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We are grateful to the Charles Edison Fundfor their financial support in the initial printing of this booklet.


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1976, Thomas Alva Edison Foundation, Inc.1981, Second Printing1983, Third Printing1986, Fourth Printing


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T O T H E Y O U N G P E O P L E O F A M E R I C A

The initial publication run of this, the eighth in the EdisonExperiments series, was made possible by a grant from theCharles Edison Fund, named for a departed dear friend.

Charles Edison, like his father before him, Thomas Alva, was aman of manifold interests and energies. Although not scientificallyoriented in the manner of his father, Charles was, nonetheless, asuccessful experimenter in his own right.

He introduced innovations into government as Secretary of the

Navy and Governor of New Jersey; he initiated social reforms andadvanced techniques in the businesses he headed; and he gave un-stintingly of his time, talents and treasury to bettering the futurewhile preserving the best of the past.

Thomas Edison left with us 1,093 patents, most of which are stillbeing used in the service of man. As Charles Edison once re-marked, his father would have been very pleased by this, but itwould have given him far greater satisfaction to know that hisname was being used as an inspiration to young men and womento follow in his footsteps.

I urge you to consider these areas for your career. Science andengineering offer excitement and great personal fulfillment. Theyare, after all, superb vehicles for the improvement of life formankind.

Walker L. CislerChairman and Chief Executive OfficerThomas Alva Edison Foundation


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CONTENTS

Thomas Edison An American Folk Hero 4

Reproducing Sound the Edison Way 5

Experiment 1. A Phonograph Pick-Up

The Telegraph Relay 7Experiment 2. The Relay in Action

The Relay Coil in a Fun Project 10Experiment 3. A Secret Drawer Lock

Edisons Ore Separator 14

Experiment 4. Rejecting Counterfeit Coins

The Movies Thanks to Edison 16Experiment 5. The Spirit of 1776

Experiment 6. A Pinhole Camera

Who Turned on the Lights? 20Experiment 7. Edisons Electric Light

Experiment 8. A Light-Bulb Indicator

Replacing the Bulb with a Bell 24Experiment 9. A Portable Burglar Alarm

Edisons Power Generating System 26Experiment 10. A Speedy Electric Motor

NOTE: You need various metal strips to do Experiments 2, 3, 9, and 10.

These can be cut from a large coffee or juice can. The easiest way to do this

is to remove the bottom first. Then cut along the seam, and flatten the can.

Watch out for those sharp and jagged edges.

Be sure to scrape the metal clean when making electrical connections.

Good luck with your projects.


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THOMAS EDISONAN AMERICAN FOLK HERO

Back in the 19th century, even though Americawas still in its infant stages, we were regarded as

the most inventive nation in the world. SamuelMorse had invented the telegraph, AlexanderGraham Bell the telephone, Cyrus McCormick thereaper, Elias Howe the sewing machine, CharlesGoodyear vulcanized rubber, George Eastmanphotographic roll film . . . even Abraham Lincolnhad patented an invention of a novel riverboat.

But all through this revolutionary period of

technical progress, the accomplishments ofThomas Alva Edison placed him head and shoul-ders above all other inventors.

Edison was a driving, self-taught American whoused his intellect and burning curiosity to becomeperhaps the most productive inventor known tohistory. To the people of his time, he grew to beone of their greatest folk heroes. He was the man

who was forever making things.

Along with hundreds of other contributions,Edison gave us the phonograph, motion picturecamera, nickel-iron battery, electric railroad, mul-tiplex telegraph, carbon microphone, and, ofcourse, the electric light. Truly he belongs amongthe great builders of our country, now celebratingthe 200th anniversary of its existence.

As a Bicentennial tribute to the master inven-tor, the Thomas Alva Edison Foundation is pub-lishing this newest experiment booklet. It con-tains selected, revised experiments fromFoundation booklets now out of print. Most of the

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experiments and projects relate directly to Edi-sons more famous inventions. The others dealwith some of the scientific principles he used inachieving the 1093 inventions he gave us.

REPRODUCING SOUND

THE EDISON WAYFrom his early youth, Edison was hard of hear-

ing. Perhaps thats why he devoted much of histime to the study of sound. He knew that the vi-brations of the human eardrum, which is really adiaphragm, were communicated to the inner earand that this caused the sensation of sound.

His experiments with megaphones, vibratingdiaphragms, and the telephone transmitter wereall stepping stones to his invention of the phono-graph in 1877.

Edisons phonograph reproduced sound as fol-lows: a pick-up stylus tracking the grooves of arecording (Edison used tin foil wrapped around a

cylinder) vibrated in accordance with the soundimpressions in those grooves. Being attached to adiaphragm, the stylus caused the diaphragm tovibrate at the same rate. The diaphragm thenemitted sound waves, which were made audibleby a mechanical horn. Lets see if we can repro-duce sound the way Edison did.

Experiment 1A Phonograph Pick-Up

Materials: Frozen juice can. Aluminum foil. Small cork.Sewing needle. Phonograph record ( don't use a good one).Smooth cardboard. Ballpoint cartridge.

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HORN AND DIAPHRAGM. First, remove thebottom of the juice can with a can opener. Thenstretch a piece of aluminum foil tightly overeither opening, folding the foil edges down thesides of the can and securing the foil with astrong rubber band. Try to get this diaphragm astaut as you can.

STYLUS. To make the stylus, carefully tap theneedle through the cork until the eye end is flatwith the cork surface. Glue the back of the corkto the center of the diaphragm. You have justbuilt a mechanical sound pick-up.

WHATS THIS I HEAR? With the can openingnext to your ear, lightly scrape your finger againstthe stylus. Pretty loud, isnt it? Now, holding thepickup at an angle, let the needle rest lightly inthe grooves of your record. Well Ill be a cave-mans cousin. Thats music coming out of the can.

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SEEING SOUND. You can also demonstrate thevibrations that sound creates by converting yourpick-up to a recorder. Do this by replacing theneedle with the ballpoint cartridge. Then cut around piece of smooth cardboard the size of yourphonograph turntable. Punch a hole in the mid-

dle, and place it on the turntable. Start the ma-chine. As you hold the pen gently on the card-board, make various sounds into the can. Note thewavy line caused by the vibrations of the dia-phragm as the sounds from your voice strike it.

THE TELEGRAPH RELAY

Youve heard of a relay, havent you? Its anelectromechanical device that allows a weak forceto control a much stronger force. For example, arelay allows a switch in a safe low-voltage circuitto open or close a higher-voltage circuit.

In the telegraph system that Edison operatedand helped develop, the current flowing in the

line between two distance stations was too weakto operate the sounder. The sounder is what madethe coded clicks that the operator would translateinto a message. So to activate the sounder, a relaywas used.

Heres how it worked: The telegraph line wasconnected to a coil in the relay having many turnsof wire around an iron core. When current flowed

through the coil, meaning that a message wascoming in, the coil became an electromagnet. Theresulting magnetism caused two contacts in therelay to close. These contacts were part of a sepa-rate circuit that included the sounder and its ownpower supply. How the click intervals varied indi-cated what the message was.

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Building and testing an electromechanical relaywill give you a clearer picture of this operation.In your setup, imagine the telegraph key (really akind of on-off switch) to be miles away and the re-lay located at your end of the line. A light bulbwill serve as the sounder.

Experiment 2The Relay in Action

Materials: 2 wood blocks 4 by 2 by . A wood block 2by 2 by . Some nails, including 2 roofing nails l-1/2long. 12 of hookup wire. Metal strips. Popsicle stick.Thumb tack. 1-l/2-volt flashlight battery. 6-volt battery.6-volt bulb. Bulb socket (the kind with wires already at-tached).

RELAY FRAME. Using the drawing as a guide,nail the wood blocks together to form the frame.Then install a roofing nail about l-1/2 from theopen end. The top of the nail should be slightlybelow the top of the upright wood block. Also,mark a spot l/4 from the open end for the otherroofing nail, but dont pound that nail in yet.

ELECTROMAGNET. Put about 100 turns ofwire around the first roofing nail, leaving enoughwire to make circuit connections. Keep the wireturns close together. When finished, twist theloose ends together so they wont come apart.Now you can drive the second roofing nail in.

CONTACT ARM. For this youll have to cut a4 by 1 metal strip. Next, tape a piece of thepopsicle stick to the end of the strip. Have thestick extend l/2 beyond the strip. Near the endof the stick, press in the thumb tack, with thehead on the same side as the strip. Make sure thehead is scraped clean. Then nail the strip to the

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frame so that the tack head is directly above theoutermost roofing nail.

TELEGRAPH KEY. Make this from the lastwood block and a metal strip 4 by l/2. Bend thestrip as shown. Use round-head screws for theterminals. Now you can connect all the parts to

see the relay in action.

A MESSAGE COMES IN. Note that when the

low-voltage telegraph key is depressed (from milesaway, remember?), the nail becomes an electro-magnet and pulls the strip down. This closes thehigher-voltage circuit, lighting the bulb. Whenthe key is released, the electromagnetic field col-lapses, the strip springs upward, and the bulb cir-cuit opens.

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THE RELAY COIL

IN A FUN PROJECT

Edison used the relay principle in many of hisinventions. Its easy to see why. This principle hasthousands of applications.

Remember we mentioned a coil in the relayhaving many turns of wire around an iron core?Were going to use a coil similar to this in a funproject on the secret electromagnetic lock.

What is an electromagnetic lock? Its a verticalcoil around a nonmagnetic tube (instead of theiron core in the telegraph relay) with an iron rod

suspended in the center. The rod is supported bya piece of elastic thread and is arranged so thatpart of it extends above the tube. It serves thesame purpose as a sliding bolt in an ordinary lock.

With the magnetic lock mounted on, say, the in-side of a drawer near the top, the protruding rodprevents the drawer from being opened. Butwhen a pair of secret terminals on the outside of

the drawer are bridged, the coil yanks the roddown, thus allowing the drawer to be pulled out.When the circuit is broken, the rod will be liftedto its original position by the elastic thread.Power for the electromagnetic lock is supplied bya 6-volt battery kept inside the drawer.

Experiment 3

A Secret Drawer Lock

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Materials: 1/4 nonmagnetic tubing 2-1/2 long. 35 of hook-up wire. An 8-penny nail. Elastic thread. Metal strip. 4small nails. 2 machine screws with nuts. 6-volt battery.


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COIL. For the tubing, use copper or aluminum.Wind about 300 turns of wire around the tubing.When youve finished, wrap some tape around theentire assembly so it wont come apart.

ROD AND SUPPORT. Make the rod by cut-ting a 2 section from the middle of the 8-pennynail and filing off any sharp edges. Then lay a 3piece of elastic thread next to the rod, side byside. Tape them together at one end, as shown.Now lower the rod, taped end pointing down,into the tube until only l/2 sticks out the top.Place the remainder of the elastic over the edge ofthe coil, and fasten it securely with tape.

INSTALLING THE LOCK. Cut a metal strip 3by l-1/2, and form it around the coil. Bend the endsoutward, and punch two holes in each end to re-ceive the nails. Before mounting the lock, ener-

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gize the coil and measure the distance the roddrops. Suppose it drops l/4. This means you shouldlocate the lock on the drawer so that the rod ex-ends l/4 into the space above the top of thedrawer. If there is no space, you will have togouge a small hole above the lock to receive therod. When you have positioned the lock properly,

nail it in place.

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CONNECTING THE CIRCUIT. The batteryand lock are connected in series with two termi-nals (machine screws) that come through thedrawer from the outside. Wires from the coil andbattery are attached to these screw terminals withnuts.

Anything metallic that can touch both outsideterminals at once will be your electric key. Itcould be a coin, a scout knife, a metal-edged ruler.Of course, touching the terminals and pulling onthe drawer will have to be done at the same time.And it should be done quickly, to conserve thebattery.

FREE ADVICE. Heres an idea on how to dis-guise the outside terminals. You could attachsome sort of nonconducting (cardboard, wood,plastic) emblem or nameplate to the drawer frontand use decorative screws as terminals. But even ifyou do nothing special with the screws, no one islikely to guess the secret of how the drawer islocked or what must be done to open it.

Incidentally, when the battery inside thedrawer starts to weaken and cant quite pull therod all the way down, you can still open thedrawer by applying 6 volts (in the right + to direction) to the outside terminals, But dont letthe battery die, for then you will have a littleproblem on your hands.

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EDISONS

ORE SEPARATOR

While were still on the subject of electromag-

netism, lets take a look at one of Thomas Edi-sons inventions based directly on this principle.Its his magnetic ore separation process.

Edisons reason for developing this process wasto separate low-grade iron ore from the worthlessmaterial found with it. In the 1880s, a generalbelief was that iron ore was growing scarce. Edi-son had access to 19,000 acres of land that con-

tained, in his words, over 200 million tons oflow-grade iron ore. He thought that it would bea simple matter to extract the iron and sell it at agood price. And thats what he set out to do.

It was no small operation. His iron mine andore-processing plant at Ogdensburg, New Jersey,had miles of conveyors, giant rollers that couldcrush piano-size rocks, and the largest steamshovel in America.

The heart of the whole system was a toweringstructure that housed the ore separator. In thisbuilding, powdered rock was hoisted to the topand allowed to fall past a series of screens andlarge magnets. The iron was deflected by the mag-nets into receiving bins; the sand dropped straight

down to be carried away.We can easily make a model of this separator us-

ing sand and iron filings as the ore mixture. Butwe can demonstrate the identical principle in aless messy and more relevant way with the slug(counterfeit coin) rejector.

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Experiment 4

Rejecting Counterfeit Coins

Materials: Iron bolt 2 long with nut and 2 washers. 20of hookup wire. Thin, stiff cardboard 10 by 12. Tele-graph key from Experiment 2. Various coins and coin-sized washers (slugs). 6-volt battery.

WINDING THE ELECTROMAGNET. Place awasher at each end of the bolt and engage thenut. Wind at least four layers of wire between thewashers. After youre done, twist the loose lengthsof wire a few times to keep the electromagnetfrom unraveling.

PREPARING THE SETUP. First, put marks onthe cardboard to indicate front, back, top, andbottom. Then draw a centerline down the lengthof both the front and back. Also draw a parallelline on the back l/2 to the right of the centerline.Tape the electromagnet on this parallel line aboutl/3 of the way from the top.

On the front, glue an A-shaped piece of wood asa divider. Locate it a few inches from the bottom,and position the peak l/4 away from the center-line, toward the electromagnet.

Now were going to convert the telegraph keyto a switch. Very simple. Just cut a 3/4 metal disc,make a hole in the center, and put it under thefree screw. Also straighten the arm, and bend theend upward. The switch will be on when thearm is wedged under the disc.

HEY MA, IT WORKS. After connecting thecircuit, prop the cardboard against somethingsturdy at about a 45

o angle. From the top of the

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centerline, let several coins and slugs (washers)slide down the cardboard. If our slug rejector isworking properly (bet you forgot to close theswitch), all the slugs will be attracted to the elec-tromagnet side of the divider, and all the coinswill drop straight down . . . somewhat like inEdisons ore separator.

Thats because magnetism affects iron but not

copper or nickel (or sand). Modern coin vendingmachines detect slugs in a similar manner.

THE MOVIES

THANKS TO EDISON

During the middle years of his life, ThomasEdisons interest focused mainly on his secret

toy, the motion picture camera. He could see nopractical future for it. Yet he could not bringhimself to abandon the project. Perhaps he felt itwas a logical extension of his work on the phono-graph, which he had invented years earlier andwas still improving.

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In 1888, Edison filed a document with the U.S.Patent Office stating: I am experimenting uponan instrument which does for the eye what thephonograph does for ear . . . . This apparatus Icall a Kinetoscope.

The Kinetoscope offered the first motion picture

show in history. With it, the viewer could lookthrough a peephole and see a sequence of stop-and-go photographs that gave the illusion of con-tinuous motion. Persistence of vision made this il-lusion possible.

Although todays motion picture equipment isvastly superior to what Edison developed, persist-ence of vision is still necessary for it to work.

What is persistence of vision? It is the tendencyof the eye to continue seeing an object for aboutl/l0 of a second after the object disappears. Heresa simple experiment to demonstrate the effect.

Experiment 5

The Spirit of 1776

Materials: 2 disc of cardboard. 12 of string. Glue.

SETTING THE STAGE. On the left half of thedisc draw a large 17. Flip the disc over in bottom-to-top fashion, and draw a large 76 on the righthalf. After laying a thin bead of glue across eitherside in the horizontal direction, stretch the stringfirmly and place it on the glue.

SEEING IS BELIEVING. When the glue hasdried, twirl the disc rapidly back and forth withthe string. Thanks to the persistence of vision weall have, you will see our countrys birthyear as acomplete number. In addition, you will see whatlies directly behind the disc, which would nor-

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mally be blocked out.In developing his motion picture camera, Edi-

son used not only the persistence of vision effectbut certain optical principles as well. One of theseexplains how a camera sees an image, as shown inthe next experiment.

Experiment 6

A Pinhole Camera

Materials: Large coffee can with plastic lid (the semicleartype). Large dark cloth.

BASIC CAMERA. Its amazing how simple acamera can be, as youre about to find out. Tomake one, punch a hole about the size of a penny

in the bottom of the coffee can. Do it in the cen-ter. Then cover this hole with a disc of thin card-board, taping it down around the edges. Nowpierce a hole in the disc with a pin, put the plasticlid on top of the can . . . and theres your camera,ready to go.

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SCREEN AND LIGHT SHIELD. The plastic lidis our viewing screen. However for you to be ableto see the projected image of what you aim at, thescreen has to be shielded from light. For this pur-pose, drape the dark cloth over your head and thecamera, the way some photographers do.

A TOPSY-TURVY WORLD. Aim the cameraat something bright about 10 away. Hold the

screen a foot or so from the eye. Note that whatyou see on the screen will be upside down. This isbecause light travels in straight lines. The lightfrom the top of the object travels through the pin-hole and lands on the bottom of the screen. Simi-larly, light from the bottom of the object strikesthe top of the screen.

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WHO TURNEDON THE LIGHTS?

What do most people think of when they hear

the name Thomas Edison? The light bulb, ofcourse. Invented by Edison in 1879, it was themost practical source of artificial light producedby man since the beginning of time. In the early1800s, scientists in both the United States andEurope had experimented with hundreds of incan-descent electric lights. But they couldnt get anyof them to work, except perhaps for brief periods,until Edison succeeded.

As hard as it was to develop, the incandescentelectric light is basically a simple device. It con-sists of a coiled filament within a glass enclosurefrom which the air has been removed.

The principle on which it is based is that aglowing filament gives off both heat and light.The hotter the filament, the brighter the light.

Edisons main problem was to find the right mate-rial to use for the filament. But he also had tocreate a good vacuum to prevent the filamentfrom burning up.

After finding that carbon filaments worked best,he managed to make the filament last longer andlonger by removing more and more air from thebulb. Were going to try something similar in thisexperiment on the light bulb.

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Experiment 7

Edisons Electric Light

Materials: Wide-mouth jar with cover. 4 of hookup wire.Copper-strand lamp wire 4 long. Switch from Experi-

ment 4. Birthday cake candle on a small base. 6-volt bat-tery.

BULB. In the cover, punch two small holes justbig enough to receive the wire. Space the holesl-1/2 apart. Insert two 18 lengths of wire throughthe holes so that they will extend halfway into thejar. Now bend the wires down the sides of the cover,and tape them in place. Put a strip of tape over

the holes too.

FILAMENT. Remove one copper strand fromthe lamp wire. Wind it several times around anail. Slip the coiled filament off the nail, and con-nect it to the two wires coming from the cover.

LIGHTING UP THE DARK (WELL, NOTQUITE). Screw the cover on the jar. This is ourlamp. Next, connect the lamp in series with theswitch and the battery. Turn the lamp on andstart counting. The filament will begin to glow. Ifit continues glowing for more than 15 seconds,open the switch. Otherwise youll drain the bat-tery. Try a shorter filament. Keep doing this untilyou find a length that burns for just a few sec-onds. When you do, put on a new filament of this

length.Now were going to remove some of the air

from the lamp. Put the candle inside the jar andignite it. There turn out the room lights. Whilethe candle is burning, close the jar tightly. Whenthe candle goes out, which means it has used up a

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lot of the air, turn the lamp on once again. Hope-fully, the filament will glow a little longer thistime. Letting it glow in the dark will producea rather dramatic effect.

Experiment 8

A Light-Bulb Indicator

Materials: 2 long thin nails. 2 of hookup wire. Bulbsocket from Experiment 2. Screw-type flashlight bulb.Flashlight battery. Some tape.

We mentioned that the electric light bulb is asimple device. Well in addition, it operates in thesimplest of circuits. An example is the light-bulbindicator you are about to put together.

ASSEMBLING THE INDICATOR. Actuallytheres not much to assemble, as you can see. All

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you do is hook the light bulb and battery in seriesand attach the circuit ends to the nails. Make allconnections by soldering. But if you have no sol-dering equipment, use tape. Also cover the nailsand nail connections with tape, leaving only thetips exposed.

WHAT DO WE DO WITH IT? Lots of things.

For example you can use it in science experimentsto learn whether or not different materials andliquids are good conductors of electricity.

You can also use it to check items like flashlightbulbs or glass-tube fuses, as shown. Some of thesefuses have wires so thin you can hardly see them.If you touched the indicator nails to the ends ofsuch a fuse and the bulb lit up, youd know thefuse is OK.

But whatever you do, never use it on anythingthat is connected to a voltage source (but thenyou dont need to be told not to stick your fingerin a beehive, do you?).

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REPLACING THE BULBWITH A BELL

Similar to both your light-bulb indicator andhome-made electric light is the portable burglaralarm on page 25. Can you see the similarity? Sure

you can. All have the same three basic parts: acomponent that does something, a power supply,and a means of opening and closing the circuit.Also, all three are connected in a simple series cir-cuit. The only difference is that the burglar alarmuses a bell instead of a bulb.

The burglar alarm provides a neat way of pre-venting an intruder from opening an inward-swinging door without being heard. It is placedanywhere along the bottom of the door. When thedoor opens, it pushes against a contact arm. Thearm, in turn, closes the circuit, which triggers thealarm.

Experiment 9

A Portable Burglar Alarm

Materials: 2 wood blocks 4 by 3 by 3/4. 3 nails. Metalstrip. 2 round-head screws. 2 of hookup wire. Doorbell.6-volt battery.

FRAME AND CIRCUIT CONTACTS. Afternailing the frame together, drive one of thescrews part way into the vertical block aboutl/2 from the top. Then loop the bared end of a 6length of wire around the screw, and finish driv-ing the screw in.

Cut a strip of metal 5 by l/2. After shaping thestrip as illustrated, pierce a hole in the flat end. In

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a moment we will mount this contact arm at thebottom of the vertical block using the remainingscrew. But first lets assemble the alarm.

TYING THINGS TOGETHER. Attach two 9lengths of wire to the doorbell terminals. Put thebattery on the wood base, and hold the doorbellagainst the back of the battery. Now for a com-pact package, tie the bell, the battery, and thevertical block together tightly with tape or cord.

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FINAL STEPS. Screw on the contact arm. Thencomplete these circuit connections: Run one door-bell wire to the battery, the other doorbell wire tothe contact arm, and a third line from the uppercontact screw to the battery.

A WATCHDOG THAT NEVER SLEEPS. Thesystem should work like a charm. Anyone openinga door that is booby trapped with this alarm willbe in for quite a hair-raising surprise. Keep inmind, too, that this burglar alarm is truly porta-ble. Since it has its own power supply, you cantake it on family trips for use in hotels, motels, orhouse trailers. Maybe everyone will sleep withmore peace of mind.

EDISONS POWERGENERATING SYSTEM

Even while pursuing the electric light, ThomasEdison knew that when he eventually reached his

goal, the light wouldnt be of much use by itself.An entire central system for generating electricityand distributing it to homes would still beneeded. To Edison goes the credit for master-minding and building this system.

To make such a system come true, Edison hadto invent practically everything in it: under-ground distribution mains, insulating materials,

power switches, meters, dynamos, lighting fix-tures, fuses, and more. Certainly all of these in-ventions played an important role in the successof the system. But among the most vital was theworlds first economical direct-current (DC) gen-erator, or dynamo. This brings us to our last pro-

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ject. The big one. Its a DC motor, which is essentially the same as a DC generator.

Experiment 10

A Speedy Electric Motor

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Materials: Strap iron 6 by 5/8 by 3/32 (or 1/8) 100 of.#24 magnet wire. Two 16-penny spikes. Tape 1 wide.Daring needle or piece of coat hanger. Various metalstrips. Copper-strand lamp wire 2 long. Baseboard 7 by6 by 3/4. 4 screws. Some nails. 1 hookup wire. 6-voltbattery.

The motor were going to build has four parts:

the field magnet, armature, commutator, and apair of brushes.

MAKING THE FIELD MAGNET. Were goingto need a vise for this job. Measure 2 in fromeach end of the iron strap. Then bend these 2sections toward each other until the ends areabout 3 apart.

Leaving 6 of wire for final connections, startwinding the magnet wire along the 2 base of theiron strap. Put on 400 turns. When finished, wrapsome tape around the windings to keep them inplace and protect them.

ARMATURE AND SHAFT. The two l6-pennynails provide the backbone for the armature. Cut

each of them to a 2-1/2 length, measuring from thetop of the head down. Tape them as shown. As ac-curately as possible, find the mid-point of the as-sembly. Then insert the shaft (darning needle or6 length from coat hanger) between the nailsright through the tape, allowing 2 to stick outthe other side. Next comes the winding.

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We will be putting on four layers of wire. Beginright next to the shaft. Leaving some wire for cir-cuit connections, wind neatly toward the nailhead. Keep each turn of the wire close to thepreceding turn. Upon reaching the nail head,double back toward the shaft. Then make anothertrip to the same nail head, and return again to the

shaft.

At this point we cross over to the other side ofthe armature without changing our coiling direc-tion, and repeat the entire procedure. Two wireends should now be extending from the center ofthe armature. Cut them down to about 2, andscrape the tips bare for connecting to the commu-tator terminals. (Note: Magnet wire has a decep-

tively clear varnish-like insulation on it, whichmust always be scraped off when making a con-nection.)

THE COMMUTATOR. For the terminals, cuttwo 1 by l/2 metal strips. Shape them around anykind of l/2 diameter cylinder so that the length ofthe terminals runs with the length of the cylinder.Then if you can, solder the armature tips to the

ends of the terminals. Otherwise, pierce eachterminal with a small nail, loop an armature tipthrough the hole, and twist tightly.

Now we must build up the shaft diameter tohold the commutator terminals.. Do this by wrap-ping 1 tape on the longer end of the shaft about3/4 from the armature. Keep wrapping until al/2 diameter cylinder is formed.

After looping the excess wire around the arma-ture, place the commutator terminals on therolled tape as shown on page 30. The space be-tween the long edges of the terminals should beequal on both sides of the commutator. And these

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spaces should face the same direction the nails do.Put a thin strip of tape around each end of thecommutator to keep it together. This completesthe armature-commutator-shaft assembly. OK sofar?

SUPPORTS FOR SHAFT AND BRUSHES. Forthe shaft supports, cut two strips 3-l/2 by l-1/4.

Fold them in half so that the width is now 5/8.Bend a 3/4 segment 90

ofor the base, and fold over

about l/4 at the top for added stiffness. Standingeach support vertically on a flat surface, measure2 upward from the surface. Either drill or puncha hole at this point just big enough to receive themotor shaft. While youre at it, put a couple ofholes in the base for the nails.

To make the brush holders, cut two strips 2-l/2by l/2. In each one, bend a small segment forthe base, and put a hole in the middle for a screw.Two 1 pieces of copper-strand wire will serve asthe brushes. They should be soldered to the hold-ers on the sides that will face the armature. with

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l/2 of copper extending above the holders. Ifsoldering is not possible, try wrapping longer cop-per strands around the holders (scraped clean) andtaping them on.

PUTTING THE MOTOR TOGETHER. Mountthe motor parts on the baseboard as shown onpage 27. When doing so:

Secure the field magnet to the board with a2-l/4 by 1 metal strip and nails.

Keep the clearance between armature endsand field magnet fairly small.

Use tape collars to keep the shaft from mov-ing back and forth.

Mount the brush holders with screws. Adjustthem until the copper strands are vertical.Also, fan out the strands for better contactwith the commutator.

CONNECTING THE CIRCUIT. A good motordeserves a switch (and we didnt build a junkymotor, right?). Make the switch arm from a metalstrip 4 by l/2. Cut a 3/4 disc for the othercontact. Use screws for the switch terminals.

In making the connections, follow the diagramon page 32 (as you can see, its a series circuit).Dont forget that the clear insulation must be

scraped off the ends of the magnet wire.

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THOMAS ALVA EDISON FOUNDATIONAdvancing Science, Technology and Engineering Education

Officers

MADELEINE EDISON SLOANE IIHonorary Chairman

WALKER L. CISLERChairman and Chief

Executive Officer

JAMES G. COOKPresident and Chief

Operating Officer

PAUL J. CHRISTIANSENVice President

PAMELA DAWN HURSTAssistant Vice President

DONALD R. MANDICHTreasurer

THOMAS J. UNGERLAND

Secretary

Trustees

ENG. MOHAMMED MAHER ABAZAMinister of Electricity and Energy

Arab Republic of Egypt

ARNALDO ANGELINI, Ph.D.Presidente

I t a l y

Ente Nazionale Per LEnergia Elettrica

A. AYMONDRetired Chairman

Consumers Power Company

D. JEFFREY BADDELEY

Vice President, Secretary

and General CounselSargent-Welch Scientific Company

JAMES A. BAKER

Executive Vice President

General Electric Company

L. K. CHENChairman

Taiwan Power Company

Taiwan

PAUL J. CHRISTIANSEN

PresidentCharles Edison Fund

WALKER L. CISLERChairman

Overseas Advisory Associates, Inc

ASHTON B.COLLINS, Jr.

Reddy Communications, Inc

JAMES G COOK

MICHAEL E. DeBAKEY, M.D.President and Chief Executive OfficerBaylor College of Medicine

LOUIS DeHEEM

President de LAssociation VincotteBelgium

WILLIAM O. DOUBPartner

Doub and Muntzing, Chartered

JAMES L. EVERETTChairman and Chief Executive Officer

Philadelphia Electric Company

JOSEPH M. FARLEYPresident

Alabama Power Company

WILLIAM CLAY FORD

Vice Chairman, Board of DirectorsFord Motor Company

RAYMOND H. GIESECKE

Retired Chairman

McGraw-Edison Company

LEON HESSChairmanAmerada Hess Corporation

NIELS W. HOLMChief Operating OfficerNovo lndustries

SOL KINGRetired Chairman

Albert Kahn Associates, Inc.

CARL THEODOR KROMER, Ph.D.Retired Director Badenwerk

Federal Republic of Germany

F. MAHMOUDIANAssociate

Overseas Advisory Associates, Inc

DONALD R. MANDICHChairman and Chief Executive Officer

Comerica, Inc

RICHARD E. MARBURGER, Ph.D.

President

Lawrence Institute of Technology

WALTER J. McCARTHY, Jr.Chairman and Chief Executive Officer

The Detroit Edison Company

WILLIAM McCOLLAM, Jr.President

Edison Electric Institute

WILLARD F. McCORMICKChairman

JAMES H. McNEAL, Jr.President

The Budd Company

JUNG-KI PARK

Korea Electric AssociationKorea Electric Power Corporation

COURTLAND D. PERKINS, Ph.D.Retired PresidentNational Academy of Engineering

JOHN W. PORTERPresidentEastern Michigan University

JOHN T. RYAN, Jr.Chairman

Mine Safety Appliances Company

DAVID C. SCOTT

Chairman and Chief Executive OfficerAllis-Chalmers Corporation

JOHN D. SELBY

Chairman. President and

Chief Executive Officer

Consumers Power Company

JOHN EDISON SLOANE

John Edison Sloane, Inc.

MADELEINE EDISON SLOANE, IIAttorneySouthern Pacific Transportation Company

HAROLD W. SONNPresident and Chief Executive Officer

Public Service Electric and Gas Company

GEORGE A. STINSONRetired Chairman

National Steel Corporation

SEIICHI TANAKA

Chairman

Japan Electric Association

CHARLESTRETHOWANChairmanState Electricity Commission of Victoria

Australia

THOMAS J. UNGERLAND

Associate General CounselUniDynamics Corporation

EDWIN VENNARD

Private Consultant

Greenwich. Connecticut

FRANK M. WARRENChairman and Chief Executive Officer, Retired

Portland General Electric Company

EDWARD J WILLIAMS

edison ch5

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