The Giant book of electronics projects

496 Pages·1982·50.929 MB·English

by  coll.

No. 1367
$19.95
THE GIANT BOOK ,OF
ELECTRONICS
: PROJECTS
~ BY THE EDITORS OF 73 MAGAZINE
FIRSTEDITION
FIRSTPRINTING
CopyrightC 1982byTAB BOOKSInc.
PrintedintheUnitedStatesofAmerica
Reproductionorpublicationofthecontent inanymanner,withoutexpress
permission of the publisher, is prohibited. No liability is assumed with
respecttotheuseoftheinformationherein.
LibraryofCongressCataloginginPublicationData
Mainentryundertitle:
TheGiantbookofelectronicsprojects.
Includesindex.
1.Electronics-Amateurs' manuals. I.73 magazine for
radioamateurs.
TK9965.G498 621.381 81-18243
ISBN0-8306-0078·7 AACR2
ISBN0-8306-1367·6(pbk.)
Contents
,
Introduction
1 Power Supplies and Regulators 1
A Basic 13.S-V, 25-A Power Supply-A 12 Volt Power
Supply-A2Q-Amp,Adjustable,Regulateddc Supply-Dual
Voltage Power Supply-Another Dual-Voltage Supply-
Heavy-DutyPowerSupply-FMPowerSupply-LowVoltage
Power Supply-Adjustable Bench Supply-Versatile Power
Supply-Inexpensive Power Supply-Three Terminal
Regulators-The 723 Voltage Regulator-Adjustable Elec-
tronlc Load
2 General Test Equipment 75
Meterless Ohmmeter-An Ohmmeter for Solid-State
Circuits-Build an Audio VOM-VOM Design-Rx and Cx
SubstitutionBoxes-Wide-RangeRfResistanceBridge-AC
Wattmeter-RFWattmeter-Capacity Meter-AudibleTran-
sistorTester-VersatileTransistorTester-Semiconductor
Test Gadget-Use With Your Scope-Bargain Zener
Classifier-IC Audio Frequency Meter-Effective Radiated
Field Meter-Simple Bridge for Measuring Meter
Reslstance-FieldStrength Meter
3 Special Test Equipment 119
Signal Generator-Signal Tracer-An Audible. LogiC
Probe-TV Test Unit-Power Supply Tester,Using a Load
Bank-Frequency Counter-Frequency Standard-Audio
Function Generator
4 Amplifiers 155
General Purpose Preamp-Bargain Preamp-Inexpensive
400WattAmplifier-SO WattAmplifier for 1296MHz
5 Radio And TV Receivers 171
A Simple Recelver-HF Receiver-Five Band Receiver-
Low-CostReceiverfor SatelliteTV-WWV-t0-8Q-Meter Con-
verter
0_
6 Transmitter, Transceivers, and Accessories 207
The Keycoder 1-A Vest Pocket QRP Rig-A Miniature
Transceiver-Easy QRP Rig-Allband QRP Rig-Two-Meter
Synthesizer-A$10PhonePatch-FastScanATVTransmitter
7 Antennas, Mounts, and Matchers 281
Antenna Basics-The "No Antennas" Antenna-The Better
Vertical-A Tribander for the Attic-Triband Dual Delta-A
Trapped Dipole-Super Loop Antenna-A Fortified Two-
MeterWhip-ThePotted J-BrewUpa BeamforTwo-The
Collinear Beam-The Monster Quad-Four-Band Mobile
Antenna-Inexpensive Beam-Multiband Ground Plane-
The Magnetic Mount-Magnet Mount Antenna for Two
Meters-A Deluxe QRP Transmatch-No-Wire Antenna
Switch-Home-BrewingaParabolic Reflector-DisconeAn
tenna for 1296MHz
8 Batteries And Battery Chargers 359
Nicad Batteries-The Nicad Conditioner-Low Cost Trickle
Charger-Home-Brew an HT Charger-Regulated Nicad
Charger-AJunk-BoxHTCharger-AChargerwithAutomatic
Shutoff-ABatteryVoltage Monitor-Storage Batteries
9 Various Electronic Devices and Gadgets 387
AnAutomaticThertnostat-e-JunkBoxAnemometer-Build a
6D-Hz Frequency Monitor-The Super Clock-Touch-Tune
fortheVisuallyHandicapped-AVisualSignal for theDeaf-
VHFNotch Filter-How to MakeYour OwnCrystal Filters
Overvoltage Protection Circuit-The Panic Button-Build
This Mini-Counter
10 Special Projects and Useful Information 441
A Simple Car Voltage Regulator-Solid-State Car
Regulator-Home-Brew Circuit Boards-TV Games-'-New
Lifefor OldTransformers-New Life for OldKlystrons
11 Easy One-Evening Projects 479
World's Smallest Continuity Tester-Simple Field-Strength
Meter-BuildaCoaxSwitch-SuperSimplen Generator-
LineNoiseSuppressor-SimpleDiodeTester-TheCapacitor
Comparator-SimpleTRSystem-BlownFuseIndicatorsfor
Low Voltage--Gravity Detector-Solar'Powered Alignment
Tool
Index 497
-----.--~----_.-------------~
Introduction
This bookofelectronicprojectsrepresentssome ofthe verybest
projectstoappear in73Magazine. Hereisonevolumeyouwillfind
projects for electronics experimenters, amateur radio operators,
and just anyone who has an interest in the exciting world of
.electronics. Theseprojectscover the wholegamut ofelectronics.
From power supplies to test equipment and from receivers to
transmittersyou'llfinditallinthesepages. Youcanbuildyourown
antenna or your ownamplifier, and there are even some simple
;one-evening projects tohelp yougetstartedthe easy way!We've
tried our bestto give youa real smorgasbordoftriedand tested
electronicsprojects that everyonefromthe beginnertothe oldpro
willfindinterestinganduseful. Sodigoutyourjunkboxes, heatup
your soldering iron, and enjoy!
v
-----------
Other TABbooks by the authors:
No. 801 MasterHandbook ofHamRadioCircuits
No. 805 99 TestEquipmentProjects You CanBuild
No. 806 ThePowerSupplyHandbook
No. 1169 TheGIANTHandbook ofComputerProjects
No. 1369 TheGIANTBookofComputerSoftware
No. 1443 AmateurRadioExtra-ClassLicenseStudyGuide-2nd
Edition
vi
Chapter 1
Power Supplies and Regulators
Ifyou're goingtobuildelectronicprojectsyou'llneedsome wayto
power them. Ofcourse, batteries canbe usedfor some projects,
andotherscanbe powereddirectlyfromthe ac line, butformany
projects you'llneed apermanentpower supply thatprovidesjust
the right voltage. In this chapter you'll find a variety of power
suppliesandregulatorsthatcanbeconstructedexactlyasdesigned
or modifiedto fit your exact needs.
1
ABASIC 13.8-V, 25-APOWER SUPPLY
The 13.8-volt ham radio transceiver has really come ofage.
Manyofthese units are great for mobile operation, but when it
comes to fixed-station use, the transceivers can really come up
short-primarilybecause ofthe comparativelyhighcurrentvalues
they draw onpeaks.
Thetwo-meterFM andpolice-scannerindustrieshave given
usavarietyof13.8-volt, low-currentpowersupplieswhichinmany
casescanbeboughtmore cheaplythanbuilt. However, the seem
inglyrarified 13.8-volt,fifteen-amp(orhigher)powersupplyisnot
that easy to come by, which really limits the possibilities with
transceivers drawinganywhere from sixteen to 20 amperes.
The Circuit
The power-supply circuit uses 2N3055 transistors. Youcan
tailor yourcurrentcapabilitybythenumberofpasstransistorsyou
use. I wanted a25-Ampsupply, so Iused five 2N3055s. Youcan
figureroughlyonetransistorforevery5Ampsyou'llbedrawing.In
a lO-Ampsupply, onlytwo transistors wouldbe used, andso on.
See Fig. 1-1and Table 1-1.
The 2N3055isanNPN powerdevice built intoaTO-3 case.
The3055isoneofthe more easily comebytransistorsandisvery
cheap. Because ofthe power these little devils are going to be
dissipating,heatsinksshouldbeemployed. Iusedaheatsinkwith
approximately27square inches ofsurface areawithfourhalf-inch
fins, which cools nicely. Extreme heat can quickly mess up the
transistorjunction(nottomention anicepaintjob). Before secur
ingthe transistors to the heat sink, applysome silicone thermal
compoundbetween the 3055s and the surface ofthe heat sink to
provide a goodpositive heat transfer.
Ihavealwaysused the rule ofthumbthat ifyoucan't touchit,
youcanblowit. Ifyoudon't care to goheat-sinkshopping, use a
coolingfan.Ifyouuseafaninadditiontothe heatsink, besurethe
air circulates inlinewiththe fins. Blowingair perpendicularlyto
the finssetsupstanding waves-theaerodynamic kind-andtur
bulence and the coolingeffect is minimal.
Transistor-mountinghardwareisnice, butIdidn'tfeel that it
was necessary. Iattachedthe transistorsdirectlyto the heatsink
and then mounted the whole heat-sink assembly on a sheet of
PlexiglasTMattachedtofour standoffs. Since the transistorcase is
commontothecollector, Itappedascrewintooneoftheheat-sink
finsandthis becamemycommoncollectortiepoint. Itisimportant
2
--- ~.---------~-
tokeep allleadlengths constant. Afterdrillingmatching holes for
the base andemitterpins inthe heat sink, heavy-gauge wire was
soldered(carefully)toeachemitter pinthrougha0.25-ohmresis
tor,andthenasecondpieceofwirewasattachedtoeachbasepin.I
then had onlyto connect the rest ofthe circuit to either the heat
sink or one ofthe two bus wires.
Youmayor maynot have difficultylocatinga suitable trans
former capableoftaking120Vacandsqueezingitdownto17to24
V ac. I was lucky enough to locate an old, beat-up, ex-battery
charger transformer at a hamfest whichgave me 120/17Vac. I
thinkyouwillfindoldbatterychargersto beagoodsourceforthe
transformer you willneed. Remember, the transformer must be
capable ofcarrying the current you are going to draw from your
power supply. I paid$3.00 for my transformer and felt robbed; I
haveseenthemforadollar.Yes,youdotakearisk,butremember,
even ifthe transformerisnogood, it isanexcellentsourceof#14
AWGantenna wire (or larger)!
Intherectifiercircuittherearetwoavenuestofollow.Youcan
buyfourdiodesandmakeyourbridgeoryoucandoasIdidanduse
oneofthe niftyone-inch-squareepoxybridgerectifiers. Thelittle
one-inch jobs are convenient because you don't have to mess
around figuringwhichend is the anode and whichis the cathode.
+,
Ordinarily, the expoxied bridgesare simplymarked ac,ac, and
As always, no matter what you dofor rectification, be sure
yourrectifierisratedforthe currentyouwillbeneeding. Most of
Fig.1-1.Power supplyschematicdiagram.
3
Table 1-1.PartsUstFor25Amp Supply.
C1-13,OOO-uF,25-Velectrolyticcapacitor
C2-1Q.uF,25-Velectrolyticcapacitor
C3-0.22-uF,1Do-Vtubularcapacitor
C4,CS-O.01-uF,500Vceramiccapacitor
D1-D4-25-Adiodesorepoxy bridge rectifier(seetext)
D1-DS-1N4004diodes
F1-Fuse,SAmp
F2-Fuse,30Amp
01,02,03, 04,OS-2N30SStransistors
R1-12Q.Ohm4-Wresistor
R2-3000-0hm,VZ-Wresistor
R3-SOO-0hm,1-Wpotentiometer
R4,RS,R6,R7,R8-0.25-0hm, 1-Wresistor
IC1-7812voltage regulator
S1-SPSTswltcn
S2-6-posltionwafer switch
T1-120/17·24-Vacpowertransformer(seetext)
Miscellaneous: NE1neon bulb, binding posts, line cord, Q.25-Vdc
voltmeter,Q.3Q.Aammeter,heatsinks,chassis,blower,fuseholders;
andbulb socket.
the little squarebridges are ratedbetween20and35amps. Iam
usingaSemtech-Alpac7905onlybecause Ihappened to haveone
onhand. Motorola, InternationalRectifier, VARO,andEDlmake
excellent equivalents.
Voltage regulation depends on adequate filtering and an IC
known as a 7812. After much experimentation. I found that my
voltage regulation (as well as hum attenuation) improved as I
increased the value offilter capacitor C2. Starting out with 2000
ILF, Iworked mywayupwardto 13,000ILF. ThoughInowhavea
37,OOQ-ILFfilter capacitor inthe circuit, 13,000ILFseemedtobe
enough.The amountoffiltering achieved bygoingfrom13,000to
37,000 ILFis very, very slight and detectable onlywith a scope.
Obviouslyonecan't ignorethethoughtthat if13,000ILFisgood,a
higher value wouldbe better, but let me caution youenthusiastic
high-capacity freaks against installing 150,000-ILF capacitors
without limiting inrush current. I haven't experimented beyond
37,000 ILF.
The 7812voltage regulator is anICdevice capable ofmain
taining excellent regulation as longas the input voltage falls be
tween 14.6 and 19volts nominally. Anumber of companies are
producing the 7812 and it generally has some sort of prefix or
suffix, but the digits remain the same.
4