Fun Projects 37 Chapter

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                            (P)
                        PROBE
                uNrvERsAL
              probe be usedto testalmost
Thisultra-simple    can                    every        compo-
                                                electronic
nent.         reSiStorS, SwitcheS, tranSformerS, wires,
     CapaCitOrS,      fuses,        COils,         diOdes,
etc.,canbetested thissimple
                with         circuit.
                                                                      l
                                              in
Onlythreecomponents usedandtheycaneasily housed a small
                  are                   be                            I
                                                                      I
plastic performing a portable
      box,       as         unit.
Thecircuitconsists       of          tester
                 basically a continuity    witha visual          by
                                                        indication
an LED. current flowbetween
       lf      can            theprobes LEDglows; not,theLED
                                        the          if
remains otf.
      flowing
Current            probes verylowto avoidoverloading tested
             between     is                        the
components.
A schematic       of         Probe shown Figure1.Asyoucan
           diagram theUniversal   is     in
                     components usedin thisproject.
see,onlythreeelectronic       are
                                                   can
                viewis shownin Figure2.The components be
           layout
A components
housed a small andnoON-OFF
     in      box              sutitch necessary.
                                    is

Whenmounting, carewithposition thetwopolarized
           take              of                      the
                                             components"
LEDandpowersupply.
Thepower    conslsts twoM cells.
       supply      of
AnON-OFF switch notnecessary thecircuit otfwhen probes
              is           as         is       the   are
separated.
Current      the
       through componentunder is determined thevoltage
                               test          by         drop
across LED(about
      the         1.6Vfor red LEDsand 1.8Vfor yellow     and
                                                    LEDs),
resistance R1.
         of
           Fnf0cr urffimiltl|m
                st




Figure I




Figure2


                            m
lunProlects ue txDelhemcl
         ffi

                   PartsList - Universal
                                       Probe
      LED - Common
                 red,greenor yellowLED

      R1   - 470ohm,114W,5%
                          resistor

      PP1,2 - Redand blackprobes

      81   - 3V - two AA cells




                         ldeasto Explore
Scienceprojects:

      o Usethis probein to find materials conduct do not conduct
                                        that        or
      electric
             current.
                    Severalothersimple            in         can
                                       experiments electricity be
      conducted using probe:for
                     this        example, showhowa switch  works, or
      how a potentiometer used as a rheostat controlsthe currentflow
      accross LED.
              an

              howthe LEDproduces light.
      o Explain                its
      o Usethisprobeto explain                (Remember DC
                               howa diodeworks.        that
      is usedin the probes         allowing current flowonlyin
                         and diodes,      the     to
      onedirection.)
      o Thiscircuit alsobe usedas a monochromatic
                  can                         source lightin
                                                   of
                involving
      experiments       optics.




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