fun electronics projects for the experimenter

Transcription

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61149
F[jIlI
PHOJ[OT$
r
ths
fo
illu|EII
F
d
F-
llr tln hoilmomtl
rurProlcGB
withAmerican,
Duringmorethan20 years,the author,as a collaborator
haspublished
a large
magazines*,
electronics
andLatinAmerican
European
circuitsusingcommonparts.
of practical
assortment
in thisvolume,mostof whichyou
areincluded
Nowmanyof thoseprojects
rangefromfuntypesthroughpractical
Theprojects
canbuildin oneevening.
types.Of course,thereareotherdevicesthatcan be
typesto amusement
aboutcircuitsor components.
usedto teachyousomething
for
intended
featureofthesesprojects
aretheldeasto Explore,
Animportant
practical
projects
research.
in scienceor to usein
lookingfor
students
Wecanconsider
thisbookas a sourcebookof theeasiestandfun-to-make
createdandpublished
bytheauthorduringthese
of projects
of thehundreds
years.
last
But,as the projectsare in a widerangeof types,we shouldseparatethe
or
intotwogroups:
theoneswhowantto improve
experimenters
electronics
interest,suchas computers,
expandsomeotherareaof theirelectronics
audio,securityandevengames;andthe oneswho
radio,instrumentation,
circuitsanddevicesor wantnew
aboutelectronic
wantto learnsomething
ideasto usein scienceprojects.
acceshereincanbestand-alone
asindividual
described
Mostoftheprojects
possible
they
be
so
that
can
the
have
been
designed
wherever
circuits
sories;
gangedwithoneor moreotherprojects.
manyprojects
of audio
Forexample,
outor high-power
canbegangedwithaudioamplifiers
etfectsor generators
putstages.
thatcanbemadein
withfewlow-cost
components
Alltheprojects
aresimple,
oneevening
of work.
we addedcodesafter
Tomakeit easyforthe readerto choosethe projects
the
whomtheyareintended:
thekindof experimenterfor
eachtitleto indicate
"E'
"P"
project
practical
(Practical)
The
code
built
for
use.
indicates
a
code
to
(Experimental)
forthe experimenter
indicates
thatthe projectis intended
teachsomething
aboutcircuitsor devlces.
trolrcc
Of course,you can also find projectswith both codes(E and P)whichcan
dther be mountedto teachsomethingorknd be usedfor a practicalend.
The presentations
of the projectsare practical.Electronicscomponentsare
listedwith eachcircuitdiagram.But secondarypartssuchas sockets,chassis, enclosures,miscellaneous
hardwareand so on, are not specified,since
the readeris free to choosethesenon-criticalitemsaccordingto his preferencesand demands.
The mannerin whichthe circuitswork and can be modifiedis explainedin
practicaltermsso the readercan acquiresomeknowledgeof practicalelectronicsas he progressesthroughthe book.
Althoughmanyof the projectswe enjoyedconstructing
as theyaredescribed
here,youmaythinkof possiblemodifications.
Wejust recommend
thatyougo
aheadand modifythe circuitsto yourpersonalends.Thereis a wide latitude
in circuitmodifications
and mostof themwill be of valueto the experimenter
whowantsto see howthingswork,eventhougheachproject'sprimaryintent
is forthe builderwhodesiresa functionalitemof equipmentas the resultof his
work.
As the bookincludeseasy-to-build
projects,the authorhopesit will helpyou
to learnmanyof the fundamentals
of electronicsin an easyandfun way,and,
you're
if
a student,providea sourcefor schoolprojects.
NewtonC. Braga
. Mini-Projects
is thetitleof a columnpublished
bytheauthorduringseveral
yearsin a BrazilianElectronics
MagazinenamedEletr6nicaTotal
(TotalElectronics).
frnFdocahlhclnulmtmol
(E/P)
MlcRo-PowERLEDFLASHER
A simpleLEDflashercan be builtwitha TLC7555Timerusedas a lowdeteranddriveto an LED.lC1runsin a lowfrequency
frequency
oscillator
0.1and5 Hzbut
is intherangebetween
minedbyR?R3andC1.Frequency
youcanalterit bychanging
canrangefrom1 to 10uF.
Cl.Thiscapacitor
where
inapplications
byR2/R3ratioandis important
Dutycycleisdetermined
youneedreduction
Figure1 showsfixedresisof energyconsumed.Though
potentiometers
you
if you prefer.The
can usetrimmer
torsfor R2 and R3,
anddutycycle
potentiometers,
thefrequency
arehandyforaltering
ofcourse,
of theoscillator.
WithpowersuppliesbeRl valuesdependuponthe powersupplyvoltage.
6 and9
tween5 and6 volts,R1is 470ohms.Withpowersuppliesbetween
power
9 and
intherangebetween
supplies
volts,Rl is 560or680ohms.With
circuitdrainsonly250uAfroma 6-volt
12volts,Rl mustbe 1,000ohms.The
powersupply.
At
LEDFlasher.
fortheMicro-Power
diagram
Figurel showstheschematic
theheartof thecircuitis lOl, a 555timer.
the Microdiagramas a guidewhenassembling
Usethe partsplacement
placement,
as chasterminal
strip
using
a
Flasher.
Components
PowerLED
sis,is shownin Figure2.
suchas the LED
components,
of polarized
Takespecialcarewithpositions
capacitor.
andelectrolytic
putthe
correctly,
Afteryouaresurethatyouhavewiredallthecomponents
TheLEDshouldflash.
in thebatteryholder.
batteries
H.lGtt@
R1
560s,
Dl
1N914
Rg
4KT
c1
4.7pF
Figure I
l{"
Figure2
I
It
mtnfffifrtchrmlffi
I
I'
LEDFlasher
PartsList - Micro-Power
lC1
- TLC7555CMOSIntegratedOircuit- Timer
LEDI - Commonred,greenor yellowLED
D1
- 1N914generalpurposesilicondiode
Rl
- 560 ohm, 114W,5%
resistor
R2
- 1,000,000
ohm, 114W,5%resistor
Rg
- 4,700ohm, 114W,5%resistor
C1
- 4,7 uF,6IM/DC electrolytic
capacitor
C2
- 10 UF,12 W\/DCelectrolytic
capacitor
81
- 6 to 12VAA cells,9V batteryor powersupply
ldeasto Explore
learnmoreaboutthe circuitand devices:
o AlterR2andR3 (minimumvaluesare 1,000ohmsforboth)andsee
howthe flashingratechanges.Of course,if youwant,youcan replace
trimmerpotentiometers.
R2 and R3 with 1,000,000-ohm
o Explainhowthe astable555 worksin this circuit.
o AlterC1 in a rangebetween1 and 100uF andobserveflashingrate
alteration.Explainwhathappens.
o Whatis duty-cycle?
FroFGtltlmPomrlMmficr
Scienceexperiments
withthe clrcuit:
o LED ls a monochromatic
lightsource.Youcan performsome experimentsin opticsusingthiskindof lightsource.Chromaticfilterscan
be usedin someexperiments
involvingLEDs.TrytouseLEDsof different colors(red,yellow,greenand,if possible,blue).
. Lightflashes,as the onesproducedby this circuit,can be usedin
hypnoticexperiments.
o The circuitcan be used to indicateoperationof otherelectronic
devices.Wiredto the powersupplyof a monitoreddevice,the blinker
LEDwillindicateits operation.
Remember
thatthetheoryin thisbookis specifically
relatedto the associated
projects.This
experiments
and
bookis designedas an introduction,
notas an
in-depthtreatmentof electronics.lf you are interestedin findingout more
aboutthe subjectstouchedon in this book,severaltextscan be foundfor
furtherreading.
r
frnPrrre$hrfiosrrhdlu
_
FLIP-FLOP(E)
SET-RESET
WiththispQectwe canshowhowtwoNANDgatesof a 7400lC (TTLIntegratedGircuit)
canbe wiredto performas an R-Sflip-flop.
pulsesto be
thatneedsnegative-going
flip-flop
Thiscircuitisa pulse-triggered
a
Thiscircuitoperatesas follows:as we see,it haltwg_outngls;
triggered.
(LED2).When
outputcalledO
andaninverted
nolmdoutputcalledO (LED1)
theyare
because
vice-versa
will
be
0
and
oneoutputis 1theothernecessarily
complementary.
as shownin
ThecircuithasalsotwoinputsnamedS (SET)andR (RESET)
wherethetriggersignalsareapplied.
diagram,
theschematic
R inputiswiredto Q outputandS inputiswiredto Ooutput,forminga closedloopforthedigitalsignals.
triggerpulseis appliedto S inputtheoutputQ swingi
Whena negative-going
to the 1 staie.As thistutputis wiredto R input,the 1 statecausesoutputQ
tofallto a 0 level.ButQ outputis alsowiredto S inputcausinga feedbackthat
To
makesitsoutputremainat 1 alsoatterthetriggerpulsehasdisappeared.
negaa
apply
we
should
states,
theoutput
again,changing
triggertheflip-flop
p!-going pulseto R input.This
pulsecausestheoutputto goto 1, andasthis
outputis wiredto R input,thetriggerpulsealsocausestheoutputQ to goto
0level.
Azeroin thisoutputgoesto R input,andalsoafterthetriggerpulsedisappearstheoutputsremainin theirstates.
Seethatthe circuithastwo stablestates,andwe onlycan changethese
pulsesappliedto its inputs.
stateswithsetor reset(S or R) negative-going
wiringa
flip-flopandcanbe constructed
Ourprojectis a manually-triggered
switchto the R-Sinputsas shownin Figure1.
twoLEDs.LED1glowswitha 1 at Q outputand
Logicstatesareindicateqby
LED2glowswitha 1 at d outPut.
Ffd0crzsH-i$fff,llHrr
Thecircuitmustbe powered
powersupplyas it usesa
by a S-voltregulated
TTLlC.Currentrequirements
rangetypically
from5 to 15 mA.
placement
Components
ona smallprinted-circuit
boardisshownin Figure2.
Experiments
likethiscanalsobeperformed
onwhatelectronics
experimenterscall"breadboards".
Theseareboardson whichthe partsof experiments
canbe temporarily
assembled.
By usingbreadboards
it is notnecessary
to
teo\/7 $1"
t'\tt
ffin
Figure I
Figure 2
r8
Frndrctrffithe halmffil
"solderlessboards"
This is why theyare alsocalled
solderthe components.
The circuitcan be usedto teachmuchaboutflip-flops,usedin computersas
countersand in memoriesand manyotherapplications.
Observation:In digitalelectronicsan electricalsignalis eitherhigh or low.
Thesetwo statesale usedto representbinarybits 1 and0. Sincedigitallogic
lOs operatefrom a single-endedpowersupply,a high state representsa
a voltagenear 0V'
voltagenearthe supplyvoltageanda lowstaterepresents
FUP-FIoP
PanrsLsr - SET-RESET
fC1
- 74OOTTL IntegratedGircuit
LEDs
- Red,greenor yellowcommonLEDs
R1,R2
- 330 ohm, 114W,5Y"resistors
51
- SPDT toggleswitch
ldeasto ExPlore
Tolearnmoreaboutthecircuitanddevices:
countercircuit.Mountother
flip-flopis a fundamental
o Thecommon
unitslikethisand usethemto explainhowcountersandmemories
circuits.Eachflip-flopcanstorea bit.
workin computer
andhowthey
betweenR-SandJ-Kflip-flops
. Findtheditferences
areusedin logiccircuits.
usingthiscircuit:
andprojects
Scienceexperiments
anduse
(reed)switchor a microswitch
o Replace
51 bya-magnetic
lt candetectand
memoryin experiments.
thiscircuitas a one-event
processis
whena Switchin an lure,alarm,or mechanical
memorize
closedfora moment.
-
tf
I
ff ilo lrnulmrnml
HnProfmB
(P)
MIN|-METRONOME
metronome
whichyoucanbuildintoa small
Hereis a dandytwo-transistor
plasticcase.Youcan usean old nonworking
radioto housethis
transistor
gadget.In mostcaseyou can merelyremovethe maincircuitrybut retain
speakerand
someparts,suchas the on-otfvolumecontrolpotentiometer,
just
the following
batteryholder.lf youhavedonethis,youhave eliminated
items:SPKR,51,and81.
withtwoorfourAAcellsanddrainsabout10mA.
Thecircuitcanbepowered
potenByadjusting
stbrtqclacking.
As soonas 31 is closed,themetronorfle
"beat'or
youwishto set.
frequency
of clacking
tiometerP1youfindthe
yourmetronome
youhaveonlyto synchronize
witha commercial
Tocalibrate,
typeor anyknownsource.
At theheart
fortheMini-Metronome.
diagram
Figurel showstheschematic
which
amplifier,
direct-coupled
of thecircuitareQ1 andQ2,as a two-stage
pulses.
generate
intervalled
to
the
circuit
allows
usinga terminalstrip
of themetronome,
Figure2showsa mechanicalview
"chassis"
forthesmallcomponents.
as
suchas Gl, C2 andthe transistor,
components,
Positionof the polarized
in themounting.
shouldbe observed
rt
;fdcr8
P1
1M
ilrl-IrEwm
*_J
Q2
Bc5s8
R1
10K
Q1
|
st\
|
t
t
c2d
100pFT
I
+r\
c1
lOpF
l
I
I
t ?
l a r :
R2
1K
| 3/6V T-
SPKR
4l8A
Ftgure 1
Figure2 \
t0
_--HftFCIFfrilTtrlffiHT
-
PartsList - Mini Metronome
Q1
- 8C548 NPNtransistor
Q2
- 8C558 PNPtransistor
51
- SPST toggleor slideswitch
81
- 3V or 6V - two or four AA cells
SPKR- 4 or I ohm,2 to 4-inchloudspeaker
P1 -
1,000,000ohm Potentiometer
Rl
- 10,000ohm, 1l4W,5olo
resistor
PA
C1
- 10 pf, 6 VVVDCelectrolytic
capacitor
C2
- 10 Uf, 6 WVDC electrolyticcapacitor
ldeasto ExPlore
To learnmoreaboutthe circuitanddevicesor to get betterperformance:
in the rangebetween1 and 10 pF.
o ReplaceG1 by anycapacitor
whatwillhappento thebeatrate.Explainit'
Observe
andpower
Q2withaTlP32ona smallheatsink
o Replace
transistor
haveextrapowerfor
thecircuitfroma 9V or 12Vpowersupply.You'll
andcanuseit in largerplaces.
metronome
yourexperimental
o . RemovePl andtouchwithyourfingersthe pointswhereit was
Canyouexplainwhatis goingon?
wiied.Willthecircuitoperate?
-
2a
Prtlm8 thl-ilrtrrnrm
Scienceexperiments
andditferent
usesforthecircuit:
o Themetronome
canbe usedin gymnastic
exercises
or in running
to findthecorrectrhythm.
Themetronome
canbe housedin a small
plasticbox,powered
bycellsandeasilycarriedwiththerunner.
o Biological
experiments
withsoundscanbe madewiththisdevice;
experiments
in animalconditioning,
forexample.
n
filnH.f0c03ffisrhoilm
PENDULUMALARM (E/P)
thisalarm,enabling
sensortriggers
thatswingsthependulum
Anymovement
a relay.
homesandotherplaces
Thecircuitcanbeusedto protectcars,largeobjects,
Thisdevicecanalsobe
asthesensorcanbe usedto detectanymovement.
at theendof thesection.
as suggested
experiments,
usedforscientific
suchas sirens,horns,lamps,
soundsystems,
Therelaycandrivepowerful
etc.Thecircuitcan be poweredby a l2-voltbattery(whenusedin cars,for
drainisverylow(about100uA)whenthe
Current
ora powersupply.
instance)
batterylife.
extending
relayis deenergized,
Alarmis shownin Figurel.Thecircuit
circultofthePendulum
Theschematic
the
whichenergizes
Rectifier),
hasas its heartan SCR(SiliconControlled
relaywhenthe sensordetectsanymovement.
usinga terminalstripas chassis,
viewof thecircuitmounting,
A mechanical
is shownin Figure2.
Youcan
to the powersupplyvoltage.
Relaycoilvoltageis chosenaccording
or,forheavyloads,a
usea miniDPDT1AMiniRelay(RadioShack275'249)
relays
are ratedlo 12
10AminiSPDTrelay(RadioShack275-248).These
is about320 ohms).As
VDCand drainonly38 mA (theircoil resistance
typescanbe used,youshouldtakecarewithterminallayout.
equivalent
wiredbetween
switch(Push-On)
Resetcanbemadewitha momentary-typ6
theSCRanodeandcatode,or by usingtheon-otfswitch.
suchas the SCRanddiode,shouldbe
components,
of polarized
Positions
occurswhen
::t::r":tairs areatsosivenin Fisurc2.Noricethatoperation
any
barewiretouchesthe ringduring movement.
thevertical(orhorizontal)
2l
fl0l0c|| Penilulumlhrm
(sEETEXT)
X1
R1
scR
Ttc106
Figure I
Figure 2
'B
m'lrfrctstrhrhuffim
PartsList - PendulumAlarm
Rectifier
Silicon
Gontrolled
SCR -TlC106or equivalent
D1
- 1N914or equivalent
general-purpose
silicondiode
K1
- 12Vrelay(seetext)
S1
- SPSTslideor toggleswitch
Rl
- 22,OOO
resistor
ohm,114W,5%
R2
- 10,000ohm,114W,5%
resistor
X1
- Pendulum
sensor(seetext)
ldeasto Explore
Tolearnmoreaboutcircuitanddevices:
lamp.Doesthe
o Replacerelaywitha 12Yx 200mAincandescent
circuitwork?
if therelayis
o Explain
whatDl is doinginthiscircuit.ls it necessary
lamp?
replaced
byan incandescent
o Explainhowan SCRworks
usesforthiscircuit:
andditferent
Scienceprojects
o ReplaceX1 by a reedswitchto get an alarmtriggeredby a magor otherkindof
X1bf a microswitch
neticsensor.You
canalsoreplace
switch.
momentary
o In biological
the alarmcan be usedto detectsmall
experiments
in animaltrapsor cages.
movements
t0
Frfhct | ?oildumllrrm
o ReplacingXl by two metalwiresenablesthe circuitto be triggered
by water.Waterleveldetectorscan be madeusingthis kindof sensor,
and it can be usedin manyexperiments
and practicalapplications.
o lnstalledin yourcar,thiscircuitcanbe usedas an alarm,drivingthe
hornor a siren.
o By replacingX1 witha largemetalplate,the circuitcan be usedto
detectwind.Air flowcan movethe plateso thatthe barewiretouching
the loopcausesthe alarmto trigger.
runPnFctlollhEnul
(P)
RF PRESELECTOR
MEDIUM-WAVE
is poorinthemediumAMreceivers
of mostmoderately-priced
Thesensivity
alsodropsotfsharplywithintheupperpart
waveband.worseyet,selectivity
to images,noiseand
highlysusceptible
or tn" band,makingine receiv-er
heterodYnes.
annoying
can'tmakeupforthese
Eventhebestantennaanda goodboosteramplifier
in a commonreceive/sfrontend.But,usingan RFpreselector
deficiencies
willgiveyou
antennainputterminals
andthereceiver's
b;trd; theantenna
quality.
in the reception
realincrease
input
antenna
withthereceive/s
impedance
theantenna
Thiscircuitmatches
of thetunedstation'
thefrequency
according
Preselector'
diagramof the Medium-wave
Figure I showsschematic
viewof the circuit,whichcan be housedin a
Figure2 showsan exploded
smallplasticbox.
ferrite
wire,woundon a 5/16-inch
Ll is formedbyturnsof No.28enameled
The
form.Tapsaremadeeach15 or 20 turnsandits numberis notcritical'
numberof taPscanbe altered.
preselector'
Attachyourantennaand groundto the inputterminalsof the
thebest.posiand,bychoosing
Tuneto thedesiredstationonyourreceiver,
bestsignal'
the
find
CV
clipon theitrip anObyadjusting
tionof thealligator
antennawilldependuponthestationyouwantto tune'A ranTherequired
throughthe A{ band'
domlengthof wiie will giveiairlygoodperformance
for best
ts ano150feetarerecommended
withlengthsb-etween
Antennas
performance.
-
tf
Filf0cr5 tdhmtmtrlffiffir
A
To Receiver
G
Figure I
Figure2
{
el
g l
r
HrfilFcNrtrffisuhM
_
-
-
-
-
!
RF Preselector
PartsList - Medium-Wave
L1
- Medium-Wave
Coil - see text
CV
- 365 pF miniaturevariablecapacitor
X1
- Alligatorclip
- 2-positionbarrierstriP
ldeasto ExPlore
Tolearnmoreaboutthecircuitanddevices:
inthiscircuit.
of a goodgroundconnection
o Explain
theimportance
"impedance"?
of
Whatis the meaning
o Usea newcoilwith20 turnsandtapsevery3 turnsto tuneshortwavestations.
o Makea seoondcoil(20turns)on the sameferriterodto plugthe
antennaandground.
ftnFillectiffimmlhleilcr
LURE (P)
FISHING
ELECTRONIC
to attract
thesoundof wetbugsmillingaboutthesurface
Thiscircuitimitates
fish.
curious
in a frequency
operating
The circuitis basicallya Hartleyaudiooscillator
byanAAcell,it canhousedina clean
200and2,006Hertz.Powered
between
onthe
emptypeanutbutterjarwiththe buzzercircuitrymountedupside-down
.ofti.Vou mustbe carefullnotto drillin sucha wayasto allowwaterto leak
tnrougnthecap.siliconrubbercanbe usedto closeanywaterleak'
1,000Hz'but
approximately
CapacitorClwouldgivea resonantfrequencyof
in theaudiorange'
p1 wouldgivea wid6variation
in signaltonegenerated
it to
connecting
asa transducer,
earphone
Youcanalsousea low-impedance
the secondcoil(output)of thetransformer'
thecap,throwS1ON,putthecoverbackon,anddrop
unscrew
Tooperate,
20
thefishlureintothewaterintnevicinityof whereyouwillbefishing'Allow
tone'
adiustP1to a newsignal
minutesbeforereelingthemin.lf necessary,
diagral for the FishLure.observethatthe
Figure I showsthe schematic
is notusedin thiscircuit.
coilof thesmallaudiotransformer
se-condary
FishingLure,usinga terminalstripas
detailsof the Electronic
construction
is not
chassis,is shownin Figute 2. The exactlocationsof components
critical.
withcentertransformer
Any500:8or 1,000:8transistor
T1 isalsonotcritical.
tappedprimarycanbe used.we canalsosuggestthatanysmalltransistor
with'
canbe experimented
transformer
EO
Pnm 0 $oe[cnhHshlnf
lun
S1
1.5V
(') SEETEXT
R1
1K
Figure 1
!
Figure 2
It
Fr}Idccufor[nHrcilmEmGl
PartsList- ElectronicFishingLure
Q1
- 8C548 general-purpose
NPNsilicontransistor
T1
P1
- 500:8or 1,000:8transistor
transformer
(RadioShack2TS-1380
is suitablefor thistask)
- 100,000ohm trimmerpotentiometer
R1
- 1,000ohm,114W,5%
resistor
C1
- 0.01uF metalfilmor ceramiccapacitor
S1
- SPSTtoggleor slideswitch
BZ
- Piezoelectric
transduceror crystalearphone
(RadioShack273-073
or equivalent)
- 1.5V AA cell
81
ldeasto Explore
To learnmoreaboutthe circuit:
o ReplaceBZbya low-impedance
tweeteror smallloudspeaker
connectedto the transformersecondarycoil.
o ChangeC1 valuesin the rangebetween0.001and0.22 uF.Observewhat hapenswith tone pitch.A higher-value
capacitorgivesa
lowertone.
o The circuitalso operatesfrom a 3V or 6V powersupplywithout
makinganychanges.
ft
Plolocl6 HGGtorlcHrillululc
Scienceand ditferentusesfor the device:
o Youcanmakeseveralexperiments
in animalconditioning,
including
the onesthat livein the water.Tryto alterthe RC network(P1,R1 and
Cl) to get tonesof ditferentpitch.Tryto usediodes,smalltransformer
coils and other passivecomponentsin this experiment.Soundslike
thoseproducedbysongbirdscanbe generatedwitha fewcomponents
arrangedin the correctway.Can you discoverhow to do it?
o Removethe piezoelectric
transducerandwireelectrodesin itsplace.
The devicecan be useas a nervstimulator.
Experiments
withanimals
and plantscan be made.What physiological
functionsare atfected?
Can circadianrhytmsor internalbiologicalclocksbe atfectedby continuousexposureto sounds?
o Electrodesplacedintowaterand wiredin placeof the transducer
will producea currentfield.Youcan pedorminteresting
scientificwork
relatinghowfishandotherWaterbeingsreactto the currentfield.Can
the currentfieldsaffectphysiological
functions?lf you experiment
with
plants,selecta fast growinghouseplant.
80
ftn rdccEhr[tcHnilmms
AM RECEIVER(RE)
FREE-POWER
"extracted"
This projectusesa strangewayto get lts power.lt usespower
Witha reasonably
transistor.
fromthe tunedstationto giveto the amplifier
produces
a strong
type
of
detector
this
envelope,
strongappliedmodulation
output.
demodulated
thecloseryouareto a strongstation,the morecurrentyourradio
Naturally,
willbeableto supply.
possible
to delivera strongsignalto
youmustdoeverything
Forbestresults,
good
antennaandground,the lata
Werecommend
detector.
thetransistor
groundcomposed
beingmadeto a waterpipeor solidexternal
ter preferably
forensuring
of a pipedrivenat least5 feetintomoistearth.Thisis important
pickup.
signal
maximum
I
thelongertheantenna(upto about100
lf youhaveplentyof spaceavailable,
feet),thebetterthe results.
ObAM receiver.
diagramof the Free-Power
thatworksas a
transistor
servethatthe heartof the circuitis a germanium
andaudioamplifier.
detector
placement
on a terminalstripusedas a chassisis shownin
Gomponents
boardthatcanbe
Figurc2.Theterminalstripcanbefixedonan experiment
materials.
and
tools
usingsomecommon
constructed
canfindgermasuchasGE-2or2N107.You
transistor,
Ql is anygermanium
Nonworking
radioreceivers.
AMtransistor
inoldnonworking
niumtransistors
(ferrite
andthe loopstick
AM radioscan alsosupplythe variablecapacitor
rod).
earphones
Low-impedance
crystaltype.
mustbea high-impedance
Earphone
don'tfunctionin thiscircuit.
_
Pnffi r Foailrmlilrsrffi
Figure I
s-4^o
Figurc 2
t8
r
frn?nfffihrucmlffi
--
PartsList - Free-PowerAM Receiver
Q1
- seetext
- NPNor PNPgermanium
transistor
XTAL - CrystalearPhone
L1
- seetext
- LooPstick
CV
- 365pFvariablecapacitor- seetext
Rl
- 12,000
resistor
ohm,114W,57"
C1
- 1 uF,25WVDCelectrolytic
capacitor
ldeasto ExPlore
Tolearnmoreaboutthecircuit:
o ReplaceLl by 15turnsof No.28 wire,woundon a ferriterod,to
stations.
tuneshort'wave
R1andC1
diodeandremoving
o Byreplacing
Ql witha germanium
thisradiointoa simplecrystalset'
you'litransform
4,7}Oand47,000ohmsto getbetter
o AlterR1in a rangebetween
used'
on thetransistor
performance,
depending
witha silicontype,suchasthe8C548'What
o Replace
thetransistor
withsensivitY?
willhaPPen
uses:
thecircuitand,uncommon
scienceprojectinvolving
lf you
andtellaboutradiohistory.
o Explainhowcrystalsetsfunction
in moreradiohistoryseveraltextscanbe foundin the
areinterested
publiclibrarY.
tryto findinformao lf youwantto learnmoreaboutradioreceivers,
types'
andsuper-hereterodyne
tionaboutheterodyne
-
tl
HEFfdffiffnrffilmrbl
FLASHER(E,P)
DUAL-LED
witha 4093CMOSlG,to producea
oscillator,
Thiscircuitusesa one-gate
flasherin two LEDsor a bi-colorLED.The circuitcan be
50%duty-cycle
powered
bya 3 to 12-voltpowersupplyandis usefulin severalexperiments
canuseit as partof alarms,warningsystems,
applications.You
andpractical
here'
as wewilldescribe
games,toys,andsomescientific
experiments,
to the
R2andR3valuesdependuponthe powersupplyvoltage,according
table:
following
Power Supply
R2, R3
3 Volts
220 ohms
5 Volts
330 ohms
6 Volts
470 ohms
9 Volts
820 ohms
12Volts
1,000ohms
outputstagedrivingincandesFormoreoutputyoucanusea transistorized
to observelightetfectson animalsandplantscan
centlamps.Experiments
withthiscircuit.
beconducted
flashrate.Flashratecan be adiustedby P1,butCl
Pl andC1 determine
to the application
alsocanbe alteredin a largerangeof values,according
youintendforthedevice.
Flasheris shownin Figure1.Onegate
fortheDual-Led
diagram
Schematic
andtheothertwoareusedas inverters.
of a 4093lC is usedas oscillator
placement
on a PC boardis shownin Figure2.Youcanalso
Components
circuit.
boardto mountit as an experimental
or solderless
usea breadboard
pieces,suchas LEDs,eletrolytics
andlC,shouldbe
Position
ofthepolarized
observed.
tf
trmAl ld.|nm*ol
,,
P1
tM
R1
100K
---t,
I
I
z ' i
-,- . \ \-_
,
cl
l
1pF
LEDl
(.) SEETEXT
Figure 1
t{
3 E
+3a
12V
ov
c1
nDr
Figure2
ft
lol thcDttrcfimcntot
IunPlolects
PartsList- Dual-LedFlasher
lC1
- 40938CMOSintegrated
circuit
LED1 - bi-coloror redand greencommonLEDs
(RadioShack276-012l
resistor
ohm,114W,5%
R1 - 100,000
R2,3 - resistoraccordingto powersupplyvoltage- see text
P1
- 1,000,000
ohm potentiometer
C1
- 1 uF,25 WVDCelectrolytic
capacitor
ldeasto Explore
To learnmoreaboutthe circuitand devices:
o ReplaceC1 with capacitorsin the rangebetween1 and 47 uF.
Observehow highervaluesalterthe flashrate.
No changein the
o InfraredLEDscanbe usedin someexperiments.
originalcircuitis necessary.
Scienceanddifferentusesfor the circuit:
o RemoveP1 and R1 and wireat this ponta touchsensoror elecdevice
trodes.Youcan controlthe flashrateby touch.A bio-feedback
can be madethis waY.
o By wiringthe lC"spin 1 to an externalcircuit,the flashercan be
controlledby a logiclevel.CMOScircuitscan be usedto controlthe
flasher.
il
,
, Pnml mu+nnmr
o Mount
theLEDs
inplace
ofthelenses
o,".ffi
flashratecanbeadjusted
to makean hypnotic
or relaxingLtfect.
Combinethiswitha touchsensorandyouhavean uncommon
bio-feedbackdevice.You
canalsousethiscircuitto makeexperiments
incircadianrhythmsor internalbiological
clocks,determining
howtheycan
bealteredbylightpulses.
Various
theorieshavebeenproposed
about
thissubject.
. Psychiatrists
are usingphototherapy
to helpsomepatients.
can
youfindsomeapplication
forthecircuitin thisfield?
. Pl alsocanbe replaced
byresistive
transducers,
suchas LDRsor
NTCs,to givea light-or temperature-dependent
flash-rate
circuit.Experiments
canbe madewithconductivity
of materials
by connecting
pl withtheprobesin thiscase.
probesin serieswithR1.Replace
g l
IunProfccts
forstGIrDcIlmGntGl
6V X 1A POWERSUPPLY(P)
youwillneed
In orderto performexperiments
andprojectsinvolvingelectricity
a sourceof voltage.Voltagerequirements
for commonprojects,suchas the
onesin thisbook,dependupontheirapplications,
and typicallyrangefroma
few milliamperes
to one or two amperes.
lnsteadof usinga batteryyou can use a circuitcalleda powersupply.
The powersupplywe showherecan be usedto provide6V x 1A regulated
outputto the experimental
and practicalcircuitsdescribedin this book.The
outputvoltageis fixedby the lC.
Figure l showsthe schematicdiagramfor this powersupply.lOl is a voltage
regufator,
#7806. The "06"indicatesthat it is a 6-voltregulator.
Figure2 showsthe componentslayout,usinga terminalstripas chassis.
The completeprojectcan be assembledin a smallplasticbox.The integrated
circuitshouldbe mountedon a heatsink.
Youcan alsoadd an LEDin series
with a 470 ohm resistor,wiredin the outputof the circuitto indicatethat it is
on.
Externalcircuitscan be connectedto the powersupplywith alligatorclips.
Positionof the polarizedpieces,suchas diodes,the lC, and electrolyticcapacitors,mustbe observed.
Thetransformer
isn'ta criticalpartof this project.Typeswitha secondarycoil
rangingfrom7.5 to 12 voltsand currentsbetween500 mA and 14 can be
used.
5f
trolrctg 8ur ll Pil0tsuillr
c2
D2
1N4002
T1
12 + 'l2Y
1A
c1
tl_
100pFT
I
I
=
lou
1000pF
Figure I
2
Fiaure
t
55
mFrtmctrtrtrHilffi
PartsList - 6-VoltPowerSupply
lOl
- 7806positive
three-terminal
regulator
T1
- Transformer:
primary117VAC; seconda
x 1A
ry 12+12Y
D1,2 - 50Vx 1A- 1N4002
or equivalent
siliconrectifier
diodes
C1
- 1,000uF,25WVDCelectrolytic
capacitor
C2
- 10uF,12WVDCelectrolytic
capacitor
S1
- SPSTswitch
ldeasto Explore
Tolearnmoreaboutthecircuitor altertheperformance:
o ReplacelC1bya 7805,7809or 7812if youwanta 5V 9Vor 12V
powersupply.Youmayalso haveto changethe transformer
with a
117:15+1
5V usinga7812.
.
Explainhowthecircuitworks.
o Whatis theditference
betweenan ACanda DCcurrent?
Scienceanduncommon
applications:
o Thispowersupplycanbe usedin chemical
experiments,
suchas
the onesthatinvolvecurrentflowthroughsubstances.
Experiments
involving
electrolysis
andelectroplating
aretwothatcanbesuggested.
potentiometer
(100ohms,5 watts)shouldbe
A variablewound-wire
wiredinserieswiththepowersupplyoutputto limitcurrent
flowthrough
theload.You
canalsousetheLightDimmerdescribed
inthisbookfor
thistask.
!a
Plrflct g 0ur lt Pilil $utilr
by this
lampscan be supported
o 6V 200 mA smallincandescent
with
work
to
light
sources
powersupply.
lamps
are
excellent
These
microscopes.
physics,
mechaninvolving
o Smallmotorsandlampsinexperiments
power
powered
with
advansupply
from
this
be
robotics
can
icsand
tages.Youdon'thaveto spenda lotof moneyon cellsor batteries.
o Allcircuitsdescribed
inthisbookwhichrequirea 6Vsupplycanbe
powered
bythispowersupply.
poweradapterforyoui6V
o Thecircuitcanbe usedas an excellent
etc.
suchas smallradios,calculators,
equipment,
plantgrowth.Seinvolving
o 6V lampscanbe usedin experiments
box
or cardboard
lecta fastgrowinghouseplantanduse.adarkroom
in
an
experiment
be
used
filters
can
with
Lamps
colored
to coverthem.
growthanddevelopment.
involving
o Circadian
rhythmscan alsobe studiedusinganimalsor plants.
on at nightandotfat day.Whatphysiological
Lampscanbe powered
couldbe atfected?
functions
5t
mFilncNsfffirHrufinrm
rNsEcTREPELLENT
(P)
Somecontinuous
soundscanrepelinsects(andalsoattract).
Thefrequency
andintensitydependsuponthe application
andtypeof insectandcan be
foundthroughexperimentation.
Thecircuitshownheregenerates
a continuous
soundthatcan be usedto
repel(orattract)sometypesof insects,
or in scientific
experiments
involving
animals.
Ourinsectrepellent
canbe powered
by9Vbatteries,
twoM cellsor fourAA
cells,andits lowcurrentrequirements
will extendthe lifeof thosecellsor
batteries.
FigureI showstheschematic
diagramof the lnsectRepellent.
Theheartof
thecircuitis a 7555lC,a CMOStimerwiredasanaudiooscillator
anddriving
piezoelectric
a
transducer.
placement
Thecomponents
printed-circuit
ona homemade
boardis shownin
Figure2. Exactplacement
is notthatcritical.
Allthecomponents
andthepowersupplycanbehoused
ina smallplasticbox.
Transducer
BZis a crystalearpiece
or a piezoelectric
transducer,
suchasthe
RadioShack273-073.
pieces,suchas c2 andthe powersupply,mustbe
Position
of the polarized
carefully
observed.
Usingthe insectrepellent
is veryeasy.Youonlyneedto adjustthe trimmer
potentiometer
P1to producea soundwiththesamepitchas the insectyou
intendto repel.Experimentation
shouldbemadeuntilyoufindthebestsound
to repela specificinsect.
60
E led l0 In$octidhm
R2
4K7
cl
0.047p.F
Figure 1
Figure2
01
ftrF||f|Gilthlhsuh!|m
PartsList - InsectRepellent
R1
- TLC7555
CMOSintegrated-circuit
timer
- Crystalor piezoelectric
transducer
RadioShack273-073
or equivalent
- 10,000ohm,114W,5%
resistor
R2
- 4,700ohm,114W,5%
resistor
P1
- 100,000ohmtrimmerpotentiometer
c1
c2
capacitor
S1
- SPSTslideor tdggleswitch
B1
- 3V (2 AA cells),6V (4 M cells),9V (battery)
c1
BZ
ldeasto Explore
Tolearnmoreaboutthecircuitor getbetterperformance:
. Powerful
outputcanbeobtained
witha transistorized
outputstage
as shownin Figure3.Thepowertransistor
shouldbe mounted
on a
heatsink.The
transducer
isa low-impedance
loudspeaker
r:anging
from
4 to 8 ohms.
o Experiments
withultrasound
cahbe madewiththiscircuit:reduce
Cl to 1200pFandusea piezoelectric
tweeterastransducer.
Remove
thesmalltransformer
usedin thesetweeters
andplugthetransducer
directlyto thecircuitoutput.outputsin frequencies
as highas40,000
Hzcanbe produced
bythiscircuit.
o Explainhowsoundscan be produced
by electronic
transducers
suchas theoneusedin thisproject.
?nhd l0 InrstirDdhnt
o Whatareultrasounds?
applications:
andditferent
Science
a Of course,you can testthe realetfectsof this deviceon several
canbeconducted
biological
experiment
An attractive
kindsof insects.
basedon thiscircuit.
o Etfectsof soundson plantgrowthor development
can be conalterthecircaductedusingthiscircuit.Cansounds(qrultrasounds)
of plantsandinsects?
dianrhythms
o Thecontinuous
toneproduced
bythiscircuitcanbeusedinalarms
by
Miceandothersmallanimalsare repelled
or warningsystems.
powerful
ultrasounds.
o Replace
a light-dependent
circuitnowbecomes
R2byanLDR.The
withlightandsoundscannowbe conducted
Experiments
oscillator.
usingthedevice.
6 to 12V
Figure3
08
HnPnlmts||]mHlo|lmeml
(E/P)
GENERATOR
ULTRASONIC
upto
Dogs,mice,batsandotheranimalscanhearsoundswithfrequencies
Hz.Thereareseveralkindsof insectsthatcanalsohearor reactto
4O,O0O
sound
thesesounds.The circuitwe proposehereproducesa continuous
abovethe humanlimit,or a rangebetween18,000
in frequencies
emission
andcan be usedin
and40,000Hz.Thesesoundsare calledultrasounds
applications.
andpractical
severalexperimental
in
herecanbeusedto scaredogsandotheranimals,
Thedevicewedescribe
applications.
andmanyotherinteresting
experiments,
biological
outputpower
piezoelectric
hasits maximum
transducer
Therecommended
between700 and 3,000Hz, but it alsowill operateat higherfrequencies
emittinglesspower.
powersupplyis fourM cellsor a 9-voltbattery.
Therecommended
18,000and40,000Hz,butyoucan
approximately
Ourprojectrunsbetween
C1,in a rangebetween470pFand0.001
easilyalterthisrangebychanging
by C1.
canbe setby P1in the rangedetermined
uF. Frequency
upto 500kHz.
in frequencies
thatthe40938lC willoscillate
Remember
usingthe fourgatesof a
Generator,
circuitof the Ultrasonic
Thecomplete
circuit,is shownin Figute 1.
40938integrated
placement
boardis shownin Figurc2.
on a printed-circuit
Components
willbe
Thecircuitcanbe housedin a smallplasticboxandthe transducer
fixedin thefrontpanel.
Takecarewiththe positionof the polarizedparts,suchas the transistor,
andpowersupply.
capacitor
electrolytic
on a heatsink'
operation,
Q1 shouldbe mounted
Forcontinuous
coil
witha secondary
is nota criticalpart.Anytransformer
Thetransformer
from100to 500mAcanbe usedin thisproject.
ranging
-
00
F.lect ll uftmmlcecmntu
Figure I
Figure2
0t
HiFrrN.Gt3ffimmdlmrfit]
PartsList - UltrasonicGenerator
circuit
lC1 - 40938CMOSIntegrated
Tl
- 8D135medium-power
- Piezoelectric
transducer
RadioShack273-090or equivalent
- Transformer:
primary117VAC;secondary
6Vx100mA
R1
- 10,000
resistor
ohm,114W,5%
R2
- 1,000ohm,114W,5%
resistor
Pl
- 100,000
ohmtrimmerpotentiometer
C1
- 4,700pF ceramicor metalfilmcapacitor
C2
- 100uF,12\M/DCelectrolytic
capacitor
S1
81
- 6V or 9V - AA cellsor battery- seetext
Ql
BZ
ldeasto Explore
Tolearnmoreaboutthecircuitor to getbetterperformance:
o Youcanreplacethepiezoelectric
transducer
bya commontweeter.
T1 andBZandplacethetweeterbetween51 andQl's colRemove
power?
lector.Canyoumeasurethe generated
ultrasound
. Thecircuitcanalsogenerate
soundin theaudiblerange.Replace
in therangebetween
0.02and0.1uF.
Cl bya capacitor
o Explain
transultrasounds
andhowtheyareproduced
byelectronic
ducers.
0l
P'rhct tt Uhffuh8emn0r
o Whatis a piezoelectric
material?
Scienceandditferent
applications:
o Severalexperiments
canbe madeusingultrasounds.
Youcanexperiment
withdogconditioning.
youcancalla dog
Usingthisoscillator
usingan inaudible
sound!(inaudible
to humans)
o Ghoose
a capacitor
between
0.01and0.047uFto produce
sounds
bothin the audiorangeandultrasound
range.Youcan nowconduct
experiments
to determine
the exactupper-limit
frequencyheardby
humans.You
alsocanconductexperiments
withanimals.
lt willbe importantto havea frequency
counteron handto do thiswork.
o ReplaceBZbyelectrodes.
Thecircuitwillgenerate
a high-voltage
outputthatcanbeusedin nervestimulation.
Usea 10,000ohmpotentiometer
to adjustoutputvoltageat thispoint.Pulsescanreachpeaks
as highas 400volts.
o To get pulses(fornervestimulation
you
and otherexperiments)
onlyhaveto replace
C1witha 1 uFcapacitor
andP1witha 1,000,000
ohmpotentiometer.
Pulsesin the raterangebetween
0.1persecond
per
to 10 secondcanbe generated
withthischange.
o Thiscircuitcanalsobeusedasa fluorescent
lampinverter.
A commonfluorescent
lamp(4 to 20 wafts)in placeof the transducer
will
glow,evenonethatis weakenoughto notfunctionon theAC power
line.
00
Hr PnhG[slorl[c
milmmt
DC LAMPDIMMER(E,P)
Thiscircuitcanbe usedto controltheamountof currentin an incandescent
lamp andalsoa DC motor.lf youchangethe amountof currentthrougha
And if youchangethe amountof current
lampyou changeits brightness.
througha DCmotoryouchangeitsspeed.lnputvoltagecanrangefrom6 to
12 voltsandcurrentdrainin the outputis up to 2A.Youcan alsousethis
it intoa
circuitin the outputof a 6V or 12Vfixedpowersupply,converting
variable
0 to 6 voltor 0 to 12voltsupply.
Thecircuitcan be
shouldbe mountedon a heatsink.
Thepowertransistor
fixedon the
withthetransistor
housedina smallplasticboxandtheheatsink
outside.
of a car'spanellampsandin
Thecircuitcanbe usedto controlbrightness
to controlDCmotorspeedalonga widerangeof values.Also,sevrobotics
usingthis
currentflowcontrolcan be performed
involving
eralexperiments
circuit.
current
Thecircuitactsas a variableresistoror rheostatwiththe principal
pothe
through
flowing
control
current
andthe
flowingthroughthetransistor
is onlya fewmilliamperes.
Currentthroughthepotentiometer
tentiometer.
diagramof the DC dimmeris shownin Figurc t. Ql is an
The schematic
usedin thisproject.
component
andtheprincipal
NPNpowertransistor
doesnot showon
layoutis shownin Figure2. Thetransistor
Components
the heatsink,however.
current
canbe used,buttakecarewiththe maximum
transistors
Equivalent
theycan control.Typessuchas TlP31andTlP41can be usedto control
in Rl valuemustbe
Also,a furthermodification
lampsup to 2 amperes.
value,thatcurrentis
madeto ensurethat,whenP1is set nearits minimum
flowingthroughthelamP.
as
areused,takecarewiththeirterminalpositions,
transistors
lf equivalent
theycanbe ditferent.
AD
Prrfoct12 DG
hmr Iilmmu
F1
5A
Q1
2N3055
+12V
IN
oul
I:
Figure I
Figure2
t3
Hr]||Fc0tffimDculmffir
PartsList - DCLampDimmer
Q1
- 2N3055 SiliconNPNpowertransistor
P1
- 4,700ohm potentiometer
R1
- 470ohm,2W,.5"/"resistor
F1
- 5A fuse
:
ldeasto Explore
o Youcan usea PNPpowertransistor,
inverting
inputpolarization.
ExplainwhythiscircuitcanonlycontrolDCcurrents.
o A Darlington
transistor
canbe usedto reducecurrentflowthrough
potentiometer.
Replace
P1witha 100,000
ohmcommonpotentithe
ometerand Rl witha 10,000ohm,1/4wattresistorwhenusinga
powertransistor.
TlPl10canbe usedin thiscase.
Darlington
o Whatis a rheostat?
applications:
Scienceanduncommon
o Youcan usethiscircuitto controlbrightness
light
of microscope
A 6V lampcanbe usedfor thattaskandthiscircuitwillbe
sources.
wiredbetweenthe lampand a 6V powersupply.The 6V regulated
powersupplydescribed
in thisbookis idealforthisapplication.
o Experiments
in electrolysis
canbe current-flow
andelectroplating
controlled
by usingthiscircuit.
a Thiscircuitcan be usedto controlsmallmotorsin roboticsor in
physics
experiments.
tl
ffi|m n mllmDllmmei
o The amountof currentin currentfieldscan be controlledby using
this circuitand a DC powersupply.Experimentsinvolvingelectrotropismcan be attempted.
Try to put plantswithina coil to observethe
influenceof the magneticfield on theirgrowthand development.
Rememberthat there is a magneticfield arounda coil of wire that is
carryinga current.
Figure3 showshowthis experimentcan be arranged.
The coil is formedby 10 to 50 turnsof commonNo.1I to 22wirearounda
cardboardboxor woodform.An ammeterin serieswiththe coilcircuitcan be
usedto controlthe amountof currentusedin the experiment.
Rememberthat too much currentwill causethe coil and the transistorto
overheat.lt is a good ideato add a lampin serieswith the coil circuit.The
lampwill add resistanceto the coil circuit,reducingcurrentflow to a safe
level.
Figure 3
t5
IunPiilcctsfuh scilmmu
(E)
AUDrOOSCILLATOR
audiblesignalsin the
oscillator
can generate
Thislow-power
experimental
loudspeaker
or a low-ima
small
2,000
Hz,
driving
100
and
rangebetween
by2 twoor fourAAcellsor a
pedance
Thecircuitcanbe powered
earphone.
forthiscircuitdependupon
Currentrequirements
fixed6 voltpowersupply.
impedance
and rangetypithe powersupplyvoltageandthe loudspeaker
callyfrom10to 300mA.
frequency
andcan be set withina
P1 adjuststhe operating
Potentiometer
ohmscan be used,
up to 1,000,000
largerangeof values.Potentiometers
rangelowerlimitto about10Hz.
thefrequency
changing
for
0.01andO.22uFaresuitable
andvaluesbetween
C1canalsobealtered,
in thelowerpart
frequencies
LargeC1valueswillproduce
experimentation.
of therange.
Thecircuitcan be usedas partof alarms,games,toysandto learnmore
oscillators.
abouttransistorized
Q1 andQ2
diagramof the Audio-Oscillator.
FigureI showsthe schematic
amplifier
andRl/Cl is theclosedloopthattakesthe
forma directed-coupled
signalbackfromtheoutputto theinput.
,
.
usinga terminalstripaschasthelayoutofthecomponents,
Figure2shows
andpowersupplycanbe housedin a smallplastic
sis.All the components
box.
homemade-type
switch,butyoucanalsouseanSPST
Thekeyis atelegraph
if you
A keyis recommended
operation.
toggleor slideswitchforcontinuous
pracor
in
demonstrations
Morse
sender
asa
Code
wantto usetheoscillator
tice.Youcanwirethe pointsA and B to the contactsof a relayto usethe
circuitas partof an alarm.
tt
Pf.lcctl8 ftllrosoilrt|l
cl
0.047pF
B1
3TO6V
Figure I
k-\
Figure2
t0
mFmf0cilsffmHrulmdu
:
PartsList - AudioOscillator
Q1
- 8C548generalpurposeNPNtransistor
Q2
- 8C558generalpurposePNPtransistor
SPKR- 4 or 8 ohmsmallloudspeaker
K
- Telegraphic
key- Seetext
81
- 3 to 6 volts- twoor fourAAcells
Ri
- 10,000
ohm,114w,5%
resistor
R2
- 1,000ohm,114W,5%
resistor
Cl
ldeasto Explore
o ChangeC1fora capacitor
in therangebetween
0.01and0.22uF.
Thefrequency
rangeof the produced
tonewillbe altered.
With0.01
uF or lowervaluesfor Cl, the circuitwillproduceultrasounds.
Usea
tweeteror a piezoelectric
transducer
in thiscase.
. Replace
Q1witha TlP32orTlP42andpoqerthecircuitwitha 12
getmuchmorepowerin theoutput.
voltsupply.You'll
.
Explainwhyoscillators
needa closedloopto the signalto work.
Scienceprojects
andotherapplications:
o Experiments
in acoustics
canbemadewiththisdevice.
Thecircuit
canproduceanytonebetween10and20,000Hz,andevenhigher.
tt
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o A telegraph
stationcanbe simulated
withthiscircuit.
Youcanfind
MorseCodein anybookabouttelegraphy.
o Byreplacing
K witha reedswichwiredto pointsA andB,thecircuit
willoperateas an alarm.
o Experiments
involving
conductivity
of materials
canbe madewith
probesplugged
to pointsA andB.
o Connectresistive
transducers
as LDRsandNTCsat pointsA and
B to geta light-dependent
or temperature-dependent
oscillator.
a Usingtwo metalrodsas sensors,
the circuitcan be useas a lie
detectoror bio-feedback
device.ReplaceCl witha 0.22or 0.47uF
pulsesat the speaker.
capacitor
andadjustPl to getseparated
The
pulseratewillbealteredwhentheskinconductivity
oftheinterrogated
personchanges
whilein a stateof straindueto a lieor stress.
o A 117V+V x 250mAtransformer
canreplaceSPKRto produce
pulses
high-voltage
in nervestimulation
Thegenerated
experiments.
pulsescanreachvoltages
as highas 400Vpp.
o Experiments
in animalphysiology
canbeconducted
usingsounds
projects.
or highvoltageas described
in other
Growthof plantssubmittedto high-power
soundsor high-voltage
fieldscan be observed
usingthiscircuitwithpractical
experiments.
o ACfieldscanbegenerated
byreplacing
thespeaker
witha 2O-turn
coil.Theplantsor animalscanbe positioned
withinthecoil'selectric
field.Seethesameexperiment
usingthe DCDimmerforcoilandexperiment
details.
tl
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AUDIOSWTTCH(E/P)
Thisaudiocontrolled
relayhasa largenumberof applications
andis interestingto theexperimenter
whowishesto explore
theworkinguniverse
of relays
andaudioor soundcontrolled
circuits.
Anaudiosignalintheamplitude
rangebetween
1Vppand5 Vpptriggersthe
pointsA andB.
relay,powering
on thedevice,wiredbetween
Relayvalueis determined
bypowersupplyvoltage.
Fora 12voltpowersupplyyoumustusea 12voltrelay.Gurrent
draindepends
uponthepowersupplyvoltageandalsotherelayused.Usinga12Yx 38 mA(RadioShack275248'1relay,
thecurrentdrainis lowenoughto allowtheuseof common
cellsin
the powersupply.
0.01and1.0uF,anddetermines
thesensitivity
of the
Cl canrangebetween
at lowfrequencircuitin theaudiorange.Largevaluesgivemoresensitivity
cies.
inputandneedsa strongaudiosignalto
Thiscircuithasa high-impedance
operate.
diagram
oftheAudioSwitch.
thatthe
Observe
heartof thecircuitis a commongeneral-purpose
NPNtransistor
thatactsas
a DCamplifier.
forthisproject.
Thecomponents
ln Figure2we showlayoutof components
canbesoldered
ona terminal
stripusedaschassis.The
terminal
stripcanbe
flxedon a woodenboard.
Position
of thepolarized
components,
suchasthediodes,powersupplyand
capacitor
C2,mustbe observed.
To usethisaudiorelayyou haveto wirepontsA andB to the outputof an
powerrequiredis 5 watts)andadjustthevolume
(minimum
audioamplifier
controlfor bestoperation.
A smalltransistor
therelaywith
outputtransformer
shouldbeusedto operate
low-impedance
signals,
suchastheonesfromtheoutputof audioamplifiers.
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1N914
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TEXT
D1
R1
1N914 ,t0K
B1
6OR9V
Figure I
Figure2
05
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Figure3 showshowto usethistransformer.
R,dependsontheoutputpowerof theamplifier
andis givenbelow:
I
OutputPower
0 to 1 watt
1 to 10watts
47 ohms,1/4watt
10to 25 watts
100ohms,'ll4watI
25 to 50 watts
220ohms,ll2watt
PartsList - Audio Switch
t0
Q1
- 8C548general-purpose
D1
- 1N914general-purpose
silicondiode
D2
- 1N4002siliconrectifierdiode
Kl
- 6V or 12V relay- see text
R1
- 10,000ohm,1/4W,5%resistor
Cl
- metalfilm or ceramiccapacitor- see text
C2
capacitor
81
- 6V or 12Vcells,powersupplyor battery
;TrM lf rilm$nilH
ldeasto Explore
Tolearnmoreaboutthecircuitanddevicesor to getbetterperformance:
o ReplaceQl witha Darlington
(suchas a BCS17)and
transistor
resistorR1 with100,000
ohms.Thecircuitwillincrease
in sensitivity.
o ExplainhowC1functions
in thiscircuit.
Scienceanddifferent
applications:
o Connect
thecircuitto anaudioamplifier
output,witha mioophone
pluggedto theamplifier
input.You'll
havea sound-operated
switch.
o Thiscircuitwitha microphone
andan audioamplifier
canbe used
to closea trapwith soundactivationor to activatea recordingwith
sounds.
Youcan alsouse it to photograph
an explosion
or the crashof an
produced
objectbytriggering
a flashwiththe
sound.
o The audiooutputof a multimedia
systemin a computercan be
usedto controlexternal
deviceswiththiscircuit.
R;
FRoM
AM P L T F T E R
ourPUT
l-----+x
IIF
3lE
''l
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ro
AUDlos\
L._--_-{'Y
8: 1000
o
Figure3
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(P)
6 VOLTSFROM12V BATTERTES
Withthisadapteryoucan power6 volt(upto 1A)devices,suchas recorders,
CD players,calculators,radios,batterychargers,etc.,fromyourcar battery.
The currentadapteris pluggedinto the vehiclelightersocketand is small
enoughto be housedin a very compactplasticbox.
Only four componentsare used.The lC determinesthe outputvoltageand
shouldbe mountedon a heatsink.Capacitorsare polarizedcomponents,
so
you mustobservetheirpositionwhenmounting.The
fuseis veryimportantin
orderto protectthe deviceand car wiringagainstshorts.
Outputvariesaccordingto the deviceyou are applyingpowerto. DC extension cableswith plugsto fit the deviceto be poweredshouldbe used.Take
care with the outputpoles.Checkif your devicehas a positiveor negative
polein the centralterminal.
The schematicdiagramof the 12Vto 6V x 1Aconverteris shownin Figure 1.
The principalcomponentis lC1, a 6V voltageregulatorthat operateswith
inputvoltagesrangingfrom I to 35 volts.
Componentslayoutis shownin Figure 2. Allthe componentscan easilybe
housedin a plasticbox.
The integratedcircuitcan be changedto alterthe outputvoltage.You
can use
a 7809for 9V x 1A outputor a 7805for 5V x 1A output.
It is very importantthat no partsof the componentsusedin this circuittouch
one another.The lC has short-circuit
and thermalprotection.
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Figure 1
Figure2
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PartsList - 6 VoltsFrom12VBatteries
lC1
- 7806Integratedcircuit
C1
- 1,000uF,16 WVDCelectrolytic
capacitor
C2
capacitor
Fl
- 2A fuse
ldeasto Explore
Tolearnmoreaboutthedeviceor to getbetterperformance:
o Replace
theintegrated
circuit(lOl) witha 7805or 7809to getoutputvoltagesof 5Vand9V.
o Explaintheditference
between
thislinearvoltageregulator
anda
powersupplies.
switch-mode
regulator
usedin computer
o Thiscircuitcanalsobeusedin nonregulated
powersupplies
to get
a regulated
x
1A
6V
output.
o lt'spossible
powersupplyby replacing
to geta negative
regulated
the7806witha 7906lC.Doa searchforinformation
aboutthischange
in theproject.
Scienceprojects
anduncommon
uses:
a Youcan usethis downconverter
to powerfourAA cell-powered
circuitsfroma 12Vbatteryin scienceexperiments.
o 6V lampsusedas lightsourcefor microscopes
can be powered
fromthe car batteryusingthisdownconverter.
Fieldwork
usinga microscope
canbe conducted
usingthiscircuit.
t2
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(E)
TRANSMITTER
oNE-COMPONENT
by thosewithno patiencefor
Hereis a projectthatshouldbe constructed
wireis usedto builda complete
building.
Onlyonecomponent
electronics
lesstransmitter!
lt is a CW(conradiosignals.
wayto generate
Ofcourse,thisis thesimplest
and is powerfulenoughto plunkdowna signal
tlnuouswave)transmitter
on the550kHzto 7 MHzband.
anywhere
uponpowersupplyvoltageandis inthe
Thefundamental
frequency
depends
reaching
100kHzand1 MHz,buttherearestrongharmonics
rangebetween
upto 7 MHz.
Asyoucan
diagram
ofthissimpletramsmitter.
Figure/ showstheschematic
a 4049CMOSlC thatis formedby six
see,we haveonlyonecomponent:
areused.
ln thisprojectonlyfiveinverters
inverters.
fromAAcellsor batteryandcurrentdrainis verylow.
Thecircuitis powered
projectyoucan placethe lC on a universal
solderless
As an experimental
board.Theantennais a singlewire2 to 5 feetlong.
A commonAM (mediumwaveor shortwave)receiveris placednearthe
upto somefeetaway.
A signalcanbetunedin fromdistances
transmitter.
showninFigure2.
Therearetwowaysto tunethetransmitter,
wechangethepower
isvoltage-dependent,
Inthefirstcase,asthefrequency
Usea 12voltpowersupplyandadjustthevoltagein the lC
supplyvoltage.
in thefeedback
capacitor
withP1.Inthesecondcase,we includea variable
loopto alterthefrequency.
Transmitter
PartsList - One-Component
lC
- 4069or 4049CMOSintegratedcircuit(onlythis!)
(Anda powersupply,of course)
30
PnftGtl0 FGmnmil
Tnmillt0l
l*
lC1= 4O49B
1 oe
Figure I
Figure2
-
0t
n;||FdFilDgnntr
l&as to Erplore
Tolearnmoreaboutthe circuitanddwice:
o Explainhowradiosignalsaregenerated
andWhywedon'tneeda
tunedcircuit.
o Whyshouldan evennumberof gatesbe usedin thiscircuit?Will
an oddnumberwork?
o Whycanyoutuneinthesignalson morethanonepointof thedial?
Scienceprojects:
o Sendtelegraphsignalsthrougrh
a wallusingthiscircuitastransmitter andan AM radioas receiver.
o Explainhowcomputercircuitscangonerateradiosignals(noise),
usingthiscircuitas an example.
It
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WIRELESSFMTRANSMITTER(E/P)
Thesecircuitshavealwaysbeenpopularfor bothutilityandentertainment
purposes.
TheFMtransmitter
described
hereis builtwithfewcomponents
tosavespace
powered
andcost.Thecircuithasonlyonetransistor
is
and
bytwoorfourAA
cells.
The broadcasting
frequency
of the unit,in the rangebetween88 and 108
MHz(FMband),is determined
by Ll andthevariable
capacitor
CV (a 2Oor
L1consists
30 pFtrimmercapacitor).
of fourturnsof No.22wire,woundin a
singleclose-spaced
layeron a 112-inch
form.Thecoilis centertappedwhere
it is wiredto theantenna
terminal.
Anypieceof stitfwirewillserveas theantennaandwillgivegoodcoverage.
Forbetteroperation,
antennalengthshouldbe between
5 and15inches.
Tryoutyourunit at anyconvenient
deadspotonthetheFMband.AdjustCV
to thebestsignal.Thesignalscanbetunedin distances
upto 150feet.
A schematic
diagramof the FMtransmitter
is shownin Figure1.Onlyone
transistor
as usedas a high-frequency
oscillator.
AnysmallRFNPNtransistor canbe usedforthetask.
placement
Components
boardis shownin Figure2.Capacitorsare criticalcomponents
and shouldbe the typesindicatedin the
partslist.Don'tusemetalfilmcapacitors
insteadof the ceramiccapacitors
whicharecalledfor in thepartslist.
Youcanalsousea terminalstripas chassisas shownin Figure3,butkeep
allthecomponent
terminals
andwiringshortto avoidinstability.
Thecircuitcanbehousedin d smallplasticboxalongwiththepowersupply.
Avoidtheuseof metalboxesto housethecircuit.
pieces,suchas the electretmicroTakecarewithpositionof the polarized
phone,electrolytic
capacitor
andpowersupply.
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R2
10K
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Q1 \
8F494
R4
47
Figure 1
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Figure2
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PartsList - WirelessFMTransmitter
Q1
- 8F494RF silicontransistor
MIC - two-terminal
electretmicrophone
L1
- coil - see text
CV
- trimmercapacitor(20 to 50 pF)
R1,3 - 4,00ohm,114W,5%
resistor
R2
- 10,000ohm, 114W,5%
resistor
R4
- 47 ohm,1l4W,5%resistor
C1
capacitor
C2
- 0.01 uF ceramiccapacitor
Cg
- 4.7 pF ceramiccapacitor
C4
S1
81
- 3V or 6V - two or fourAA cells
A
- antenna- see text
ldeasto Explore
To learnmoreaboutthe circuitor to get betterperformance:
o ReplacetransistorQ1 with a2N2218and powerthe circuitfrom a
9V battery.The
signalswillbe tunedin fromdistancesup to 1,500feet.
o The circuitcan be usedas a "bug"to hearsecretconversations.
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Figure 3
Placethe circuitinsidea falsebook on a deskto pick up conversations.
o Explainhowthe transmitterworks.
o Whatare radiowavesor electromagnetic
waves?
o What is FrequencyModulation(FM) and AmplitudeModulation
(AM)?Explainthe ditferences.
IunPlolects
folu|elrrcr|memcl
Scienceprojectsusingthistransmitter:
o The transmittercan be usedto pickup remotesounds.Youcan fix
it in animalpensor jailsto monitorthemremotely.
o The mikecan be placedin the focusof a parabolicreflectorto
concentrate
sounds.Birdsandotheranimalsintheforestor otherplaces
can be heardusingthissystem,as suggestedin Figure4. An interestingstudycan be madeinvolving
localsongbirds.
o Youcan usethis transmitterfor an experimental
broadcastin your
schoof.However,don't use long antennas becauseFCC rules are
severeregarding strong illegal radio emissions in the FM band.
Figure 4
100
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HIGH-POWER
(E)
AUDIOOSCTLLATOR
Thishigh-power
produces
versionof anaudiooscillator
a strongaudible
tone
usinga piezoelectric
transducer.
All fourgatesexistingin the 4093lC are
usedin thisprojectto drivethetransducer
witha goodaudiosignal.
The circuitcan be usedin alarms,toys,as a standalone
projectto teach
aboutoscillators
specifically,
or in experiments
usingcontinuous
soundsin
thefrequency
rangebetween
100and10,000Hz.
piezoelectric
The recommended
transducer
emitsmaximumoutputpower
700and3,000Hz,butit willalsooperatein otherfrequencies
between
with
lesspower.
Powersupplyvoltagerangeis between
5 and12volts.Currentrequirements
dependuponthepowersupplyvoltage,rangingfrom10to 50 mAtypically.
Pl adjuststhe tonefrequency.
Cl can be alteredwithina largerangeof
valuesas indicated
in theschematic
diagram,
shownin Figurel.
placement
Components
boardis shownin Figurc2.You
canalsomountthecircuitusinga solderless
boardforexperimental
applications.
Allthecomponents
(ifusedaspowersupply)
andthebatteries
canbehoused
in a smallplasticbox.
BZ canbe replaced
witha commonpiezoelectric
tweeter.
But,in thiscase,
youshouldopenthetweeterandremove
thesmalltransformer
frominsideit.
Thentheoutputof thecircuitshouldbeconnected
directlyto thesmallpiezoelectrictransducer.
lt!
I
Ptrhctl0 lbhPmllulh0scllhu
+5Vto +12V
tc1 - 40938
Figure 1
tr r-.
9
o
o
\\
.J
.J
P1
Figure2
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PartsList - High-Power
AudioOscillator
P1
- 40938CMOSintegrated
circuit
- Piezoelectric
transducer
(RadioShack273-090
or equivalent)
- 100,000
ohmpotentiometer
Rl
- 10,000
ohm,114W,5%
resistor
C1
- 1200pFto 0.047uFceramicor metalfilmcapacitor
lOl
BZ
ldeasto Explore
Tolearnmoreaboutcomponents
anddevices:
o Thiscircuitcanalsoproducesoundin the ultrasound
band.Using
a 1,200pF capacitor
for C1,the rangewill reachan upperlimitof
about100,000
Hz.
o Explainhowa push-pull
outputstageoperates.
Scienceanduncommon
applications:
o Thiscircuitcanbe usedfor animalconditioning
or in experiments
involving
sounds.
o Byreplacing
Pl withsensors,
suchas LDRs(LightDependent
Resistors)or NTCs(Negative-Temperature
Coefficientresistors),tone
frequency
willbe light-dependent
or temperature-dependent.
-
fl2
o By replacing
Pl withtouchsensorsor electrodes,
wecanusethe
circuitas lie detectoror bio-feedback
The soundpitchwill
devices.
dependuponskinresistance.
PnfccrlE lllti-'lrdlilllr0sd[ru
o The circuitcan also be usedas a fish attractoror in experiments
BZwithwiresimmersed
involving
wateranimalsandsounds.Replacing
works
into waterwill generateelectriccurrentfieldsfor experimental
involvingthe influenceof thesefieldson fish or otherbeings.
o Someanimals,suchas miceandrats,arescaredoff by ultrasounds.
to determinethe frequencies
The circuitcan be usedin experiments
that are moreetfectivefor this task.
Seeotherprojectsinvolvingsoundsfor newideasto explore.
1t8
Itn P10l0ct3
lu ha Euoilmomcr
TIMER(E/P)
Smallhomeappliances
andcircuitscanbeturnedonattera timedelayrangingfromsecondsto minutesusingthissimpletimer. Schoolandhobbyist
experiments
canbetime-controlled
by usingthiscircuit.
Theunithasa constant-current
sourceto chargecl. Cl andPl adjustthe
timerange.You
canalterC1withina rangeof 100and1000uFto change
the
timerange.
I
l
t
Usinga 1 ampererelayyoucancontrolACloadsupto 100wattswiredto the
117VACpowerline.
Tooperatethe unit,connectthe loadto the relaycontacts(pointsA andB,
usedas a switch)andadjustP1to the desiredtimedelay.Press52 do dischargeCl completely
. ThencloseSl to start.Aftertheadjusted
timedelay,
therelaywillclose,andtheloadwillbe powered
ON.
Conversely,
byusingtheNC(Normally
Closed)contacts
of therelayyoucan
turna deviceOFFaftertheadjusted
time.
Tousetheunitagainyoumustpress52 to discharge
C1 beforestarting.
diagramof the tlmer.Observethe ditferent
components
usedin thisproject:
(UJT)andan SCR
a unijunction
transistor
(SiliconControlled
Rectifier).
An mechanical
viewis shownin Figure! usinga terminalstripas chassis.
All thecomponents
andpowersupplycanbe housedin a smallplasticbox.
Takecarewith'positions
of criticalcomponents,
suchas the UJI, SCR,diodesanddlectrolytic
capacitors.
Therelaydependsuponthepowersupplyvoltageandvoltagedropthrough
the SCR.Thisdropis about2 volts,so youneedto use6 to 7.S-volt
relays
witha 9-voltpowersupply.
TheSCRneedn'tbe mounted
on a heatsink,
as thecurrentdrainis low.
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ej
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R2
12Oa
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il-" *.
1O0pF
SCR
Ttc106
(.)sEE
TEXT
Figure I
e e €rO O
Figure2
thatcurrent
to powerthistimer.Remember
UseAA cellsor a transformer
drainis lowonlywhenthe relayis notenergized.
IunEofccts
for[n trnel|mcmcr
PartsList-Timer
Q1
- 8C548NPNgeneral-purpose
silicontransistor
Q2
- 2N2646unijunction
transistor
SCR - TlC106siliconcontrolled
rectifier
D1,2 - 1N4002silicondiodes
R1
- 47,OOO
ohm,1/4W,5%resistor
R2
- Lz}ohm,1/4W,5%resistor
R3
- 100ohm,1/4W,5% resistor
P1
C1,2 - 100 uF,12WVDCelectrolytic
capacitors
K1
- Relay- see text
51
S2
- NormallyOpenmomentary
switch
81
- 9V - six AA cells
ldeasto Explore
To learnmuchaboutcircuitand devicesor to get betterperformance:
a Explainhow a constant-current
sourceoperates.
o Explainhowa UJTand SCRoperate.
o AlterC1 to get highertimedelays.Tryvaluesup to 1,000uF.
tl0
?rutctlg fhtr
projects
usesforthisdevice:
anduncommon
Science
o All experiments
thatneedtime-delay
controlcanusethisdevice,
as longas thetimedelayneededfallsin the rangeof thistimer(betweena fewsecondsand minutes).
Usea commonwatchas refer.
enceto makea scaleforthe potentiometer.
a Thecircuitcanbe usedto activate
witha
experiments
dangerous
to reachsafedistance.
theexperimenter
safetime-delay
allowing
o Trapscan be armedaftera time-delay,
can
so the experimenter
avoidthetraphimself.
o Chemical
processes
usingthistimer.Anyaudio
canbe controlled
in thisbookcanbe useas warningcircuitwhen
described
oscillator
wiredto therelayoutput.
110
l
lunPilcrahr[n mrdmotmcl
(E/P)
MrcRoAMRADIO
ThismicroAMradiowilltunestrongstationsinthefrequency
rangebetween
530and1,600kHz.
Thecircuitusesonlyonetransistor
as the amplifier
andwitha transformer
poor
Asthecircuitisvery
drivesa smallloudspeaker.
inamplification,
it needs
Theantennashouldbe from15to 50 feetlongforbest
a longwireantenna.
results.
A goodgroundconnection
is alsoimportant.
Of course,thisis a smallinexpensive
transistor
radiowithlowlistening
volume,particularly
on a weakstation.lf the stationis too weak,replacethe
SPKRbya low-impedance
earphone.
Thepowersupplyis formedbytwoor fourAA cellsandcurrentdrainis very
low,extending
theirlife.Thecircuitdrainsonlyfewmicroamperes.
L1 is a tappedloopstick,
connected
to variablecapacitor
CV. Theseitems
canoftenbe foundin non-working
transistor
radios,as wellas the speaker
andtransformer.
diagramforthisproject.DiodeDl actsas a
T1 is a commontransistoroutput
detectorand Q1 as an audioamplifier.
transformer.
ln Figure2 we showthe components
layout.All the components
can be
housedina smallplasticbox.A terminal
stripis usedaschassisinanexperimentalversion.
(1,000:8)
T1 is a transistor
transformer
andthe SPKRis a miniature
type.
But,if youhavean unworking
AMradioyoucangetthesepartswithoutspendinganymoney.
To use,closeSl andtuneto the desiredstationby adjusting
CV.Youcan
gain.
adjustR1forthebestresultsaccording
to yourtransistor
r22
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c1
O.1pF
Figure I
Figurc2
n8
lilmhG8ffimffifipror
l
PartsList - MicroAM Radio
Q1
NPNtransistor
D1
germanium
dlode
L1
- loopstick- seetext
CV
- 365pFvariable
capacitor
T1
- Transistor
1,000:8
transformer
speaker
SPKR- I ohmsx 2 in.miniature
R1
- 2,200,000
resistor
ohm,114W,5%
Cl
- 0.1uFceramicor metalfilmcapacitor
Sl
- SPSTtoggleor slldeswitch
81
- 3 or 6V - twoor fourAAcells
ldeasto Explore
o Replace
andfind
transistor,
suchasa BC517,
Ql witha Darlington
and
a bettervaluefor R1.Valuesin the rangebetween2,200,000
10,000,000
ohmscanbe used.
o Replace
L1by20turnsof No.28wireona ferriterodandtrytuning
Position
oftheL1tap
stations.
Usea longwireasantenna.
short-wave
get
to
best
selectivity
and
sensibility.
mustbe carefully
studied
o Experiment
witha crystalearpiece
intheplaceofT1 andSPKR.A
10,000ohmresistor
shouldbewiredin parallelwiththeearpiece.
I
l
i
I
Fnllcr 20 ffilrilmlh
operate.
receivers
o Explainhowcrystalsetsor direct-detection
o Definetheterm"selectivitt''.
o Whatis a galena-crystal?
Scienceprojects:
howantiqueradioreo This receivercan be usedto demonstrate
as
lt canbepresented
whenradiowasfirstinvented.
ceiversoperated
"modern
galena
in
a
demonstration.
receiver
of a crystalor
version"
a
AM
exhibitcan be madewiththisset,the free-power
An interesting
(described
in thisbook),anda crystalset.
receiver
a The circuitcan alsobe usedas an RF "snitfe/',detectingradio
band.
circuitsintheAMorshort-wave
byexperimental
signalsproduced
get
a sensitive
ReplaceLl witha 1,000uHchokeandremoveC1to
RFsnitfer.
r2[
l.r ht Inoilmmllt{n EofoGB
TOUCHSWITCH(E)
bya simpletouchwith
lampsandmotorscanbecontrolled
Smallappliances,
by Pl fora
circuit.LoadsareONduringthetimeadiusted
thisexperimental
byusingtheNC(normally
to morethan10minutes.conversely,
fewseconds
time.
aftertheadjusted
youcanalsoturnotf an appliance
closed)contacts
be placedfar
Thesensoris formedbytwosmallmetalplates,andshouldn't
at thesamemomentThemetalplatesarefinger-touched
fromthecircuit.
on
depending
froma 6- or 12-voltpowersupply,
Thecircuitcanbe powered
proiect'
to
this
with
powersupplies
therelayused.Donotusetransformeless
powersuppliesare not
shorts.Transformerless
avoidshocksor dangerous
shockhazard.
a dangerous
fromtheAc-powerlineandrepresent
isolated
bycurrentupto 50 mA'
K1is a relaywith6- or 12-voltcoilandis energized
Withrelaysin this rangeyoucan powerthe touchswitchfromAA cells(6
volts)or smallPowersuPPlies.
Switchis showntn Figurcl.The circuitusesa 555
of theTouch
A schematic
P1'
byadjusting
lC timeras itsheart,andtimedelayis determined
printed-circuit
board,is shownin
usinga smallhomemade
circuitmounting,
diaFigure2.lf you:dliketo etchyourownboardusethispartsplacement
gramas guide.
ln Figure3weshowthesensorthatcanbemadewithtwosmallmetalplates
belong.A maximum
orwoodbase.Wiresto thesensorshouldn't
ona-plastic
to avoiderraticoperation.
lenghtof 10feetis recommended
and
capacitors
suchastheelectrolytic
components,
Pos16nof the polarized
A and B. Reto terminals
Loadis connected
diodes,shouldbe observed.
memberthatthe relayactsas a switch.
to avoiddangerpowersupplies
Don'tpowerthiscircuitfromtransformerless
ousshocksandshorts.
use a
controlcanbe addedto thiscircuitin a simplemanner.
A sensitivity
forthistask.
ohmpotentiometer
1,000,000
-
nt
:
t
!
Ffdrcr2l luGnil||tc[
lr \<^B
R3
10K
lfi
a2
8C548
R1
100K
B1
a12V
c2
lOO!f
Q1
8C548
(.) sEE TEXT
Figure 1
Figure2
t2t
Hr Frdrctslolho Dndmomcl
PartsList -Touch Switch
lC1
- 555 integratedcircuit,timer
NPNtransistors
Q1,2 - 8C548general-purpose
D1
- 1N914silicondiode
Kl
- relay- see text
Rl
- 100,000ohm, 114W,5%
resistor
R2
- 47,OOO
resistor
ohm,114W,5%
R3
- 10,000ohm,114W,5%
resistor
R4
- 1,000ohm,1l4W,5olo
resistor
P1
- 1,000,000
resistor
ohm,114W,5%
C1
- 10 to 470 uF,12 WVDCelectrolytic
capacitor- see text
C2
capacitor
S1
81
- 6 or 12V- M cells,batteryor powersupply
ldeasto Explore
or to learnmoreaboutthecircuit:
Togetmoreperformance
tranbyreplacing
Ql witha Darlington
o Sensitivity
canbeincreased
sistor,suchas a BC517.
pointsY andX youcanuse
o Byconnecting
a reedswitchbetween
thiscircuitdo detectmovement.Fixa smallmagneton the pieceto
acton the reedswitch.
rtl
lu!
I
l
I
frrfcct2l frrcDSffi
'3
Figure 3
Scienceanduncommon
applications:
. Thiscircuitcanbe usedto closea trap.Thetouchsensorwilldetectwhentheanimalentersthetrap.
o Projectsthatneeda wayto detectmovements,
switching
anyload,
made
with
this
kind
like
microswitches,
canbe
circuit.Several ofsensors,
pendulum
sensorsor anyothermomentary-type
switchcanbe used
inthiscircuit.
pointsA andB.Alsoconnecta 100,000
o Connect
an LDRbetween
poleofthepowersupX andthenegative
ohmpotentiometer
between
ply.You'llhavea light-operated
relayor remotecontrol.
A flashof light
produced
lightercanclosethe relay,
by a lanternor evena cigarette
powering
theload.Thecircuitcanbe usedto detectflashesof lightin
FixtheLDRintoa telescope
scienceexperiments.
andyoucandetect
meteorfallings.
a Experiments
involving
thunderstorms
at nightcan be conducted
Thefirstflashof lightning
automatically
usingthiscircuit.
canbe used
to powerONtheequipment.
t8l
IunPruiects
forfie lrDollmcmel
SIMPLEFLUORESCENT
(E/P)
LAMPTNVERTER
tube(from7 to 4Owatts)froma 6Thiscircuitwilllighta commonfluorescent
or 12-voltpowersupply,suchas ni-cadcells,D cells,car batteryor other
source,withoutneedof a chokeor starter.Eventhe oldtubeswhichno longer
functionat all on AC powerlineswilllightwhenusedforthispurpose.(Some
of them,though,maybe too weakto lightwhenthe circuitis poweredfrom6
beforehand.)
or 12 volts.Youshouldexperiment
light,in trailers,signaling,
etc.
Youcan usethe deviceas an emergency
By poweringthe fluorescentlampwith a transformerpowersupplyyou inavoidingdangerousshocksor shorts.
creasesafetyfactorof an experiment,
Currentdrain,typicallyrangingfrom 100to 800 mA,dependson the characteristicsof the lampused,the powersupplyvoltage,and the transformer.
to the drainedcurrent.Experiments
should
The lampwillbrightenaccording
be done with some ditferenttransformersand oscillatorfrequenciesto get
out of the circuit.
betterperformance
High
oscillatordrivinga transformer.
Basicaly,the circuitis a low-frequency
light.
to'lighta fluorescent
voltageis obtainedfromthe transformer
The trimmerpotentiometer
allowsfrequencyadjustmentto get betterperformance.
Schematicdiagramof the FluorescentLampInverteris displayedinFigure
oscillatorwith a pairof
1.As you see,the circuitconsistsof a low-frequency
transistors.
complementary
Componentslayout,usinga terminalstripas chassis,is shownin Figure2,
placement
is not critical.
Components
Transistor
Q2 shouldbe mountedon a largeheatsink.Tlis a 6V x 450 mA or
secondarycoil) trans12Y x 450 mA transformer.lf a CT (center-tapped
wires.
formeris you shoulduse onlytwo of the threesecondary's
Fof0ct22 $mjollutsctmlmffilnu
I
Figure I
Figure2
BE
IunPnf0cFful[o H$lmilu
from300to 800mA
currents
withsecondary
withtransformers
Experiments
9 and15Vcanbe madeto getbetterperformance.
betweeen
andvoltages
lampis poweredwithhighvoltagesthatcan be
Warning:Thefluorescent
connecandwhenhandling
Takecareof the wires'insulations
dangerous.
tionsto thedevice.
PartsList - SimpleFluorescentLampInverter
Q1
- 8C548- generalpurposeNPNsilicontransistor
Q2
-T,P42- PNPpowertransistor
T1
- Transformer:
117VAC;6V x 450 mA or 12Yx 450 mA
Xl
- Fluorescent
lamp- see text
P1
- 470,000ohms- trimmerpotentiometer
R1
- 10,000ohms,1/4-watt,5% - resistor
R2
- resistor
- 1,000ohms,114-watl,5%
C1
- 0.047uF - metalfilm caPacitor
ldeasto Explore
Tolearnmoreaboutthecircultor to getbetterperformance:
o Tryto usea ferritetransformer
in placeof T1.Thecircuitperformancewillincrease.
o Explain
workinthiskindof circuitandwhytranshowtransformers
formersdo notworkin DCcircuits.
applications:
anduncommon
Scienceprojects
lampandyou'llhave
o Replace
Xl byansmallultravioletfluorescent
Prolcct22 SlMcHurlr$mtlrmtlflmcl
materials
Manymaterials,
including
a mineralor fluorescent
searcher.
percentage
glow
theoneswitha high
of calcium,
will
whenilluminated
Manyexperiments
by ultraviolet.
and demonstrations
can be made
plantsandfluorescent
involving
minerals,
materials
.
o An interesting
withplantsis to studytheetfectof ultraexperiment
plants'growth
violetradiation
onditferent
orgermination.
lrradiate
severalbatchesof variousseeds,suchas tomato,been,squash,etc.,
reaching
withUV andthenplant.Because
of increasing
UVradiation
theearthdueto depletion
oftheozonelayer,theetfectofthisradiation
plant
lifeis of concernto us all.
on
o Compareetfectsof ditferentlightwavelengths
to seedgermination.Thewavelenghts
rangefrom200to
of incoming
solarradiation
(nm).
3,000nanometers
UV radiationis between380and400 nm.
batchesto
Selectseedsfromcommonplantsandexposeditferrent
wlththediferent
UVand/orcommonlight(redto blue).Whathappens
Youalsocanconductthe experiment
not
seedsduringgermination?
onlywithseeds,butplantsandinsects.
o Highvoltagepresentin the 117Vtransformer
coilcanbe usedin
Pleaseadda 10,000ohmpotentiomnervestimulation
experiments.
eter to controlthe appliedvoltageif the circuitis intendedto be used
haspeaksashighas400V!
voltagein thetransformer
onhumans!The
o Fluorescent
lightcanalsobeuseinexperiments
withinsects.
Some
lnsect
kindsof insectsareattracted
by light(visibleandultraviolet!).
trapscanbe constructed
usingthiscircuitas base.
o Fishandotheranimalscanbeattracted
light.A cirbyfluorescent
powered
forfieldwork.
cuit
bycellsor batteryis important
o Alternate
methods
offarmpestcontrolcanuselight,visibleaswell
partof thespectrum.
lnsecttrapscanbe
as radiation
in theultraviolet
inverters.
withfluorescent
lamp
Forfurtherinformation:
constructed
Alliance
for Sustainable
Agriculture
Thelnternational
1701University
Avenue
SE
(612)331-1099
Minneapolis,
MN55414
tft
loriln Hmilmrmel
tunPtoiGcts
TOUCHON/TOUCHOFF RELAY (P)
toolsand
AO-powered
appliances,
suchas lamps,smallhomeappliances,
otheritems,can be controlledby yourfingertipsusingthis circuit.Also,test
can be controlled
by thiscircuit.You
canturnon
equipment
andexperiments
any load by first touchingtime sensorX1, then turn it otf by touchingXl
again.Thereis no shockhazard,as the controlcircuitis completelyisolated
fromthe AC powerline.
The controlcircuitis poweredfrom four or eightAA cells,or, if you prefer,a
powersupplyrangingfrom 6 lo 12 voltsaccordingto the relaycoil.
powersuppliesbecausetheyare not isolatedfrom
Don'tusetransformerless
the AC powerlineand can causesevereshocksand shorts.
The schematicdiagramof theTouchOnffouchOff Relayis givenin Figure 1.
producing
The circuitusestwo lOs.The 555 timerworksas a monostable,
one controlpulsewhenthe sensoris touched.The 4013 is a flip-flopthat
controlsthe relayby a transistor.
placementon a homemadeprinted-circuit
boardis as shownin
Components
Figure2. Componentlayoutshouldbe alteredif the relayusedin the project
is an equivalentof the type indicatedin partslist.
Relaycoil voltageis determinedby the powersupplyvoltageand the load
Youcan use a mini 1A DPDT(RadioShack275-2491
currentrequirement.
12V,280ohm,43 mA,andwireit as shownin thefigure,or useanothertype
of relay,dependingon the loadrequirements.
A 10A SPDT mini-relay(RadioShack 275-278)is suitablefor heavyduty
appliances.
As a simplerule,you can use a 6- or 12-voltrelaywith coil currentsranging
from 10 to 100mA andcontactsup to 10A,accordingto the taskyou havein
mind.
Positionsof the polarizedcomponents,
suchas the diode,electrolytic
capacitors and transistor,shouldbe observed.
1f0
I
ttfbcr 28 lfHhrlilcrffirht
6a
<c0
/J
EA
*o o$ s b
trt
o
N(')
95
t
@
DE
a to
dl
Figure 1
tfl
I
lunlrulcctsfor$c Hlrilmcmcl
PoOO
o{
_d
ta-
-o|
E
Figure 2
Sensorarethe Sameas the'TouchSwitch"pQect describedin this book.
Don't use metallicbox to housethe device,as there are parts connected
directlyto the AC powerline.Be sure that thereare no powerline contacts
withthe lowvoltagecircuitto avoidshocksand dangerousshorts.
The loadis connectedas shownin Figure 3, to be ON whenthe relaycoil is
Youcan also use the normallyclosedcontactsto turn otf a load
energized.
whenthe relaycoil is energized.
are highwhenthe relaycoil is enerRememberthat currentrequirements
That is
gizedand lowwhenthe transistorQ2 is otf (relaycoil nonenergized).
an importantfactorto considerif you are usingbatteriesto powerthe unit.
$2
ErleG[20 Iffi mtltrEl0rr.trr
plugthe
Afteryouaresurethatyouhavewiredallpartsofthecircuitcorrectly,
powercordintothewallsocket.
Youcannowtestthecircuit.
Theload
a loadto theoutput(relaycontacts)
andtouchthesensor.
Connect
powered
shouldbe
ONif all is OK.
PartsList -Touch On/TouchOff Relay
lC1
- 555 Integratedcircuit- timer
lC2
- 40138CMOSintegratedcircuit- dualflip-flop
NPNsilicontransistors
Q1,2 - 8C548General-purpose
D1
- 1N914General-purpose
silicondiode
K1
- Relay- see text
R1,2, 5
- 100,000ohm,114W,5%
resistors
R3,4 - 47,OOO
resistors
ohm,114W,57o
RO
- 1,000ohm,114W,5%
resistor
Cl
capacitor
C2
- 0.1 uF ceramicor metalfilm capacitor
Cg
- 4.7 uF,12 WVDCelectrolytic
capacitor
C4
capacitor
S1
81
- 6 or 12V (accordingto relay)- see text
X1,2 - sensor- seetext
fl8
HntnffiLlt
' :
I
I
Inchm
-r
<
-
!
1l
11rv I I
JI
Figure3
ldeasto ExPlore
Tolearnmoreaboutthe circuitor to get betterperformance:
can be obtainedby replacingQl with a
o Betterperformance
suchas a 8C517.
transistor,
Darlington
placedbetween
thebaseof Q1and
o A 100,000
ohmpotentiometer
adjustment
thenegativepoleof thepowersupplywillgivea sensitivity
forthecircuit.
as usedin thiscircuit,works,andthefunco Explainhowa flip-flop,
tionof theC3/R5networkin thisproject.Explainwhythecurrentflowingthroughthefingerswhenthesensoris toucheddoesn'tcauseany
shockhazard.
youcanpoweroN theloadwhen
o Depending
upontheapplication,
is possible
(toreducepowerconsumption).That
relayis notenergized
usingthe normallyclosedcontactsof the relay.
-
u
PililiGr2E lffim/rdclffirffiu
uses:
anduncommon
Scienceprojects
. By connecting
a reedswitchbetweenpointsX1 andX2 you can
itemsinexperiments
of mechanical
usethecircuitto detectmovement
to actontheswitch.
item
moving
projects.
on
the
Justatfixa magnet
or
withthiscircuitbyusing
o Experiments
canbeconducted
withanimals
X1 andX2.
between
connected
transducers
appropriate
o An LDRcan be usedto controlthe circuitwitha flashof light.A
onor otf.
lighteletc.,canbeusedto turnappliances
lantern,
cigarette
frr theHnoilmcmot
ftn Prulccts
(E)
GALVANOMETER
EXPERIMENTAL
galvanometer
describedhere can detectcurrentsas low
The experimental
operates
and uses unusualparts.This galvanometer
as few microamperes
other
several
galvanometers
foundin multimetersand
as commoncommercial
analoginstruments.
that thereis a magOne purposeof this experimentcan be to demonstrate
(Oersted
Experiment).
electricity
neticfieldarounda coilthatthat is carrying
an electriccurrentflowThe operatingprincipleis verysimpleto understand:
ing acrossa coil (or a wire)producesa magneticfield.The fieldcan act on a
mobilemagneticmetalpiece,suchas a compasspointeror a blade,as shown
in the figuresherein.The compassor blademovementindicatesthe presenceof a current.
galvanometer,
Figure I showsthe two basicversionsof the experimental
usinga commoncompassand usinga blade.ls very importantto observe
the correctpathfor the currentflow in the coil.The coil shouldbe wiredexactlyas shownin the figure.
The resistorcan
ln Figure 2 we havea circuitto operatethe galvanometer.
moresensitive
resistor,
the
higher
the
The
ohms.
100
to
100,000
rangefrom
Experimentto find the highestresistorvaluethat can
is the galvanometer.
causethe pointerto move.
The coil is madewith 50 to 200 turnsof No.28 to 32 wire on a paperform.
The higherthe numberof turns,the
sensitivity.
Numberof turnsdetermines
galvanometer.
moresensitiveis the
can be detectedwith a carefully
Gurrentsas low as a few microamperes
madeprototype.
fl8
I
PlrlGGt
2f mdhuml3rilrmmr
Figure 1
Figure2
tfO
I
Er?nhcrrtrhbahn$
L1
- coil- seetext
X1
- Compassor blade- seetext
ldeasto Explore
Toget betterperformance
o Experiment
withseveralcoilswithdifferent
numbers
of turnsand
comparesensitivity.
Scienceprojects:
o Demonstrate
howOersteddiscovered
fieldarounda
the magnetic
wire that is carryingelectricityand how moderngalvanometers
are
constructed.
o Wherecangalvanometers
canbe used?Whatarevoltmeters
and
ammeters?
o Determine
by connecting
it in
thesensitivity
of yourgalvanometer
(DCmA or uA scale)and a 100,000ohm
serieswitha multimeter
potentiometer.
fit
Hnr|0Fctsfr$r
ftdmomr
_
ALARM (E/P)
OVER-TEMPERATURE
when
transducer
beepsbya piezoelectric
intermittent
Thiscircuitwillproduce
in
this
circuit
use
preadjusted
You
can
value.
risesovera
the temperature
silicondiodebutan NTC
is a common
etc.TheSensor
greenhouses,
heaters,
canalsobe usedif youchangesomecomponents'values.
positions
of R1andPl withDl willcausethedeviceto operate
Exchanging
alarm.
as an under-temperature
lGla (pins1,2and3)
bytwooscillators.
signalis generated
Theintermittent
lOlc (pins8, 9 and10)
lCl b andlOlc (oscillators).
thatcontrols
is aninverter
ratefor the
the modulation
thatprovides
oscillator
is a very-low-frequency
frequency
its
4)
has
(pins5,6 and
Thesecondoscillator
secondoscillator.
audiotonecanbealteredbyadjustbyR2andC1.Theproduced
determined
ingbothC1andR2withina largerangeof values.
Forportableusea small9Powercomesfroma 3- to lS-voltpowersupply"
Currentdrainis verylow,about0.5mAwhen
voltbatteryis recommended.
thetoneis otf.Whenthetoneis on,currentdrainrisesto about5 mA.
Alarmis shownin Figurc 1. lOl, a
of the Over-Temperature
A schematic
and twoas butfer'inverters.
as oscillators
40ggB,hastwogatesoperating
printed-circuit
boardis shownin
placement
on a homemade
Components
PCboard.
usinga single-sided
Figure2.Youcanmadeyourprototype
diodeD1(usedas sensor),
especially
components,
of thepolarized
Position
placed
fromthedeviceby using
far
Thissensorcanbe
shouldbe observed.
or waterfalling
commonwiring.Youmusttakesomecareto avoidhumidity
atfectthealarmoperation.
ontothesensor,whichwillcauseadversely
or a
or equivalent)
(RadioShack27g-O7g
transducer
BZ is a piezoelectric
crystalearpiece.
to getsoundat the deis adjustedby P1.Setthispotentiometer
Operation
you can replacethe
To get a morepreciseadiustment
siiedtemperature.
potentiometer.
by a multi-turn
commontrimmerpotentiometer
ltf
Pfrfrcl25 M-Iomnnurulhm
vcc
+3Vto +15V
P1
10M
R1
100K
Figure 1
0V +Vcc
+
Figure2
yourfingersto seehowit works:whenthetemperaGetthesensorbetween
turerisessomedegreesthecircuitwillproducea serieof beeps.lsolatethe
willstop.
sensor,andaftersomesecondssoundemission
ftnPniloctsfi$e mdlffibl
Alarm
PartsList - Over-Temperature
lC1 - 4093CMOSintegrated
circuit
R1
- 1N914or 1N4148
purpose
general
silicondiode
- Piezoelectric
transducer
or crystalearphone
(RadioShack273-073
or equivalent)
- 100,000
resistor
ohm,1l4W,5olo
R2
- 33,000ohm,114W,5%
resistor
R3
- 2,200,000
resistor
ohm,114W,5%
Pl
- 10,000,000
ohmtrimmerpotentiomer
Cl
C2
Cg
capacitor
D1
BZ
ldeasto Explore
To learnmoreaboutthecircuitor to getbetterperformance:
o AlterbothR2 andC1 to changetonepitchor bothR3 andG2to
rate.
altermodulation
o Replace
Dl witha 10,000
to 100,000
ohmNTC,Rl witha2,200
to 1,000,000
ohmpotentiometer,
ohmresistor,
andP1witha 100,000
get
new
kind
of
sensor.
to
a
o Tryto adda power{ul
suchas
outputaudiostageusinga transistor,
projects
in thisbookfor
Seeother
a 8D135anda smallloudspeaker.
suggestions
abouttheconfiguration.
r50
;
j
I
I
!
Pnfocfl
25 ow-lcmrunnnilnm
Scienceprojectsand otherapplications:
o Chemicalprocessesthat involveheatchangescan be controlled
usingthis alarm.The sensorshouldbe protectedagainstmoisture
and waterin experiments
involvingliquids.
o ReplaceD1 by an LDRor photodiode.
The circuitwill operateas a
lightalarmor darkalarm,dependingupon sensorposition.
Withan
LDRit wouldbe betterto replaceP1 witha 1,000,000ohm potentiometer and R1 with a 10,000ohm resistor.Lensesplacedin frontof the
LDRor phototransistor
can be usedto increasesensitivity.
o The circuitcan alsooperateas a water-level
alarmby usinga twowire sensorto replaceDl. The sensoris madewith two barewires.
The wires are separatedby a distanceof about2 or 3 inches.The
watercompletesthe circuitwhilethe wiresare immersed.Whenthe
waterlevelfallsbelowthe wires,the circuitis openedandthe alarmis
triggered.
. o Temperature
in greenhouses,
animalpens,incubatorsand aquariums can be monitoredusingthis device.And if workingwith an LDR
involvinglightcan be conducted.
as the sensor,experiments
tut
Im Pnlmtsfol lhcHncdmcml
TESTER(P)
GAPACTTOR
capacitors
andothertypes
Thiscircuitcanbeusedto testmetalfilmceramic
in a rangeof valuesbetween470pFto 10 uF.
of capacitors
a tonedetermined
thatproduces
Thedeviceis formedbyanaudio-oscillator
to thecircuit.The
undertest.Probesconnectthecapacitor
bythecapacitor
A falling
capacitors.
toneis higherforlower-value
frequency
of theproduced
a badcapacitor.
toneindicates
willproin the rangebetween1 and10 uF,the oscillator
Testingcapacitors
audiopulses,workinglikea metronome.
duceseparated
bytwoor fourAA cells,andcurrentdrainis verylow.
thevalueof
according
to setan audibletoneat thespeaker,
P1 is adjusted
beingtested.
thecapacitor
values.Twocapacitors
Youcan alsousethisdeviceto comparecapacitor
withthesamevaluewillgivethesametone.
Testeris shownin Figute 1.The
diagramof the Capacitor
Theschematic
workingas a directtransistors
circuithasas its hearttwo complementary
unis provided
byresistorR1andthecapacitor
Feedback
coupledamplifier.
dertest.
placement
on a terminalstripis shownin Figure2. Usethis
Gomponents
partsplacement
the terminalstripandwhen
as a guidewhenassembling
thecircuitintoa box.
housing
to avoidinstability.
shouldbe shortas possible
components
Termination
and
capacitor
suchas theelectrolytic
components,
Position
of thepolarized
undertest
Thecapacitor
powersupply,
whenmounting.
shouldbe observed
clipsas shownin Figure2.
is placedin thecircuitbytwoalligator
Thecircuitcanbe housedin a smallplasticbox.
r0!
I
?nhcrfi ffiffiFnr
P1
1M
.-l
Q2
BC558
R2
4K7
Q1
AnA/iA
cl
'l00pF
I
II
-L
81 ._
3/6V T
*l(
:tCAPACITOR
UNDER
TEST
S1 \
R1
1K
4/8n
Figure I
Figure2
til
HiFilIOEEI*IhHruffiUT
j
PartsList - GapacitorTester
Q1
NPNtransistor
Q2
PNPtransistor
R1
- 1,000ohm,114W,5%
resistor
R2
- 4,700ohm,114W,5%
resistor
P1
- 1,000,000
resistor
ohm,114W,5%
Cl
- 100uF,6 WVDCelectrolytic
capacitor
Cx
- capacitor
in test
S1
81
-3orOV-2or4M-cells
SPKR- 4 to 8 ohms- 2to4 in.loudspeaker
ldeasto Explore
To get betterperformance
or to learnmoreaboutthe clrcuit:
o ReplaceP1 with 10,000,000
ohmsto testcapacitorsunder470pF.
Don'ttouchthe alligatorclipsor probeswhentestingsmallcapacitors
bellow1,000pF.
o Explainhowcapacitorsfunctionin this circuit.Whatis feedback?
It2
Frohc|28 Grrrcllrlffi
uses:
anduncommon
Scienceprojects
o Mountanexperimentalcapacitor
foilandpaperas
usingaluminum
thevalue
Testthecapacitor
dielectric.
usingthisdeviceandcompare
withknowncapacitors.
o Experiments
involving
transducers
can be conducted
capacitive
(A/D)
withthiscircuit.Thecircuitcanbe usedas an analog-to-digital
quan(ananalog
Thesecircuitscanconvertcapacitances
converter.
quantity).
(a
With
appropriate
converinto
frequencies
digital
an
tity)
counterto measure
to usea frequency
sionscaleit will be possible
capacitances.
r03
frn Frloclslr ho Htcrlnnrur
(VP)
TESTER
coNTrNUrrY
suchas diodes,resiscomponents
Thiscircuitcanbe usedto testelectronic
lamps,
fuses,
switches,
loudspeakers
andmanyothtors,coils,transformers,
undertestis indicated
byan LED.
ers.Thestateof thecomponent
themisvery
between
orwhentheresistance
Whentheprobesareseparated
is low
(more
is
When
the
resistance
the
LED
otf.
than
1,000,000
ohms)
high
(thetransistor
is in a conduction
state)theLEDis on.
Current
froma 6- or 9-voltsupply(AAcellsor battery).
drainis lessthan10 mAwiththe LEDon.R2valuedependson the power
Fora 9V supplywe recommend
820or 1,000ohmsfor R2.
supplyvoltage.
Testeris givenin Figure1.TwotranA schematic
diagramof theContinuity
pair.Theconfiguration
reducesthe current
sistorarewiredas a Darlington
probesto microampere
values.
flowbetween
placement
on a terminalstrip,usedas chassis,is shownin
Components
of thetransistors
andLED.
to observepositions
Figure2. lt is veryimportant
clipsto
Housethe devicein a smallplasticboxanduseprobesor alligator
undertest.
connectthecomponents
PartsList - ContinuityTester
PNPsilicontransistors
Ql, 2 - 8C558general-purpose
LED - Commonred,greenor yellowLED
R1
- 100,000
resistor
ohm,114W,5%
R2
- 470ohm,114W,5%
resistor- seetext
S1
81
- 6Vor 9V (fourAAcellsor battery)
PPl,2 - Redandblackprobes
r80
l
;ilm
2t Grilmlufc$ct
Figure I
Figure2
t0t
IunfrofoctsffimHEaffirSl
ldeasto Explore
Togetbetterperformance
or to learnmoreaboutcircuitanddevices:
o InvertpowersupplypolesandLEDposition
anduseNPNtransistors.Willthecircuitoperateas theoriginalversion?
A transistor
such
asthe8C548canbeusedinthisexperiment.You
canalsoreplace
the
LEDandR1witha 6-voltx 50 mAsmallincandescent
lamp.
o Determine
the highestresistance
thatcanbe connected
between
probesthatcausesthe LEDto illuminate.
Scienceprojects:
o Conductability
of chemical
substiances
canbedetected
or demonstratedwiththiscircuit.Usetwobarewiresas probes.
o By replacing
youcanuse
theLEDwitha 0-200uAmicroammeter
thiscircuitas a liedetector.
Smallchangesin skinresistance
canbe
detectedin thisway.Skinresistance
alterswithstressor bythe straln
causedby an interrogation
session.
o Experiments
withplantscan be conductedinvolvingalterationin
placedon theirleafs. An interestthe resistance
between
electrodes
ing studyaboutthis subjectis foundin the book The SecretLifeof
Plants
byPeterTompkins
andChristopher
Bird.Theauthors
associate
phenomena
plants
in
electrical
to a rudimentary
nervoussystem.
IB
j
l
IunftmctsffincHlulnrrnr
LEDBARGRAPH(E/P)
Thiscircuitdrivesten LEDsin response
to an analogvoltageappliedto its
inputandcan be usedto providea visualindication
of the instantaneous
powerbeingdeveloped
by an audioamplifier.
lt canalsobe usedto provide
visualindication
of variable
eventsin scienceexperiments.
Youcanextendtheprojectby usingtwochipsandyou'llbe ableto continuouslymonitor
theaudiooutputpowerof bothchannels
ofyourstereosystem.
Thecircuitcanbe usedwithamplifiers
rangingfrom0.1to 100watts.
In somecasesyoushouldusea smalltransformer,
wiredas in Figurc1,to
isolatethe inputandmatchimpedances.
Thisls necessary
whentheamplifierhasa low-output
impedance.
Resistor
R, is chosenaccording
to theoutputpowerof theamplifier.
ValuesaregiveninTable1.
Table1
Amplifier
OutputPower
Rx
-
0.1 to 1 watt
1 to 5 watts
10 ohms, ll2watl
5 to 20 watts
22 ohms,1 watt
20 to 50 watts
47 ohms,1 watt
50 to 100 watts
100ohms,2watts
A schematic
diagramof the LEDbargraph
is showninFigure2.Thecircuit
usesan LM3914lC to drivethe LEDs,converting
voltagesintooneof ten
outputs.
Thecomponents
areplacedon a printed-circuit
boardas shownin Figure3.
lf youd liketo buildyourcircuitthesameway,youcanetchyourownboard
usingthesolderandcomponent-side
templates
shownin thisfigure.
l
j
I
F!|ffi 2t llDlrlrruh
I
(-)SEETABLE
8:1000o
TRANSF'RMER
Figure I
+6112Y
18
't7
16
15
14
13
12
11 . 10
tcl
1M3914
5
D1
R1
1N914 10K
Figure2
fn
HmHdcctslrrilcHpilmmu
Figure 3
P2 adjuststhe dynamicrangein whichthe circuitoperates.P1 adjustssensiYoucansetthevalueto a fixedpointby
tivityanddependson the application.
usinga trimmerpotentiometer.
Audiocomesfrom the loudspeaker
outputof the amplifier.Any smalltranscoil can be used.
formerwith a high-impedance
coil and a low-impedance
Any smalltransformerwith a 117VAC primary,secondaryratedfrom 5 to
12.6volts,and currentratingsbetween100and 500 mA can be used.
Positionof the polarizedcornponents,
suchas LEDs,diode,and electrolytic
capacitor,shouldbe observed.
Bass responseis providedby C1.Youcan alter this componentwithinthe
rangegivenin the schematicdiagramto achievebestperformance.
Rememberthatthe highestappliedvoltageto the inputshouldn'texceedthe
powersupplyvoltage.
ltf
FililGct28 ltB hntiln
PartsList - LEDBargraph
lC1
- LM3914Integrated
circuit(National)
LEDs - Commonred,yellowor green
D1
- 1N914or 1N4148generalpurposesilicondiode
Rl
- 10,000ohm, 114W,5%
resistol
R2
- 470ohm,114W,5%
resistor
P1
P2
C1
- 1 to 10 uF,12 WVDCelectrolytic
capacitor- see text
ldeasto Explore
o Determinethe voltagelevelthat turns on each LED usinga DC
powersupplypluggedto the inputof the device.
. By wiringprobesat the positivepowersupplyline and the input
meter.
you can usethis circuitas a digitalresistanceor conductance
SciencepQects:
o Thiscircuitcan replacethe commonmultimetertoindicatevoltage
The visualetfectis better.
variationsin experiments.
o lt can alsobe usedin the outputof a lb detectoror bio-feedback.
o Conectan LDRbetweenthe inputand (+)for a digitalphotometer.
wire an NTCbetween(+) and the input.
Fora digitalthermometer
o Thiscircuitcan also replacethe LEDand resistorin the Continuity
can be performed.
withadvantages,
Testerandthe sameexperiments,
fl5
forllc Hrulnrnmr
IunPl0f0cts
LTQUTDS
SHAKER (P/E)
A toy'ssmall DC motorcan be usedto mounta liquidsshaker.The shaker
can be used in chemicalexperimentsto mix substancesquicklyand efficiently.
The circuitis poweredfrom the powersupplyline (to avoidthe expenseof
batteries),but thereis no shockhazardbecausean isolationtransformeris
used.Of course,for fieldworkyou can also poweryour mixerfrom common
AA cells.
DC
The transformeris chosenaccordingto the motorvoltage.A four-AA-cell
(a
motorrequiresa 6+6voltx 500 mA transformer 6-voltcentertappedtransformer).A two-AA-cellDC motorrequiresa 3V x 500 mA transformer.
Securethe motorinto a smallcylindricalplasticbox.Use a longshaftto attach a smallplasticscrewpropeller.
Figure l showsthe schematicdiagramof the electronicpart of the circuit:a
powersupply.The diodesare common50V x 1A siliconrectifiers,and C1 is
not critical.C1 shouldbe in the rangebetween100and 1,000uF.
Figure 2 showsa mechanicalview,usinga smallterminalstripas chassis.
The fuse is importantto avoidseveretroublesif shortsoccur.
resistorand can be alteredaccordingto the motor.
Rl is a current-limiting
with for betterperVafuesbetween4.7 and 100ohmscan be experimented
formance.
capacitor,
Positionof the polarizedparts,suchas the diodesand electrolytic
shouldbe observed.Rememberthat the motorrotatescloclcriseor not accordingto the voltagepolarization.
tt8
PnFrt 20 lhffiSmilor
D1
1N4002
F1
6+6V
500mA
Figure l
Figure2
il
att
l
Iur?rd0c0ihlh0mhmml
PartsList - LiquidsShaker
D1,2 - 1N4002silicondiodes
T1
- Transformer:
117 VAC:6+6Vx 500 mA - see text
S1
F1
- 500 mA fuse
C1
capacitor
R1
- 15 ohm,2W,SYo
resistor
M
- smallDC motor(3 to 6 volt)
ldeasto Explore
Tolearnmoreaboutcircuitanddevicesor to getbetterperformance:
to the DGmotor
according
o AlterR1to achievebetterperformance
4.7and'l00ohms.
used.Tryvaluesbetween
in thisbookto geta speed
o Usethe DC LampDimmerdescribed
R1if thedimmeris used.
controlforthe motor.Remove
thecircuit.
geta regulated
outputfrom
o Usethe6VDCconverterto
uses:
anduncommon
Scienceprojects
experiments,
o Thispowersupplycan be usedin electro-chemical
andelectroplating.
suchas electrolysis
witha fanblade.Experiment.
o Replace
thescrewpropeller
in
watercurrents
involving
o Thedevicecanbe usedin experiments
suchas aquariums.
smallplaces,
of a smallDC
movement
o Otherapplications
thatrequirecontrolled
motorcanusethiscircuit.
rft
tunEobcrsbr thcEoedmcrFl
(P)
STGNALTRACER
methodforservicSignaltracingbymeansof a signaltracerotfersa valuable
whena
Thismethodis oftenemployed
equipment.
inga varietyof electronic
AMandFMreceivdead,butrathermalfunctioning.
circuitis notcompletely
TV sets,etc.,canbe servicedusing
multimedia
amplifiers,
ers,CD players,
thissimplesignaltracer.
I
l
transistor
direct-coupled
The circuitwe showhereconsistsof a two-stage
Whentheprobeis usedin theRFmode
Thecircuithastwoinputs.
amplifier.
thedetectordiodeis insertedintothecircuit.Whenthe probeis usedin the
audiomodethe signalis applieddirectlyto the baseof the firsttransistor
(o1).
As the circuithas a low-poweroutput,a gaincontrolis not used.
The circuitis poweredfromtwo M cells,and currentdrainis onlyfew milliamperes.Sincethe circuitdrawssuch low current,long batterylife can be
expected.
Figure I showsthe schematicdiagramof the signaltracer.R1 determines
the gain of the amplifierstageand can be alteredto get betterperformance
dependingon the transistorsused.
Figure2 showsthe signaltracermountedon a terminalstrip,whichis used
one is an NPNandthe otheris a
as a chassis.liakecarewiththe transistors;
you
will not work.
the
with
the
other
circuit
PNP.lf
switchone
This projectcan be housedin a smallplasticbox.The sizeof the plasticbox
is determinedby the speakersize.Positionof the polarizedpiecesshouldbe
observed.
Itf
I
i
.l
I
Ftdcct80 $llmllnecr
RF
Dl
1N34
1
A+Fl
B+
AUDIO
I
C 2 +
C1
0.1pF
100pF
SPKR
4l8A
Cr-
(coMMoN)
Figure I
Figure2
1t[
l
milnFGtslorhsulmmt
PartsList - SignalTracer
Ql
Q2
PNPsilicontransistor
D1
- anygermanium
- 1N34or equivalent
transistor
R1
- 1,500,000
resistor
ohm,114W,5%
C1
- 0.1uFceramic
or metalfilmcapacitor
C2
capacitor
SPKR- 4/8 ohms- 2 or 4 in.smallloudspeaker
S1
81
- 3V - twoAAcells
ldeasto ExPlore
o Explainhowsignaltracersareusedforservicework.
o ChangeRl valueto achievebetterperformance.
o Usethetracerin a smallAM radioto studyitsoperation.
earphoneto get a poro Replacethe speakerby a low-impedance
plastic
box.
tableunitthatcanbe housedin a verysmall
Scienceprojects:
in experiments
o Thetracercanbe usedto detectsignalsproduced
in thisbook.
currentfields,as described
involving
with
audioamplifier
o The tracercan be usedas an experimental
pickupsor microphones.
suchas piezoelectric
transducers
-
rt0
lcr thsHDcilmomol
lril Plolocts
oNE-EVENTREGISTER(P/E)
Thisis a one-bitmemorythatcan be usedto storea simplebit of information,
or closed-trapdetector,or a touchsensor.
suchas a remotepower-failure
The circuitoperatesas follows:When the resistancebetweenthe alligator
poweringON the LED.
clipsfalls,the SCRis triggered,
The SCR and LED stay in the ON stateevenafterthe appliedpulseto the
the event.
inputis gone.So the device"memorizes"
or a touch
The sensorcan be a magneticswitch(reedswitch),a microswitch,
switch.A simpletouchswitchis a metalplatewiredto G2.To get bestsensitivity,G1 needsa goodground.Youcan alsouse as sensortwo metalplates
that are touchedat the sametimeto triggerthe circuitON.
The circuitis poweredby fourAA cellsandcurrentdrainis verylowwhenthe
LEDis off.Whenthe LEDis on, currentdrainis lessthan10 mA.
To resetthe deviceyou only haveto toggleS1. Anotherway to resetthe
circuitis to wire a momentaryswitchbetweenthe anodeand cathodeof the
SCR.Sensorscan be wiredto the devicewith longunshieldedwires.
Theschematicof the One-Eventis shownin Figure l.ThoughR2and R3 are
if you prefer.A
shownas fixed,you can use a 1,000,000ohm potentiometer
fromthe register.
sensitivityadjustmentwill get betterperformance
Figure 2 showsthe One-eventRegister,on terminalstrip mounting.As it is
an experimentalcircuityou can also use a solderlessboardto installthe
components.
The circuitcan easilybe housedinto a smallplasticbox.Observethe posisuchas the LED,SCRand powersuptionsof all the polarizedcomponents,
plv.
if TlC106is used.OtherSCRs,suchas the
ResistorR3 is onlynecessary
R3.
require
don't
MCRl06andCl06,
tg0
i
I1
i
Pldrct8t 0nG,tnmiulsl
R3
47KO(")
Figure I
Figure2
t0l
folt[e trrcilmentcl
IunPloiects
Register
PartsList- One-Event
Rectifier
SCR - TlC106or MCR106SiliconControlled
LEDs - Red,yellowor greencommon
R1
- 470ohm,114W,5%
resistor
R2
- 100,000
resistor
ohm,114W,5%
R3
- 47,000ohm,1/4W,5%resistor- seetext
S1
81
-6V-fourAAcells
clips
G1,2 - Alligator
ldeasto Explore
or to learnmoreaboutthe circuit:
Toget betterperformance
o Youcan replaceR1 and the LEDwith a buzzeror audiooscillator
to get an alarm.But, rememberthattherea voltagedropof about2
voltswhencurrentflowsthroughthe SCR.Thisvoltagedropcan be
compensatedby addingtwo or threevolts to the powersupply.For
voltagefor the
instance,if you use a 6-voltrelay,the recommended
volts.
powersupplyis 8 or 9
on the
o As currentdrainis verylowwhenthe LEDis off,depending
intendeduse,51 can be removed.
.
192
Explainhowthe SCRoperatesin thiscircuit.
FrFcr 8l holnillrffr
Scienceanduncommon
applications:
.
o Youcanconnectan LDRbetween
Gl andG2fora light-operated
memory
one-event
or alarm.A singleshortpulseof lightcantrigger
thecircuit.
o Usethiscircuitto knowwhensomeonetouchesan objectwhen
you leaveit unattended.
Youcanalsoknowif someoneenteredyour
roomwhenyouwereout.
a By usingtwo barewireas sensors,youhavea water-level
alarm.
TheLEDwillglowwhenthewatertouchesthetwobarewiresat the
sametime.
r0l
tm ?rulecs
ffffrc Enalmntal
(E)
NO|SEGENERATOR
is to producenoisein the AM radio
Thepurposeof thissimpleexperiment
band.Thecircuitcanbe usedto showhowbrushmotorsandgeneralappliin radio,
in the radioband,interfering
anceswithmotorscangenerate.noise
radio
services.
TV,and
communication
noiseis tooweakto causeany
Thecircuitis verysimpleandthe produced
problem
(FCCrulesaboutnoiseandradiointerference
are
to radioreceivers.
willinterfere
Thenoiseproduced
bythisexperiment
onlyin receivers
severe.)
justa fewteetaway.
Theschematic
diagramof thedeviceis shownin Figure1.Theheartof the
rapid
key,producing
circuitis a smallDC motorthatworksas a automatic
variation
in thecurrentflow.
is shownin
viewofthecircuit,usinga terminal
stripaschassis,
A mechanical
including
thepowersupply,canbe fixedon a
Figure2. Allthecomponents,
plasticboard.
toy can be usedin this
AnysmallDC motorobtainedfroma nonworking
project.
Thepowersupplydependsuponthemotorused.
fromanynonworking
AM radio.
CVandL1canbeobtained
Youcan get morepowerfor the RF noiseby wiringa pieceof wireto the
butlimitthiswireto nolongerthan6 feet.Ll is formed
antenna(A)terminal,
No.
wirewoundon a ferriterod(diameter
andlengthare
100
turns
of
28
by
notcritical).
ona deadpoint
Byadjusting
CV youcantryto tunethesignalto bestronger
of theAM radioband.
100
l
I
i
H.ret 32 td$r8ononnr
(.)ser rEXT
B1
3/6V
cl
L1
(.)
Figure I
Figure2
t0,
lfi tncHlcllmcntel
IunPloiects
PartsList - NoiseGenerator
B1
- 3 to 6V - cellsor battery- see text
T
- Keyor SPSTtoggleor slideswitch
c1
- 0.1 uF ceramicor metalplatecapacitor
CV
- 365 pF variablecapacitor
L1
- loopstick- see text
M
- 3 to 6V DC motor
ldeasto Explore
To learnmoreaboutthe circuitor to get morepedormance:
bandby replacing
o Tryto produceRF noisein the high-frequency
produce
you
signalsin the
can
coilon a ferriterod
L1.Witha 3Q-turn
rangebetween2 and7 MHz.
.
ExplainhowRF noiseis Produced.
o Find out throughreferencebookshow Marconiand otherradio
pioneersgeneratedradiowavesfromtheirtransmitters.
applications:
Scienceand uncommon
o Youcan showhow antiqueradiotransmittersoperatedusingthis
usinga keyin place
circuit.Morsecodedmessagescan be transmitted
o f5 1 .
o Explainwhy this noisegeneratorcan be usedto transmitvoicesignals.
modulated
198
fu lf,olltOilm0mil
RmftJoGts
-
(E)
OHMMETER
EXPERIMENTAL
arecheapandeasyto find,anyonewhowantsa
ohmmeters
As commercial
goodinstrument
forhisownusewillnotbuildone.Butyoucanbuilda simple
howit worksor studyhowthebigonesaremade.
to demonstrate
ohmmeter
herecaneasilybemadefroma milliammedescribed
Thesimpleohmmeter
and
demonstrations
andcanbe usedin experiments,
ter or microammeter,
manyotherapplications.
canmeasurea
Andsincethisohmmeter
is alsoa voltmeter.
Ourohmmeter
we can saythat it is, in practice,a
largerangeof voltagesand resistances
0 and12volts
Inthe rangebetween
canbe measured
Voltages
multimeter.
(therangeusedto poweralmostall circuitsin this book),and resistances
0 andinfinite.
between
willbe 5,000ohmspervolt.
thesensitivity
lf usinga2OOuA microammeter,
of commonmultimeters.
Thisvalueis typicalof severalcommercialtypes
from100
valueranging
witha full-scale
Butyoucanuseanyotherammeter
performance.
best
uAto 1 mA.SimplychangeRl to achieve
is shownin Figure1.Notethat
oftheexperimentalohmmeter
Theschematic
thatcaneasilybehousedina smallplasticbox.
weuseonlyfourcomponents
is notcritical,andyou
mounting
Layoutis shownin Figute2. Components
canreplacethe bananajacksby probesor anyothermethodto makeexternalconnections.
on the meato theexternalbananajacksdepending
Probesareconnected
surementyou intendto make.To measurevoltage,the red probeis conresistance,
to J2.Tomeasure
nectedto J1 andtheblackprobeis connected
connectthe redprobeto J1 andthe blackprobeto J3. Putthe probestoscale.
of zeroat the instrument
getherandadjustP1to getan indication
themeterscale
to calibrate
it is possible
Byusinga seriesof knownresistors,
Startfrom0 (withJl andJ2 shorted),andnotethe
to readohmsdirectly.
acrossJl andJ3.
areconnected
whenlk,2k, etc,reslstors
meterreadings
202
PlUoGt
88 S0ftncmlol|ffir
Figure I
Figure2
Aftercalibrating
the deviceto readohms,use a variablepowersupplyto
calibrate
thevoltagescale.
Position
of thepolarized
components,
suchAstheammeter
andpowersupply(cells),mustbe observed.
fmH!ffifrthomilmffi
PartsList - ExperimentalOhmmeter
81
-3V-twoMcells
R1
- 10,000
resistor
ohm,114W,5%
Pl
- 47,000ohm,1l4Wtrimmerpotentiometer
M1
- seetext
- 0-200uAmicroammeter
l
l
jacks
J1-3 - banana
ldeasto Explore
o Explainhowresistance
andvoltagescalesoperateinthisohmmeter.
powersup. Calibrate
usinga variable
thescalesof yourohmmeter
plyandsomeknown-value
resistors,
as described
above.
o Calculate
valuesreadin the meterand compare
the resistance
resultsconDoyourcalculated
withthe realvaluesof usedresistors.
previous
firm
studies?
applications:
anduncommon
Science
o Youcanusetheohmmeter
to determine
sensorandmediaresismultiif youdon'thavea commercial
tancesin severalexperiments
meter.
o Bywiringa47,OOO
between
ohmpotentiometer
Jl andJ3 youcan
indicator.
canbedirectly
Cursorpositions
usethisdeviceasa position
intocurrentas indicated
bythemeter.A scaleof anglescan
converted
to readdegreesdirectly.
be arranged
2U
ll
l
I
lol lhoScilmaml
tunPrrlacts
NERVES(P/E)
TESTYOUR
Thiscircuitputsyourmanualskillsto a livelytest.Asshownin theschematic
arounda wire.
the circuithasa smallloopthatyoumustnavigate
diagram,
coursewithout
Theobjectof thegameis to guidetheloopovertheweaving
touching
thewire.
I
or quiverof the handandthe ringwillcontactthe
A slightmisdjudgement
(butinoffenthecircuitthatwillproducea noticeable
wire,enabling
weaving
sive)shock!
to playthe gamedependslargelyon the sizeof the loop
Theskillrequired
andthedegreeof twistandturnin thewire.
by
thenumberof timestheplayeris atfected
Scoringis a matterof counting
(or
wins.
person
no
touch)
lowest
total
with
the
a shock!The
froma D cell,asthecurrentdrainis highwhentheloop
thewire.Whennotin use,don'tleavetheringandwiretogether.This
touches
willcausethebatteryto rundownin a shorttime.
of thedeviceis shownin Figurel.The heartof theproject
A circuitdiagram
pulsesup to 400
thatconverts1.5VDCintohigh-voltage
is thetransformer
volts.
is shownin Figurc2.
viewof themounting
A mechanical
canbe housedin a smallplasticbox.Wiresto the loop
All the components
whenthe
andweavingwireshouldbe 2 or 3 feetlongto preventpull-outs
playeris struck.
the pointswherethe playertouchesandthe
between
the isolation
Observe
wire.ThetwowiresthatconnectX2 shouldbetwisted.
weaving
coilrangwitha 117VACprimaryandsecondary
T1 is anysmalltransformer
3 and9V.Currentdraincanrangefrom100to 500mAwhenthe
ingbetween
wiretouchestheloop.
2t0
j
,l
Prdcct8f lostlbul lorms
B1
1.5V
- ^ n ^ Ay\^
-v
u/v
x2
Figure 1
Figure2
240
fotthcH[eilmentel
IunProlec$
PartsList-TestYour Nerves
81
- Anytransformer
witha 117VACcoiland low-voltage
text
see
secondary
-1.5V-Dcell
X1
- Loop- see text
X2
- Weavingwire - see text
T1
ldeas to Explore
o Explainwhythe transformer
doesnot operatewith DC butthatthis
projectis ableto generatehighvoltageusingthatdevice.
o Whathappensif the loopis placedtogetherwiththeweavingwire?
Why it is necessaryto avoidthis condition?
Scienceprojects:
o Changesin the projectcan be madeto generatehighvoltagefrom
can be triedusingthis simple
Nervestimulation
cellsin experiments.
circuit.
o Neonor fluorescent
lampswiredbetweenthe loopand wire will
can be usedto
flashwhenthe loopand wiretouch.Thisexperiment
generated
by the circuit.
provethat highvoltageis
210
tunPnfcffilcrlhcHloilmcmr
BEEPER(E)
WTRELESS
produces
a beepthatcanbetunedonanydead
tranJmitter
ThisFMwireless
when
pointof the FMbroadcast
band.Thecircuitcanbe usedas a localizer
persons.
wireless
alarm.
it
a
Youalsocanuse as
to objectsor
attached
I
Thesignalcan be tunedon commonFM radiosin a rangeup to 150feet.
versionaregivenbelow.
fora far-reaching
Alterations
l
beepof about1 Hz.An audiotoneis
an intermittent
Thecircuitproduces
by R2
is determined
generated
by lClb (pins5, 6 and4) anditsfrequency
values
R2.Resistor
by adjusting
andC2.Youcaneasilyalterthisfrequency
if you
with
or,
100,000
can
be
experimented
ohms
and
between22,OOO
R1.
prefer,
ohmscanreplace
100,000
ohmsin serieswith10,000
rateis per R1 andC1.Valuesarevariable.ForC1,valuesbeRepetition
to testfortheidealvalueof
tween0.15and1 uFcanbetried.lt is important
application.
depending
on the intended
thiscomponent,
diagramof thewirelessbeeperis shownin Figure1.Three
Theschematic
andone
signals,
gatesof a 4093lGareusedto generate
thelow-frequency
signal.
the high-frequency
is usedto generated
RFtransistor
printed-circuit
placement
boardis shownin
on a homemade
Components
inthis
high-frequency
stage.Capacitors
iscriticalforthe
Figure2. Placement
stageshouldbe ceramic.
a ferrite
offourturnsof No.18or 20wireona1l2 in.formwithout
L1consists
core.
5 and10incheslong.
is formedbya pieceof barewirebetween
Theantenna
to get betterperforto anytap on the coil.Experiment
It canbe connected
mance.
canusefourM-cellsor
Thepowersupplycurrentdrainis about10mA.You
a 9V batteryto powerthetransmitter.
relay
of a relay.The
bythecontacts
alarm,51 canbereplaced
Fora wireless
in
this
application.
the
transmitter
with
interface
the
alarm
is usedto
tfl
l
l
?rfhct85 tlrulmclcomr
lC1= 40938
c4
R3
8l<2
4700pF
CV
c3
0.O1pF
Q18F494
R5
47
Figure I
Figure2
Anotherwayto interface
an alarmwiththe transmitter
is to connectrelay
pointsA andB in theschematic.
contacts
in serieswithC3 or between
See
moredetalsin ldeasto Explore.
lol theErrcilmentct
IunPruiccts
PartsList-Wireless Beeper
fl0
lC1
- 4093CMOSIntegrated
Circuit
Q1
- 8F494or equivalent
NPNRF silicontransistor
L1
- coil- seetext
CV
- trimmercapacitor- 20 to 40 pF maximum
R1
- 2,200,000
ohm,114W,5%
resistor
R2
- 39,000ohm,1/4W,5% resistor
R3
- 8,200ohm,114W,5%
resistor
R4
- 6,800ohm,114W,57o
resistor
R5
- 47 ohm,1/4W 5% resistor
C1
- 0.22uF ceramicor metalfilmcapacitor
C2
Cg
C4
- 4,700pF ceramiccapacitor
C5
- 4.7 pF ceramiccapacitor
CG
A
- antenna- see text
S1
81
- 6 to 9V - fourAA cellsor 9V battery
Prdcct8[ f,hrlcsslmnr
, ldeasto Explore
o Youcancontrolthe beeperoscillator
by lOl, pins1 and5. Put
thesepinstogether.
Whenin a highlogiclevelthe circuitproduces
intervalled
beeps.Whenin a lowlogiclevelthecircuitstops.
. Replace
circuitwitha 12VpowersupQl by a2N2218.Powerthe
ply.Signalscannowbetunedfromdistances
upto 1,500feet.A 5- to
the rangeof thetransmitter.
6-footantennawillincrease
or uncommon
applications:
Scienceprojects
. Housethiscircuitin a boxandtellsomeone
to hideit.You'llfindit
by usinga smallFMreceiver.
o Thetransmitter
canbeusedto trackanimalsbyfixingit ona collar.
o Youalsocanusethetransmitter
to monitorremotesensorsin experiments.
The circuitscan powerON the transmiter
or triggerthe
oscillator
as indicated
above.
m
IunPnf0cts
f.l ftOEnct|momcr
(E/P)
ELECTROSCOPE
thepresence
Anelectroscope
is aninstrument
thatcanbeusedfordetecting
versionof the
of an electricstaticcharge.We describeherean electronic
traditional
electroscopHnethatis madewithgoldfoilsplacedintoa glass
jar.Thiscircuitcan alsobe usedfor "snitfing"
highvoltagewithoutactually
circuitry.
makingcontactwithdangerous
the sensor,is simplypokedintothe electric
A metalring,whichconstitutes
field.Thisoperation
mustbedonewithcautionto avoidcontactwiththeconductorscarryingthe highvoltage.
(Vande
withhighvoltagegenerators
Youcanusethedevicein experiments
andin manyotherapplications
at homeor school.
Graaffaccelerator)
powered
fromfourM cellsor a 9V baftery.
Thecircuitis portable,
linesis
Presence
of a staticchargeor a strongfieldcreatedby high-voltage
indicated
byan LED.
is showninFigurel.The circuit
Theschematic
diagram
of theElectroscope
gates
4093
lC
work
as
buffers
andinverters,
drivingthe
of a
that
usesfour
circuitsresultsin
inputof the CMOSintegrated
LED.The high-impedance
to detectstaticcharges.
highsensivity
printed-circuit
boardas
All the components
are mountedon a homemade
shownin Figure2.
canbe housedinto
SensorX1 is a smallbarewirelop.Thecompletedcircuit
TheLEDshouldbe placedin a visible
a smallplasticboxwiththe batteries.
pointof thebox.
Touse:
A pieceof paperorplasticstroked
Bringa charged
sourceclosetothesensor.
materialwill
do.AdjustPl to getbettersensitivity.The
witha rodof insulating
to theelectricchargemovement.
LEDwillglowaccording
220
l
I
I
Pnlmt80 llrctrscorc
6
8
Figure 1
l"
H
Figure2
nl
lunlrolmlslsrtrtltsulmur\tr
PartsList - Electroscope
IC1
Circuit
LED - Commonred,yellowor greenLED
X1
- Sensor- seetext
P1
- 1,000,000
ohm potentiometer
R1
- 22,000,000
resistor
ohm,114W,5%
R2
- 100,000
resistor
ohms,114W,5%
R3
- 1,000ohms,114W,5%
resistor
S1
81
- 6V or 9V - fourAA cellsor 9V battery
ldeasto Explore
learnmoreaboutthe circuitor to get betterperformance:
candetectclouds'
a Connectthe sensorto an externalantenna.You
electricalchargeas theypassoverhead.
.
Explainhowthe circuitworks.
couldbe performedto show
o An interesting
studyor experiment
howstaticchargesare producedand howtheycan be detected.
222
frFct 80 llccmsGm
Scienceand uncommon
applications:
I
o In allthe experiments
that can be conductedwith a commonelectroscope,the electronicversioncan replaceit.
.
Determinethe polarityof the chargethat makesthe LEDto glow.
o Staticchargescouldhavesomeinfluenceon animalsand plants.
project,
An experimentto
supportthisaffirmation
canbeconducted.This
of course,will involvesomespecialequipmentsuchas a high-voltage
generator(Vande Graaffor other)and an electroscope.
Selectseeds
from commonplantssuchas tomatoesand beans,and exposeseveral batchesof seedsto a statichigh-voltage
field.What are the effectson seed germination?ls plantgrowthalso atfectedby electric
fields?
22N
forho mcilmcmGl
IunFnilrcts
(P)
PROBE
uNrvERsAL
compoprobecanbe usedto testalmosteveryelectronic
Thisultra-simple
wires,
diOdes,
tranSformerS,
COils,
fuses,SwitcheS,
reSiStorS,
nent.CapaCitOrS,
etc.,canbetestedwiththissimplecircuit.
areusedandtheycaneasilybe housedin a small
Onlythreecomponents
plasticbox,performing
as a portableunit.
by
testerwitha visualindication
of a continuity
Thecircuitconsistsbasically
glows;
probes
LED
if
not,
the
LED
the
the
an LED.lf currentcanflowbetween
remainsotf.
the tested
Currentflowingbetweenprobesis verylowto avoidoverloading
components.
Probeis shownin Figure1.Asyoucan
oftheUniversal
diagram
A schematic
areusedin thisproject.
components
see,onlythreeelectronic
can be
layoutviewis shownin Figure2.The components
A components
housedin a smallboxandnoON-OFFsutitchis necessary.
the
components"
ofthetwopolarized
takecarewithposition
Whenmounting,
LEDandpowersupply.
of twoM cells.
Thepowersupplyconslsts
asthecircuitis otfwhentheprobesare
AnON-OFFswitchis notnecessary
separated.
bythevoltagedrop
undertestis determined
Currentthroughthecomponent
acrossthe LED(about1.6Vfor red LEDsand 1.8Vfor yellowLEDs),and
resistance
of R1.
l
I
I
Fnf0crst urffimiltl|m
Figure I
Figure2
m
ffi ue txDelhemcl
lunProlects
PartsList - UniversalProbe
LED - Commonred,greenor yellowLED
R1
- 470ohm,114W,5%
resistor
PP1,2 - Redand blackprobes
81
- 3V - two AA cells
ldeasto Explore
Scienceprojects:
o Usethis probein to find materialsthatconductor do not conduct
in electricity
can be
electriccurrent.Severalothersimpleexperiments
showhowa switchworks,or
usingthisprobe:forexample,
conducted
how a potentiometer
used as a rheostatcontrolsthe currentflow
accrossan LED.
o Explainhowthe LEDproducesits light.
o Usethisprobeto explainhowa diodeworks.(Remember
thatDC
is usedin the probesand diodes,allowingthe currentto flowonlyin
onedirection.)
o Thiscircuitcanalsobe usedas a monochromatic
sourceof lightin
involving
experiments
optics.
228
fol l[o Hncilmcmu
luil ?rufocE
RELAY(E)
TONE-ACTTVATED
Whenthistone
Thiscircuitcanbe usedto recognize
a toneby itsfrequency.
whichcouldsupplypowerto a
is presentin a circuitthe relayis energized,
selected
appliance.
the circuitcanbe usedas partof a toneWiredto the outputof a receiver,
receiver
wirelessremotecontrol.The
canbe a commonFMradio
modulated
application.
depending
on theintended
or an infraredreceiver,
Hz.Thecircuitis
Thecircuitcanbe usedwithtonesrangingup to 1O0,0OO
tunedbyP1.
remote
Inputsof otherunitscan be wiredin parallelto get a multi-channel
frequencies.
controlsystem.Takecareto avoidusingharmonic
The schematicdiagramof the ToneActivatedRelayis shownin Figure 1.
PLL(PhaseSemiconductor
TheheartofthecircuitistheLM567lC,a National
Q1.
LockedLoop)thatdrivesthe relaythroughtransistor
printed-circuit
placement
boardis shownin
on a homemade
Components
when
in
frequencies
above
is notcritical,but
operating
Figure2. Placement
to avoidlongconnections.
50,000Hzit is important
Therelayis anytypewitha 6Vcoilandcurrentratedforvaluesbetween10
and100mA.
casuchas thediodeandelectrolytic
Position
of thepolarized
components,
pacitor,
shouldbe observed.
Touse:
to pointsX andY.
or audiooscillator
Wirethe outputof an audiogenerator
100mVand1 V peakhaveamplitude
in a rangebetween
Thesignalshould
AdjustP1to triggertherelay.Reducethesignalamto-peakforbestresults.
plitudeandtrimP1 forthebestperformance.
292
I
l
Fdmt 88 Imleffirulfo|u
X
IN
c5
100pF
P1
100K
rc1
LM567
Q1
8C558
N
L+
ilKl
il F)
(.)sEETEXT
Figure 1
Figure2
2NE
forthclrDcflmentcl
IunPlolects
PartsList -Tone-ActivatedRelay
lC1
- LM567Integrated
Circuit(National)
Q1
- 8C558 general-purpose
PNP siticontransistor
D1
silicondiode
P1
K1
- relay- 6V - see text
R1
- 10,000ohm,114W,5%
resistor
C1,4 - 0.1 uF ceramicor metalfilmcapacitor
C2
C3
- 0.O47ceramicor metalfilmcapacitor
C5
capacitor
ldeasto Explore
o Explainhowa PLL (Phase-Locked
Loop)works.
o Whatare harmonics
of a signal?
uses:
Scienceand uncommon
o Remotesensorscan be usedto closethe relay.Usingan oscillator
to producethe tone,the wiresusedcan be very long,reachingdistancesup to 5 miles.
ztl
Pnbct 88 lom{silrrtdtffiU
o Youcanusea smalloscillator
astransmitter
andthiscircuitaspart
of a receiver
to activate
devicesbytelephone
line.
o Connect
theinputof thiscircuitto theoutputof an audioamplifier.
Pluga microphone
you
to theinputoftheamplifier.
Withsomepractice
cancontroltherelaybywhistling.
o Youcan alsousethistone-activated
relayto controlappliances
fromyourcomputer,
usingthe multimedia
audiooutput.Writea programto produce
a tonewhenanicononyourWindows
screenisclicked
withthe mouse.
o Thetonecanbeusedto turnontherelayif thecircuitis plugged
to
theaudiooutputof yourcomputer.
Threemodesof operation
arepossible:
a) By adjustlng
the lengthof thetonepulseyoucanturnon any
appliance
connected
to the relayduringthistimeinterval.
Theapplipulse
will
ance turnotfafterthe
ends.
b) Usinga monostable
witha 555timer,forinstance,
a shortpulse
canturnon theappliance
attera preadjusted
timeinterval.
c) Usingthe turn-on-and-otf
circuit,described
in thisbook,you'll
havea bistableoperation:
a clickon the icon'turnson the appliance
controlled
bytherelay,andthene)ftclickturnsit otf.
2ffi
hn FeffiEluth Hl0ilmentol
(E)
LIGHTCOMPARATOR
Thisdevicecan be usedto comparetwo lightsourcesby theirintensities.
canbe conducted
usingthis.Youcancompare
Severalopticalexperiments
lightor compare
colorsusingspecialfilters.
colorsof surfaces
by reflected
Resisor LDRs(LightDependent
ThesensorsusedareCdSphotoresistors
part
in the red
tors)thathavepeaksensitivity
of the spectrum(7350angstromsor 735nm).
whichvariesaslightfallson
Asthenamesuggests,
theLDRhasa resistance
falls.In total
As thelightintensity
increases,
resistance
itssensitive
surface.
by
ohmsor more.llluminated
resistance
canbe highas 1,000,000
darkness
fallsto 100ohmsor less.
directsolarlight,the resistance
Bridgeequilibrated
by twoLDRsandan
Ourcircuitis a simpleWheatstone
potentiometer
(Pl).
ddjustable
thesameamountof light,P1canbe adWhenthetwo LDRsarereceiving
justedto geta nullindication
(M1).
ontheammeter
wecancompare
anothersourceof lightwith
lf weuseoneLDRas reference,
A newadjustment
of Pl canrevealthe
thisbyusingtheotherLDRassensor.
thetwolightsources.
difference
between
is shownin Figure 1. No
The schematic
diagramof the lightcomparator
project<nly
resistors.
transistors
areusedin this
layout,usinga terminalstripas chassis,is shownin Figure2.
Components
Wiresto the
Theterminalstripcanbe fixedin the plasticboxusingscrews.
problems.
sensorcanbe as longas 6 feetwithoutinstability
TheLDRsshouldbe mountedintotwosmallopaquetubesto receivelight
Ml shouldbe a zerofromdifferentsourceswithoutoutsideinterference.
wouldbe suitable.
A 50-0-50uA microammeter
centermicroammeter.
Thecircuitcanbepoweredfromtwoor fourAAcells,andcurrentdrainis very
low,extending
batterylifeto manymonths.
280
I
I
I
tr.Fcr 8S llrn8.ffirry
P1
10K
R2
1K
Figurc I
0 0-Q o o o
Figure2
280
folllroHDeilmcmel.
IunPlolccts
PartsList- LightComparator
Resistors)
LDR1,2 - Common1cmLDRs(LightDependent
or CdSphotosensors
M1 - 50-0-50uA ammeter- seetext
resistor
R1,2 - 1,000ohm,114W,5%
R3
- 4,700ohm,114W,5%
resistor
P1
51
81
- 3 to 6V - two or fourM cells
ldeasto Explore
o Useothertypesof sensors,suchas phototransistors
in the circuit.
Whatis the ditference?
.
Explainhowan LDRor CdScelloperates.
o Usea convergentlensin frontof the cellsfor moresensitivity.
Scienceprojects:
o Severalexperiments
involvinglightsourcesin opticscan be made
usingthiscircuit.
o Comparethereflections
frompaperusingdifferent
butequal-power
Whichof them
lightsources,suchas incandescent
and fluorescent.
has the betterperformance?
a lt is possibleto changethiscircuitintoa temperature
comparator.
Justreplacethe LDRswithNTCs.
IunHorloots
hr dn Hlcilmontal
ELECTRONTC
ORGAN(E/P)
in audiowhichwouldmakea nicetoyfor
experiment
Thisis an interesting
children.
The
a keyon a keyboard.
a musicalnoteby pressing
Thiscircuitproduces
bya smallspeaker.
soundis produced
Theelectronic
organwillplayonlyonenoteat a time,butthenumberof notes
is unlimited.
Ditferenttonescan be selectedby pressingditferentkeys,as in a common
byC1,whichcanbealteredwithin
rangeisdetermined
organ.Tonal
electronic
0.022uF(forhighernotes)and1 uF
Valuesbetween
a largerangeofvalues.
(forlowernotes)canbe experimented.
bellin yourhomeor to monitor
Youcanalsousethiscircuitas a multi-tone
sensors
the keyswithditferent
severalplacesat the sametime.Replacing
produce
when
closed.
tones
(reedswitches,
will
ditferent
for instance)
Organis givenin Figurel.The
ofthesimpleElectronic
A schematic
diagram
are diThetransistors
oscillator.
circuitconsistisof a simpletwo-transistor
loudspeaker.
a
small
rect-coupledanddrive
layout,usinga terminalstripas chassisis,shownin Figure2.
Components
Thecircuitcanbe housedin thesameboxas thekeyboard.
Eachtrimmerpotentiometer
ln Figure3we showthelayoutof thekeyboard.
notes.
is usedto adjustindividual
from3 to
fromAAcellsor a powersupplyranging
6 volts.
boardor withsmall
canalsobe madefroma printed-circuit
The keyboard
probe
plate
thecorresponding
plates.
is
a
metal
touched
by
Wheneach
metal
circuitclosesanda musicaltoneis produced.
2A
i
Fnhcrf0 Hwu|ccrw
Pl
tn
.' $fsz
c1
0.047pF
Figure I
Figure2
UF
ffi mGH[erlmcntel
lunProiccls
Figure 3
PartsList- ElectronicOrgan
Q1
Q2
51-4 - keyboard-see text
ohmtrimmerpotentiometer
P1-4 - 1,000,000
R1
- 10,000ohm,114W,5%
resistor
C1
C2
capacitor
55
81
- 3 or 6V - AA cells
SPKR- 4/8 ohm,2to 4 in.- smallloudspeaker
246
Erm $ IhcurdG&Hn
ldeasto Explore
To learnmoreaboutthe circuitor to get beilerpedormance:
o AlterCl in the rangegivenin the textto producea differentrange
of sounds.
o Explainhowthe circuitworks.
o Try to replaceR1 with a networkformedby small transformers,
diodes,resistors,capacitorsand othercomponents.
Modifications
in
the tonepitchcouldbe foundthis way.
Scienceand uncommonapplications:
o ReplaceS1,S2,etc.,withditferentkindsof switches.You
can identity the closedswitchby the tone.
o Useonly one potentiometer
coupledto a cursor.Youcan produce
musicby rapidlychangingcursorpositionand pressingthe series
switch.
o The samekeyboardcan be usedin otheraudiooscillators,
resulting in ditferentconfigurations
of electronicorgan.
AI
-frtF|lhcfisl|]srmh!ild
-
(E)
LIGHT-ALARM
EXPERIMENTAL
alarmwhichuses
light-activated
of a simplebutetfective
Thiscircuitconsists
A lightfallingon the LDRturnson the SCR.
onlya halfdozencomponents.
Thelampwillremainonuntilthepoweris otfor 51 is usedto resetthecircuit.
p1 adjustssensitivity
to theapplication.
according
lens.
theLDRcanbe housedin an opaquetubewitha convergent
sincethereis a voltagedropof
A 6-voltlampcanbe usedwithoutproblems
about2 voltswhenin theONstate.
asyoucanreset
is shownlnFigure1.51 is optional,
diagram
Theschematic
thecircuitbyturningoffthe powersupply.
strip,isshownin Figure2.Thelampcan
usinga terminal
layout,
Components
also
byan LEDin serieswitha 470ohmresistoror abuzzer.You
be repfac'ed
it.
with
lamp
the
replacing
cancontrolan audiooscillator,
from50to 250mA
Any6Vlampranging
Thelampisn'ta criticalcomponent.
canbe used.
ona
SCRneedn'tbemounted
GdSphotoresistor.The
TheLDRis a common
as thecurrentis verylow.
heatsink
Light'Alarm
PartsList- Experimental
Rectifier
Controlled
SCR -TlC106Silicon
LDR- seetext
LDR - Gommon
Xl
- 1,000,000
ohmPotentiometer
- 6V incandescent
lamP- seetext
Bl
- 6-9V- fourAA cells,D cells,batteryor powersupply
S1
- SPSTmomentary
switch
P1
nEa
I
I
{
Ffrlcc[fl m|l|m0rlutm{Hil
Figure I
Figure2
251
lol he lrncflmGntGl
lunProlecls
ldeasto ExPlore
o ReplaceX1 witha 6V relayto controlexternalloads.Wirea 1N914
kick from
diodein parallelwith the relaycoil to preventhigh-voltage
or other
canalsocontrolsmallaudiooscillators
theSCR.You
damaging
devices.
alarm.
o Changepositionof the LDRwith P1 to get a dark-activated
work'
Resistors)
o ExplainhowLDRs(LightDependent
Willthe circuitoperateas
o Replacethe LDRwitha phototransistor.
you want?
Scienceprojects:
o This circuitcan be used to monitortraps or eventsthat involve
objector animalmovements.
o SeveralLDRscan be wiredin parallelto monitormorethan one
alarm,when P1 switches
placeat the sametime.In a dark-activated
position
withtheLDR,morethanoneLDRcanalsobe used.But,inthis
case,you mustwirethe LDRsin series.
2n2
I
mHdffihlmmilnmbr
(E/P)
PHOTOMETER
in
forLDRsareassensingelements
applications
Someof themostcommon
photography
andalsoexperilightmetersfor
counters,
alarms,photo-relays,
mentsin optics.
hereis a simplelightmetermadefroman LDR(Light
Theprojectdescribed
anda 3V
a 0-200uA microammeter,
Resistor
or Photoresistor),
Dependent
batteryformedby twoAA cells.
ratio.
resistance
LDRwitha highdark-to-light
Useanygeneral-purpose
youdon'tneedan ON-OFF
forshortdurations
Sincethecircuitis operating
switch.Justputthecellsin the batteryholderwhenusingthe unit.
to the rangeof yourworkinglightintensity.
Pl adjustssensitivity
is notcritical.
Theammeter
ofthePhotometer.
Anytypewithfullscalerangingfrom100uAto 1 mAcanbe used.
device
aschassis.The
view,usingaterminalstrip
a mounting
Figure2shows
canbe housedin a smallplasticbox.ThemeterandLDRareplacedon the
frontpanel.
youneedto adjustP1.Tryvalues
usedis outof specification,
lf theammeter
between10,000 and 100,000ohms.The LDRcan be housedin a small
ontheapplication.
opaquetube,depending
250
j
i
I
tnmfl
rtmmu
Figure I
Figure2
2tl
foltfielrneilmGntGl
IunPlolects
PartsList - Photometer
Resistor)
LDR - AnycommonLDR(LightDependent
M1
- 0-200uA - meter- see text
P1
R1
- 10,000ohm,114W,5%
resistor
81
- 3V - two AA cells
ldeasto Explore
.
in placeof the LDR.
Try to use a phototransistor
o Replacethe ammeterby a commonmultimeter.
o Youcan replacethe LDRby an NTCand convertthe deviceintoa
meter.
temperature
Scienceprojectsusingthe device:
canbe conducted
lightmeasurement
o Anyexperiment
thatinvolves
usingthisdevice.
o Youcan calibratethe meterscaleusinga commonphotography
photometeras reference.
258
IunFd0rthlhrmoilmmEl
GENERATOR
SEQUENCE
G/P)
putto workbyusingit asa sourceof clockpulsesfor
Anastablemultivibrator,
is thebasisforthiscircuit.
a 4017counter,
or as a
in a rangeof one-of-ten
randomnumbers
Wecanuseit to generate
projects
in
other
applications.
or
0-to-9counterin science
onepulseeachsecondfor
Youcanalsoadjusttheclockso thatit supplies
orat home.lf youalterthe
experiments
usingthecircuitasa timerinscientific
timerangecan be changedso that it suppliesone
clockpulsefrequency,
pulseeachminuteor ten minutes.In thiscase,thetimerangewillriseto 9
(in1- or 1O-minute
steps)!
or 90 minutes
minutes
youcanchange
the
generator
demonstrations,
inlogiccircuits
Asa sequence
switch
a momentary
connecting
of the555to monostable,
astableoperation
it.
or anysensorthatcanbe usedto trigger
uponthe
andR3depends
from6 to 12Vsupplies,
ifthesupplyvoltageis6V.
Usea 470ohmresistor
voltageofthepowersupply.
power
is 12V.
supply
used
if
the
Usea 1,000ohmresistor
the pulseraterangeandcan be altered.Values
C1 determines
Capacitor
thathighervaluesmean
between1 and1,000uF canbe used.Remember
lowerpulserate.
used.
onthecapacitor
Pl adjuststhepulseratewithin100:1,depending
The
diagramof the SequenceGenerator.
theclockpulsesanda 4017CMOSlC,
circuitusesa 555lCtimerto generate
to drivetenLEDsas indicators.
a counterand1-of-10decoder
printed-circuit
boardis shownin
placement
on a homemade
Components
to mountit.
boardor breadboard
Figure2, Youcanalsousea solderless
capacitor,
pieces,
suchastheLEDsandelectrolytic
ofthepolarized
Positions
shouldbeobserved.
2t2
Frrlst18 So|uonce
Ernrrm
tc2
40178
3
2
4
7
'
1
0 1
5
6
9
1
1
Figure I
PartsList - SequenceGenerator
lC1 - 555- Integrated
circuit,
timer
,C2 - 4017- CMOSIntegrated
circuit,counter
LEDs- Gommon
red,yellowor green
P1
- 1,000,000
ohmpotentiometer
Rl,2 - 10,000ohm,114W,5%
resistors
Rg
- 470ohm,114W,5%
resistor
Cl
- 10uF/l6WVDCelectrolytic
capacitor
208
Iunlrcloctstcr$o HnGrlmcntcr
P1
+6/1?r/
l o v
Figure2
ldeasto Explore
o Wirea momentary
switchbetweenlO1'spin 3 and lO2'spin 14 to
controlthe counter.You
can stopthe counteranytimewiththisswitch.
a Explainhowcounterssuchas the 4017work.
o Couldyou alterthe circuitso that it countsto any valuebetween2
and9?
261
Frrffi f8 $oucmrGmcnnr
Scienceanduncommon
uses:
o Wirethe 555as a monostable
multivibrator
and usean LDRas
sensorto triggerit.Thecircuitwilloperateas a pulse-of-light
counter.
o Usethiscircuitina project
pulses
aboutcomputers.You
canproduce
to be countedusingtheexperimentalflip-flop
in thisbook.
described
o Experiments
onESP(Extra-Sensory
Perception)
canbeconducted
usingthiscircuit.
Random
numbers
ina scaleof 1-to-10
canbegeneratedusingthiscircuit.
20[
lort[oHnorlmom0l
ftn Prohcts
(E/P)
TNJECTOR
STGNAL
(multiin doingsomeservicingon youraudioequipment
lf you'reinterested
find this squarewavegeneratorto
media,for instance)you will undoubtedly
be a handytool.Youcanalsousethiscircuitin RFstagesin AM/FMreceivers,
as highas 100MHz.
harmonics
arestrongin frequencies
sincethe oscillator
In this arrangment,frequencyis determinedby capacitorC2, resistorsR1
and R2,and D1. Thefrequencycan be alteredby the valuesof resistorsand/
or capacitorsselected.In our circuitthe oscillatorrunsat about1,000Hz.
The outputsignalwaveformis squareand the outputswingsthe full power
supplyvoltage,whichcan be anythingbetween3 and 12 volts (we recommenda 3-voltpowersupplyif you want a portableunit).Supplycurrentis
typicaly10 uA, extendingbatterylife.
Figure I showsthe completeschematicdiagramof the SignalInjector.lC1 is
by C2,R2
is determined
Frequency
a 555timer,wiredas an audiooscillator.
and R1.Youcan changeC2 withina largerangeof values.
Figure 2showsthe homemadePGboardwherethecomponentsaremounted.
A small3V batterycan also be usedif you wanta very compactmounting.
'Tronf'ofan audio(or RF)
A signalinjectoris usedfrom the "bacK'tothe
circuit.Forinstance,to usethe signalinjectorwith an AM receivelapplythe
signalfrom the probeat the baseof the outputtransistor.lf that stageand
everythingafterit operatescorrectlythe signalwillbe heardin the speaker.lf
the outputstageprovesto be OK, movebackto the baseof the drivertranapplythe
is working.Then,
outputsignalwillbe higherif everything
sistor.The
volume
it
the
towardsthefrontof thecircuitby injecting at
signalprogressively
control,detectorstage,lF stagesand the mixer.
Thecircuitcan be housedin a smallplasticboxandconnectedto the external
circuitthrougha probeand an alligatorclip. Figure 3 representsa possible
housingarrangement.
Totestthe signalinjector,applythe signalto the inputof any audioamplifier.
208
Prdsr lf
$lnrllnhGhl
O.O1p.F ppl
Figure 1
PP1
G1
OV
?
+3V
Figure2
200
IunPlolec$lorthoHneilmGilGl
PartsList- SignalInjector
lC1
- TLC7555CMOSintegrated
circuit- timer
D1
- 1N4148or 1N914general-purpose
silicondiode
resistor
R1,2 - 10,000ohm,114W,5%
C1
- 10 uE 6 WVDCelectrolytic
capacitor
C2
- 0.047to 0.1 uF ceramicor metalfilmcapacitor
C3
S1
81
- 3V - two AA cells
PP1 - Probe
G1
I
- Alligator
clip
ldeasto Explore
o Whathappenswiththe waveshapeif D1 is removed?
o Whycanthe circuitbe usedin frequencies
as highas 100MHzif it
generates
a 1,000Hz signal?
o Replacethe lC witha common555 (bipolar).
The circuitwillwork,
version.
is
higher
than
in
the
original
the
current
drain
but
o RemoveC3 and powerthe circuitfrom a 5V powersupply.The
signalinjectorcan nowbe usedin TTL logiccircuits.
210
Pnftct lf
$$illnhcbl
o Rl and R2 areshownas fixedresistorsin this project.
Youcan
(1,000,000
changetheseresistors
to a potentiometer
ohms,for ingenerate
stance)inserieswitha 1,000ohmresistorto
signalswithina
largerangeof frequencies
andduty-cycles.
Scienceprojects
usingthesignalinjector:
o Thecircuitcanbe usedas a simplebio-stimulator
in biological
experiments.
power
levels
high
Stimulation
as
asthe
supplyvoltagecan
beachieved.
Theselevelscanbe usedin directnervestimulation.
o Wirea piezoelectric
transducer
orcrystalearphone
to theoutputof
thissignalinjector.
A toneof about1,000Hzwillbe produced
andcan
be usedin experiments.
Figure3
ztl
forthcHloilmcnbr
HnProlcct$
(E)
METALDETECTOR
Youcan use this simplemetaldetectorto locateplumbingpipes,electrical
wiringinsidewalls,find a lostwatchor coin at the beachor evena treasure
with goldcoinsburiedyearsago by pirates.
whereyoucan showthe magnetic
Youcanalsousethe circuitin experiments
diamagnetic,
propertiesof materials.The
betweenparamagnetic,
ditferences
and nonmagneticmaterialscan be shown.Interestingexperimentscan be
conductedusingthe metaldetectordescribedhere.
This circuitwill detectthe presenceof metallicobjectsthroughany nonconductivematerialsuchas dirt, wood,stone,plasteror plastic.
With a littlepractice,you will be able to detectmetallicobjectsto depthsof
overseveralinchesand will giveyou a fairlygoodideaof theirsize.
methodto detectan object.
Our circuitusesthe beat-frequency
in
Thefrequencyof the searchcoiloscillatorchangeswhenthe conductance
the field of the searchcoil changes.Therefore,when metalscomewithina
shortdistanceof thecoil,thefrequencyis changed,whichin turnchangesthe
pitchof the audiblesound.
The soundis producedby the speakerof a commonAM receiverthat tunes
the coiloscillator.
A schematicdiagramof the MetalDetectoris shownin Figure 1. Observe
Youcan also use a
oscillator.
that the circuitis a very simpleone-transistor
power
the
supplypolarity.
general-purpose
inverting
transistor,
PNPsilicon
usinga terminalstrip
of the electroniccomponents,
The physicalarrangment
part
of this projectis the search
as chassis,is shownin Figure2.Thecritical
coil.
The searchcoil is woundin a large6-inchplasticFrisbee.Beginby securing
one end of the enameledmagnetwire form (18 to 22 AWG)with masking
forma loopin the magnetwireforthe center
tape.On thetenthwrap(haltway)
tap,thencontinueuntilyou completethe 20 turnsof wire.
rcbct l5 tcfirl !0bcbr
c1
22AOpF
Figure 1
Figure2
ttE
lunPnlec$lorlltcHlcrlmcntor
to securethe coilwirefirmly,as one looseloopin the coil
It is veryimportant
willcausethe detectorto be unstable.
To use:
Fix a smallportableradiocloseto the oscillatoras shownin Figure 3.
Tunethe radioto a freepointof the rangebetween550and 1,600kHz.Adjust
tunethissignalas a whistle.lf youcan'tfind
CV in thesearchcoiloscillatorto
the oscillatorsignalin theAM band,reduceor enlargethe searchcoilby a few
turns.
Passingthe searchcoil over a metallicobjectwill changethe pitchof the
changeoccurs,you shouldbe directly
whistle.Whenthe mostpronounced
overthe metalobject.
Figure3
2t6
PnFGrt5 ftfiilromau
PartsList - MetalDetector
Q1- 8C548general-purpose
Ll - Searchcoil- seetext
CV- 365pF - anyvariablecapacitor
(fromnonworking
AM radio)
C1 - 2,200pF ceramiccapacitor
C2- 0.1uFceramiccapacitor
Rl - 10,000ohm,114W,5%
resistor
51 - SPSTslideor toggleswitch
81 - 6 or 9V - fourAA cellsor 9V baftery
ldeasto Explore
o Makeexperiments
withditferent
kindsof materials
to seehowthe
detectorworkswitheachone.
o Explain
whathappens
whena metalobject
is introduced
in a magneticfield.ls thereanywayto identifythe metalbeingdetected?
o Thecircuitcanalsobe usedas an RFsignalgenerator.
Togetthe
signalfromthisoscillator,
probe
connecta
to thecollector
of thetransistorwitha 1,000pF capacitor
andan alligator
clipto theemitter.
m
forhc trncilmcmcl
IunProiecls
Scienceprojectsand uncommonapplications:
o Severalexperimentsinvolvingmetaldetectioncan be conducted
usingthissimplemetaldetector.An examplewouldbe a workto show
andnon-magnetic
diamagnetic
betweenparamagnetic,
the differences
materials,as suggestedearlier.
o The searchcoil can be modifiedto applyRF signalsto plantsor
on
to find the effectsof RF (RadioFrequency)
animals.Experiments
plant
growth
this
made
with
circuit.
germination
be
can
or
seed
218
tio ffiotlmeilor
HnFnlccosfu
-
SET(E)
GRYSTAL
no batterypowerat all canbe
whichrequires
radioAM receiver
A complete
crystal
Theclassiccircuitof thewell-known
createdwitha fewcomponents.
or
diodeas detector,
canbe basedon a germanium
radioor crystalreceiver
if youprefer,theoriginalgalenacrystal.
antennatuningcoil
Figure I showsthe classiccircuit.L1 is a proprietary
(365to 500
variablecapacitor
woundon a papertubeandCl is a matching
radios.
transistor
canbe foundin old non-working
pF).Avariablecapacitor
Youcanalsofindthediodein thesesetsanduseit forthisproiect.
is
Virtuallyany diodecan be used,and the onlyothercircuitcomponent
higha
be
must
Theearphones
acrossthe output.
C1,connected
capacitor
(headphones).
type
impedance
good
groundconnection
is essentialfor
aerialandgoodphysical
Anexternal
reception.
ThecircuitwilltuneAM bandradiostationsnotfarfromyourhome.
layoutis shownin Figurc2.
Component
wireon a f -inch
L1 is formedby 100turnsof No.22to 28 AWGenamelled
papertube.
diameter
PartsList - CrystalRadio
D1
- 1N34or anygermanium
diode
L1
- Coil- seetext
CV
- 365to 500pFvariablecapacitor
C1
- 470pF ceramiccaPacitor
- High{mpedance
(2,000to 10,000
ohms)phone
PHONE
2t2
,
t
Prdcerl0 Gl'$|ds0r
Figure 1
Figure2
ldeasto Explore
o Usean audioamplifier
to getbetterreception.
o Replace
thecoilby 100turnsof No.22lo 28 wireon a ferriterod.
SciencepQects:
o Thissetcanbe usedto demonstrate
howold-timeradioreceivers
operated.
Explainhowa galenadetector
works.
lu h0 Euol|mcmcl
fr nPfcf0Gts
LLED
TEMPERATURE-CONTRO
(E)
oscrLLAToR
withthis temperature-dependent
experiments
Youcan conductinteresting
pitch
Thesensor
temperature
of a sensor.
the
Tone
depends
upon
oscillator.
of this
silicondiode.The reverseresistance
is a commongeneral-purpose
junction
temperature.The
circuitcanoperate
onthe
diodeisslight,dependent
-20and+100degreesCelsius.
rangetypically
between
in a temperature
canbealteredina large
rangedepends
uponCl.Thiscomponent
Frequency
to
uF
rangeof values.Valuesbetween0.01and 0.47 can be substituted
produce
tonesin theaudiorange.
"clicks"
of
uponthetemperature
witha ratedependent
lf youwantto produce
Metal
film
or
1
uF.
0.47
and
with
values
between
the sensor,try capacitors
canbe usedin thiscircuit.
ceramiccapacitors
nearthepointwhereit beginsto run.
Pl youcanputtheoscillator
Byadjusting
makingit operateas a
risewilltriggertheoscillator,
Then,anytemperature
temperature
alarm.
fromtwoorfourAAcells,andcurrentdrainis low.
diodecanbeprotected
silicondiode.The
Thesensoris anygeneral-purpose
andwater.
againstmoisture
is shownin
Oscillator
Theschematic
diagramof theTemperature-Controlled
wirefor
FigureL Thesensorcanbewiredto thecircuitbya longtwisted-pair
remoteoperation.
layout,usinga terminalstripas chassis,is shownin Figure2.
Components
youcanalsomountit on
purposes,
forexperimental
Asthecircuitis intended
board.
a solderless
should
suchasthediodeandpowersupply,
components,
Position
ofpolarized
be observed.
288
PfjrGtO lMdtroffiffi
Figure 1
Figure2
zal
IunProlccts
foltln Hnulmomcl
Iled OsciIlator
PartsList- Temperature-Contro
NPNsilicontransistors
Q1, 2 - 8C548general-purpose
Q3
D1
silicondiode
P1
- 1,000,000
ohm potentiometer
resistors
R1,2 - 10,000ohm,114W,5%
R3
- 1,000ohm,1/4W,5%resistor
Cl
S1
81
- 3V or 6V - two or fourAA cells
S P K R- 4 o r I o h m s - 2 o r 4 i n . l o u d s p e a k e r
ldeasto Explore
To learnmoreaboutthe circuitor to get betterpedormance:
o By replacing
circuitwilloperD1withan LDRor phototransistorthe
oscillator.
ate as a light-controlled
o Explainwhy the resistanceof the sensorvarieswithtemperature,
thiscircuit.
controlling
o Replacethediodewitha transistor(conection
is madeusingcollector and emitterterminals).Explainwhythisdevicecan alsobe usedas
a temperaturesensor.
200
ftltfct|'Iffi|tG|lI
Scienceprojects
or uncommon
uses:
o Youcan usethis circuitas a biofeedback
deviceby replacingthe
Thesubject,holdingthe sensorin hand,
sensorwithtwoelec,trodes.
canlearnhowto controlthetonethroughstressandbreathing
management.The
circuitalsooperates
asa liedetector
usingthisconfiguration.
o Anyexperiment
involving
temperature
variations
canbeconducted
usingthiscircuit.
2tt
forthoHmlhcmcl
frn FdGG03
SIREN (E/P)
FREQUENCY-MODULATION
Actingon a capacitorcharging,one oscillator(pins1,2 and 3 of lC1) can
modulateanotheroscillatorin frequency,as describedin this project.The
producedtonesthusrunfromhighto lowandvice-versaat a ratedetermined
by the firstoscillatorfrequencyand also by P1 and P2 adjustments.
The circuitcan be usedas a siren,part of alarms,gamesand manyother
With a 12Y powersupplythe outputpoweris up to a wattage
applications.
representing
an excellentaudiolevelin a loudspe,aker.
The basiccircuithas tone, modulationrate and depthadjustedby trimmer
potentiometer.There
thatcan be changedto alter
arealsosomecomponents
the performanceof the siren.G1, for instance,determinesmodulationrate
depthand rateand
andcan rangefrom 1 to 47 uF.C2 determinesmodulation
can also be alteredwithina large rangeof values.C3 determinetone frequency,rangingfrom0.01to 0.1 uF.
Powersupplycan rangefrom6 to 12V.Witha 12Vpowersupplycurrentdrain
is as highas 2 or 3 amps.Fl is importantto preventproblemswith shorts.
Ql is a powerFET and equivalentscan be used.Youalso can replacethis
transistorwith a DarlingtonNPN powertransistorsuch as TlP110,but you
mustalsoadda seriesresistorwithbaseterminal.Usea 10,000ohm resistor
tor this task.
Siren is shownin Figure 1.
The schematicfor the Frequency-Modulation
Observethattwo gatesare usedas oscillatorsandthe othertwo of a 40938
lC are usedas butfer-inverters.
boardis shownin
Componentsplacementon a homemadeprinted-circuit
purposes
the circuitcan also be mountedon a
Figure 2. Forexperimental
solderlessboard,andit is importantto placethetranslstoron a largeheatsink.
should
capacitors,
suchas electrolytic
Positionof the polarizedcomponents,
be observed.
typefor betterperformance.Installingit
The speakershouldbe a high-power
in an enclosurewill providebettersoundlevel.
PrdrctfE ffiSftm
t r c ;
ES
Ytlo
sst
ETE
EF
s5
6
lrf
z
=
I
.lI-
d *(\l {
o
o
z
l!
E
a
=
tr
rH
EE
Figure I
208
Iur Plolccts
lol[rc Bueilmomol
Siren
PartsList- Frequency-Modulation
lC1
Circuit
Q1
- lRF630or equivalent
PowerFET
SPKR- 4 or 8 ohms,4- to 8-inchspeaker- see text
F1
- 5A fuse
R1
- 100,000ohm,114W,5%
resistor
R2
resistors
R3,4 - 10,000ohm,114W,5%
P1
- 2,2OO,OO0
ohm trimmerpotentiometer
P2
P3
C1
- 4.7 uF,16WVDCeletrolytic
capacitor
C2
- 1,000uF,16 WVDCelectrolytic
capacitor
C3
capacitor
C4
- 0.022uF ceramicor metalfilm capacitor
ldeasto Explore
To learnmoreaboutthecircuitor to getbetterperformance:
o ExplainhowPowerFETswork.
o AlterCl , C2 andC3to createnewsounds.
2gl
Prolcct
fE Inrucnclfrilulrdrn$lrcn
SPKR
Figure2
o Wire pins 1 and 5 togetherand to an externalcontrolcircuit.The
sirencan be controlledby externallogiccircuits.
o Determine
the logiclevelin pins10 and 11 whenpins1 and 5 go
low.Whatwill happenwithcurrentdrainin this case?
o ReplaceQ1 by a TlP31or 8D135to operatewith lesspower.The
powersupplyshouldbe reducedto 6 or gV in this case.
Scienceprojectsand uncommonapplications:
o ReplaceR1 with an LDR and experimentwith a light-controlled
siren.
o Usethis sirenas part of alarms.
o Usingthis sirenyou can generatespecialsoundsto experiment
withanimalconditioning.
o Modulatedultrasounds
can be producedby reducingC4 to values
pF.
as fowas 2,200or 4,70O
205
foltDclrnoilmcmGl
tunProiects
colNTossER(E/P)
theflippingof a coinby merelypressingS1' Of course,
Thiscircuitsimulates
can't
version,if usedfor importantdecisions(or experiments),
the electronic
be loadedor weightedand is 100%random.
in a frequencyrate deterThe circuithas two LEDsthat flick alternatingly,
minedby C1,whenpoweris ON.Whenyou press51 the circuitstopsimmediatelyandonlyone LEDremainsON.
Powersupplycan rangefrom5 to 12 volts,andthismeansthatyoucan use
version.
AA cellsin a Portable
Cl,
to the intendedapplication:
can be alteredaccording
Somecomponents
use
also
for instancecan be alteredin a rangefrom0'01 lo 0-47uF.Youcan
a touchsensorto stopthe tosseror increaseR1'svalueto up to 10,000,000
ohms.
The schematicdiagramfor the coin tosseris shownin Figure 1. Only one
g"t" " 49gglC is uied as oscillatorto producerandompulsesin this circuit'
boardis shownin
componentsplacementon a homemadeprinted-circuit
Figire2. The circuitcan easilybe housedin a smallplasticbox.
casuchas the LEDsand electrolytic
Positionof the polarizedcomponents,
pacitor,shouldbe observed.
298
?rrm$
+5Vto+12V
c2
100pF T
t:
tcl
1t44@,38
tcz
40138
teout
1
R1
t0K
Figure I
PartsList - CoinTosser
lcl
circuit
LEDs- Commonred,yellowor green
S1
- SPSTMomentary
switch
R1,2 - 10,000ohm,114W,5%
resistors
R3
- 1,000ohm,1l4W,S%resistor
C1
C2
- 100uE 16WVDCelectrolytic
capacitor
Glhlm
HnPl.lrGtsffimHFdmcntcl
_d
9
Figure2
ldeasto Explore
canbe usedto driveincandeso Insteadof usingLEDs,transistors
centlamps.
o Sl can be placedas far as you wantfromthe circuit.Common
parallelwirecanbe usedforthistask.
thatthe
o Explainhowa flip-flopworksandhowyoucanguarantee
circuitis 100%random.
80c
mFa
..': r0 Grhlrcu
Science
anduncommon
applications:
o YoucanconductESP(Extra-Sensory
Perception)
experiments
using
thiscircuit.51 canbe placedfarfromthe LEDsfor betterresults.
o Experiments
withprobability
theorycan be conducted
usingthis
circuit.
o Tryto couplea sequence
generator
to the oscillator
usedin this
circuitto geta 1-to-10ratflecircuit.
tfl
Hntt|!ffifiiloHruhm
(E)
PLASMAOSCILLATOR
feedback
thatcanbe usedin an uncommon
medium
A flameis a conductive
canbe
Thisconfiguration
of an audiooscillator.
loopto controlthefrequency
flame.
a
of
of theconductivity
usedas a confirmation
matbythe'Tourth"
inthisprojectis controlled
described
Theaudiooscillator
"plaSma"
part
of an
or an ionizedgaS,and Canbe usedas
ter state,the
physics.
in
experiment
interesting
by a simplematchor a candleandtheflickering
Theflamecanbe produced
sound.
thegenerated
etfectwillmodulate
on the
between1 and 500 Hz, depending
The circuitrunsin frequencies
andflamepositions.
electrodes
is shownin Figurel.The high
of thePlasmaOscillator
diagram
A schematic
in thisproject.A flametypically
of a 40938is fundamental
inputimpedance
in the rangeof tenthsof megohms.
hasa resistance
positioning
is shownin Figure2.
Theprintedcircuitboardforthecomponents
Sensordetailsarealsogivenin thatfigure.Twowires,oneplacednearthe
other,withabout1 inchof baredlengthas shownin the figure,formthe
"plasmasensof.Theflameshouldinvolvethetwobaredwiresat the same
to operate.
currentto flowandtheoscillator
timeto allowthefeedback
can replacethe transistor
transducer
An outputstageusinga piezoelectric
canbepowered
Witha lowercurrentdrainthisconfiguration
andloudspeaker.
fromfourAA cellsor a 9V battery.
-
3tf
tYrlrd 50 Plrsmr
0scmrbr
+5 to 12V
lC1 = 40938
SPKR
4l8n
Q1
8D135
OR
TIP31
X1
PI.ASMA
Figure I
PartsList- PlasmaOscillator
lOl
- 40938CMOSIntegratedCircuit
SPKR- 4/8 ohm 4-inchloudspeaker
Q1
- 8D135orTlPSl PowerNPNsilicontransistor
R1
- 10,000ohm, 1l4W,5olo
resistor
R2
X1
- Plasmasensor- see te)ft
C1
- 1,000to 4,700pF ceramicor metalfilmcapacitor
t05
fil h0 mOilmcmcl
fr nP?0lc0ts
SPKR
X1
+61+12V
Figure2
ldeasto Explore
o Explain
whythecircuitdoesn'toperateusinga neonorfluorescent
lampas a plasmamedium.
o Explain
is.
what"plasma"
o Youcanalterthiscircuitto useit as a flamealarm.
300
Frm60
lffiScffiffi
applications:
Science
a Otfcourse,thebasicideaofthisprojectisto useit inanexperiment
plasma.
gasloseselecinvolving
Plasmais produced
whenanionized
trons.Thethe gasconvertsin a "soup"of freeelectronsandionized
atoms.
o Usedifferentkindsof flames,suchasthoseproduced
bymatches,
gas,paper,etc.,andcompare
pitch.
theirconductivity
tone
by'the
ilt

fun electronics projects for the experimenter

Transcription

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