Fun Projects 35 Chapter

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                      BEEPER
               WTRELESS     (E)
ThisFMwireless        produces beep canbetuned anydead
             tranJmitter      a    that            on
point the FMbroadcast
     of              band. circuit be usedas a localizer
                          The    can                    when         I
        to     or
attached objects  persons. alsocanuseit as a wireless
                         You                        alarm.
                                                                     l
Thesignal be tunedon common radios a range to 150feet.
          can                  FM      in   up
                                                                     l
          for           version given
Alterations a far-reaching    are    below.
                                                                     l
         produces intermittent of about1 Hz.An audiotoneis
Thecircuit       an            beep
                                                        by
generated lClb (pins5, 6 and4) anditsfrequency determined R2
        by                                   is
andC2.Youcaneasily                            R2.
                  alterthisfrequency adjusting Resistor
                                    by                 values
between22,OOO and 100,000  ohmscan be experimented or, if you
                                                  with
prefer,
     100,000ohms series 10,000
                 in       with      ohms replace
                                         can      R1.
Repetition is per R1 andC1.Values variable. C1,values
         rate                      are         For          be-
tween                                                   value
      0.15and1 uFcanbetried. is important testfortheideal
                           lt          to                    of
thiscomponent,depending the intended
                      on            application.
Theschematic         of        beeper shown Figure1.Three
             diagram thewireless    is      in
gates a 4093lGareused generate low-frequency
    of                  to      the                  and
                                              signals, one
RFtransistor used generated high-frequency
           is     to       the           signal.
Components placement a homemade
                   on             printed-circuit
                                              boardis shownin
      2.        is                                      in
                             high-frequency Capacitorsthis
Figure Placementcriticalforthe            stage.
stage     be
     should ceramic.
              turns No.18or 20wire a1l2 in.form
L1consists four
         of       of              on           without ferrite
                                                     a
core.
Theantenna formed a piece bare
           is      by      of     wirebetween and10inches
                                             5              long.
                                                          perfor-
It canbe connected anytap on the coil.Experiment get better
                 to                           to
mance.
Thepower  supply     drain about mA.You usefourM-cellsor
               current    is    10    can
a 9V battery power transmitter.
           to     the
Fora wireless alarm, canbereplaced thecontacts a relay.The
                    51             by           of           relay
is usedto interface alarm
                  the                    in
                         withthetransmitter thisapplication.

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                                             ?rfhct85 tlrulmclcomr



                lC1= 40938                  R3
                                    c4      8l<2
                                  4700pF
                                            CV

                                    c3
                                   0.O1pF


                                             Q1-
                                            8F494
                                               R5
                                               47




                             Figure I




                             Figure2


       way
Another to interface alarmwiththe transmitter to connect
                     an                     is         relay
       in       with        points andB in theschematic.
contacts series C3 or between     A                     See
moredetalsin ldeas Explore.
                  to
IunPruiccts theErrcilmentct
         lol

                 PartsList-Wireless Beeper
      lC1   - 4093CMOSIntegrated
                               Circuit

      Q1    - 8F494or equivalent          transistor
                              NPNRF silicon

      L1    - coil- seetext

      CV    - trimmer       -
                    capacitor 20 to 40 pF maximum

      R1    - 2,200,000         resistor
                      ohm,114W,5%

      R2    - 39,000ohm,1/4W, resistor
                            5%

      R3    - 8,200          resistor
                   ohm,114W,5%

      R4    - 6,800ohm,114W,57o
                              resistor

      R5    - 47 ohm,1/4W 5% resistor

      C1    - 0.22uF ceramic metalfilmcapacitor
                           or

      C2    - 0.047uF ceramic metalfilmcapacitor
                            or

      Cg    - 0.01uF ceramic metalfilmcapacitor
                           or

      C4    - 4,700pF ceramic
                            capacitor

      C5    - 4.7 pF ceramic
                           capacitor

      CG    - 0.1 uF ceramic
                           capacitor

      A              -
            - antenna see text

      S1    - SPSTslideor toggleswitch

      81    - 6 to 9V - fourAA cellsor 9V battery




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                                       Prdcct f,hrlcss
                                            8[        lmnr

                     , ldeasto Explore
          performance to learnmore
Togetbetter        or                 the
                                  about circuit:
     o Youcancontrol beeper
                      the       oscillator lOl, pins1 and5. Put
                                         by
     thesepinstogether.                                 produces
                       Whenin a highlogiclevelthe circuit
     intervalled    Whenin a lowlogic
               beeps.                     the
                                     level circuit stops.
     . Replace by a2N2218.
              Ql           Powerthecircuit a 12Vpower
                                         with         sup-
     ply.
        Signals nowbetuned
              can                               feet.
                           fromdistances to 1,500 A 5- to
                                        up
                 will    the
          antenna increase range thetransmitter.
     6-foot                       of
      projects uncommon
Science      or       applications:
     . House circuit a boxandtellsomeone hideit.You'll it
               this   in               to           find
     by using smallFMreceiver.
             a
     o Thetransmitter beused track
                   can      to         by      it
                                 animals fixing ona collar.
     o Youalsocanusethetransmitter monitor
                                to            sensors ex-
                                         remote     in
     periments. circuits power the transmiter trigger
               The        can   ON             or      the
     oscillator indicated
             as         above.




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