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Preface 2

Chapter 1: Basic Components & Circuits 2

1-1 Electricity 3

1-2 Wires 4

1-3 Batteries 5

1-4 The Switch 6

1-5 The Lamp 6, 7

1-6 The Base Grid 7-9

1-7 Series and Parallel Circuits 9-10

1-8 Short Circuits 11

1-9 Solder 11

1-10 Schematics 12

Summary & Quiz 13

Chapter 2: Motors & Electricity 14

2-1 Motors 15, 16

2-2 Motor Circuits 16-19

2-3 Fuses 19

2-4 Your Electric Company 20, 21

2-5 Static Electricity 22

2-6 Types of Lamps 23

2-7 Types of Switches 23

2-8 Electricians 23

Summary & Quiz 24

Chapter 3: Resistance 25

3-1 Resistors 26

3-2 LEDs 26, 27

3-3 The Photoresistor 28

3-4 Resistors in Series & Parallel 28, 29

3-5 Resistance 30

3-6 Resistance of Water 31

3-7 Introduction to Logic 32

3-8 Digital Electronics 33

Summary & Quiz 34

Chapter 4: Electronic Soundand Integrated Circuits 35

4-1 Electronic Sound 36-38

4-2 Whistle Chip 38

4-3 The ICs in Snap Circuits® 39, 40

4-4 Description of IC projects 44, 42

Summary & Quiz 42

Summary of Components 43, 44

For Further Reading 44

Glossary 45, 46

The Snap Circuits® project manual includes lots ofuseful information in addition to the projectsthemselves, as listed below. The project manualsummarizes much of the lesson in the StudentGuide while adding troubleshooting information.

Much of the text in all chapters is color-codedgreen and blue so that instructors can easily adaptthe course based on the skills and interests of thestudents. The orange boxes are more advancedmaterial while the brown boxes are consideredadditional/background material, either cangenerally be omitted without a significant impact onthe course.

The Project Manual contains:

1. Parts List (partial, continued in second manual)2. How To Use It - brief description of how to make

connections and understand the circuitdrawings.

3. About Your Snap Circuits® Parts - briefdescription of what each component does(partial, continued in second manual).

4. DO’s and DON’Ts of Building Circuits - briefbut important guidelines for building circuits(additional guidelines are in second manual).

5. Basic & Advanced Troubleshooting -systematic testing procedure for identifyingdamaged parts (continued in second manual).

6. Project Listing7. Projects 1-101

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What is electricity? Nobody really knows. We onlyknow how to produce it, understand its properties,and how to control it. It can be created by chemistry(batteries), magnetism (generators), light (solarcells), friction (rubbing a sweater), and pressure(piezoelectric crystals).

Electricity is energy that can be used tosave us effort (electric toothbrushes anddishwashers), heat things (electric heaters andmicrowave ovens), make light (light bulbs), andsend information (radio and television). Butelectricity can also be dangerous if abused (electricshock).

Batteries

Generator

Solar Cells

ElectricToothbrush

Dishwasher

MicrowaveOven

ElectricHeaterLight Bulb

Radio

Television

In this section you will learn about basic electricalcomponents and circuits. By building circuits usingSnap Circuits, you will begin to understand theelectrical world. Electric Shock

Rubbing a Sweater

This booklet is an introduction to the exciting worldof electronics. Following the “Learn by Doing®”concept, electronics will be easy to understand byusing Snap Circuits® to actually build circuits as youlearn about them. This booklet emphasizes thepractical applications of electronics, withoutbogging down in mathematics.

Why learn about electronics? Electronics plays animportant and increasing role in our everyday lives,

and so some basic knowledge of it is good foreveryone. Learning about it teaches how to doscientific investigation, and the projects developbasic skills needed in today's world.

The first pages of the Snap Circuits® projectmanuals contain a brief description of the parts inSnap Circuits®, along with brief guidelines forbuilding circuits.

PiezoelectricCrystal

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The name electricity came from the Greek namefor amber, the material in which electrical effectswere first observed. What do you think of electricityas being? Electricity is one of the fundamentalforces of nature. At its most basic level, it is anattraction and repulsion between sub-atomic (very,very, very, very tiny) particles within a material.

This attraction/repulsion is referred to as anelectrical charge; it is similar to and closelyrelated to magnetism. These attractions/repulsionsare extremely powerful but are so well balancedout at the sub-atomic level that they have almost noeffect on our lives.

As an example, electrical attraction is about1,000,000,000,000,000,000,000,000,000,000,000,000,000 times more powerful than gravity (gravityis what causes things to fall to the ground whenyou drop them). However electrical attraction is socompletely balanced out that you don’t notice it,while gravity effects are always apparent becausethey are not balanced out.

Gravity is actually the attraction between objectsdue to their weight (or technically, their mass). Thiseffect is extremely small and can be ignored unlessone of the objects is as big as a planet (like theearth). Gravity attraction never goes away and isseen every time you drop something. Electricalcharge, though usually balanced out perfectly, canmove around and change quickly.

For example, think about how two sweaters cancling to each other when you take them out of thedryer. This is due to an electric charge that hasbuilt up between them. There is also a gravityattraction between the sweaters, but it is alwaysextremely small.

Electronics is the science of working with andcontrolling electricity. Many work-savingappliances like dishwashers, hairdryers, and drillsare electrical but not electronic. Electronicproducts use electricity to control themselves,using parts like resistors, capacitors, andtransistors. Electrical appliances are onlycontrolled mechanically.

Most products you bring from your old house toyour new house are electronic (such as TVs,computers, touch-tone phones, radios, mostbattery operated products), but not all (such ashairdryers, electric power tools).

Electricity is the movement of sub-atomicparticles (with their electrical charges) through amaterial due to an electrical charge outside thematerial. Electricity will be easier to understand ifyou think of the flow of electricity through circuitsas water flowing through pipes.

A good way to think of the difference betweenelectrical and electronic products is to think aboutmoving into a new house. Most products in theempty house are electrical (such as all the wiringand switches in the walls, rotary phones,dishwashers, electric ovens, air conditioners,most types of thermostats).

Wires can be thought of as large, smooth pipesthat allow water to pass through easily. Wires aremade of metals, usually copper, that offer very lowresistance to the flow of electricity.

The electric current is a measure of how fastelectricity is flowing in a wire, just as the watercurrent describes how fast water is flowing in apipe. It is expressed in amperes (A, named afterAndre Ampere who studied the relationshipbetween electricity and magnetism) or milliamps(mA, 1/1000 of an ampere).

With Snap Circuits the wires you will use havebeen shaped into snap wire strips, to makeinterconnection easy. These work the same asany other wires you might find in your house,since they are made of metal.

Electricity Water

If you have the Snap Circuits® parts nearby thenpull out the wires and look at them. They havenumbers such as 2, 3, 4, 5, or 6 depending on thelength of the wire connection. There is also a 1-snap wire that is used as a spacer or forinterconnection between different layers.

Wires can generally be as long as desired withoutaffecting circuit performance, just as using gardenhoses of different lengths has little effect on thewater pressure as you water your garden. Howeverthere are cases where the length and size of a pipedoes matter, such as in the water lines for yourentire city or in an oil refinery. Similarly, wire lengthand size are important for electric power linestransporting electricity from a power plant in aremote area to a city, and in circuits used in radioor satellite communication.

If you were to look inside an electronic device inyour home (make sure it’s not plugged in) youmight see a lot of wires of different colors. Theactual wires are all the same color of metal, butthey have a protective covering over them. Thecolors are used to easily identify which wire iswhich during assembly and repair of the circuit.

The covering is also used to prevent different partsof a circuit from connecting accidentally.

Try to imagine the total length of wire used in all theproducts in your home!

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To make water flow through a pipe we need apump. To make electricity flow through wires weuse a battery. A battery creates an electricalcharge across wires. It does this by using achemical reaction and has the advantage of beingsimple, small, and portable.

Voltage is a measure of how strong the electriccharge from your battery is, and is similar to thewater pressure. It is expressed in volts (V, andnamed after Alessandro Volta who invented thebattery in 1800). Notice the “+” and “–” signs on thebattery. These indicate which direction the batterywill “pump” the electricity, similar to how a waterpump can only pump water in one direction.

The 0V or “–” side of the battery is often referred toas “ground”, since in house or building wiring it isconnected to a rod in the ground as protectionagainst lightning.

Battery power is much easier to use in electronicsthan the electricity that powers your home. This isbecause most electronic circuits only need a lowvoltage source to operate; all the electricityproduced by your electric company comes at ahigher voltage, which must be converted down. Ifa circuit is given too much voltage then itscomponents will be damaged. It is like having thewater in your faucet come out at higher pressurethan you need, and it splashes all over the room. Ifwater in a pipe is at too high of pressure then thepipe may burst. Batteries are selected to give yourcircuit just the voltage it needs.

Your Snap Circuits® uses two 1.5V batteries in aholder (snap part B1, actual batteries are notincluded). Notice that just to the right of thebattery holder pictured below is a symbol, thesame symbol you see on the battery holder.Engineers are not very good at drawing picturesof their parts, so when engineers draw pictures oftheir circuits they use symbols like this torepresent them.

Water Pump

Battery

Battery Holder (B1) Battery Symbol

Batteries are made from materials like zinc andmagnesium dioxide, electricity flows as thesereact with each other. As more material is usedup by the reaction, the battery voltage is slowlyreduced until eventually the circuit no longerfunctions and you have to replace the batteries.Some batteries, called rechargeable batteries(such as the batteries in your cell phone), allowyou to reverse the chemical reaction usinganother electric source. That way the batteriescan last through years of use.

Challenge: Try to count how many batteries arein your home, your count will probably be low.Many products that use your house power alsohave batteries to retain clock or programmedinformation during brief power outages (such ascomputers and VCRs).

Since you don’t want to waste water when you arenot using it, you have a faucet or valve to turn thewater on and off. Similarly, you use a switch toturn the electricity on and off in your circuit. Aswitch connects (the “closed” or “on” position) ordisconnects (the “open” or “off” position) the wiresin your circuit.

Just as the plumbing industry has a wide range ofvalves for different situations, there are manytypes of switches used in electronics. The typeshown below is called a slide switch, because youslide it back and forth to turn it on and off. SnapCircuits® includes one of these (part S1), shownbelow. As with the battery, the slide switch isrepresented by a symbol, shown to its right. If youhave the Snap Circuits® parts nearby, take out theswitch and look at it.

You can think of slide and press switches like thewater faucet in your kitchen (which pours out wateruntil you turn it off) and a water fountain in a schoolor movie theater (which only squirts out water aslong as you are pressing the button).

Switches in modern electronics come in manydiverse forms. Challenge: Try to count how manyare in your home or car; you will be amazed. Thereare slide, press, membrane, rotary, push-button,and other switches controlling nearly everything.

SlideSwitch

Closed Position

Open Position

Another type of switch is the press switch, andSnap Circuits® also includes one of these (partS2). When you press down the two pieces ofmetal touch, so electricity can flow. When you letgo of it, the electricity stops. Its symbol is markedon the snap part, though on many professionalelectronics drawings both slide and pressswitches use the symbol for the slide switchbecause they really perform the same function.

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In a lamp electricity is converted into light, thebrightness of the lamp increases as more electriccurrent flows through it. You can think of a lampas a water meter, since it is showing us how muchcurrent is flowing in a circuit just as a water metershows how much water is flowing in a pipe. Water Meter

Slide Switch SymbolSlide Switch (S1) Press Switch SymbolPress Switch (S2)

While occasionally lamps are used to indicate howmuch electricity is flowing in a circuit, they aremostly used to light our homes, businesses, andstreets. Although scientists had beenexperimenting with electricity for years, the firstpractical use of electricity occurred when inventorThomas Edison used it to light a bulb similar to

these. For many years electricity was used almostexclusively for lighting. That has since changed.Now only a small percentage of the electricityproduced in the United States is used for lightingwith the rest going to a vast range of uses ineveryday life that Edison would never haveimagined.

The water in your home flows through pipesmounted in the walls and floors of your home, andsimilarly the electricity in your house flows throughwires mounted in the walls and ceilings of yourhome. But the wires in your walls take a lot of hardwork to install and then can’t be moved.

Most products that use electricity are small, easy tomove, and easy to build. That is because they havealmost all of their components and wires mountedon “circuit boards” such as these:

Boards like these are used in almost all electronicproducts, look inside any radio or computer andyou will find them. Note that the “wires” connectingparts mounted on the circuit board are literally“printed” on the surface of the board; hence circuitboards all are called “printed circuit boards” orPCBs.

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Light Switch

Outlets

To Fuse Box

Snap Circuits® includes a lamp (part L1, shownbelow). If you have the parts with you, take it outand look at it.

Just as there are different types of water meters towork with different pressures and volumes of water,

there are also different lamps. Lamp L1 is a low-pressure meter, and works with voltages (electricalpressures) of up to 2.5V. Higher voltages than thatwill damage the bulb, so always make sure to usethe correct lamp.

The electrical symbol for a lamp is shown here.

Lamp Symbol

2.5V Lamp (L1)

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In the same manner Snap Circuits® uses a clearplastic base grid with evenly spaced posts tomount the snap parts and wires and to keep themtogether neatly. It has rows labeled A-G andcolumns labeled 1-10 to easily identify points inyour circuit. You don’t need the base to build yourcircuits, but just try building one of the largercircuits without it! The base grid is shown here,next to a picture of a typical circuit industry boardbefore parts are mounted.

Base Grid PC Board

So far we’ve talked about wires, batteries,switches, lamps, and circuit boards; now it’s time toput them together to form a circuit. Consider thiscircuit (which is project 1 on page 8 of the projectmanual):

Turning on the switch turns on the lamp. Thiscircuit is the same circuit used to turn on a lamp inyour home. The only differences are the batteriesare really power from the electric company, thelamp is larger and bright enough to light up theroom, the switch is really a switch on the wall, andthe snap wires are really wires in the wall and thecord to the lamp.

You can think of the electricity flowing through thebattery, lamp, switch, and wires in the above circuitas if it were water flowing through a pump, watermeter, valve, and pipes:

Note that each of the Snap Circuits® in the projectmanuals has a box next to it so that you canmark off the circuits as you build them.

Water Meter

Pump

Valve

In electronics, the “on” position of a switch is alsocalled the “closed” position. Similarly, the “off”position is also called the “open” position. This isbecause the symbol for a slide switch is similar to thesymbol for a door in an architect’s drawing of a room:

The electronics symbol for a slide switch should bethought of as a door to a circuit, which swings openwhen the switch is off. The “door” to the circuit isclosed when the switch is on. This is shown herein drawings using the part symbols:

Open Switch (turned off)

Closed Switch (turned on)

Walls

Door

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In case you haven’t noticed, the batteries produce3V and the lamp is made for voltages up to 2.5V.Don’t worry, you will not damage your bulb. Thevoltage rating of the batteries (1.5V from eachbattery) is actually the voltage they produce whenthe electric current flowing from them is low, as thecircuit current increases the voltage produced bythe batteries is reduced. Think again of the lampas a water meter - the lamp is bright so there mustbe lots of current flowing, hence the voltage islower and the lamp is safe. You can see from the

water diagram that with only a pump, an openvalve, and a meter there is nothing to slow downthe water flow and the pump will move the water asfast as it can.

Why does the battery voltage drop as currentincreases? Remember that a battery produceselectricity from a chemical reaction. Not only isthere a limited amount of the chemicals in a smallbattery (batteries slowly get weaker as you usethem), but also not all of the material can reacttogether at the same time.

There are two ways of arranging parts in a circuit,in series or in parallel. Here are examples:

The parts within these series and parallel sub-circuits may be arranged in different ways withoutchanging what the circuit does. So these sub-circuits are the same as the ones on the left:

Parallel Circuit

Series Circuit

Parallel Circuit

Series Circuit

Large circuits are made of combinations of smallerseries and parallel circuits. For example, thesesmall sub-circuits:

. . . may be combined into this larger circuit:

Consider this mini-circuit: If both switches are on, the lamp will light. If oneswitch is off then the lamp will be off, because theswitches are in series.

If you connected several lamps in series then oneswitch would turn them all on or off. But if one of thebulbs was broken then none would light. Strings ofinexpensive Christmas lights are wired in series; ifone bulb is damaged then the entire string does notwork.

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Note that battery holder B1 has two 1.5V batteriesconnected in series, these add together to produce3V. If you had several battery holders, you couldconnect them in series to get higher voltages:

3V + 3V = 6V

For all of the Snap Circuits® projects, the parts maybe arranged in different ways without changing thecircuit. The order of parts connected in series or inparallel does not matter - what matters is howcombinations of these sub-circuits are arrangedtogether. For example, in project 1 you may swapthe locations of the switch and lamp withoutaffecting the circuit operation in any way becausethey are connected in series.

The choice of whether to use a series or parallelconfiguration in a circuit depends on theapplication, but will usually be obvious. Forexample the overhead lights in the rooms of yourhome are all connected in parallel so that you canhave light on in some rooms and off in others, butwithin each room the light and switch areconnected in series so the switch can control thelight.

Batteries can also be placed in parallel. Placingtwo batteries in parallel allows them to last longer,or to supply more current at the same time.

Think of each battery as a storage tank thatsupplies water. If you put two in parallel, you canget more water (current), but the pressure (voltage)stays the same.

Consider this mini-circuit:

If either switch is on, the lamp will light. If oneswitch is off then the lamp will still be on, becausethe switches are in parallel.

In this circuit you could swap the locations of theswitches with each other (because they are both inparallel) or the batteries with the lamp (they areboth in series), but if you swap the lamp with one ofthe switches then the circuit will be different. Allelectric circuits are made up of combinations ofseries and parallel circuits, from simple ones likethese to the most complex computers.

If you connected two lamps in parallel then if one isbroken, the other would still work. Most of thelamps in your house are wired like this; if a bulb isbroken on one lamps then the other lamps are notaffected.

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Every circuit will include a power source (thebatteries), a resistance (which might be aresistor, lamp, motor, integrated circuit, etc.),and wiring paths between them and back.When wires from different parts of a circuit connectaccidentally then we have a “short circuit”. You'veprobably heard this term in the movies; it usuallymeans trouble.

A short circuit is a wiring path that bypasses thecircuit resistance, creating a no-resistance pathacross the batteries. This will damagecomponents and/or quickly drain yourbatteries. Be careful not to make short circuitswhen building your circuits. Always check yourwiring before turning on a circuit.

The name “short circuit” refers to how the currentthrough the circuit bypasses (jumps around) othercomponents in the circuit. It is the “easiest” paththrough the circuit, it is not always the “shortest”.

Here are some examples:

In a short circuit, there is nothing to limit the current in a circuit. However thechemical reaction in a battery cannot supply unlimited current, so the batteryvoltage drops to zero volts. This is called “overloading” the batteries. Thisoverload produces heat and damages the batteries. Think of this as a pumppumping water in a loop as fast as it can until it burns out.

The placement of parts onto circuitboards and the application of solder toconnect and hold them in place areusually done automatically with specialmachines. In fact, the microprocessorsused in modern computers are sofinely designed that they are almostimpossible to solder by hand.

Soldering Machine

Solder is used to make electrical connections to components ona printed circuit board. It is a special metal made of tin and leadthat melts at relatively low temperature (about 500OF). Solder isapplied and melted around a joint where a connection is beingmade; it creates a solid bond between the metals.

Soldering Iron

Solder

Before Soldering After Soldering

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The circuit diagrams in the Snap Circuits® manualsare easy to understand and build your circuits from.But what if you wanted to write down your owncircuit? These diagrams are not very easy to draw.There are also many ways of building the samecircuit. For example, you could use a jumper wireinstead of a 2-snap wire.

The Snap Circuit® diagrams give you moreinformation than you really need. They tell you howto build it, when all you really need to know is howit will work. You can find your own way to build it.

Notice the symbols marked on the parts. Thosesymbols are used in engineering circuit diagrams,which are called schematics. For example, SnapCircuits® project 153 is shown here with anengineering schematic for it:

Schematics are easy to draw, and the part symbolsused are international standards. Note that wiresin a schematic are just lines, and can be as long asyou like. Schematics are a flexible way of drawingcircuits, and can be re-drawn in many differentways. For example, the above schematic couldalso be drawn as:

Here are some more schematic examples:

Note that ∩ representstwo wires crossingover each otherwithout connecting.

It is important to understand schematics, sincemany circuit designs are common and can befound in books. Almost all new circuits designedare similar to some circuit that already exists. Many products sold today come with schematics oftheir designs to assist in troubleshooting problems.

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Summary of Chapter 1:

1. The electric current is a measure of howmuch electricity is flowing in a wire, and isexpressed in Amperes.

2. The voltage is a measure of the electricpressure exerted into a wire or circuit by abattery or other power source, and isexpressed in volts.

3. Switches are used to turn on or turn off theflow of electricity in a circuit.

4. A light bulb converts electricity into light.

5. Most electronic products have componentsmounted on circuit boards with the wiresliterally printed on the board surface.

6. Electrical circuits are all combinations ofseries and parallel configurations.

7. A short circuit is a no-resistance pathacross a power source, and causesdamage to components and batteries.

8. Solder is a special metal that is melted tomake solid electrical connections.

9. Schematics are engineering drawings ofcircuits using symbols.

Chapter 1 Practice Problems1. The flow of electricity is measured in ___________.

A. gallons B. minutes C. amperes D. volts

2. To turn on a switch, you ___________ it.A. voltage B. open C. pressurize D. close

3. Three of the choices below are the same circuit withthe parts arranged in different ways. Which choiceis a different circuit?

4. Which of these is a short circuit?

A B

Answers: 1. C, 2. D, 3. D, 4. C

C D

A B

C D

1. Draw a schematic for a circuit that consists ofthree lamps powered by a battery.

2. For each room in your home, make aschematic drawing showing how the lamps andswitches controlling them are connectedtogether.

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In this chapter you will learn about generators andmotors. A generator uses mechanical motion tocreate electricity and a motor uses electricity tocreate mechanical motion. This statement may notseem important to you but it is actually the foundationof our present society. Nearly all of the electricityused in our world is produced at enormousgenerators driven by steam or water pressure. Wires

are used to efficiently transport thisenergy to homes and businesses where it isused. Motors convert the electricity back intomechanical form to drive machinery andappliances. The most important aspect ofelectricity in our society - more important than thebenefits of the Internet - is that it allows energy tobe easily transported over distances.

Note that “distances” includes not just largedistances but also tiny distances. Try to imagine aplumbing structure of the same complexity as thecircuitry inside a portable radio - it would have to be

large because we can’t make water pipes so small.Electricity allows complex designs to be made verysmall.

Water flowing under pressure in a pipe or a fast-moving stream can be used to turn apaddlewheel. If the paddlewheel was linked to afan blade then you could use the water pressureto turn the fan, perhaps to cool yourself on a hotday. If the water was flowing very fast due to highpressure, then you could get the fan moving fastenough it might create a strong airflow like apropeller on a plane.

A similar thing happens in a motor, with electricityinstead of water. A motor converts electricity intomechanical motion.

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Snap Circuits® includes one motor, shown here with itssymbol. Snap Circuits® also includes a fan, which isused with the motor. An electric current in the motor willturn the shaft and the motor blades, and the fan bladeif it is on the motor.

How does electricity turn the shaft in the motor? The answer ismagnetism. Electricity is closely related to magnetism, and anelectric current flowing in a wire has a magnetic field similar to thatof a very, very tiny magnet. Inside the motor is a coil of wire withmany loops wrapped around metal plates. This is called anelectromagnet. If a large electric current flows through the loops, itwill turn ordinary metal into a magnet. The motor shell also has amagnet on it. When electricity flows through the electromagnet, itrepells from the magnet on the motor shell and the shaft spins. Ifthe fan is on the motor shaft then its blades will create airflow.

Magnet

Electromagnet

Shaft

Power Contacts

Consider this circuit (which is project 2):

When the switch is on, current flowsfrom the batteries through the motormaking it spin. The fan blades willforce air to move past the motor. Becareful not to touch the motor or fanwhen it is spinning at high speed.

Motor Symbol Motor (M1) Fan Blade

Shell

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Motors are used in all electric powered equipmentrequiring rotary motion, such as a cordless drill,electric toothbrush, and toy trains. An electricmotor is much easier to control than gas or dieselengines.

The electromagnetic effect described above alsoworks in reverse - spinning a magnet next to a coilof wire will produce an electric current in that wire.This is what happens in a generator, which usesmechanical motion to create electricity. In anelectric power plant, high-pressure water (from adam) or steam (heated by burning oil or coal) isused to spin a paddlewheel linked to magnets. Themagnets create an electric current in a coil of wire,which is used to power our cities.

In theory, you could connect your Snap Circuits®

motor directly to the 2.5V lamp and spin the fanblade with your fingers to light the lamp. In reality,it would be impossible for you to spin the motor fast

enough to produce enough current to get even aglimmer of light from the lamp.

To summarize, a generator uses mechanicalmotion to create electricity and a motor useselectricity to create mechanical motion.

MagnetCoil of Wire

Water Flow

Consider this circuit (which is project 5):

If the switch is on, the lamp will light and the fan willspin. If the lamp or the motor is broken then neitherwill work, because they are in series.

Since the lamp and motor are in series, the voltagefrom the batteries will get divided between them. Inthis circuit more of the voltage will be used at thelamp than at the motor.

If the fan was not on the motor then the motor wouldspin much faster but the lamp would not be asbright. The motor needs more voltage to spin faster,so there is less voltage available to light the lamp.

Consider this circuit (which is project 6):

If the switch is on, the lamp will light and the fan willspin. If the lamp or the motor is broken then theother will still work, because they are connected inparallel. Since the lamp and motor are in parallel,the full voltage from the batteries would be appliedto both. So the fan would spin faster than for thecircuit in project 5, which divided the batteryvoltage between the lamp and motor.

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You know that the AA batteries used to power yourSnap Circuits have + and – markings on them,called polarity markings. The chemical reaction inthe batteries only makes the electric current flow inone direction. To make the current flow in the otherdirection you just reverse the batteries (all batteriesin the same circuit must be reversed). The motoralso has + and – markings, because if the direction

of current flow through is reversed than the motorwill spin in the opposite direction (reversing theelectric current reverses the magnetic fieldgenerated, which reverses the direction the shaftspins). The lamp, switch, and wires have no such+ and – markings on them because they work thesame regardless of which way the current isflowing.

Now consider this circuit (which is project 80), withthe fan on the motor:

In this circuit the lamp will not be at full brightness,even though the full battery voltage is applied to it.Do you know why? Remember that as the circuitcurrent increases, the voltage produced by abattery is reduced. The motor draws a highcurrent, very high when it first starts up with the fanon. The chemical reaction in the batteries can’tsupply such a high current, so the battery voltage(electrical pressure) drops.

If your instructor has a meter to measure voltage,ask him to measure the battery voltage with theslide switch on and off. You would see the voltagedrop to under 2.5V when the switch is on.

Push the press switch (S2) to add the speaker tothe circuit and increase the circuit current evenmore. This will make the lamp less bright.

Take the fan off the motor and turn on the switchagain. The lamp will be brighter now. It doesn’ttake as much current to spin the motor without thefan, so the battery voltage doesn’t drop much.

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Consider this circuit (which is project 11):

If the switch is turned off when the motor isspinning at full speed, the fan will rise into the air.Be careful not to touch the motor or fan while it isspinning at high speed. In this circuit the fanblades suck in air and push it down to the table.

How does the fan rise? Think first about how youswim. When your arms or legs push water behindyou, your body moves ahead. A similar effectoccurs in a helicopter - the spinning blades pushair down, and create an upward force on theblades. If the blades are spinning fast enough, theupward force will be strong enough to lift thehelicopter off the ground.

While the switch is on, the motor rotation locks thefan on the motor shaft. The fan does not spin fastenough to lift the entire circuit off the ground.Sometimes there may be enough lift to make thebase grid hover around the table like a puck on anair hockey table.

When the motor is turned off, the fan unlocks fromthe shaft. The fan rises into the air like ahelicopter, since it is no longer held down by theweight of the full circuit.

By placing the lamp in series with the motor, thevoltage at the motor is reduced. The motor speedwill be reduced, so the fan will probably not fly off.

If the motor polarity were reversed (+ on the right),the fan would never fly. The fan blades aresucking in air around the motor and pushing itstraight up. If you hold a sheet of paper above thefan, you will see it get pushed up and away fromthe fan.

Consider this circuit (which is project 12):

If you hold a sheet of paper above the fan, you willsee it get sucked toward the fan.

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Occasionally electronic products/componentsbreak due to people using them incorrectly,accidents, natural storms, bad design, orcomponent failures. Often the problem is a shortcircuit, which results in an excessively high currentflow. This high current can overheat components inthe product enough to damage them, make them

explode, or start a fire.

A fuse is usually a special wire that breaks(“blows”) when too much current flows through it. A“blown fuse” shuts down the product beforeanything can overheat or cause a fire. Although a“blown fuse” prevents the product from working,fuses are easy to replace.

Consider this circuit (which is project 13): If the slide switch (S1) is on, the fan spins and thelamp lights. If the press switch (S2) is also on,then the fan will spin faster but the lamp will be off.In this case, the full battery voltage is applied tothe motor, instead of being divided between themotor and lamp.

This is one way of controlling the speed of a fan.Commercial fans do not use this method becausethe lamp produces heat and wastes energy.Commercial fans change the amount of voltageapplied to the motor using other methods.

Imagine that one of the 2-snap wires in theprevious circuit is a fuse (as in project 14):

If the circuit is operating properly then the “fuse”acts as a 2-snap wire. However if the motorbreaks and suddenly becomes a short circuitwhile both switches are on, then there will benothing to limit the current in the circuit. A veryhigh current will flow from the batteries, and woulddamage them if it continues. This excessivelyhigh current will “blow” the fuse, creating an opencircuit just like turning off the slide switch woulddo. This will protect the batteries from damage.The motor can then be repaired and the fusereplaced.

Fuses are very important and most electronic products have one. Productsusing electricity supplied by the electric company are usually required to havethem because the high voltages and currents available here can cause severedamage and fires. Small battery-powered products usually do not have fusesbecause the batteries in them are not powerful enough to cause harm.

While many fuses must be replaced when blown, flipping a switch can resetsome types. Every home has an electrical box of such fuses, to isolate anyproblems in one room from the rest of the house and your neighbors. Butthese fuses protecting your home take a much higher current to “blow” themthan a fuse used in a radio.

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A “blackout” occurs when part of a city is cut offfrom the power plants supplying it with electricity.The city will appear “black” from the air at night,since there are no electric lights on. This is usuallydue to accidents or storms, but is also done toconfuse attacking bombers in war.

A “brownout” occurs when power plants cannotsupply enough current to a city during highdemand, and must reduce the voltage below 120V.This sometimes occurs on hot days in summerwhen everyone is using their air conditioners.

Batteries are widely used because they are easy-to-use, safe, and portable. For example, SnapCircuits® can be used on a camping trip in a remotewilderness as long as you have batteries. You caneven take along spare batteries because they aresmall and easy to carry.

What if you wanted to take a microwave oven onthe camping trip? A microwave oven uses a lot ofelectricity, so the batteries for it would be large,heavy, expensive, and wouldn’t last long. Heavy,high-power products like microwave ovens are notmoved often.

Only a tiny portion of the electricity used in ourworld comes from batteries. The rest is producedat enormous electric power plants, operated byyour local electric company. The electricity fromthese power plants is available at the electricaloutlets in the walls of your home. The cost ofelectricity from the electric company is much lessthan the cost of electricity from batteries.

The voltage of the electricity supplied by theelectric company is 120V, much higher than thevoltage of the batteries in Snap Circuits®. This isavailable at each of the electrical outlets in yourhome. The current available is very large, since itmust power products like dishwashers and TVs.

Our lives are much easier and more fun by havingsuch power available by simply plugging into anelectrical outlet. This amount of electricity is alsovery dangerous, and it will kill anyone who abusesit. While accidents involving electricity are rare,they kill people every year. Never put anythinginto an electrical outlet except an electricalplug. Battery-powered products are safe, sincesmall batteries are too weak to hurt people.

The protective plastic around the wires to plug in alamp are all that protects you from the full power ofelectricity. Damaged electrical cords shouldalways be unplugged and repaired. Rememberthat electricity travels through water, so don't useelectric products while taking a bath (battery-powered products are fine).

Your home has fuses that automatically turn off theelectricity in your home if there is an electricalproblem, such as a short circuit. These fusesprevent electrical problems in your home fromaffecting your neighbors, but they do not protectyou.

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For a demonstration of this, consider this simplecircuit (which is projects 55-56):

Make a paper disc with lines on it like the oneshown here (a sample for cutout is on page 46 ofproject manual #1). Tape it to the fan blade andplace it on the motor. Place this circuit under awhite fluorescent light in your home or school(don’t use an ordinary incandescent lamp). Asthe speed changes you will notice the white linesfirst seem to move in one direction then they startmoving in another direction.

Do you know why it does this? The reason isbecause the lights are blinking 60 times a secondand the changing speed of the motor is acting likea strobe light to catch the motion at certainspeeds. To prove this, go into a dark room and trythe same test with a flashlight. The light from aflashlight is constant, so you won’t see this effectand will always see the lines move in the samedirection.

The fluorescent lights are blinking because theyuse the AC power from the electric company. Aflashlight uses DC power from batteries.

Note: Some new fluorescent lights use anelectronic ballast and they also produce aconstant light.

The electricity supplied to your home and school byyour local electric company is not a constantvoltage like that from a battery. It averages about120V but is constantly changing, due to the designof the generators that produce it. This is not aproblem, since all equipment that uses it accountsfor this change.

An electrical signal that is changing is called analternating current, or AC. Because of this, thepower from the electric company is also called ACpower. An electrical signal that is constant andunchanging is called a direct current, or DC. Thepower from a battery is also called DC power.

You may have noticed that sometimes you can getan electric “zap” in your home or school, howclothes stick together when you take them out ofthe dryer, or when taking off a wool sweater on adry day. Occasionally differences in electricalcharge build up between things, called staticelectricity. The things, which might include yourbody, are storing electrical charge. They mightstore a very small amount of electrical charge athigh voltage. This is just like a cloud storingelectrical charge before a thunderstorm.

The name “static” is used to describe the electricalcharge build-up because the charge is not moving

around to disperse. “Static cling” refers to howclothes sometimes cling to each other in the dryer,due to static electricity. Static electricity in theatmosphere causes the “static” (erratic noises) youhear on your AM radio when reception is poor.

Static “zaps” occur when an electrical current flowsto equalize the charge difference. Though thevoltage might be high, the current is small and theduration is short. The actual “zap” occurs becausethe voltage is high enough to “jump” across a high-resistance material (usually air), making a smallspark as it happens.

Though the “zap” might sting you briefly, theseeffects do not harm people. However, these staticzaps can damage some types of sensitiveelectronic components and electronics

manufacturers have to protect against it. Suchprotection includes static wrist straps, conductivefloor matting, and humidity control. The parts inSnap Circuits® will not be damaged by static.

In the same way, clouds can build up a static electrical charge.This charge might become very large, and it is spread out over theenormous volume of the clouds. Lightning occurs when thiselectrical charge discharges into the ground, and can be verydestructive. Lightning is looking for the lowest-resistance path fromthe clouds to the ground.

Do you know why you often“see” lightning before you“hear” it? It is because lighttravels faster than sound.

Large aircraft can build up a largeelectrical charge during a long flight. Awire similar to a lightning rod is usuallyconnected to an aircraft shortly afterlanding, as a precaution against static zap.

Since people have less resistance than air, standing in an openfield during a thunderstorm is very dangerous. Houses andother buildings have “lightning rods” to protect them, whichare metal bars from the roof into the ground. Their purpose isto encourage lightning to go through the rods to the ground,instead of going through the house to the ground.

Anti-Static Wrist Strap Anti-Static Floor Mat Anti-Static Ankle Strap

1. List all the products in your home that use anelectric motor.

2. Name some examples of static electricity.

Static Electricity Example:Comb your hair vigorously with a plastic comband hold the comb near some little (1cm x 1cm)scraps of paper to pick them up OR tilt the combnear a slow, steady stream of water from a faucetand see how the water bends towards it.

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There are many different ways of using electricity,so there are many types of people who workdirectly with it. The main categories areelectricians and engineers/technicians. Althoughmany people think of these as being the samecareer, they are actually very different. They attenddifferent schools, use different tools, and work indifferent places.

Electricians are the people who install electricalwiring into homes and businesses. Electriciansdeliver the electricity to your home to be used. Ittakes a lot more electricity to operate everything ina building than to operate a computer or radio, sosafety is very important and the equipment theyuse can handle high levels of voltage and current.Buildings are not easy to re-wire, so the wiringmust be reliable and safe for many years.

Electricians are trained in union and trade schools.Local government licenses them because buildingsmust be wired as per strict local building codes tobe sure they will be safe even after many years.

Electrical/electronics engineers and techniciansdesign and develop products that will use theelectricity that electricians have brought to them.Voltages and currents are much lower and safer,but circuits can be much more complex (likecomputers) and technologies change quickly.Electronic products are mass-produced infactories, unlike building wiring which must beinstalled in the building. Engineers are trained incolleges and technicians are trained in tradeschools. Government does not regulate them butproducts must meet industry safety standards.

The slide and press switches included in Snap Circuits®

are simple switches, more complex types are alsoavailable. Switches come in almost every shape andsize imaginable. There are membrane, rocker, rotary,DIP, locking, and non-locking types just to name a few.

Very often, a single switch is used to make many differentconnections. The combinations of connections for a switch areindicated in the symbol for it. Here are some examples:

The lamps in Snap Circuits® are incandescenttype, the same as the larger lamps in your home.The bulbs contain a special high-resistance wire,called the filament. When an electric currentpasses through it the wire gets so hot that it glows.Heat is also produced, and the glass bulb preventsthe filament from reacting with oxygen in the airand burning. When the voltage rating of anincandescent bulb is exceeded, the filament getsso hot it burns out. Filaments are usually made oftungsten, since ordinary copper would melt.

The fluorescent light bulbs that come in white 4 ft.tubes are the standard room lights for offices andschools. They pass electric current through a gas,usually neon. This gas emits light as the electricity

passes through it, similar to how a tungsten wiredoes. Although larger and more expensive thanordinary incandescent lamps, they are moreefficient at converting electricity into light.

The difference in heat produced betweenincandescent and fluorescent light bulbs mightsurprise you. Find a fluorescent bulb and feel theheat coming off it; you won’t feel much. Find anincandescent lamp THAT HAS BEEN OFF FOR AWHILE and turn it on. Feel the heat it produces; itsoon becomes too hot to touch. Only about 5% ofthe electricity used by incandescent bulbs isconverted into light. Without the more efficientfluorescent bulbs, our society of office buildingsmight have been much different.

Push Button RockerRotary Slide

RotarySwitch

Schematic

SlideSwitch

Schematic

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Chapter 2 Practice Problems1. Fuses are needed for all of the following reasons

except:A. They improve circuit performance.B. To prevent an electrical problem from starting a

fire.C. To limit the current in a circuit.D. People don't always use products correctly.

2. All of the following are caused by static electricityexcept:

A. LightningB. Erratic noises interrupting music on your AM

radio.C. Clothes sticking together in the dryer.D. Blackouts

3. Which circuit will spin the fan the fastest? Which willspin fan the slowest?

4. Which circuit will make the lamp the brightest?

A B

C D

A B

C D

Answers: 1. A, 2. D, 3. B/C, 4. A

Summary of Chapter 2:

1. An electric current flowing in a wire has amagnetic field.

2. A generator uses mechanical motion tocreate electricity and a motor useselectricity to create mechanical motion.

3. A fuse is a special wire that breaks whenan excessively high current flows throughit, used for safety.

4. Electrical outlets are 120V, and can supplyenough current to kill people.

5. An electrical current that is changing iscalled an alternating current (AC). Anelectrical signal that is constant andunchanging is called a direct current (DC).The electricity in homes is AC power.

6. Static electricity can cause clothes to sticktogether. Lightning occurs when staticelectricity in clouds discharges into theground.

7. Only a small amount of the electricity usedby light bulbs is converted into light, therest becomes heat.

All of the circuits and components studied inchapters 1 and 2 are commonly used by electricians,though the actual parts used will be for much highervoltages and currents than the Snap Circuits® partsrepresenting them. Electricians are concerned withgetting the electricity to where it will be used asefficiently as possible, without wasting energy.

In consumer products like toys, radios,and computers, electronics engineers andtechnicians want to control how it is used.

In this chapter you will learn about resistors, whichare used to limit and control the flow of electricity. Asan example of how important resistors are inelectronics, consider a typical AM/FM radio:

This radio contains 50 resistors, which are highlighted. The radio needs every one to operate properly.Televisions contain hundreds of resistors, and computers contain even more.

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Why is the water pipe that goes to your kitchenfaucet smaller than the one that comes into yourhouse from the water company? And why is itmuch smaller than the main water line that supplieswater to your entire town? The reason is that youdon’t need so much water. The pipe size limits thewater flow to what you actually need.

Electricity works in a similar manner, except thatwires have so little resistance that they would haveto be very, very thin to limit the flow of electricity.They would be hard to handle and break easily.But the water flow through a large pipe could alsobe limited by filling a section of the pipe with rocks(a thin screen would keep the rocks from fallingover), which would slow the flow of water but notstop it.

Resistors are like rocks for electricity, they controlor limit how much electric current flows. Theresistance, expressed in ohms (Ω, named afterGeorge Ohm) or kilohms (KΩ, 1000 ohms) is ameasure of how much a resistor resists the flow ofelectricity.

To increase the water flow through a pipe you canincrease the water pressure or use less rocks. Toincrease the electric current in a circuit you canincrease the voltage or use a lower value resistor.

The Snap Circuits® lamp you have (part L1) need ahigh current to be bright, and can be thought of ashigh current meters since their brightness is anindication of how much current is flowing in acircuit. Even the smallest resistor included in SnapCircuits will limit the current such that the lampswould not light at all. So you need a low currentmeter.

Light Emitting Diodes (LEDs) may be thought ofas one-way, low-current meters. Like light bulbs,

their brightness increases as the current throughthem is increased. But they are made fromdifferent materials and so have othercharacteristics. They are more sensitive than lightbulbs and become bright at much smaller currents,but will be damaged by high currents (which is whythey should always be used with resistors or otherparts to limit the current). They can be made toproduce specific colors of light, usually red, green,or yellow. They also completely block current flowin one direction.

Rocks

Water Flow

Screen

Snap Circuits® includes one resistor: 100Ω (R1).If you have the parts with you, take it out and lookat it.

The symbol for the resistor isthis squiggly line:

Resistor R1

Consider this simple circuit (which is project 7): If the switch is on, the LED (D1) will light. Theresistor limits the current so that the LED is notdamaged (never place an LED directly across thebattery). The LED is just like a lamp here, exceptthat it would not be as bright and would use lessbattery power. Also, an LED appears muchbrighter when viewed from above than from theside. LEDs concentrate most of their light in onedirection, unlike a light bulb which emits light nearlyequally in all directions.

If the resistor value in the circuit were increased,the LED would become much dimmer. Forexample, if the 100Ω resistor (R1) was replacedwith a 10KΩ resistor (not included), the LED lightcould only be seen if the room was very dark.

What would happen if the LED position werereversed, in a circuit like this:

Nothing will happen. The LED prevents any currentfrom flowing, and the LED will be off.

Snap Circuits® includes a red LED. The arrow inthe symbol of the part includes which direction itallows current to flow in (referred to as the forwarddirection):

Water Flow

WaterMeter

Red LED (D1)

LED Symbols

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Consider these two mini-circuits:

The first circuit has the 100Ω resistor andphotoresistor in series, the second circuit has themin parallel. Which circuit will make the LEDbrighter?

Just think of the resistors as rock piles slowingdown the flow of water in a pipe:

From the water diagrams, it should be easy to seethat the circuit with the resistors in parallel will havethe brighter LED. You can build these mini-circuitswith your Snap Circuits® parts to prove this.

Placing resistors in series increases the totalresistance, and so decreases the current to theLED. Resistors in series add together. Placingresistors in parallel decreases the totalresistance, and so increases the current to the LED.

Consider this mini-circuit:

The brightness of the LED dependson how much light shines directly onthe photoresistor. If thephotoresistor is held next to aflashlight or other bright light, thenthe LED will light. It may be dim, sowrap your hand around it to see itbetter.

Photoresistors are used inapplications such as streetlamps,which come on as it gets dark due tonight or a severe storm.

Snap Circuits® includes one photoresistor.Its resistance value changes from nearlyinfinite in total darkness to about 1KΩ whenbright light shines directly on it. Note that ablack plastic case partially shields theCadmium Sulfide part.

Photoresistor (RP)

Photoresistor Symbol

Some materials, such as Cadmium Sulfide, changetheir resistance when light shines on them.Electronic parts made with these light-sensitive

materials are called photoresistors. Theirresistance decreases as the light becomesbrighter.

As a review, consider this mini-circuit. The speakeris used here as an 8Ω resistor, its sound-makingproperties will be discussed later. Make sure thereis a bright light shining on the photoresistor (RP).

If the slide switch (S1) is on then the LED will beon, the 100Ω resistor limits the current. Turning offthe slide switch places the photoresistor in seriesand the LED becomes very dim. If both switchesare on, the speaker is in parallel with the 5.1K andso the LED becomes very bright.

You’ve learned that when you increase resistancein a circuit, less current flows (making an LEDdimmer). This relationship between voltage,current, and resistance is the most important onein electronics. It is known as Ohm’s Law (afterGeorge Ohm who discovered it in 1828):

VoltageResistance

The most basic rules for analyzingcircuits as known as Kirchhoff’sLaws (known after Gustav Kirchhoff,who stated them in 1847):

1. The total voltages driving a circuitmust equal the voltage dropswithin it.

2. All current flowing into a point mustflow out of it.

Current =

The “power” of electricity is a measure of how much energyis moving through a wire. It is expressed in Watts (W, afterJames Watt for his work with engines). It is a combinationof the electrical voltage (pressure) and current:

Power = Voltage x Current

OR

Voltage x VoltageResistance

Power =

Advanced students can computethe total resistance as follows:

Rseries = R1 + R2 + R3 + . . .

1 1 1 1= + + + . . . .

Rparallel R1 R2 R3

The total series resistance isgreater than the biggest resistor,and the total parallel resistance issmaller than the smallest resistor.

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Just what is Resistance? Take your hands and rubthem together very fast. Your hands should feelwarm. The friction between your hands convertsyour effort into heat. Resistance is the electrical

friction between an electric current and thematerial it is flowing through; it is the loss of energyfrom sub-atomic particles as they move throughthe material.

You can also compare resistors to the friction withthe ground when you walk. If there is too muchfriction (like two feet of snow) you have to go very

slow or get stuck. If there is too little friction (likeice) then you have no control and will slip and fall.

Resistors are made from carbon and can beconstructed with different resistive values, such asthe five parts included in Snap Circuits®. If a largeamount of current is passed through a resistor thenit will become warm due to the electrical friction.Resistors get warm because they exert control bywasting power as heat. Light bulbs use a smallpiece of a highly resistive material called tungsten.Enough current is passed through this tungsten toheat it until it glows white hot, producing light.

Metal wires have some electrical resistance, but itis very low (less than 1Ω per foot) and can beignored in almost all circuits. Materials, such asmetals, which have low resistance are calledconductors. The best conductor material knownis silver, but it is too expensive to be widely used.Copper is second best, and it is used in most wiresand printed circuit boards in the electronicsindustry.

Materials such as paper, plastic, and air haveextremely high values of resistance and are calledinsulators.

Electric stoves and heaters use resistors tochange electricity into heat.

You can use Snap Circuits to test whethermaterials are conductors or insulators. Considerthis simple circuit (which is project 9):

Place any material across the 2-snap wires (thecircuit shows a paperclip). If the LED is brightthen it is a conductor, if the LED is off then it is aninsulator.

Nearly all electricity produced eventuallybecomes heat. All currents flowing throughresistors produce heat in them. Light from a lampor TV produces heat in whatever it shines on. Allthe circuits in a computer produce heat, and mostcomputers have vents to get this heat out.

Draw a schematic for a circuit using a battery set,an LED, a 100Ω resistor, a slide switch, and alamp. The resistor must be used to limit thecurrent through the LED. The lamp must be on atall times, but you must be able to turn off the LED.

LEDs are made from materials calledsemiconductors, so-called because they havemore resistance than metal conductors but lessthan insulators. Most semiconductors are madeof Silicon but Gallium Arsenide is usually used inLEDs. Their key advantage is that their resistancecan be changed by the operating conditions to bevery high or very low. Transistors (currentamplifiers) are made from semiconductormaterials, and are the basic building blocks forcomputers and memory circuits.

Consider this circuit (which is project 98):

If the loose ends of the jumper wires are placedinto a cup of water, an alarm will sound. The circuitcan be used as a water detector. The tonedepends on your local water supply. If more waterwere added to the cup, the tone would changeslightly. Note that this circuit uses the alarm IC(U2) and the speaker (SP), which you will learnabout in chapter 4.

Pure water (like distilled water) has very highresistance, but drinking water has impurities mixedin that lower the resistance. What would happen ifsalt was added to the cup and dissolved in thewater?

Dissolving salt in water decreases the resistance ofthe water, so the tone of the alarm is louder andfaster. It could be used as a salt-water detector.

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Consider this circuit (which is project 47):

If the slide switch OR the press switch is on, theLED lights up. This is called an OR circuit. Whilethis may seem very simple and boring, itrepresents an important concept in electronics.Two switches like this may be used to turn on alight in your house. You could also have morethan two switches and the circuit would functionthe same way.

Now consider this circuit (which is project 48):

If the slide switch AND the press switch are on,the LED lights up. This is called an AND circuit.Two switches like this may be used to turn on thesame light in your house, the room switch and themaster switch in the electrical box.

AND and OR circuits are the basic building blocksof today’s computers, though transistors are usedinstead of switches and LEDs. Combinations ofAND and OR circuits are used to add and multiplynumbers together.

Now consider this circuit (which is project 49):

This circuit is the counter-part to the AND circuit,the LED lights in the opposite combinations of thatcircuit. It is called a NAND circuit (short for “NOTthis AND that”). This circuit can also have more orless than two inputs, though when it only has oneinput it is referred to as a NOT circuit.

OR, AND, NOR, NAND and NOT circuits are allimportant building blocks in modern computers.

This circuit is the counter-part to the OR circuit,the LED lights in the opposite combinations of thatcircuit. Engineers called it a NOR circuit (short for“NOT this OR that”).

Now consider this circuit (which is project 50):

Suppose you wanted to keep a record of how thetemperature outside was changing throughout theday. You could use a thermometer to measure it,and watch it continuously or just check it every hourand write it down. Your results might looksomething like this:

Checking it once an hour gave you a very goodrecord of how the temperature was changingthroughout the day, with much less effort thanwatching it all day long.

Digital electronics uses a series of numbers torepresent an electrical signal. If yourthermometer was electronic it might increase anoutput voltage as the temperature increased. Itwould be hard to store what that voltage wasthroughout the day, but easy to measure it andstore it as a series of numbers. The series ofnumbers could be converted back into acontinuous voltage later.

The accuracy of your digital representationdepends on how accurately and how often youmeasured the original voltage. For example, youcould get a better or worse representation of yourtemperature:

Sometimes it is easier to process information as adigital series of numbers (computers), andsometimes it is easier to use a continuouslychanging voltage (AM radios). Many products useboth methods on the same information but atdifferent times. The disadvantage of digitalsystems is that they are more complex since theyhave to store and process all the numbers. Theadvantages are that IC technology makes itinexpensive to store and process information, anddigital systems are more protected frominterference.

Computers store numbers in memory using vastarrays of transistors that are switched on or off.The OR, AND, NOR, NAND, and NOT gates areactually made up of transistors. These gates areused to add and multiply large numbers in tinypieces to form the processing functions incomputers.

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Chapter 3 Practice Problems1. The following are characteristics of an LED except:

A. They block current flow in one direction.B. They get brighter as current increases.C. They can handle very high currents.D. They can emit different colors of light.

2. To increase the current through a circuit, you . . .A. Increase the resistance.B. Decrease the watts.C. Increase the ohms.D. Increase the voltage.

3. Which of these sub-circuits will have the lowestresistance? Which will have the highest resistance?

4. Which circuit will be the brightest?

A

A B

C D

Answers: 1. C, 2. D, 3. C/B, 4. A

Summary of Chapter 3:

1. Resistors are used to limit and control thecurrent in a circuit.

2. Resistance is a measure of how muchsomething opposes the flow of electricity ina circuit, and is expressed in ohms.

3. Light emitting diodes (LEDs) are one-way,low-current light bulbs.

4. Placing resistors in series increases thetotal resistance. Placing resistors inparallel decreases the total resistance.

5. In a circuit, the current equals the voltagedivided by the resistance. This is known asOhm’s Law.

6. Power measures how much energy ismoving through a circuit, it equals thevoltage multiplied by the current and isexpressed in Watts.

7. Materials which have very low resistanceare called conductors. Materials whichhave very high values of resistance and arecalled insulators.

8. Photoresistors change their resistancewhen light shines on them.

9. All currents flowing through resistorsproduce heat in them.

10. OR, AND, NOR, NAND and NOT circuitsare basic building blocks of computers.

11. Digital electronics uses numbers torepresent an electronic signal. Theaccuracy of the digital representationdepends on how accurately and howoften the original signal was measured.

12. Computers store numbers using arrays oftransistors that are switched on or off.

D

C

B

A key advantage of semiconductors is that severaltransistors can be manufactured on a single piece ofsilicon. This led to the development of IntegratedCircuit (IC) technology around 1960. In ICs, carefulcontrol of complex manufacturing processes hasenabled entire circuits consisting of transistors,diodes, resistors, and capacitors to be constructedon a silicon base. IC manufacturing is so specializedthat particles of dust can render parts useless.

Many thousands of parts now fit into an area smallerthan your fingernail. In fact, some ICs used incomputers now have more than a million transistors

on them, and a drawing of everything onthem would be huge. Spectacularimprovements in cost, size, and reliability havebeen achieved as a result.

Further research led to the development ofmicroprocessor ICs, which can do many differenttasks based on programming that can be easilychanged. The leader of Intel Corporation onceboasted that the speed of the newestmicroprocessors doubled every eighteen months.This came to be known as Moore’s Law, and heldtrue for more than a decade.

Integrated circuits are used in everything from simpleelectronic toys to the most advanced computers.Many technologies would not have been possible

without them. A cellular phone, for example, is anextremely complex device that has been sominiaturized with ICs that it fits in your hand.

In this chapter you will learn about the integratedcircuit modules included in Snap Circuits®, andhave the opportunity to make many types ofcircuits using them. But first you will learn aboutelectronic sound.

Your electronic stereo and radioare powered by electricity andplay music, so how doeselectricity make sound? In thischapter you will find out.

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A speaker can only create sound from aCHANGING electrical signal, for unchangingelectrical signals it acts like an 8Ω resistor. (Anunchanging signal does not cause the magnet inthe speaker to move, so no sound waves arecreated).Snap Circuits® includes a speaker:

For example, compare these two mini-circuits:

When you press or release the press switch, youhear static from the speaker. When you hold thepress switch down, the speaker is silent and thelamp is not as bright as the circuit without it.

SpeakerSymbol

Speaker (SP)

A speaker converts electricity into sound. It doesthis by using the energy of a changing electricalsignal to create mechanical vibrations (using acoil and magnet similar to that in the motor).These vibrations create variations in air pressure,called sound waves, which travel across the room.You “hear” sound when your ears feel these airpressure variations.

Coil of WireVibrating Magnet

(voice coil)

Sound Waves

Suspension

Basket

Diaphragm

Spider

Voice Coil

+–

Magnet

Dust Cover

What is Sound? Sound is a variation in airpressure created by a mechanical vibration. For ademonstration of this, lay one of your stereospeakers on the floor, place your hand on it, andturn up the volume. You should feel the speakervibrate. Now place a piece of paper on thespeaker; if the volume is loud enough, you will seethe paper vibrate.

Nearly all sound waves have their energy spreadunevenly across a range of frequencies.

You can compare sound waves from your voice towaves in a pond. When you speak themovements in your mouth create sound wavesjust as tossing a rock into the pond creates waterwaves. Sound waves travel through air as waterwaves travel across the pond. If someone isnearby then their ears will feel the pressurevariations caused by your sound waves just as asmall boat at the other side of the pond will feelthe water waves. When you say a word youcreate a sound wave with energy at variousfrequencies, just as tossing a handful of various-sized rocks into the pond will create a complicatedwater wave pattern.

What is Music? Music is when sounds occur in anorderly and controlled manner forming a patternwith their energy concentrated at specificfrequencies, usually pleasant to listen to. Noise iswhen the sounds occur in an irregular mannerwith their energy spread across a wide range offrequencies, usually annoying to hear (static on aradio is a good example). Notice how somepeople refer to music that they don’t like as noise.

Another way to think of this is that the ear tries toestimate the next sounds it will hear. Music with abeat, a rhythm, and familiar instruments can bethought of as very predictable, so we find itpleasant to listen to. Notice also that we alwaysprefer familiar songs to music that we are hearingfor the first time. Sudden, loud, unpredictablesounds (such as gunfire, a glass breaking, or analarm clock) are very unnerving and unpleasant.Most electronic speech processing systems beingdeveloped use some form of speech predictionfilters.

The musical world’s equivalent to frequency ispitch. The higher the frequency, the higher thepitch of the sound. Frequencies above 3000 Hzcan be considered to provide treble tone.Frequencies about 300 Hz and below providebass tone. Loudness (the musical term) oramplitude (the electronics term) is increased bysimply sending more electrical power to thespeaker.

Sound Waves

TossedRock

WaterWaves

Boat

Frequency measures how fast somethingrepeats. It is expressed in Hertz (Hz, named afterHeinrich Hertz for his work in electromagnetism).The range of frequencies that can be heard by thehuman ear is approximately 16 to 16,000 Hz, andis referred to as the audio range.

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Build the circuit shown here (which is project 98 butwithout the cup of water).

You need one more part, and you are going to drawit. Take a pencil (No. 2 lead is best), SHARPEN IT,and fill in a shape like this:

Place a hard, flat surface beneath the paper youdraw on. Press HARD and fill in the shape severaltimes to get a thick, even layer pencil lead. Turn onthe switch and press the loose ends of the jumpersto the drawing, move them around over it. Thealarm sound will be faster if the ends are closertogether in the shape. If you don't hear any sound,add another layer of lead or put a drop of water onthe jumper ends to get better contact. You can draw your own shapes and see what kindsof sounds you can make. Wash your hands whenfinished.

Actually, pencils aren’t made out of lead anymore(although they are still called “lead pencils”). The“lead” in pencils is really a form of carbon, thesame material that resistors are made of. So thedrawings you just made should act just like theresistors in Snap Circuits.

The whistle chip contains two thin plates separated by a special high resistance material. When a voltage isapplied across them they will stretch slightly in an effort to separate (like two magnets opposing each other),when the signal is removed they come back together. If the voltage is changing quickly, then the plates willvibrate. These vibrations create variations in air pressure that your ears feel, just like sound from speaker.

Whistle ChipSymbol

Whistle Chip (WC)

This mini-circuit demonstrates how the whistlechip makes sound, just turn on the switch to hearan alarm.

You may change the sound pattern using thesame variations that projects 23-26 describe forproject 22.

Although Snap Circuits® includes several parts thatare called integrated circuits, they are actuallymodules containing a number of parts. Themodules contain specialized sound-generation andamplifier ICs and other supporting components

(resistors, capacitors, and transistors) that arealways needed with them. This was done tosimplify the connections you need to make to usethem.

1. Select an electronic product in your home andguess how many ICs are inside it. Then (withthe power disconnected from it) open it andlook to see how many there are.

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The music IC module contains sound-generationICs and supporting components. It can playseveral musical tunes that are recorded in it. Itsactual schematic is complex and looks like this:

This module has two different control inputs. TheOUT connection pulls current into the module (notout of it), usually from a speaker. This current isadjusted to make the music. Snap Circuits®

projects 15 and 16 show how to connect this partand what it can do.

Its Snap Circuits® connections are like this:

(+)

HLD

OUT(–)

TRG

Music for ~20 sec on power-up, then hold HLD to (+) power or touchTRG to (+) power to resume music.

Music IC:(+) - power from batteries(–) - power return to batteriesOUT - output connection

HLD - hold control inputTRG - trigger control input

The alarm IC module contains a sound-generation IC and supporting components. It canmake several siren sounds. Its actual schematiclooks like this:

This module has three control inputs, and canmake five siren sounds. The OUT connectionpulls current into the module (not out of it), usuallyfrom a speaker. This current is adjusted to makethe siren sounds. Snap Circuits® project 17 showsa simple way to connect this part, and projects113-117 show the connections needed to makethe five possible sounds.

Its Snap Circuits® connections are like this:

Connect control inputs to (+) power to make five alarm sounds.

Alarm IC:IN1, IN2, IN3 - control inputs(–) - power return to batteriesOUT - output connection

IN1

(–)

IN2

IN3

OUT

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The space war IC module contains sound-generation ICs and supporting components. Itcan make several siren sounds. Its actualschematic looks like this:

This module has two control inputs that can bestepped through 8 sounds. The OUT connectionpulls current into the module (not out of it), usuallyfrom a speaker. This current is adjusted to makethe space war sounds. Snap Circuits® project 19shows how to connect this part and what it can do.

Its Snap Circuits® connections are like this:

Connect each control input to (–) power to sequence through 8sounds.

Space War IC:(+) - power from batteries(–) - power return to batteries

OUT - output connection IN1, IN2 - control inputs

IN1

(+) OUT

IN2(–)

Integrated circuits are used in most electronicproducts; there are probably more than a thousandthroughout your home. The range and uses of ICsavailable is hard to imagine.

Although Snap Circuits® contains only five ICmodules, more than half of the projects use at leastone. There are many more examples of using the

parts described in the preceding chapters, such asthe whistle chip and photoresistor. Here is a shortdescription of each, the project manuals explainthem in more detail:

Suggested Projects: 38, 51, 58, 61, 81, and83.

Project 3: Uses the music IC with thewhistle chip as a vibrationsensor.

Project 4: Uses the music IC with thewhistle chip as a vibrationsensor.

Project 10: Combines the sound effects ofthe music and space war ICs.

Project 15: Uses the music IC as a doorbell.

Project 16: Uses the music IC as an alarm.

Project 17: Makes one of the alarm IC sirensounds.

Project 18: Makes one of the alarm IC sirensounds.

Project 19: This is the standard circuit usingthe space war IC.

Projects 20-21: This uses the photoresistor withthe space war IC.

Projects 22-26: Uses the photoresistor andmusic IC to control the alarm ICsiren sounds.

Projects 27-31: Uses the whistle chip and musicIC to control the alarm IC sirensounds.

Projects 32-33: Uses the whistle chip and musicIC to control the space war IC.

Projects 34-35: Uses the motor and music IC tocontrol the space war IC.

Projects 36-37: Uses the motor and alarm IC tocontrol the space war IC.

Projects 38-39: Uses the alarm IC to control themusic IC. An example of aperiodic (repeating) signal.

Projects 40-44: Uses the motor and music ICto control the alarm IC sirensounds.

Project 45: Uses the photoresistor,music IC, and alarm IC tocontrol an LED.

Project 46: Makes one of the alarm ICsiren sounds.

Project 51: The alarm IC uses thephotoresistor to sensereflections from a lamp.

Project 52: The alarm IC uses thephotoresistor to sensereflections from a lamp.

Project 53: Sound and light controlled bythe alarm IC.

Project 54: Uses the alarm IC to controlthe space war IC.

Project 58: Uses the music IC to controlthe alarm IC, with additionalcontrol from the whistle chipand photoresistor. Alsoshows how some parts canbe used as wires.

Project 60: Uses the alarm and spacewar ICs to control the motor.

Projects 61-65: The alarm IC makes soundwith the whistle chip;loudness is controlled by thephotoresistor.

Project 66: Uses the space war IC in amind-reading game.

Project 67: Uses the space war IC in amind-reading game.

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Project 68: Combines the sound effects ofthe music and space war ICs.

Project 69: Combines the sound effects ofthe alarm and space war ICs.

Project 70: Uses the alarm IC as a waterdetector.

Projects 71-76: Use either the photoresistor,whistle chip, or motor tocontrol a light using themusic IC.

Project 77: Uses the alarm and spacewar ICs to control a light.

Project 78: Makes an AND gate with themusic IC.

Project 79: Combines effects from themusic and alarm ICs.

Projects 81-82: Allows you to DRAW anactivator for the alarm IC.

Project 83: Effects from the music andalarm ICs are combined inseveral different ways.

Projects 84-85: Sound effects from the musicand alarm ICs are combinedwith the motor (in mostmanuals).

Project 86: Effects from the music andalarm ICs are combined inseveral different ways.

Project 87: Makes a fun sound with thespace war IC.

Project 88: Makes fun sounds bycontrolling the space war ICwith the motor.

Projects 89-91: The photoresistor andwhistle chip are used tocontrol the space war IC.

Projects 92-97: Uses water to control thespace war IC in various ways.

Projects 98-101: Uses the alarm IC to make awater alarm in several ways.

Summary of Chapter 4:1. A speaker uses a changing electrical signal to

make variations in air pressure.

2. All sounds are variations in air pressure thatyour ears feel.

3. Frequency measures how fast somethingoccurs, and is expressed in Hertz.

4. Audio refers to the range of frequencies thatcan be heard by human ears.

5. Integrated Circuits are miniature circuits withmany transistors, resistors, capacitors, andwires all made on a semiconductor base.

6. The ICs in Snap Circuits® are modulescontaining specialized integrated circuits andsupporting parts that are always needed withthem.

Chapter 4 Practice Problems1. Which of the following has the highest frequency?

A. A stoplight repeating its green-yellow-red cycle.B. The minutes hand on a clock passing twelve

o’clock.C. Your birthday.D. The wipers sweeping across the windshield of a

car while driving in the rain.

2. The following parts can be built into an integratedcircuit except:A. DiodesB. SwitchesC. ResistorsD. Transistors

3. Which of these electrical products is least likely tohave an integrated circuit in it?

A. LampB. Garage door openerC. CarD. Radio

4. Which of the following are advantages of integratedcircuits?

A. SizeB. ReliabilityC. CostD. All of the above

Answers: 1. D, 2. B, 3. A, 4. D

Wire Connection of other components. Various

Battery Produce electrical voltage using a chemical reaction. 1

Switch Connects or disconnects parts in a circuit. 2

Lamp Make light from electricity. 1

Printed CircuitBoard

Used for mounting and connection of components. 0–

Solder Special metal that is melted to make solid electricalconnections.

none–

Motor Make mechanical motion from electricity. 1

Fuse Used to shut off a circuit when excessive current isdrawn.

0–

Resistor Limits and controls the flow of electricity in a circuit. 1

Photo Resistor Light-sensitive resistor. 1

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LED A one-way, low-current lamp. 1

Whistle Chip Make sound from electricity, has high resistance. 1

Speaker Make sound from electricity, has low resistance. 1

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– Music IC Module to make musical sounds. 1

– Alarm IC Module to make alarm sounds. 1

– Space War IC Module to make space war sounds. 1

Basic Electricity, 736 pages, ISBN 0-7906-1041-8, Sams 61041

Basic Electricity & DC Circuits, 928 pages, ISBN 0-7906-1072-8, Sams 61072

Basic Solid-State Electronics, 944 pages, ISBN 0-7906-1042-6, Sams 61042

Beginning Electronics Through Projects, 236 pages, ISBN 0-7506-9898-5, Sams 67102

Modern Electronics Soldering Techniques, 304 pages, ISBN 0-7906-1199-6, Sams 61199

Schematic Diagrams, 196 pages, ISBN 0-7906-1059-0, Sams 61059

AC Common abbreviation foralternating current.

Alternating Current A current that is constantlychanging.

Ampere (A) The unit of measure forelectric current.

Amplify To make larger.

Amplitude Strength or level of something.

Analogy A similarity in some ways.

Audio Electrical energy representingvoice or music that can beheard by human ears.

Battery A device which uses achemical reaction to create anelectric charge across amaterial.

Blackout When part of a city is cut offfrom the power plantssupplying it with electricity.

Circuit An arrangement of electricalcomponents to do something.

Clockwise In the direction in which thehands of a clock rotate.

Coil A wire that is wound in aspiral.

Color Code A method for markingresistors using colored bands.

Conductor A material that has lowelectrical resistance.

Counter-Clockwise Opposite the direction in whichthe hands of a clock rotate.

Current A measure of how fastelectricity is flowing in a wireor how fast water is flowing ina pipe.

DC Common abbreviation fordirect current.

Digital Circuit A wide range of circuits inwhich all inputs and outputshave only two states, such ashigh/low.

Digital Electronics Using a series of numbers torepresent an electrical signal.

Diode An electronic device thatallows current to flow in onlyone direction.

Direct Current A current that is constant andnot changing.

Electric Charge An electrical attraction/repulsion between materials.

Electrical Power A measure of how muchenergy is moving in a wire.

Electricity An attraction and repulsionbetween sub-atomic particleswithin a material.

Electromagnetic Involving both electrical andmagnetic effects.

Electronics The science of electricity andits applications.

Filament A high-resistance wire used inincandescent light bulbs.

Fluorescent Lamp A lamp that creates light usinga glowing gas.

Frequency The rate at which somethingrepeats.

Friction The rubbing of one objectagainst another.It generates heat.

Fuse A device used to shut off acircuit when excessive currentis drawn.

Gallium Arsenide A chemical element that isused as a semiconductor.

Generator A device which uses steam orwater pressure to move amagnet near a wire, creatingan electric current in the wire.

Ground A common term for the 0V or“–” side of a battery orgenerator.

Incandescent Lamp A lamp that creates light usinga material that is heated until itglows.

Insulator A material that has highelectrical resistance.

Integrated Circuit A type of circuit in whichtransistors, diodes, resistors,and capacitors are allconstructed on asemiconductor base.

Kilo- (K) A prefix used in the metricsystem. It means a thousandof something.

LED Common abbreviation for lightemitting diode.

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Light Emitting Diode A diode made from galliumarsenide that has a turn-onenergy so high that light isgenerated when current flowsthrough it.

Lightning A discharge of static electricitybetween a cloud and the ground.

Lightning Rod A metal rod between the roofand ground, used to protecthouses from lightning.

Magnetic Field The region of magneticattraction or repulsion arounda magnet or an AC current.

Magnetism A force of attraction betweencertain metals. Electriccurrents also have magneticproperties.

Milli (m) A prefix used in the metricsystem. It means athousandth (0.001) ofsomething.

Modulation Methods used for encodingsignals with information.

Motor A device which convertselectricity into mechanicalmotion.

Ohm’s Law The relationship betweenvoltage, current, andresistance.

Ohm, (Ω) The unit of measure forresistance.

Parallel Circuit When several electricalcomponents are connectedbetween the same points inthe circuit.

Pitch The musical term forfrequency.

Polarity Markings indicating whichdirection a device is positionedin, usually (+) and (–).

Printed Circuit Board A board used for mountingelectrical components.Components are connectedusing metal traces “printed” onthe board instead of wires.

Resistance The electrical friction betweenan electric current and thematerial it is flowing through.

Resistor Components used to controlthe flow of electricity in acircuit.

Schematic A drawing of an electricalcircuit that uses symbols forall the components.

Semiconductor A material that has moreresistance than conductorsbut less than insulators. It isused to construct diodes,transistors, and integratedcircuits.

Series Circuit When electrical componentsare connected one after theother.

Short Circuit When wires from differentparts of a circuit (or differentcircuits) connect accidentally.

Solder A tin-lead metal that becomesa liquid when heated to above500OF. It makes a strongmounting that can withstandshocks.

Speaker A device which convertselectrical energy into sound.

Static Electricity A naturally occurring build-upof electrical charge betweenmaterials, usually at highvoltage.

Switch A device to connect (“closed”or “on”) or disconnect (“open”or “off”) wires in an electriccircuit.

Transformer A device which uses coils tochange the AC voltage andcurrent (increasing one whiledecreasing the other).

Transistor An electronic device that usesa small amount of current tocontrol a large amount ofcurrent.

Tungsten A highly resistive materialused in light bulbs.

Voltage A measure of how strong anelectric charge differencebetween materials is.

Volts (V) The unit of measure for voltage.

Watt (W) The unit measure for electricalpower.

Elenco® Electronics, Inc.150 Carpenter AvenueWheeling, IL 60090

(847) 541-3800Web site: www.elenco.come-mail: elenco@elenco.com