time. Vertical movement along the Y-axis represents volts. This shows the repeated sinusoidal change in voltage over time of a sine wave.

Dual Trace O-Scope  A dual trace oscilloscope has two vertical (Y axis) inputs. Although the spots move horizontally in unison, they move vertically independently. A dual trace oscilloscope has two Y-axis inputs that measure voltage independently.

O-Scope X10 Probe  Any test instrument takes some current from the circuit. This can be enough current to cause a voltage drop and change the way the circuit is operating….. Because of this, a X10 probe is used.

Circuits  A circuit is a path for current to flow  Three basic kinds of circuits  Open – the path is broken and interrupts current flow  Closed – the path is complete and current flows were it is intended  Short – an unintended low resistance path that divers current

Resistors in AC Circuits Resistors in AC Circuits are insensitive to frequency or phase.

The Capacitor Behavior in AC  When AC voltage is applied, during one half of the cycle the capacitor accepts a charge in one direction.  During the next half of the cycle, the capacitor is discharged then recharged in the reverse direction.  During the next half cycle the pattern reverses.  It acts as if AC current passes through a capacitor

Capacitors in AC Circuits Alternating current simply repeats the charge discharge cycle of a capacitor at a given frequency. At higher frequencies, the capacitor passes more current than at lower frequencies. Alternating current simply repeats the charge discharge cycle of a capacitor at a given frequency. At higher frequencies, the capacitor passes more current than at lower frequencies.

Capacitive Reactance  The property of a capacitor where it passes more current at higher frequencies is called capacitive reactance. It is measured in ohms, like resistance, but is different at different frequencies.  For example, if a capacitor has a reactance of 10 ohms at 100 Hz it will have a reactance of 5 ohms at 200 Hz.

Calculating Capacitive Reactance  Since the reactance of a capacitor is different at different frequencies you need to be able to calculate the reactance based on the size of the capacitor.  The formula to calculate capacitive reactance is: Where : XCXCXCXC= capacitive reactance in ohms 2222= a mathematical constant of 6.28 = frequency of the AC source voltage in hertz C= capacitance in farads

Capacitive Reactance  In the following circuit the capacitive reactance is calculated as below:  The source voltage has a frequency of 60 hertz and the capacitance is 66 microfarads. Plugging these numbers into the above formula we get:  This gives a capacitive reactance (XC) of 40.2 ohms.

Voltage and Current in a Capacitive AC Circuit  Voltage and Current in a Capacitive AC Circuit  While the voltage is low, the current is high and vice-versa.  In this case, the current is said to lead the voltage (high current followed by high voltage). Above: Voltage and current across a capacitor when a sine wave is applied. Below: Voltage and current of a capacitor during charge and discharge cycles

The Inductor  Because the magnetic field surrounding an inductor can cut across another inductor in close proximity, the changing magnetic field in one can cause current to flow in the other … the basis of transformers

Inductors in AC Circuits  Inductive Reactance  Inductors block current flow at the start of the “charge and discharge” cycles of a sine wave. The faster the cycles, the less current an inductor will pass.  This opposition to high frequencies is called inductive reactance  Higher frequencies = More inductive reactance

Calculating Inductive Reactance  The formula to calculate inductive reactance is:  X L = 2πfL XLXLXLXL= inductive reactance in ohms 2222= a mathematical constant of 6.28 = frequency of the AC source voltage in hertz L= inductance in henrys

Inductive-Capacitive Circuits  A circuit is either inductive or capacitive depending on whether XL or XC is higher.  The total reactance is the difference between the inductive reactance and the capacitive reactance:  X = Abs (X C – X L ) X=Total reactance Abs=Absolute value, meaning if the result is negative remove the minus sign X C =Capacitive reactance in ohms X L =Inductive reactance in ohms

Impedance Series Circuits  Impedance is the combination of all the resistance and reactance in a circuit. It is represented by the letter Z and is calculated with the following formula.  If this formula looks familiar, it is the same formula used to calculate the length of the side of a right triangle knowing the lengths of the other two sides (the Pythagorean theorem).

For Example:  If you have a total reactance of 25 ohms (say, 75 ohms of inductive reactance and 50 ohms of capacitive reactance) and 75 ohms of resistance, you will have an impedance of 79.1 ohms. Since the reactance's have cancelled to only 25 ohms, and there is 75 ohms of resistance, the circuit is resistive.

Impedance formula Parallel  Parallel Impedance formula is the inverse of Series formula.

Resonant Circuits  Remember that as frequency increases inductive reactance increases. Likewise, as frequency increases capacitive reactance decreases.  This means that, with any circuit having both inductance and capacitance, there must be a frequency where the inductive reactance and capacitive reactance are the same.  The frequency where inductive reactance and capacitive reactance are equal is called the resonant frequency.

Resonants

Resonant Frequency Formula: In the following circuit the resonant frequency would be calculated by plugging the values for the inductor and capacitor into the above formula: If either inductance or capacitance increases, the resonant frequency decreases and vice-versa.

Series Resonance  In the example series resonant circuit the inductor and capacitor are connected in series.  As shown here to find the total reactance, the capacitive reactance is subtracted from the inductive reactance.  Since the inductive reactance and the capacitive reactance are equal at the resonant frequency, the total reactance will be zero.  If there is resistance in the circuit, the total impedance will be the value of the resistance. Therefore, a series resonant circuit will have its lowest impedance at the resonant frequency.

Parallel Resonance  In a parallel resonant circuit, the inductor will have lower reactance at low frequencies and the capacitor will have lower reactance at high frequencies.  Therefore, a parallel resonant circuit will have its highest impedance at the resonant frequency.

Review 5: Questions Q. How does an Oscillator work? A. As the Cap starts to charge the inductor starts to create a magnetic field. When the capacitor discharges the inductor will try to keep the current in the circuit moving so it will charge up the other plate. Once the inductors field collapse the capacitor has been recharged so it discharges through the inductor. Q. What is Amplitude, Peak voltage, Peak to Peak, and RMS? A. Amplitude represents how large the wave is. Peak voltage is the maximum voltage in either direction. Peak to Peak is Maximum (+) (-). RMS is converted to DC or 70.7%. Q. Why is a X10 probe used by an O-Scope? A. To minimize circuit loading. Always multiply readings by 10.

Questions?

Section 6: Learning Objectives - Explains some uses of a filter system and why a filter is needed in electronics applications. - Know the differences between a high pass filter and a low pass filter. - Understand the differences between the types of transformers. - Be familiar with the efficiency problems with transformer.

Filters  Filters are used where a range of frequencies are desired and another range is not.  A typical use of a filter circuit is a crossover network in a speaker system. In this case it is desirable to direct frequencies above a certain point to the tweeter and those lower than that point to the woofer

RC Filters  Low Pass In a circuit made of a single resistor and a single capacitor, there is a frequency where the capacitive reactance and the resistance will be equal. This frequency is called the cut- off frequency (f CO ). Looking at the following circuit, at frequencies below the cut-off frequency more voltage will be developed across the capacitor than the resistor; at frequencies above the cut-off frequency more voltage will be developed across the resistor than the capacitor. Another definition of the cut-off frequency is the half-power point. This is because the power output of the filter is 50% of the maximum at the cut-off frequency.

RC L low pass Filter  An RC filter is typically illustrated with the following configuration. Since the circuit takes the shape of the letter “L”, it is called an “L” filter An RC “L” low-pass filter.

RC Filter Cont’d  In an RC filter circuit, the input is placed across the two components in series and the output is taken across one of the components.  If the output is taken across the resistor the filter becomes a high-pass filter; if the output is take across the capacitor the filter is a low pass filter.  The cut-off frequency of an RC filter is calculated with the following formula:  co = Cut-off frequency 2222= Mathematical constant of 6.28 R= Resistance in ohms C= Capacitance in ohms

High Pass RC Filters  When the output is taken across the resistor, you have a high Pass filter.  Another way to look at the high pass filter is that the higher frequencies are passed by the capacitor and the lower frequencies are blocked by the capacitor. An RC “L” high-pass filter

LC Filters  LC filters have the advantage of not wasting energy as power dissipated in the resistor.  In an LC filter you actually have a resonant circuit. Therefore, the cut-off frequency will be the resonant frequency.  At frequency above the resonant frequency the inductive reactance is greater than the capacitive reactance.  Therefore the voltage across the inductor is higher than the voltage across the capacitor.  At frequencies below the resonant frequency the capacitive reactance is greater than the inductive reactance. Therefore the voltage across the capacitor is higher than the voltage across the inductor.

High Pass LC Filters  If the output is taken across the inductor of an LC filter you have a high-pass filter. Another way to look at it is that the capacitor blocks lower frequencies and the inductor passes what’s left to ground

Low Pass LC Filters  If the output is taken across the capacitor of an LC filter you have a low-pass filter. Another way to look at it is that the inductor blocks higher frequencies and the capacitor passes what’s left to ground.

L Filters and T Filters  “T” filters can have any combination of components and be either low-pass or high- pass filters.

Pi Filters  Like the “T” filter, the Pi filter is usually illustrated with the components laid out in the shape of the Greek letter Pi. Like the “T” filter can use any combination of components and be either low-pass or high-pass. A low-pass CLC Pi filter A low-pass CRC Pi filter

Transformers  Joseph Henry and Michael Faraday independently discovered that a changing current in an inductor would induce a current in a nearby inductor. Credit for this property of mutual inductance has been given to Faraday.  Modern transformers are constructed by winding two coils of wire, either next to each other or one on top of the other, on a core made of either soft iron (actually, usually steel) or ferrite. The soft iron concentrates (“controls and directs”) the magnetic lines of flux in the transformer

How Transformers Work…  When an AC current is passed through one of the inductors making up a transformer, the oscillating magnetic flux crossing the other inductor induces AC current in that inductor. The inductor that has current passed through it is called the primary inductor; the inductor that has the induced current is called the secondary inductor. In this case the transformer is called a step-down transformer.

Output Voltage of a Transformer The output voltage of a transformer is determined by the ratio of coils (turns) of wire between the two inductors.

Types of Transformers  Step up/Step Down  Isolation  Impedance Matching  Tapped  AutoTransformer  Tesla Coil

Step Up- Step Down Transformer  In a step-up transformer the secondary voltage is higher than the primary voltage  In a step-down transformer the secondary voltage is lower than the primary voltage.  A step-up or step-down transformer can be reversed to perform the opposite function. However a transformer is usually optimized for either step-up or step-down operation.

What would be the ratio of this Transformer?

What would be the Ratio of this Transformer?

Isolation Transformer  An isolation transformer has the same voltage on the secondary as on the primary.  The primary and secondary may be optimized for the circuits they are intended to couple but otherwise the primary and secondary are identical.  The main purpose of an isolation transformer is to block DC currents.  They may also be used to isolate equipment from the receptacle power. These isolation transformers may have a variable output but don’t mistake a “variac” (explained) for an isolation transformer.

Impedance Matching  A matching transformer used to match the impedance between two circuits. This maximizes power transfer.

Tapped Transformer  Transformers often have taps in the secondary to make more than one voltage available.  These may be center-tapped to give two equal voltages or may have various taps to give various voltages.

Autotransformer  An autotransformer is a single coil that is tapped in such a way that the primary and secondary are different parts of the coil, although one may completely overlap the other.  A Variac is a brand name for an autotransformer with variable output.  The ignition coil of a car is usually an autotransformer.  Do not confuse with the Isolation Transformer

Tesla Coil  A Tesla coil, invented by Nicola Tesla, is a type of autotransformer that is driven by a resonant oscillator. Very high voltages and currents can be achieved with a Tesla coil.

Efficiency  Transformers are extremely efficient. However there are some losses.  Core losses  Hysteresis  Eddy Currents  Copper Losses

Core losses  Core losses are caused by power consumed by the core of the transformer

Hysteresis  Hysteresis is the resistance of a material to change the polarity of its magnetism. With each oscillation of the transformer current the polarity of the magnetic domains in the core are reversed. This consumes power and produces heat.

Eddy currents  The transformer core is made of soft iron, a conductor.  Since this core is within the oscillating magnetic field, electric current will be induced in it. This current does nothing useful and produces heat.  Transformer cores are usually made of laminated plates coated with enamel. The enamel insulates the layers of the core from each other, reducing the eddy currents.

Copper losses  Copper losses are mainly cause by the resistance of the wire that makes up the transformer.  Copper losses can be reduced by increasing the diameter of the wire. If a transformer needs to transfer a high current, larger wire must be used to reduce copper losses. Consequently a larger iron core must also be used.  Copper losses determine the maximum output current of a transformer.  When the current rating of a transformer is exceeded, copper losses cause a drop in voltage.

Decibels  The term “decibel” means 1/10 of a bel, named after Alexander Bell of telephone fame.  The bel is used to express large power ratios with smaller numbers.  One bel is a ratio of 10:1,  two bels is a ratio of 100:1,  3 bels is a ratio of 1,000:1, etc.  Since one decibel is 1/10 of a bel 10 decibels equals one bel or a ratio of 10:1. The formula to calculate decibels is: db= Power ratio in decibels Log= Base-10 logarithm P1P1P1P1= Reference power level P2P2P2P2= Compared power level

Decibels as Voltage ratios:  Decibels are only intended to express power ratios. However, since power and voltage are directly proportional to each other, decibels can also be used to express voltage ratios. The formula to calculate decibels using a voltage ratios is:

Decibels  The power ratio of 2:1 or three decibels (3db) appears frequently in nature. For example, the human ear can normally only detect differences in sound level of 3db (someone with inflammation of the inner ear may be able to detect a 1db difference).  Bandwidth is specified as the range of frequencies where the output of a circuit is less than 3db below the peak output.  Here is a table of decibels and their respective ratios. Power or Voltage Ratio Power or Voltage Ratio Decibels VoltagePower 1.26:121 2:163 10:12010 100:14020 1,000:16030 etc.etc.etc.

Review 6: Questions Q. What is the main purpose to use a high pass filter? A. To allow the high frequency to drive something like a tweeter. Q. What is hysteresis? A. Hysteresis is the resistance of a material to change the polarity of its magnetism. Q. An Isolation Transformer’s main purpose is to do what? A. The main purpose of an isolation transformer is to block DC currents. Q. A Decibles ratio of 2:1 in voltage would be what loss? A. 6 Volts.

Questions?

Section 7; Learning Objectives  Understand how a P/N junction is able to operate.  Know the types of Diodes and their purposes.  Be familiar with rectification using a half wave rectifier and a full wave rectifier.  Recognize the components of a transistor and the basic principles of operations for the transistor.

Solid State Electronics Silicon Atom  A silicon atom has four electrons in its outermost shell (the valence shell, where all chemical and electrical action takes place).  When silicon forms a crystal, each of the four valence electrons will bond with an electron from an adjacent silicon atom.  These electrons are bound tightly in the crystal lattice and are hard to move, making a silicon crystal an insulator. Silicon Crystal Lattice

Arsenic Atom  An arsenic atom has five electrons in its valence shell If a small number arsenic atoms are introduced into a silicon crystal, four of the electrons will bind with electrons in adjacent silicon atoms and the arsenic will fit into the crystal lattice. However, the fifth electron has no electrons to bind with. These “donor” electrons want to remain with the arsenic atoms because they are attracted to a corresponding proton in the atom. However, not having an electron to bond with in the crystal lattice, this extra electron acts much like the electrons in metals. The arsenic atoms in the silicon crystal can easily exchange these loose electrons. Since the donor electrons are easily moved through the crystal, it will readily conduct electrical current. A silicon crystal that is “doped” with donor atoms is called N-type silicon. N-Type Silicon Notice that each arsenic atom has an extra electron that doesn’t fit the lattice.

The gallium atom  A gallium atom has three electrons in its valence shell. If a small number of gallium introduced into a silicon crystal the three electrons will bind with electrons from adjacent silicon atoms but there will be a “hole” left with no atom. Any electrons that happen by will easily fall into the holes left by the gallium atoms but, since there is no corresponding proton in the gallium atom to hold them, they are easily pushed out of the holes. Since electrons can be easily moved through the crystal, hopping from hole to hole, the crystal will readily conduct electrical current. A silicon crystal that is doped with atoms that leave holes in the crystal structure is called P-type silicon. P-Type Silicon Notice that each gallium atom is short of one electron, leaving a hole in the lattice.

Properties of Silicon in Solid state devices Silicon Crystal Lattice N-Type Silicon Notice that each arsenic atom has an extra electron that doesn’t fit the lattice. P-Type Silicon Notice that each gallium atom is short of one electron, leaving a hole in the lattice.

P/N junction  If P-type silicon and N-type silicon are brought into contact, electrons in the N- type silicon will be strongly attracted to the holes in the P-type silicon near the junction. The attraction of the holes in the P-type silicon is stronger than the attraction of the protons in the donor atoms. However, donor electrons must remain near their atoms because they are attracted to a corresponding proton in the donor atom. The result is that, near the junction of the P-type and N- type materials, the donor electrons move to nearby holes in the P-type material and the crystal lattice becomes complete. The region is depleted of donor electrons and holes and will not readily conduct electricity A P-N Junction Look near the middle of the lattice. To the left the silicon is doped with arsenic. To the right the silicon is doped with gallium. The holes created by the gallium atoms attract the electrons donated by the arsenic atoms (the darkened electrons).

Analyzing Charge Carriers (Electrons and Holes)  To avoid confusion we must now adjust how we view the structure of a semiconductor crystal. We need to start looking at N-type silicon as material with free negative charge carriers (electrons) and P-type silicon as a material with free positive charge carriers (holes).  Now, when we look at a P-N junction we have a different picture. Think of it like this, if you dig a hole in the ground, what do you get? Not only a hole in the ground but a pile of dirt that used to be in the hole. If you put the dirt back in the hole, neither the hole nor the pile of dirt exists anymore. In the depletion region, where the electrons from the N- type side have filled the holes in the P-type side, neither the free electrons nor the holes exist, as charge carriers, anymore

Another View of a P-N Junction  Electrons in the N- type silicon near the junction have migrated to fill the holes in the P-type silicon near the junction. Charge carriers no longer exist near the junction. The depletion region is the region devoid of charge carriers.

Reversed Biased P/N Junction  When a positive potential is applied to the N-type side and a negative potential is applied to the P-type side the junction is said to be reverse biased. The free electrons in the N- type silicon are pulled out of the crystal by the positive voltage. The negative voltage applied to the P- type side floods the P-type silicon with electrons that fill the holes in the crystal lattice. Since filling the holes with electrons makes them cease to exist as charge carriers it appears that the holes have been pulled out of the P-type silicon by the negative potential. This leaves the entire crystal devoid of charge carriers. Under normal voltage levels electrical current will not flow through the crystal.

Forward-biased P-N Junction  When a positive potential is applied to the P-type side and a negative potential is applied to the N-type side, the junction is said to be forward-biased.  Free electrons are pushed toward the junction by the negative potential. The positive potential applied to the P-type side pulls electrons out of the holes so it appears that holes are pushed toward the junction.  If enough voltage is applied, the electrons and holes are forced into the depletion region. With the crystal now filled with charge carriers it conducts electrical current.  A forward biased P/N junction will take a certain amount of voltage to force the electrons to start flowing.

The Diode  A diode is an electrical device allowing current to move through it in one direction with far greater ease than in the other.  The most common type of diode in modern circuit design is the semiconductor diode, although other diode technologies exist. Semiconductor diodes are symbolized in schematic diagrams as such:

Diodes  When placed in a simple battery- lamp circuit, the diode will either allow or prevent current through the lamp, depending on the polarity of the applied voltage:

Diodes  When the polarity of the battery is such that electrons are allowed to flow through the diode, the diode is said to be forward-biased.  Conversely, when the battery is "backward" and the diode blocks current, the diode is said to be reverse-biased. A diode may be thought of as a kind of switch: "closed" when forward-biased and "open" when reverse-biased.

DIODES  Diode behavior is comparable to the behavior of a hydraulic device called a check valve. A check valve allows fluid flow through it in one direction only:

DIODES

Diodes

DIODES  For silicon diodes, the typical forward voltage is 0.7 volts, nominal.  For germanium diodes, the forward voltage is only 0.3 volts.  The chemical constituency of the P-N junction comprising the diode accounts for its nominal forward voltage figure, which is why silicon and germanium diodes have such different forward voltages.

Diodes

Diodes General Purpose Zener Light Emitting (LED)

The Diode The semi-conductor phenomena  Atoms in a metal allow a “sea” of electrons that are relatively free to move about.  Semiconducting materials like Silicon and Germanium have fewer free electrons.  Impurities added to semiconductor material can either add free electrons or create an absence of free electrons (holes).

The Diode The semi-conductor phenomena  Consider the bar of silicon at the right.  One side of the bar is doped with negative material (excess electrons). The cathode.  The other side is doped with positive material (excess holes). The anode  In between is a no man’s land called the P-N Junction.

The Diode The semi-conductor phenomena  Consider now applying a negative voltage to the anode and positive voltage to the cathode.  The electrons are attracted away from the junction.  This diode is reverse biased meaning no current will flow.

The Diode The semi-conductor phenomena  Consider now applying a positive voltage to the anode and a negative voltage to the cathode.  The electrons are forced to the junction.  This diode is forward biased meaning current will flow.

The Diode with AC Current  If AC is applied to a diode:  During one half of the cycle the diode is forward biased and current flows.  During the other half of the cycle, the diode is reversed biased and current stops.  This is the process of rectification, allowing current to flow in only one direction.  This is used to convert AC into pulsating DC.

The Diode with AC Current Input AC Voltage Output Pulsed DC Voltage Diode conducts Diode off

The Light Emitting Diode  In normal diodes, when electrons combine with holes current flows and heat is produced.  With some materials, when electrons combine with holes, photons of light are emitted, this forms an LED.  LEDs are generally used as indicators though they have the same properties as a regular diode.

Rectifier  This converts the AC from the receptacle to a pulsing DC. This is done by removing or inverting half of the AC signal. Because of the pulsing nature of the DC produced by the rectifier, the final output will always have some ripple. The type of rectifier determines the frequency of this ripple. For example, with a 60 Hz input, a half- wave rectifier will have a ripple frequency of 60 Hz where a full-wave rectifier will have a ripple frequency of 120 Hz.

Rectifier (Cont’d) Unregulated power supply with half-wave rectifier Half-wave rectified sine wave Typical ripple after filtering. Ripple frequency equals the sine wave frequency Unregulated power supply with full-wave bridge rectifier Full-wave rectified sine wave Typical ripple after filtering. Ripple frequency equals two times the sine wave frequency.

Full Wave Rectification

First Half of AC Cycle (+)

Second Half of AC Cycle (-)

FWBR in action

AC in – Pulsating DC out

Zener Diode  A Zener diode is designed through appropriate doping so that it conducts at a predetermined reverse voltage.  The diode begins to conduct and then maintains that predetermined voltage  The over-voltage and associated current must be dissipated by the diode as heat 9V4.7V

Thyristors  SCR's are the most prevalent member of the thyristor four layer diode family.  A positive pulse applied to the gate of an SCR triggers it into conduction. Conduction continues even if the gate pulse is removed. Conduction only ceases when the anode to cathode voltage drops to zero.  SCR's are most often used with an AC supply (or pulsating DC) because of the continuous conduction.  SCR's switch megawatts of power, up to 5600 A and 10,000 V.

The Transistor (Electronic Valves)  How they work, an inside look  Basic types  NPN  PNP  The basic transistor circuits  Switch  Amplifier

Transistor NPNPNPFET

The Transistor base collector emitter

NPN and PNP

The Transistor The base-emitter current controls the collector-base current

The Transistor Applying positive Voltage to the Base

The Transistor  There are two basic types of transistors depending of the arrangement of the material.  PNP  NPN  An easy phrase to help remember the appropriate symbol is to look at the arrow.  PNP – pointing in proudly.  NPN – not pointing in.  The only operational difference is the source polarity. PNP NPN

Bipolar Transistors  A bi-polar transistor is made of three layers of silicon in a P-N-P or N- P-N arrangement  Since the current that flows into the collector of a bi-polar transistor is a ratio of the current flowing into the base, bi-polar transistors are said to amplify current A small current from the base to the emitter causes a large current from the collector to the emitter (Note: conventional current is shown.). A PNP transistor works like an NPN transistor except the polarities are reversed.

Bipolar Transistors  The following illustrations show the polarity and schematic symbols for bi-polar transistors..

MOSFET Transistors  Field-Effect Transistors are constructed in several ways using metal-oxide-semiconductor technology. The leads on a FET are labeled Drain, Source and Gate.  Because the current through an FET (MOSFET) is a ratio of the gate voltage, FETs are said to amplify voltage.

Integrated Circuits  The first integrated circuits were simply a few transistor manufactured on a single chip of silicon. Today, integrated circuits are made-up of millions of transistors along with other components and interconnections.  We are concerned here mainly with digital integrated circuits. There are several families of digital integrated circuits.  The ones that will be covered here are TTL and CMOS.

TTL Circuits  TTL (Transistor-Transistor Logic) integrated circuits are made using bi-polar transistors. The gates in TTL circuits are often characterized by multiple emitters on a single transistor. TTL circuits have the advantage of speed at a sacrifice of power efficiency.  TTL circuits always operate from 5-volt power supplies (typically specified as from 4.5 or 4.75 volts to 5.25 or 5.5 volts).

TTL Nand Gate

CMOS  CMOS (Complementary Metal Oxide- Semiconductor) integrated circuits are made using MOS field-effect transistors.  Each gate is made from a complementary pair of transistors (I.e. one p-channel and one n- channel transistor).  CMOS circuits have the advantage of very low power consumption but are much slower than TTL circuits.  CMOS circuits are also very sensitive to electrostatic discharge.  CMOS circuits typically operate from power supplies ranging from 3 to 12 volts.

Pinouts  The pinout of an IC is read counter- clockwise looking from the top.  Pin one is indicated by a tab on TO-3 packages and by a dot or notch on DIP packages. Dip TO-5

Troubleshooting IC Circuits  Troubleshooting techniques for ICs are similar to other circuits.  It is important to have the internal schematics available or to be familiar with how the circuit should behave.  Since all of the components are on a single silicon chip, failure is often indicated by open an or short-circuit condition.

Review 7: Questions Q. What is an arsenic atom and its purpose? A. It is the N-type material and it contains an extra atom to fill the holes to allow voltage to flow thru once it is properly forwarded biased. Q. Does a Zener Dioad conduct in forward or reverse bias? A. Reverse bias. Q. An Isolation Transformer’s main purpose is to do what? A. The main purpose of an isolation transformer is to block DC currents. Q. A Decibles ratio of 2:1 in voltage would be what loss? A. 6 Volts.

Amplifiers  Bi-polar Transistor Amplifiers  There are three basic amplifier configurations for bi-polar amplifiers.  Common Collector  Common Emitter  Common Base  These are named for the connection that is used for the common connection in the circuit.  It is usually easier to recognize a configuration by the location of the output.  Each configuration has characteristic input and output impedances and AC voltage gain.

Common Collector (Emitter follower) The Common Collector configuration can be recognized by the output being on the emitter:  High input impedance  Low output impedance  Output not inverted  Voltage gain (A V ) of 1

Common Emitter The Common Emitter configuration can be recognized by the output being on the collector  Low input impedance  High output impedance (equal to collector resistor)  Output inverted  High voltage gain

Common Base The Common Base amplifier can be recognized by the base being tied to the circuit ground.  low input impedance  high output impedance  high voltage gain  current gain <1

Operational Amplifiers  An operational amplifier is a very high gain differential amplifier with very high input impedance and a very low output impedance.  The two inputs of an operational amplifier are labeled with plus and minus symbols.  The plus input is called the non- inverting input and the minus input is called the inverting input.

OP Amps  Differential amplifier - amplifies difference between two signals.  Can amplify very small voltage signals to a useful level.  Op Amps can require one power supply (single supply) or a positive and a negative power supply (dual supply)

An operational amplifier follows a few simple rules:  If the non-inverting input is more positive than the inverting input, the output voltage will go more positive until one of two conditions are met. Either the two inputs are equal or the output cannot go more positive (usually about 0.5 volts below the positive supply voltage.)  If the inverting input is more positive than the non- inverting input, the output voltage will go more negative until one of two conditions are met. Either the two inputs are equal or the output cannot go more negative (usually about 0.5 volts above the negative supply voltage).  The output voltage will remain stable as long as the two input voltages are equal

Op Amp Applications:  Comparator  Since there is no feedback there is no effect on the inputs based on the output voltage. Therefore, as long as the inverting input is the least-bit more positive that the non-inverting input (with the exception of unavoidable hystersis), the output voltage will go all the way to the negative supply voltage and remain there.  Likewise, as long as the non- inverting input is the least-bit more positive than the inverting input, the output voltage will go all the way to the positive supply voltage and remain there.

Op Amp Applications:  Voltage Follower  The output is fed back, 100%, to the inverting input. Following the foregoing rules, the output voltage will be automatically adjusted until the two inputs are equal.  With the 100% negative feedback, the two inputs can only be equal when the output is equal to the non-inverting input. Therefore, the output voltage will always be equal to the input voltage (at the non- inverting input). This circuit is useful to couple a circuit with high output impedance to a circuit with low input impedance

Op Amp Applications:  Non-inverting Amplifier  The output is fed back to the inverting input through a voltage divider. Following the voltage divider rules, if the feedback resistors are equal, the voltage at the inverting input will be 50% of the output voltage.  Therefore, for the inputs to be equal, the output voltage must be twice the input voltage (at the non-inverting input). The gain can be adjusted by changing the ratio of the feedback resistor values.

Op Amp Applications:  Inverting Amplifier  The non-inverting input is at the circuit ground. Therefore, the output voltage will be adjusted automatically to keep the inverting input at zero volts (inputs equal).  For this condition to be met, assuming that the feedback resistors are of equal value, the output voltage will always be equal to the input voltage but of opposite polarity.  For example, if the input (the free end of R1) is at +2.67 volts the output will be -2.67 volts. The gain can be adjusted by changing the ratio of the feedback resistor values.

Op Amp Applications:  Differential Amplifier  The differential amplifier has a voltage divider on the non- inverting input and another voltage divider in the feedback loop to the inverting input. R1 and R3 are of equal value and that R2 and R4 are also of equal value. When the operational amplifier adjusts the output voltage until the inverting and non-inverting inputs are equal, the output will always be the difference between the two input voltages (the free ends of R1 and R3) if all of the feedback resistors are equal. If the two input voltages are equal, the output will be zero volts. If voltage gain is desired the ratios of the feedback resistors can be changed.

Op Amp Applications:  DC Motor Control  Here is a simple practical application for an operational amplifier. Assume that the tachometer produces 1 volt for each 100 RPM of the motor.  If the potentiometer is set at 1 volt the op-amp will adjust its output voltage until the motor stabilizes at 100 RPM. If the motor should slow down the op- amp will increase its output voltage until the motor returns to 100 RPM.  If the output impedance of the op-amp is too high (and would be unable to supply enough current to run the motor) an NPN transistor can be inserted between the op-amp and the motor in an emitter-follower configuration.

Op Amp Applications:  Current Controller  This is actually just the non-inverting amplifier configuration. Assume that the potentiometer is set at 1 volt. The op-amp will adjust the output until 1 volt is seen at the inverting input. This means that the voltage across the sense resistor will be 1 volt regardless of the value of either feedback resistor. The current in the feedback loop can be selected by choosing a sense resistor that has the desired current at 1 volt. Since the load resistor is in series with the sense resistor the current through the Load resistor will be the same as the current through the sense resistor regardless of the value of the load resistor (the voltage across the load resistor will vary accordingly).

Power Supplies  A power supply is a circuit that changes one power delivery system to be compatible with a certain type of circuit. For example, the most common type of power supply changes the 120 VAC available at the typical power receptacle to some lower DC voltage. This is a DC power supply.  There are four possible power supply stages:  A voltage step-down  A rectifier  A filter  A regulator (optional)

Voltage step-down  Voltage step-down is usually accomplished with a transformer.  The stage is required to set the output voltage with unregulated power supplies and to reduce power loss in the regulator of regulated power supplies.  Because of the high efficiency of switching regulators this stage is not required in switching

Filter  The filter will smooth-out the pulses produced by the rectifier.  The most common filter is a capacitor placed across the load.  Sometimes an inductor is also placed in series with the load to help filter the rectified output

Regulator  A regulator is an optional stage when the demand is heavy or variable or the input source is not stable.  A standard regulator requires a low input voltage and produces a lot of heat.  A switching regulator produced little heat and can work with high input voltages. A simple regulator The zener diode is chosen to be 0.7 volts higher than the desired output frequency. The transistor parameters are not critical except that it must be able to handle the power necessary for the circuit.

Voltages in a power supply  The voltage at secondary of the transformer would typically be measured with an AC voltmeter and therefore be displayed in RMS volts.  The voltage across the filter capacitor and load would be the peak voltage across the secondary of the transformer minus any voltage lost across the diodes in the rectifier.

Switching Power Supply  A switching power supply switches the pass transistor (as in the simple regulator above) so that it is always either completely on or completely off.  The duration of the pulses are varied to control the average output voltage.  The output voltage has extreme ripple so heavy filters are used to smooth it. Switching power supply

Radio Receivers  The first section is the RF amplifier. This section determines the inherent noise level.  The mixer and local oscillator shift the received frequency to the intermediate frequency  The IF amplifier must have correct bandwidth (frequency response) in order to pass the desired signal and to reject adjacent interference.  The Demodulator extracts the original base band signal from the RF carrier.

Video Displays  The two most popular video displays are the cathode ray tube (CRT) and the liquid crystal display (LCD).  The CRT operates by sweeping a beam of electrons across a phosphorus screen that glows when hit by the electrons.  The LCD works by changing the polarization of light as it passes between cross-polarized filters.

Digital Measurements/Testing  There are a number of sophisticated instruments for testing digital circuits.  The most common, and possibly most useful, is a logic probe. A logic probe can be fairly sophisticate or nothing more than an LED in a clip-lead. It is used simply to see if the logic level on a particular connection is a one or a zero.  A Logic pulser is Sometimes used to force circuit inputs to the necessary levels for troubleshooting. A logic pulser is simply a small pulse generator.

Binary Numbers First, create a table that looks like this one. Next, write the binary number in the table. Finally, add up the numbers that have a 1 below them. The sum is the decimal equivalent of the binary number.

Converting Decimal to Binary

Binary Addition There are four rules for binary addition: 0 + 0 0 0 + 1 11 1 01 1 1 1 0 + 0 = 0 0 + 1 (or 1+0) = 1 1 + 1 = 0 and carry over to the next column to the left 1 + 1 + 1 (as with a carry from the column to the right) = 1 and a carry over to the next column to the left

Binary Addition (Cont’d)  The following two 8 bit numbers, when added together, show all the binary addition rules in action. 1 1 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 + 0 0 1 1 1 0 1 0 0 1 1 0 1 1 0 1 0 1 1 0 1 1 0 1

Hexadecimal Numbers  Hexadecimal numbers are used as shorthand for binary numbers. As you can see in the table below, each four bit binary number has a hexadecimal equivalent.

Hexadecimal  To convert any binary number to hexadecimal, break the number into groups of four and write the hexadecimal equivalent for each group. 16 bit binary number — 101101001010110 1 Broken into groups of four — 1011 | 0100 | 1010 | 1101 Hexadecimal for each group — B | 4 | A | D B | 4 | A | D Final Hexadecimal number —B4AD

Logic Gates  Most digital circuits consist of logic gates. These are representations of the functions of circuits, rather than the actual configurations.  The following gates are shown with three inputs.  Logic gates can actually have any number of inputs.

Logic Gates  The following four rules may be useful in understanding how logic gates work:  OR Gate The output is a logical one if any of the inputs are a logical oneThe output is a logical one if any of the inputs are a logical one  AND Gate The output is a logical one if all of the inputs are a logical one.The output is a logical one if all of the inputs are a logical one.  Exclusive OR (XOR) Gate -The output is a logical one if there is any difference in the inputs. - Inverter One input and one output. The output is always the opposite of the input.One input and one output. The output is always the opposite of the input.

OR/NOR GATES

AND/NAND GATES

Exclusive OR / Exclusive NOR Gates

Inverter or “Not”

Soldering  Unplated Tip  Unplated tips are rare on soldering irons used in electronics. Unplated tips can be cleaned with a file to expose the bare copper. Then the iron should be heated and coated with solder.  Plated Tip-  The favored method to clean a soldering iron tip is to wipe the hot tip on a wet cellulose sponge. However, according to the ETA also suggests a 320 grit aluminum oxide cloth on a cold tip should be used. However, if you suggest cleaning a plated soldering iron tip with emery cloth to most technicians you will get a raised eyebrow in return. Another method is to dip the hot tip in flux then wipe it on a soft cloth.

Proper Soldering Techniques Normal Circuits Normal Circuits Make a good mechanical connection Clean the soldering iron tip Tin the tip (put enough solder on the tip to make good contact with the joint) Heat the joint, not the solder Touch the solder to the joint, not the soldering iron Use only as much solder as necessary for a good connection Do not move the joint until the solder has solidified High Voltage Circuits High Voltage Circuits Leave a smooth rounded covering of solder on connections. Sharp points with high voltage can cause coronal discharge.

Questions?

Electrical Safety  Basics of Electricity:  Electrical current will not flow unless it has a complete path (circuit) that returns to its source (battery, transformer).  Current flows through you and other conductors, such as metals, earth and concrete.  Current can harm you when it flows through your body (electric shock).  Insulators resist the flow of electricity. Insulating materials are used to coat copper conducting wires and are used to make electrical work gloves. Insulators help to protect humans from coming into contact with electricity flowing through conductors.  Just as there is pressure in a water pipe, even with no water flowing, there is voltage at a receptacle, even if current is not flowing. Another word for voltage is "Potential."

Electrical Safety  How Electricity Can Harm You  Current passing through your body can cause electric shock, resulting in 3 types of potential injuries:  Burns (arcs burn with heat & radiation)  Physical injuries (broken bones, falls, & muscle damage)  At 10 mA, the muscles clamp on to whatever the person is holding.  Nervous system effects (stop breathing at 30 to 75 mA alternating current at 60Hz, fibrillation at 75 to 100 mA at 60Hz)  Fibrillation = heart is "twitching" and there is no blood flow to the body.   The heart can be damaged because it is in the path of the most common routes electricity will take through the body:  Hand-to-hand  Hand-to-foot

Electrical Safety  Plan your work and plan for safety  Avoid wet working conditions and other dangers  Use Ground Fault Circuit Interrupters. GFCI's are electrical devices that are designed to detect ground faults (when current is "leaking" somewhere outside its intended pathway). If your body provides the path to ground for the leaking current, you could receive a shock or be electrocuted. GFCI's should be used in all wet locations and on outside outlets.  Avoid overhead power lines: Position yourself so that the longest conductive object you are using (saws, poles, tools, brooms, etc.) cannot come closer than at least 10 feet to any unguarded, energized overhead line.

Electrical Safety  Use proper wiring and connectors  Use extension cords properly and temporarily:  Cords must be UL listed and have 3 prongs  Power bars must have a fuse or breaker  Do not use 2-prong, ungrounded cords in a lab  Do not run cords through walls, doors, under rugs, or across aisles  Do not repair cords--buy new ones  Make sure the total number of watts connected to the cord does not exceed the rating of the cord.

Electrical Safety  Use and maintain tools properly  Avoid wearing items such as jewelry, watch bands, bracelets, rings, key chains, necklaces, etc. that might come into contact with exposed, energized parts.  Wear correct PPE:  Hard hats rated "Class E"  ANSI-approved footwear coded "EH"

Safe Equipment  Do not use equipment that has been damaged or improperly modified.  Always use equipment according to the manufacturer's specifications.  "Live" parts (greater than 50 volts) must be guarded by one or more of the following:  An enclosure that requires a tool for access.  A locked enclosure.  An interlocked access door.  A substantial insulating guard to prevent contact.  Check cords--they should:  Be completely free of damage and deterioration.  Should always have an appropriate strain relief device where they enter the enclosure.

Electrical Safety SAFETY FIRST, SAFETY ALWAYS!!

Questions?

Electronics Technology. Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate.

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Electronics Technology. Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate.

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Presentation on theme: "Electronics Technology. Section 1: Learning Objectives. - Identify the different properties between Conductors, Insulators, and Semiconductors. - Translate."— Presentation transcript:

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