BASIC ELECTRONIC COMPONENTS - Elenco · PDF file-1-RESISTORS RESISTORS, What do they do? The...

BASIC ELECTRONIC COMPONENTS

MODEL ECK-10

Instruction Manualby Arthur F. Seymour MSEE

It is the intention of this course to teach the fundamental operation of basicelectronic components by comparison to drawings of equivalent mechanicalparts. It must be understood that the mechanical circuits would operate muchslower than their electronic counterparts and one-to-one correlation can neverbe achieved. The comparisons will, however, give an insight to each of thefundamental electronic components used in every electronic product.

Resistors

CapacitorsCoils

Semiconductors

Others

Transformers(not included)

ELENCO®

Copyright © 2016, 1994 by ELENCO® Electronics, Inc. All rights reserved. Revised 2016 REV-O 753254No part of this book shall be reproduced by any means; electronic, photocopying, or otherwise without written permission from the publisher.

ECK-10_REV-O_091416.qxp_ECK-10 9/14/16 2:49 PM

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RESISTORSRESISTORS, What do they do?The electronic component known as the resistor isbest described as electrical friction. Pretend, for amoment, that electricity travels through hollow pipeslike water. Assume two pipes are filled with waterand one pipe has very rough walls. It would be easyto say that it is more difficult to push the waterthrough the rough-walled pipe than through a pipewith smooth walls. The pipe with rough walls couldbe described as having more resistance tomovement than the smooth one.Pioneers in the field of electronics thought electricitywas some type of invisible fluid that could flowthrough certain materials easily, but had difficultyflowing through other materials. In a way they werecorrect since the movement of electrons through amaterial cannot be seen by the human eye, evenwith the best microscopes made. There is asimilarity between the movement of electrons inwires and the movement of water in the pipes. Forexample, if the pressure on one end of a water pipeis increased, the amount of water that will passthrough the pipe will also increase. The pressure onthe other end of the pipe will be indirectly related tothe resistance the pipe has to the flow of water. Inother words, the pressure at the other end of thepipe will decrease if the resistance of the pipeincreases. Figure 1 shows this relationshipgraphically.

Electrons flow through materials when a pressure(called voltage in electronics) is placed on one endof the material forcing the electrons to “react” witheach other until the ones on the other end of thematerial move out. Some materials hold on to theirelectrons more than others making it more difficultfor the electrons to move. These materials have ahigher resistance to the flow of electricity (calledcurrent in electronics) than the ones that allowelectrons to move easily. Therefore, earlyexperimenters called the materials insulators if theyhad very high resistance to electon flow andconductors if they had very little resistance toelectron flow. Later materials that offered a mediumamount of resistance were classified assemiconductors.When a person designs a circuit in electronics, it isoften necessary to limit the amount of electrons orcurrent that will move through that circuit eachsecond. This is similar to the way a faucet limits theamount of water that will enter a glass each second.It would be very difficult to fill a glass withoutbreaking it if the faucet had only two states, wideopen or off. By using the proper value of resistancein an electronic circuit designers can limit thepressure placed on a device and thus prevent itfrom being damaged or destroyed.

SUMMARY: The resistor is an electroniccomponent that has electrical friction. This frictionopposes the flow of electrons and thus reduces thevoltage (pressure) placed on other electroniccomponents by restricting the amount of current thatcan pass through it.

Figure 1

Low ResistancePipe

High ResistancePipe (rough walls) Low Pressure

High PressureThrough SameSize Opening

Water Tank


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RESISTORSRESISTORS, How are they made?There are many different types of resistors used inelectronics. Each type is made from differentmaterials. Resistors are also made to handledifferent amounts of electrical power. Someresistors may change their value when voltages areplaced across them. These are called voltagedependent resistors or nonlinear resistors. Mostresistors are designed to change their value whenthe temperature of the resistor changes. Someresistors are also made with a control attached thatallows the user to mechanically change theresistance. These are called variable resistors orpotentiometers. Figure 2 shows physical shapes ofsome different types of resistors.

The first commercial resistors made were formed bywrapping a resistive wire around a non-conductingrod (see Figure 3). The rod was usually made ofsome form of ceramic that had the desired heatproperties since the wires could become quite hotduring use. End caps with leads attached were thenplaced over the ends of the rod making contact tothe resistive wire, usually a nickel chromium alloy.

The value of wirewound resistors remain fairly flatwith increasing temperature, but change greatly withfrequency. It is also difficult to precisely control thevalue of the resistor during construction so theymust be measured and sorted after they are built.

By grinding carbon into a fine powder and mixing itwith resin, a material can be made with differentresistive values. Conductive leads are placed oneach end of a cylinder of this material and the unit isthen heated or cured in an oven. The body of theresistor is then painted with an insulating paint toprevent it from shorting if touched by anothercomponent. The finished resistors are thenmeasured and sorted by value (Figure 4). If theseresistors are overloaded by a circuit, their resistancewill permanently decrease. It is important that thepower rating of the carbon composition resistor isnot exceeded.

Figure 2

Carbon Film

Variable

Carbon Composition

THE WIREWOUND RESISTOR

Figure 3

THE CARBON COMPOSITION RESISTOR

Ceramic Rod

Wire

End CapProtective Coating

Figure 4

Insulating Paint Carbon & ResinMixture

Conductive Wire


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RESISTORSCARBON FILM RESISTORSCarbon film resistors are made by depositing a verythin layer of carbon on a ceramic rod. The resistor isthen protected by a flameproof jacket since this typeof resistor will burn if overloaded sufficiently. Carbonfilm resistors produce less electrical noise thancarbon composition and their values are constant athigh frequencies. You can substitute a carbon filmresistor for most carbon composition resistors if thepower ratings are carefully observed. Theconstruction of carbon film resistors requiretemperatures in excess of 1,000OC.

Metal oxide resistors are also constructed in asimilar manner as the carbon film resistor with theexception that the film is made of tin chloride attemperatures as high as 5,000OC. Metal oxideresistors are covered with epoxy or some similarplastic coating. These resistors are more costly thanother types and therefore are only used when circuitconstraints make them necessary.

Metal film resistors are also made by depositing afilm of metal (usually nickel alloy) onto a ceramicrod. These resistors are very stable withtemperature and frequency, but cost more than thecarbon film or carbon composition types. In someinstances, these resistors are cased in a ceramictube instead of the usual plastic or epoxy coating.

When a resistor is constructed so its value can beadjusted, it is called a variable resistor. Figure 6shows the basic elements present in all variableresistors. First a resistive material is deposited on anon-conducting base. Next, stationary contacts areconnected to each end of the resistive material.Finally, a moving contact or wiper is constructed tomove along the resistive material and tap off thedesired resistance. There are many methods forconstructing variable resistors, but they all containthese three basic principles.

Figure 5

METAL OXIDE RESISTORS

METAL FILM RESISTORS

THE VARIABLE RESISTOR

Figure 6

Carbon Film

Ceramic Rod Flameproof Jacket

Leads

MovableArm

WiperContact

StationaryContact

Thin Layerof Resistive

Material

Non-conductiveBase Material


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RESISTORSRESISTOR VALUES AND MARKINGSThe unit of measure for resistance is the ohm, whichis represented by the Greek letter W. Beforetechnology improved the process of manufacturingresistors, they were first made and then sorted. Bysorting the values into groups that represented a 5%change in value, (resistor values are 10% apart),certain preferred values became the standard forthe electronics industry. Table 1 shows the standardvalues for 5% resistors.

Resistors are marked by using different colored ringsaround their body (see Figure 7). The first ringrepresents the first digit of the resistor’s value. Thesecond ring represents the second digit of theresistor’s value. The third ring tells you the power often to multiply by. The final and fourth ring representsthe tolerance. For example, gold is for 5% resistorsand silver for 10% resistors. This means the value ofthe resistor is guaranteed to be within 5% or 10% ofthe value marked. The colors in Table 2 are used torepresent the numbers from 0 to 9.

Note: If the third ring is gold, you multiply the firsttwo digits by 0.1 and if it is silver, by 0.01. Thissystem can identify values from 0.1W to as high as91 x 109, or 91,000,000,000W. The amount of powereach resistor can handle is usually proportional tothe size of the resistor. Figure 8 shows the actualsize and power capacity of normal carbon filmresistors, and the symbols used to representresistors on schematics.

10 11 12 13 15 16 18 2022 24 27 30 33 36 39 4347 51 56 62 68 75 82 91

Table 1

Figure 7

OrangeRed

Violet Gold

27 X 103 = 27,000 W,with 5% Tolerance

COLOR VALUEBlack 0Brown 1Red 2Orange 3Yellow 4Green 5Blue 6Violet 7Gray 8White 9

Table 2

Figure 8Regular Variable

Resistor Symbols1/8 Watt

1/4 Watt

1/2 Watt


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RESISTORSSELF TEST

1. A flow of electrons through a material: a) Voltage c) Current b) Resistance d) Conductance2. The pressure that pushes electrons through a

material: a) Voltage c) Conduction b) Current d) Resistance3. A material that has very high resistance to electron

flow: a) Conductor c) Resistor b) Semiconductor d) Insulator4. A material that allows electrons to flow easily: a) Conductor c) Resistor b) Semiconductor d) Insulator5. A material that produces electrical friction and restricts

the flow of electrons: a) Conductor c) Resistor b) Semiconductor d) Insulator

6. A resistor that is made by wrapping a wire around aceramic rod:

a) Carbon Film c) Thermistor b) Carbon Composition d) Wirewound7. A resistor made by heating powder and resin in an

oven: a) Carbon Film c) Thermistor b) Carbon Composition d) Wirewound8. A resistor made by depositing a very thin layer of

resistive material on a ceramic rod: a) Carbon Film c) Thermistor b) Carbon Composition d) Wirewound9. One of the preferred values for a 5% resistor: a) 4000W c) 77W b) 560W d) 395W10. The amount of wattage a resistor can handle is

determined by: a) Value c) Current b) Voltage d) Size

THEORYCircle the letter that best fits the description.

PRACTICEOpen the bag marked “resistors” and fill in the table below.

Color 1 Color 2 Color 3 Color 4 Value Percent Wattage

EXTRA CREDITUsing a razor blade or sharp knife, scrape away the paint on the body of one resistor and determine the type ofconstruction used to make it. Try and determine all of the materials used including the metals used to make theleads.


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CAPACITORS, What do they do?Capacitors are components that can store electricalpressure (Voltage) for long periods of time. When acapacitor has a difference in voltage (ElectricalPressure) between its two leads it is said to becharged. A capacitor is charged by forcing a oneway (DC) current to flow through it for a short periodof time. It can be discharged by letting an oppositedirection current flow out of the capacitor. Considerfor a moment the analogy of a water pipe that has arubber diaphragm sealing off each side of the pipeas shown in Figure 9.

If the pipe had a plunger on one end, as shown inFigure 9, and the plunger was pushed toward thediaphragm, the water in the pipe would force therubber to stretch out until the force of the rubberpushing back on the water was equal to the force ofthe plunger. You could say the pipe is charged andready to push the plunger back. In fact, if theplunger is released it will move back to its originalposition. The pipe will then be discharged or with nocharge on the diaphragm.

Capacitors act the same as the pipe in Figure 9.When a voltage (Electrical Pressure) is placed onone lead with respect to the other lead, electronsare forced to “pile up” on one of the capacitor’splates until the voltage pushing back is equal to thevoltage applied. The capacitor is then charged to thevoltage. If the two leads of that capacitor areshorted, it would have the same effect as letting theplunger in Figure 9 move freely. The capacitor wouldrapidly discharge and the voltage across the twoleads would become zero (No Charge).What would happen if the plunger in Figure 9 waswiggled in and out many times each second? Thewater in the pipe would be pushed by the diaphragmthen sucked back by the diaphragm. Since themovement of the water (Current) is back and forth(Alternating) it is called an Alternating Current or AC.The capacitor will therefore pass an alternatingcurrent with little resistance. When the push on theplunger was only toward the diaphragm, the wateron the other end of the diaphragm moved justenough to charge the pipe (transient current). Justas the pipe blocked a direct push, a capacitor clocksdirect current (DC). An example of alternatingcurrent is the 60 cycle (60 wiggles each second)current produced when you plug something into awall outlet.

SUMMARY: A capacitor stores electrical energywhen charged by a DC source. It can passalternating current (AC), but blocks direct current(DC) except for a very short charging current, calledtransient current.

CAPACITORS

Pipe Filled with Water

Rubber DiaphragmSealing Center of Pipe

Plunger

Figure 9


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CAPACITORS, How are they made?There are many different types of capacitors used inelectronics. Each type is made from differentmaterials and with different methods. Capacitors arealso made to handle different amounts of electricalpressure or voltage. Each capacitor is marked toshow the maximum voltage that it can withstandwithout breaking down. All capacitors contain thesame fundamental parts, which consist of two ormore conductive plates separated by anonconductive material. The insulating materialbetween the plates is called the dielectric. The basicelements necessary to build a capacitor are shownin Figure 10.

Perhaps the most common form of capacitor isconstructed by tightly winding two foil metal platesthat are separated by sheets of paper or plastic asshown in Figure 11. By picking the correct insulatingmaterial the value of capacitance can be increasedgreatly, but the maximum working voltage is usuallylowered. For this reason, capacitors are normallyidentified by the type of material used as theinsulator or dielectric. Consider the water pipe withthe rubber diaphragm in the center of the pipe. Thediaphragm is equivalent to the dielectric in acapacitor. If the rubber is made very soft, it willstretch out and hold a large amount of water, but itwill break easily (large capacitance, but low workingvoltage). If the rubber is made very stiff, it will notstretch far, but will be able to withstand higher

pressure (low capacitance, but high workingvoltage). By making the pipe larger and keeping thestiff rubber we can achieve a device that holds alarge amount of water and withstands a high amountof pressure (high capacitance, high working voltage,large size). These three types of water pipes areillustrated in Figure 12. The pipes follow the rule thatthe capacity to hold water, (Capacitance) multipliedby the amount of pressure they can take (Voltage)determines the size of the pipe. In electronics theCV product determines the capacitor size.

CAPACITORS

THE METAL FOIL CAPACITORSoft Rubber

Figure 12

Stiff Rubber

Stiff Rubber

Larger Size

Large CapacityLow Pressure

Low Capacitybut can withstandHigh Pressure

High Capacity and can withstand High Pressure

Figure 10

Lead 1

Nonconductive Material

Conductive Plate

Lead 2

Figure 11

Lead 1

Paper or Plastic Insulator

Conductive Foil

Lead 2


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DIELECTRIC CONSTANT, What is it?The dielectric (rubber diaphragm in the water pipeanalogy) in a capacitor is the material that canwithstand electrical pressure (Voltage) withoutappreciable conduction (Current). When a voltage isapplied to a capacitor, energy in the form of anelectric charge is held by the dielectric. In the rubberdiaphragm analogy the rubber would stretch out andhold the water back. The energy was stored in therubber. When the plunger is released the rubberwould release this energy and push the plungerback toward its original position. If there was noenergy lost in the rubber diaphragm, all the energywould be recovered and the plunger would return toits original position. The only perfect dielectric for acapacitor in which no conduction occurs and fromwhich all the stored energy may be recovered is aperfect vacuum. The DIELECTRIC CONSTANT (K)is the ratio by which the capacitance is increasedwhen another dielectric replaces a vacuum betweentwo plates. Table 3 shows the Dielectric Constant ofvarious materials.

To make a variable capacitor, one set of stationaryaluminum plates are mounted to a frame with asmall space between each plate. Another set ofplates are mounted to a movable shaft anddesigned to fit into the space of the fixed plateswithout touching them. The insulator or dielectric inthis type of variable capacitor is air. When themovable plates are completely inside the fixedplates, the device is at minimum capacitance. Theshape of the plates can be designed to achieve theproper amount of capacitance versus rotation fordifferent applications. An additional screw is addedto squeeze two insulated metal plates together(Trimmer) and thus set the minimum amount ofcapacitance.

CAPACITORS

Air, at normal pressure 1 Mica 7.5

Alcohol, ethyl (grain) 25 Paper, manila 1.5

Beeswax 1.86 Paraffin wax 2.25

Castor Oil 4.67 Porcelain 4.4

Glass flint density 4.5 10 Quartz 2

Glycerine 56 Water, distilled 81

Table 3

THE VARIABLE CAPACITOR

Figure 13

Frame

MovablePlates

Shaft

Fixed Plates

Trimmer


The amount of charge a capacitor can hold(capacitance) is measured in Farads. In practice,one farad is a very large amount of capacitance,making the most common term used micro-farad orone millionth of a farad. There are three factors thatdetermine the capacitance that exist between twoconductive plates:

1. The bigger the plates are (Surface Area),the higher the capacitance. Capacitance(C) is directly proportional to Area (A).

2. The larger the distance is between the twoplates, the smaller the amount ofcapacitance. Capacitance (C) is indirectlyproportional to distance (d).

3. The larger the value of the dielectricconstant, the more capacitance (Dielectricconstant is equivalent to softness of therubber in our pipe analogy). Thecapacitance (C) is directly proportional tothe Dielectric Constant (K) of the insulatingmaterial. From the above factors, theformula for capacitance in Farads becomes:

C = 0.244K Picofarads *

C = Capacitance in Picofarads (Farad x 10-12)K = Dielectric ConstantA = Area of one Plate in square inchesN = Number of Platesd = Distance between plates in inches

Example Calculation for Capacitor shown in Figure 14.C = 2.24 x (1 x 1)(2 - 1) / (.01) = 224 Picofarads or0.000224 Microfarads.

* If A and d are in centimeters change 0.224 to0.0885.

The older styles of capacitors were marked withcolored dots or rings similar to resistors. In recentyears, the advances in technology has made iteasier to print the value, working voltage, tolerance,and temperature characteristics on the body of thecapacitors. Certain capacitors use a dielectric thatrequires markings to insure one lead is always keptat a higher voltage than the other lead. Figure 15shows typical markings found on different types ofcapacitors. Table 4 gives the standard values usedand the different methods for marking these values.

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CAPACITANCE, How is it calculated?

CAPACITORS

A(N-1)d

Figure 14

0.01 inch

Glass K=10

1 inch

1 inch

CAPACITOR VALUES AND MARKINGS

Figure 15

B682KK

+10+16V

2200

mF 25V

10mF 25V

RadialElectrolytic

AxialElectrolytic

DiscTantalumElectrolytic

Chip(no

markings)


-10-

CAPACITORSVoltage

1Code2

Cap. Value3

Typical Markings4 5

Tolerance (%)6

Markings7

4 0G 100pF 100pF 101 +5% J5.5 0L .001mF .001 102 +10% K6.3 0J .015mF .015 152 +20% M10 1A .002mF .002 202 –10% +30% Q16 1C .0022mF .0022 222 –10% +50% T25 1E .003mF .003 302 –20% +80% Z35 1V .033mF .033 333 SPECIAL A50 1H .047mF .047 47363 1J .05mF .05 R05 Temperature

Markings80 1K .068mF .068 R068100 2A .1mF .1 104 NP0 {<10ppm / OC}110 2Q .15mF .15 154 N100 {<100ppm / OC}125 2B .2mF .2 204 N220 {<220ppm / OC}160 2C 2.2mF 2.2 2R2 N820 {<820ppm / OC}180 2Z 22mF 22 22 Y5F200 2D 100mF 100 100 Y5T220 2P 220mF 220 220 Y5V250 2E 470mF 470 470 X5F315 2F 1000mF 1000 1000 Z5U

Capacitor markings vary greatly from onemanufacturer to another as the above table shows.Voltages may be marked directly (200V) or coded(2D). The value of capacitance may be markeddirectly on the part as shown in columns 4 and 5(note that .001mF and 1000mF have the samemarking, but the difference in size makes the valueobvious). The number 102 may also be used torepresent 1000 (10+2 zeros). In some instances the

manufacturer may use an R to represent thedecimal point. The tolerance is usually printeddirectly on the capacitors. When it is omitted, thestandard tolerance is assumed to be +80% to –20%for electrolytics. Capacitance change withtemperature is coded in parts per million per degreeC, {N220 = 220/1,000,000 or .022%}, or by atemperature graph. See manufacturersspecifications for complete details.

CAPACITOR SYMBOLSFigure 16 shows the schematic symbols used to representcapacitors. The + symbol indicates that the capacitor ispolarized and the lead marked with the + sign must alwayshave a higher voltage than the other lead. The curvedplate, plate with sides, and minus sign also indicate thecapacitor is polarized and these leads must always be at alower voltage than the other lead. The arrow crossingthrough the capacitor indicates of capacitance is variable.

Figure 16 +–

Standard VariablePolarized


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CAPACITORSSELF TEST

1. A flow of electrons in one direction: a) AC Voltage c) Alternating Current b) Direct Voltage d) Direct Current2. When two conductive plates are moved closer

together Capacitance will: a) Increase c) Stay the Same b) Decrease d) Vary Downwards3. The name given to the material between a capacitor’s

plates: a) Air c) Conductor b) Dielectric d) Insulator4. Electrons flowing in and out of a wire: a) AC Voltage c) Alternating Current b) Direct Voltage d) Direct Current5. If the size of the conductive plates is increased,

capacitance will: a) Increase c) Stay the Same b) Decrease d) Vary Downwards6. A capacitor will block: a) AC Voltage c) Alternating Current b) Direct Voltage d) Direct Current

7. When electrons are forced onto one plate of acapacitor:

a) Polarization c) Storage b) Discharging a) Charging8. A capacitor lead that is marked with a + must always be: a) Grounded c) At higher voltage than the other lead b) At highest voltage d) b & c9. A small disc capacitor marked 100 has a value of: a) 100mF c) 100pF b) .00001F d) 100F10. A large electrolytic capacitor marked 100 has a value

of: a) 100mF c) 100pF b) .00001F d) 100F11. If a dielectric is changed from air to distilled water the

capacitance will: a) remain the same c) decrease b) increase 81 times d) drop in half12. A dielectric that stores energy with no loss: a) Does not exist c) Pure Glass b) Air d) A perfect vacuum


PRACTICEOpen the bag marked “capacitors” and fill in the table below.

EXTRA CREDITWhat happens to the total capacitance if you connect twocapacitors as shown in Figure 17. Hint, use water pipeanalogy and try to calculate equivalent if one water pipe.

Type CapacitanceValue

WorkingVoltage

Polarized(Y/N)

OtherMarkings

Figure 17

10mF

20mF

? mF

Table 4


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INDUCTORSINDUCTORS, What do they do?The electronic component known as the inductor isbest described as electrical momentum. In our waterpipe analogy the inductor would be equivalent to avery long hose that is wrapped around itself manytimes (see Figure 18). If the hose is very long it willcontain many gallons of water. When pressure isapplied to one end of the hose, the thousands ofgallons of water would not start to move instantly. Itwould take time to get the water moving due toinertia (a body at rest wants to stay at rest). After awhile the water would start to move and pick upspeed. The speed would increase until the friction ofthe hose applied to the amount of pressure beingapplied to the water. If you try to instantly stop thewater from moving by holding the plunger, themomentum (a body in motion wants to stay inmotion) of the water would cause a large negativepressure (Suction) that would pull the plunger fromyour hands.

Since Inductors are made by coiling a wire, they areoften called Coils. In practice the names Inductorand Coil are used interchangeably. From the aboveanalogy, it is obvious that a coiled hose will passDirect Current (DC), since the water flow increasesto equal the resistance in the coiled hose after anelapsed period of time. If the pressure on theplunger is alternated (pushed, then pulled) fastenough, the water in the coil will never start movingand the Alternating Current (AC) will be blocked.The nature of a Coil in electronics follows the sameprinciples as the coiled hose analogy. A coil of wirewill pass DC and block AC. Recall that the nature ofa Capacitor blocked DC and passed AC, the exactopposite of a coil. Because of this, the Capacitorand Inductor are often called Dual Components.Table 5 compares the properties of capacitors andinductors.

PlungerWater Pipe

Large Hose Filledwith Water

Figure 18

Capacitor InductorBlocks Direct Current Blocks Alternating CurrentPasses Alternating Current Passes Direct CurrentVoltage in Capacitor cannot change instantly Current in an Inductor cannot change instantlyQuick Voltage change produces large Current Quick Current change produces large VoltageStores Energy in Electric Field Stores Energy in Magnetic FieldCurrent leads Voltage Voltage leads Current

Table 5


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INDUCTORS, How are they made?In order to understand how inductors are made, wehave to change our water pipe analogy slightly toinclude the effect of magnetic fields. Consider twopipes filled with water and small magnets attachedto the walls of the pipes with rubber bands as shownin Figure 19. The moving magnets, due to theoriginal current, pull the magnets in the second pipeand force a small current to flow in the samedirection as the original current. When the rubberbands are fully stretched, the induced current willstop, even though the initial DC current is stillflowing. If the original current is an AC currenthowever, it will induce a continuous AC current inthe second pipe because the magnets will moveback and forth, pulling the magnets in the secondpipe back and forth.

Consider the two coiled pipes shown in Figure 20.When the pipe is stretched out (increased length) asin coil 1, the adjacent turns have little affect on eachother. In coil 2 (decreased length) the magnets ineach turn of the pipe are linking and the amount of“apparent mass” in the pipe seems to increase. Inan inductor, pushing the coiled wire closer togethercauses the inductance of the coil to also increase,and stretching the coil out will lower the inductanceof the coil. In other words, the inductance of a coil isindirectly proportional to its length. If the diameter of

the coil is increased, it will take more hose to form aloop, and the amount of water will thereforeincrease. More water means a larger “apparentmass”. Inductance will also increase in a coil if thecross sectional area increases. Inductance isdirectly proportional to area.

Consider the affect of adding more turns to coiledpipe. The amount of material to push (mass) isincreased and the amount of linkage is increaseddue to more magnets available. This causes the“apparent mass” to increase at a greater rate thanwould be expected. When making an inductor, theactual inductance is directly proportional to thesquare of the number of turns.The final factor to consider when making a coil is thecore material at the center of the coil. If our pipewrapped around a material that contained manymagnets, they would also link to the magnets in thepipe. This wouldincrease the “apparentmass” of the water inthe pipe. The tinymagnets in the corewould rotate as shownin Figure 21 and forcethe water to keepmoving in the samedirection. Placing aniron core at the centerof an inductor willdirectly increase theinductance by anamount equal to thepermeability of thecore material.

INDUCTORS

Figure 20

Figure 21

Coil 1

Coil 2

Many tinymagnets

IN

OUT

Figure 19

InducedCurrent

InitialCurrent


-14-

INDUCTORSINDUCTANCE, How is it calculated?Reviewing how coils are made will show thefollowing:1. Inductance of a coil is indirectly proportional to

the length of the coil.2. Inductance is directly proportional to the cross

sectional area.3. Inductance is proportional to the square of the

number of turns.4. Inductance is directly proportional to the

permeability of the core material.

From the above information the formula forinductance of a simple iron core would be:

L =

Where:L = Inductance in microhenrysN = Number of turnsm = Permeability of core materialA = Cross-sectional area of coil, in square inchesl = Length of coil in inches

This formula is good only for solid core coils withlength greater than diameter.

N2mA10l

TRANSFORMERS, How are they made?Placing different coils on the same iron core asshown in Figure 22 produces the electroniccomponent known as the Transformer. If a DCcurrent is forced through the center coil, the othertwo coils will only produce a current when theoriginal current is changing. Once the DC currentreaches a constant value, the other two coils will“unlink” and produce no flowing current if loaded. Ifthe generator voltage is continuously changing as inFigure 22, it will produce a current that changes withtime. This changing current in the center coil willproduce similar currents in both of the end coils.Since the bottom coil has twice the number of turns(twice the magnetic linkage), the voltage across thiscoil will be twice the generator voltage. The power inan electronic device is equal to the voltage acrossthe device times the current through the device(P=VI). If the voltage doubles on the bottomwinding, then the current must become 1/2 due tothe law of conservation of power (Power cannot becreated or destroyed, but can be transformed fromone state to another). Since the bottom coil iswound in the same direction as the generator coil,the voltage across the coil (top wire to bottom wire)will be the same polarity as the generator voltage.The top coil is wound in the opposite direction

forcing the core magnet rotation (Called flux by thePros) to push the current in the opposite directionand produce a voltage of the opposite polarity. Sincethe number of turns in the top coil are the same asthe generator coil, the voltage and current (Powerthat can be taken from the coil) will also be equal.This ability to transform AC voltages and ACcurrents influenced early experimenters to call thisdevice a Transformer.

Figure 22

VoltageGenerator

Iron Core –V

OppositeVoltage

ii

½i

2V2N Turns

N Turns

Direction ofCore MagnetRotation Dueto Current i


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TWO MORE LAWS ABOUT INDUCTORSFaraday’s Law states that any time a conductormoves through a magnetic field (Figure 23) avoltage is generated. Because of this principle, it ispossible to attach a magnet (or coil) to a rotatingdevice and produce large amounts of electricalpower (the Hoover Dam for example).Lenz’ Law states that the induced currents in aconductor passing through a magnetic field willproduce a magnetic field that will oppose the motionbetween the magnet and the conductor. To producea large amount of electrical power, a largemechanical force is required (conservation ofpower).

Most inductors are custom made to meet therequirements of the purchaser. They are marked tomatch the specification of the buyer and thereforecarry no standard markings. The schematic symbolsfor coils and transformers are shown in Figure 24.These symbols are the most commonly used torepresent fixed coils, variable coils, andtransformers.

The Q (figure of merit) of a coil is the ratio of theinductive reactance to the internal series resistanceof the coil. Since the reactance and resistance canboth change with frequency, Q must be measured atthe desired frequency. Anything that will raise theinductance without raising the series resistance willincrease the Q of the coil; for example, using an ironcore. Lowering the series resistance withoutlowering the inductance will also raise the Q, moreturns of larger wire for example. Q is important whenthe inductor is used in a resonant circuit to block orselect desired frequencies. The higher the Q, thetighter the selection of frequencies become.

The Inductor prevents current from making anysudden changes by producing large opposingvoltages. Magnetic coupling can be used totransform voltages and currents, but power mustremain the same. Coils and transformers can beused to select frequencies.

INDUCTORS

Figure 23

Wire

Lines of Flux

Motion ofMagnet

S N

INDUCTANCE SYMBOLS AND MARKINGS

THE Q FACTOR IN COILS

SUMMARY

Figure 24

Fixed Coils Variable Coils

Iron CoreTransformer

Tunable Transformer

XLr


-16-

SELF TEST

1. The inductor is best described as: a) Induced Voltage c) Electrical Storage Device b) Long Wire d) Electrical Momentum2. When wires in a coil are moved closer together, the

inductance will: a) Increase c) Stay the Same b) Decrease3. Another word used to represent an inductor: a) Wire c) Transformer b) Coil d) Conductor4. If the diameter of a coil is increased, the inductance will: a) Increase c) Stay the Same b) Decrease5. If the number of turns in a coil is decreased, the

inductance of that coil will: a) Increase c) Stay the Same b) Decrease6. An inductor will block: a) Alternating Voltage c) Alternating Current b) Direct Voltage d) Direct Current

7. When an iron core is placed into the center of a coil, theinductance will:

a) Increase c) Stay the Same b) Decrease8. If voltage in a transformer is stepped down, the current

will: a) Increase c) Must Stay the Same b) Decrease9. When a conductor is moved through a magnetic field: a) Power is created c) Magnetic field is reduced b) A voltage is d) a & c generated on the wire.10. The Q factor of a coil is equal to: a) Wire quality c) Ratio of inductance b) Ratio of reactance to resistance to resistance11. If windings on a straight rod are in the same direction,

the induced voltage will have: a) Same amplitude c) Same polarity b) Different amplitude d) Different polarity12. An inductor stores energy in its: a) Electric field c) Core b) Magnetic field d) Wires


PRACTICEUsing the coil supplied, answer the following questions.

EXTRA CREDITWhat happens to the total inductance if you connect twocoils as shown in Figure 25. Hint, remember the coiledhose analogy and try to calculate equivalent if one coiledhose.

Figure 25

10mH

? mH

INDUCTORS

Is the coil wound on an iron form? Yes ____ No ____What prevents the wire from shorting? ________________________________________How many turns are on the coil? _____________________Example: Using a length of 0.1”, a radius of 0.02”, permeability of 14 for the iron core, and 56 turns, calculatethe inductance of the coil and record here: ________________________

20mH


-17-

SEMICONDUCTORSTHE DIODE, what is it?The diode can be compared to the check valveshown in Figure 26. The basic function of a checkvalve is to allow water to flow in only one direction.Once the force of the spring is exceeded, the platemoves away from the stop allowing water to passthrough the pipe. A flow of water in the oppositedirection is blocked by the solid stop and plate. If ittook a pressure of 0.7lb to exceed the spring force,the flow of water versus pressure might look likeFigure 27. In electronics, this curve would representthe typical silicon diode if pounds per square inchequaled volts and gallons per minute equaledamperes. Of course, the amount of current that flowsthrough the diode must be limited or the device couldbe damaged. Just as too much water through thecheck valve could destroy the plate (shorted diode).If the diode is made of Gallium Arsenide, it wouldtake approximately twice the voltage to produce aflow of current (spring in Figure 26 is twice asstrong). The energy level required to “turn on” aGallium Arsenide diode is so high, that light isgenerated when current starts to flow. These diodesare called “Light Emitting Diodes”, or simply LEDs.

The transistor is best described as a device thatuses a small amount of current to control a largeamount of current (Current Amplifier). Consider adevice fabricated as shown in Figure 28. A smallamount of “Base Current” pushes on the L1 portionof the lever arm forcing check valve D1 to open,even though it is “reverse biased” (pressure is indirection to keep check valve shut). Keep in mindthe base current would not start to flow until thecheck valve D2 allowed current to flow (0.7lb). If thecurrent ratio through D1 and Base was equal to thelever arm advantage, then I1 / Ib = L1 / L2. Call thisratio Beta (b) and let L1 = 1 inch and L2 = 0.01 inch.Then b = 100 and I1 will be 100 times Ib. Since bothcurrents must pass through D2, I2 = I1 + Ib. Thesesame principles apply to a silicon NPN transistor. I1becomes collector current (IC), and I2 would beemitter current (IE). b = IC / IB and IE = IB + IC.

THE TRANSISTOR, what is it?

Spring

Solid Stop

Movable Plate

Water-tight Pivot

Figure 26

Figure 270.7

Pressure (lbs per square inch)

Curre

nt (g

als. p

er m

in.)

Figure 28

Base Current

IbL1

L2

I1 D1

D2

I2

LeverArm

NPN Transistor

Pivot


-18-

SEMICONDUCTORSTHE PNP TRANSISTORFigure 29 represents the water pipe equivalent of aPNP transistor. The emitter releases current thatsplits into two paths. The base current “forces open”the collector check valve which collects all thecurrent except the small amount that goes into thebase. The direction of current in the PNP transistoris opposite that of the NPN transistor. Because ofthese differences, the emitter of the PNP is usuallyreferenced to the power supply voltage and theemitter of the NPN is usually referenced to groundor zero voltage. In both transistors, the currentamplification factor (Ic/Ib) is called Beta (b).

In Figure 30 the center of a small section of a pipeis made of thin, flexible rubber and that rubber issurrounded by water from a third pipe called thegate. When pressure is applied to the gate, therubber pinches off the current from the source to thedrain. No current flows from gate to drain or source.This device uses a change in gate pressure tocontrol the current flowing from source to drain.

Since there are no check valves, the current canflow in either direction. In other words, this deviceacts like a variable resistor. The Field EffectTransistor (FET) also controls current betweensource and drain by “pinching off” the path betweenthem. The level of voltage on the gate controls theamount of current that will flow. Since no DC currentflows in or out of the gate (only momentarily a smallamount will flow to adjust to new pressures as in acapacitor), the power used by the gate is very closeto zero. Remember, power equals voltage timescurrent, and if the current is zero, the power is zero.This is why FETs are used in the probes of testequipment. They will not disturb the circuit beingtested by removing power during a measurement.When a second gate section is added (pipe andrubber) between the source and drain it is called aDual Gate FET. In our water pipe analogy of the FETtransistor, the rubber must be very thin and flexiblein order to “pinch off” the current from the source tothe drain. This means it could be easily damaged bya small “spike” of high pressure. The same is true ofan electronic FET. A high voltage “spike” (StaticElectricity) can destroy the gate and ruin the FET. Toprotect the FET, they are sometimes packaged withmetal rings shorting their leads, and a fourth leadmay be added to the metal case containing thetransistor.

Figure 29

Base

IB

IE = IB + ICPNP Transistor

THE FIELD EFFECT TRANSISTOR

Figure 30

Collector

EmitterIE

IC

Drain

Source

Gate

FET Transistor


-19-

SEMICONDUCTORSTHE INTEGRATED CIRCUITIf the water pipe analogies of the resistor, diode,transistor, and very small capacitors could beetched into a single block of steel you would havethe equivalent of the Integrated Circuit inElectronics. Figure 31 represents such a device.This block of steel would have to be very large toinclude all the mechanical parts needed. Inelectronics, the actual size of a diode or transistor isextremely small. In fact, millions can be fabricated

on a piece of silicon no larger than the head of a pin.Photographic reduction techniques are used togenerate the masking needed to isolate each part.These masks are then stepped and repeated inorder to make many separate integrated circuits atthe same time on a single substrate. Using massproduction techniques, these circuits aremanufactured, packaged, and sold at prices muchlower than the equivalent discreet circuit would cost.

SEMICONDUCTOR SYMBOLSFigure 32 shows the common symbols usedin electronics to represent the basiccomponents. Integrated Circuits are usuallydrawn as blocks with leads or as a trianglefor operational amplifiers. The Zener diode(voltage reference diode) is used in thereverse direction at the point of breakdown.

Figure 32

Diode LED ZenerDiode

PNP NPN FET

Figure 31

The Integrated Circuit

8

714

1


-20-

SEMICONDUCTORSSELF TEST

1. The diode is best described as: a) Switch c) Electrical Storage Device b) Check Valve d) Electrical Momentum2. A silicon diode begins to conduct current at

approximately: a) 7 volts c) 0.7 lb. b) 0.7 volts d) 7 lbs.3. NPN transistors have: a) 2 leads c) 2 diodes b) 3 leads d) b & c4. NPN and PNP transistors are used to: a) Create Power c) Control Current b) Change Resistance d) Control Capacitance5. The ratio of collector current to base current in a

transistor is called: a) Beta (b) c) Current Control b) Amplification d) FET

6. A diode made of Gallium Arsenide is called: a) Zener Diode c) LED b) Power Diode d) Detector Diode7. A Field Effect Transistor controls Source to Drain current

by: a) Diode Conduction c) Base Voltage b) Base Current d) Gate Diode8. A Zener Diode is used as: a) Voltage Reference c) Resistance Control b) Current Reference d) b & c9. An Integrated Circuit contains: a) Diodes and Resistors c) Inductors b) Transistors and Small d) a & b Capacitors10. If the arrow in the symbol for a transistor points toward

the base lead, the transistor is a: a) NPN Transistor c) FET Transistor b) PNP Transistor


PRACTICEOpen the Semiconductor bag and answer the following questions.

EXTRA CREDITConnect the LED (light emitting diode) to a 9 volt battery(not provided) as shown in Figure 33. Why is the resistornecessary? If the LED does not light up reverse thebattery leads. Why does the LED only light whenconnected a certain way?

Figure 33

How many of the devices are diodes? __________How many of the devices look like transistors? __________How many integrated circuits are included? __________Was a Light Emitting Diode included? __________How are the diodes marked to show which end current will not go into? __________

TwistedLeads

LED

1000WResistor

9VBattery


-21-

MECHANICAL PARTSPRINTED CIRCUIT BOARDS, What are they?A printed circuit is a conductive pattern glued to oneor both sides of an insulating material. Holes arepunched or drilled through the conductor and boardto allow the interconnection of electronic parts. Inthe case of a double sided board, the holes areplated to provide a connection between theconductors on both sides of the board. This methodprovides considerable space savings over handwiring and allows for automated insertion andsoldering of parts. A more uniform product isproduced because wiring errors are eliminated. Theinsulating material thickness may vary from 0.015”to 0.500”. The most widely used base material isNEMA-XXXP paper base phenolic. Copper is themost common conductive material glued to thebase. The common thicknesses of the copper foilare 0.0014” (1 oz./sq. ft.) and 0.0028” (2 oz./sq. ft.).

For single sided boards, the copper is laminated tothe board and then screened and etched away.Double sided boards use a plating process andconductive ink to achieve the desired layout.

Figure 34

InsulatingMaterial

Wrong

Copper

Correct

DESIGN RULESAfter a the breadboard has been tested, there aresome design rules used to layout the printed circuitboard. A few of these basic rules are listed here:1. Diameter of punched holes should not be less

than 2/3 the board thickness.2. Distance between punched holes or between

holes and board edge should not be less than theboard thickness.

3. Holes should not exceed more than 0.020” of thediameter of the wire to be inserted in the hole(machine insertion may require more, but leadsshould be “clinched”).

4. Conductor widths should be large enough tocarry current peaks. A width of one tenth of aninch (1 oz./sq. ft. copper) will increase intemperature 10OC at a DC current of 5A.

5. Conductor spacing must be capable ofwithstanding applied voltages. If a voltagedifference of 500 volts exists between two copperruns, they must be separated by at leads 0.03” toprevent breakdown.

6. Avoid the use of sharp corners when laying outcopper (see Figure 34). Sharp corners producehigh electric fields that can lower breakdown.Sharp corners will also make it easier for copperto peel from the board.

7. Heavy parts must be mounted to prevent boarddamage if the unit is dropped.

8. The printed circuit board must be fastened toprevent leads from touching the case or any otherobject mounted near the board.

9. Mounting hardware must be designed to preventboard stress (warping or excessive torque).

Note: The PC board is included with this kit is onlya sample and will not be assembled.


-22-

MECHANICAL PARTSTHE TOP LEGENDThe component side of a printed circuit boardshould always have a drawing showing theplacement of the parts and their schematic marking(R1, R2, etc.). This drawing is called the TopLegend. When a board needs to be repaired, theschematic becomes the “road map” and the toplegend becomes the “address” on the part. Figure35 shows the correlation between the Schematicand the Top Legend.

Different parts have been discussed. A printedcircuit board to interconnect these parts has beendiscussed. Now it’s time to talk about the “ElectronicGlue” called Solder. Soldering wire is composed ofTin and Copper with a rosin or acid core. Acid coresolder should never be used on electronic boardssince the acid will damage the components. Acidcore solder is mainly used to attach metals (copperwater pipes for example). When tin and copper aremixed, the melting point of the mixture is lower thanthe melting point of either tin or copper. The point atwhich the melting point is the lowest is when themixture equals 99.3% tin and 0.7% copper. This iscalled the eutectic (u tek’tik) point of the mixture.The most common flux placed at the center of thishollow wire alloy is Rosin based. Removing the fluxfrom the board requires a chemical that can dissolverosin. In recent years many water soluble fluxeshave been developed. These fluxes can beremoved by washing the boards in water.After the parts are placed in the holes on the printedcircuit board, their leads should be trimmed andbent. A good mechanical connection will improve thesoldering capability of the parts by forcing the partand copper on the board to rise to the sametemperature. Positioning the soldering iron correctlyand using the right amount of heat are crucial to agood solder job. Solder practicing is highlyrecommended (Elenco® Solder Practice Kit ModelSP-1A).

SOLDER, The Electronic Glue

Figure 35

Schematic

Printed Circuit Board

R1

C1

R2

B+

T1D1

C2Q1

R1

C1

R2

T1D1

C2

Q1


There are many other mechanical parts used bymanufacturers of electronic equipment. Most ofthem fall into the category of switching or connectingcircuits. In Figure 36, five of the six parts shown areused to switch or connect signals to the printedcircuit board. Only the spacer falls into a differentcategory, called mounting. The switch is used toredirect current or voltage from one circuit toanother. The wire nut is used to hold two twistedwires together and insulate them (prevent them frombeing bare and exposed) at the same time. The PCboard male and female connectors are used toattach wires from controls or other circuits to theprinted circuit board. The Earphone Jack is used tobring a signal from the printed circuit board to anearphone. The spacer holds the printed circuit boardaway from the case to prevent leads from shortingto the case.

There are many different methods for mountingprinted circuit boards. The simplest method is usingmachine screws and spacers. Figure 37 showssome of the common screw heads used byelectronic manufacturers. The oval head screw inFigure 37 has a tapered end that will cut into themetal and make a thread for the body of the screw.The self-threading screw eliminates the need for anut and lockwasher but can produce metalfragments that must be removed to prevent shortsfrom occurring.

-23-

MECHANICAL PARTSOTHER MECHANICAL PARTS MOUNTING HARDWARE

Figure 37

Round Head

Pan Head

Fillister Head

Flat Head

Oval Head Self-threading

Figure 36

Switch Wire Nut

Female Connector

Earphone Jack Female

Spacer

PC Board MaleConnector


-24-

MECHANICAL PARTS

SELF TEST

1. Copper patterns on a Printed Circuit Board shouldalways be:

a) As thin as possible c) Rounded b) Sharp and square d) On one side only2. The distance between conductors on a printed circuit

should be large enough to: a) Etch easily c) Clean b) Solder across d) Prevent voltage breakdown3. The top legend shows: a) Copper path c) Schematic b) Part placement d) Hole numbers4. The schematic shows: a) Part placement c) Hole sizes b) Copper path d) Electrical connections

5. The material the copper is glued to on a printed circuitboard is called a:

a) Conductor c) Resistor b) Semiconductor d) Insulator6. Solder with the lowest melting point has a ratio of tin

to lead of: a) 63/37 c) 40/60 b) 60/40 d) 37/637. Solder made for electronic parts has a: a) Hollow Core c) Acid Core b) Rosin Core d) No Core8. The type of screw NOT mentioned in this course is: a) Sheet Metal c) Round Head b) Machine d) Self-threading


PRACTICEOpen the Mechanical bag and answer the following questions.

EXTRA CREDITWhat is the function of the mechanical part included in the bag that was not mentioned in the instruction sheets?

How many of the following parts were in the mechanical bag?Switches ______ Male PC Board Connectors ______Earphone Jacks ______ Wire Nuts ______ Spacers ______ Round Head Screws ______Pan Head Screws ______ Flat Head Screws ______Self-threading Screws ______ Sheet Metal Screws ______


-25-

ANSWERS TO QUIZZESPAGE 5

Type Capacitance Value Working Voltage Polarized (Y/N) Other Markings Disc 33pF N — Mylar 0.001mF 100 volts N K Electrolytic 10mF 25 volts Y — Electrolytic 220mF 25 volts Y — Electrolytic 10mF 50 volts Y — Electrolytic 10mF 35 volts Y — Electrolytic 220mF 16 volts Y —

COLOR 1 COLOR 2 COLOR 3 COLOR 4 VALUE PERCENT WATTAGE Brown Black Black Gold 10W 5% 1/2 Watt Brown Green Brown Red 150W 5% 1/4 Watt Brown Black Red Gold 1,000W 5% 1/4 Watt Brown Red Red Gold 1,200W 5% 1/2 Watt Red Yellow Red Gold 2,700W 5% 1/2 Watt Brown Black Orange Gold 10,000W 5% 1/2 Watt Blue Red Orange Gold 62,000W 5% 1/4 Watt Orange Orange Green Gold 3,300,000W 5% 1/2 Watt Brown Black Blue Gold 10,000,000W 5% 1/2 Watt Brown Green Blue Gold 15,000,000W 5% 1/4 Watt

1.c 2.a 3.d 4.a 5.c 6.d 7.b 8.a 9.b 10.d

PAGE 111.d 2.a 3.b 4.c 5.a 6.d 7.d 8.c 9.c 10.a 11.b 12.d

PAGE 161.d 2.a 3.b 4.a 5.b 6.c 7.a 8.a 9.b 10.b 11.c 12.bPractice: No - the coil is not wound on a metal core. Enamel coating on wire prevents it from shorting.There are 2 turns on the coil. Calculated inductance is 64 microhenrys.Answer to Extra Credit: 30mH

PAGE 201.b 2.b 3.d 4.c 5.a 6.c 7.d 8.a 9.d 10.bPractice: 3 Diodes 3 Transistors 1 Integrated Circuit Yes, 1 LEDA line is painted around the end that blocks current. LED uses flat side to indicate blocking end.Answer to Extra Credit: Resistor is necessary to limit current and prevent LED from damage. LEDs arediodes that only pass current in one direction.

PAGE 241.c 2.d 3.b 4.d 5.d 6.a 7.b 8.aPractice: 1 Switch 1 Female 1 Male 1 Earphone Jack 1 Wire Nut 2 Spacers 1 Round 9 Pan1 Flat Head 2 Self Threading 2 Sheet MetalAnswer to Extra Credit: Part in bag that was not mentioned included one strain relief to hold a line cord.Parts included for further study were 2 thicknesses of rosin core solder and 1 printed circuit board.

Answer to Extra Credit: 30mF


-26-

Space War GunK-10

Rapid fire or single shot with 2flashing LEDs.

0-15V Power SupplyK-11

A low-cost way to supplyvoltage to electronic games, etc.

0-15VDC @ 300mA

Christmas TreeK-14

LED Robot BlinkerK-17

You’ll have fun displaying thePC boardrobot.Learn aboutfree-runningoscillators.

Digital BirdK-19

You probably have never hearda bird sing this way before.

Nerve TesterK-20

Test your ability to remain calm.Indicates failure by a lit LED ormild shock.

Yap BoxK-22A

This kit is a hitat parties.Makes 6excitingsounds.

Burglar AlarmK-23

Alarm for your car, house, room,or closet.

Whooper AlarmK-24

Can be used as a sounder orsiren.

Metal DetectorK-26

Find new money and oldtreasure. Get started in thisfascinating hobby.

Pocket DiceK-28

To be used with any game ofchance.

FM MicrophoneAK-710/K-30

Learn about microphones,audio amplifiers, and RFoscillators. Range upto 100 feet.

Telephone BugK-35

Our bug is only the size of a quarter,yet transmits both sides of at e l e p h o n econversationto any FMradio.

Sound Activated SwitchK-36

Clap and the light comes on . . .clap again and it goes off.

Lie DetectorK-44

The sound willtell if you are lying. Themore you lie,the louder the sound gets.

Motion DetectorAK-510

Use as a sentry,messageminder, burglaralarm, or aroomdetector.

Two IC AM RadioAM-780K

New design - easy-to-build,complete radio on a single PCboard. Requires 9V battery.

Transistor TesterDT-100K

Test in-circuit transistors anddiodes.

0-15VDC Variable VoltageDC Power Supply Kit

XP-15KIdeal for students,technicians, andhobbyists. Greatfor breadboarding.

Auto-scan FM Radio KitFM-88K

Unique design - two-IC FMreceiver with training course.

EDUCATION KITSComplete with PC Board and Instruction Book

Requires 9V batteryRequires9V battery

Requires9V battery

Requires9V battery

Requires9V battery

Requires9V battery

Requires 9V batteryRequires9V battery

Requires9V battery

Requires 2“AA” batteries

Training course incl.

No batteriesrequired! Requires 9V battery

Requires9V battery

Requires9V battery

Requires9V battery

Produces flashingcolored LEDsand threepopularChristmasmelodies.

Requires9V battery

Requires9V battery


ELENCO®

150 Carpenter AvenueWheeling, IL 60090

(847) 541-3800Website: www.elenco.com

e-mail: [email protected]


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