Docstoc

Fun Projects 47 Chapter

Document Sample
Fun Projects 47 Chapter Powered By Docstoc
					          lu
fr nPfcf0Gtsh0 Euol|mcmcl

                            LLED
           TEMPERATU E-CONTRO
                   R
                              (E)
                     oscrLLAToR

Youcan conduct                          with
                           experiments this temperature-dependent
                 interesting
          Tone
oscillator.   pitchdepends                               The
                           upon temperature a sensor. sensor
                                  the          of
is a common  general-purpose silicon      The
                                    diode. reverse           of
                                                    resistance this
diode slight,
       is    dependent the
                        on    junctiontemperature.The canoperate
                                                   circuit
in a temperaturerange                  -20
                              between and+100degrees
                      typically                          Celsius.
          range
Frequency depends        upon                             in
                              Cl.Thiscomponent bealtered a large
                                              can
rangeof values.  Values between 0.01and 0.47                     to
                                             uF can be substituted
produce tones theaudio
              in          range.
lf youwant produce
          to         "clicks" a ratedependent thetemperature
                            with              upon                of
the sensor, capacitors
           try           withvaluesbetween                   film
                                          0.47and1 uF.Metal or
ceramiccapacitors be usedin thiscircuit.
                  can
Byadjusting youcanputtheoscillator thepoint
          Pl                    near                 to
                                          where begins run.
                                              it
Then, temperature willtrigger oscillator,
    any           rise         the                     as
                                         making operate a
                                               it
          alarm.
temperature
                                                  is
                                             drain low.
Thecircuit bepowered twoorfourAAcells, current
         can       from              and
                                     diode beprotected
Thesensor anygeneral-purpose diode.The
        is                silicon        can
      moisture water.
against      and
Theschematic                                      is
                                         Oscillator shown
            diagram theTemperature-Controlled
                   of                                     in
FigureL Thesensor bewired thecircuit a long
                 can     to        by      twisted-pair for
                                                     wire
remoteoperation.
Components layout,using terminal as chassis, shown Figure2.
                       a       strip        is     in
Asthecircuit intended experimental
           is        for                  you           it
                                   purposes, canalsomount on
           board.
a solderless
       of        components, asthediode power
Position polarized       such         and        should
                                            supply,
be observed.


288
PfjrGtO lMdtroffiffi




Figure 1




Figure2


                       zal
IunProlccts tln Hnulmomcl
         fol

        PartsList- Temperatu       Iled
                           re-Contro OsciIlator
      Q1, 2 - 8C548general-purpose silicon
                                NPN      transistors

      Q3      - 8C558general-purpose silicon
                                  PNP      transistor

      D1      - 1N914
                    general-purpose diode
                                 silicon

      P1      - 1,000,000
                        ohm potentiometer

      R1,2 - 10,000         resistors
                  ohm,114W,5%

      R3      - 1,000ohm,1/4W,5%resistor

      Cl      - 0.047uF ceramic metalfilmcapacitor
                              or

      S1      - SPSTtoggle slideswitch
                          or

      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 withan LDRor phototransistorthe willoper-
                      D1                          circuit
                              oscillator.
      ate as a light-controlled
      o Explain  why the resistance the sensorvarieswithtemperature,
                                  of
                this
      controlling circuit.
      o Replace diodewitha transistor
                 the                 (conection madeusingcollec-
                                              is
                             Explain thisdevice alsobe usedas
                    terminals).
      tor and emitter              why         can
      a temperature sensor.




200
                          ftltfct|'Iffi|tG|lI

      projects uncommon
Science      or       uses:
    o Youcan usethis circuitas a biofeedback      by
                                            device replacing the
          with              The
    sensor twoelec,trodes. subject,            the       in
                                        holding sensor hand,
    canlearnhowto control tonethrough
                         the             stress breathing
                                              and           man-
    agement.The      also         as
               circuit operates a liedetector        this
                                                 using configu-
    ration.
    o Anyexperimentinvolving        variations beconducted
                           temperature       can
        this
    using circuit.




                                                           2tt

				
DOCUMENT INFO