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    Re: Heath Hezzanith question
    From: Greg R_
    Date: 2007 Oct 22, 21:41 -0700

    --- "Greg R."  wrote:
    
    > a current of 20 mA (0.2 A)
    
    Oops, dropped a zero from the previous post - that should obviously be
    0.02 A, not 0.2.
    
    --
    GregR
    
    
    
    > --- Chuck Taylor  wrote:
    >
    > > Bonus question:  What size resistor would I need?
    >
    > Bonus answer: It's a simple voltage divider/Ohm's Law problem. You'll
    > be dropping 1.3 V across the resistor (3.0 - 1.7), and a current of
    > 20 mA (0.2 A) through the series circuit gives a resistance of 65
    ohms
    > if I did the math right.
    >
    > --
    > GregR
    >
    >
    >
    > > Why not use an LED?  Radio Shack sells a 5 mm red LED for $1.99. It
    > > draws 20 ma at 1.7 volts (typical).  My sextant takes two penlight
    > > batteries (3 volts). To make this work without smoking the LED, I
    > > would need to solder in a resistor of the proper value in order to
    > > drop the voltage to 1.7 volts. But first I would have to do the
    > math
    > > to compute the proper value for the resistor. I think I'll stick
    > with
    > > the red marker. :-)
    > >
    > > Bonus question:  What size resistor would I need?
    > >
    > > Cheers,
    > > Chuck Taylor
    > >   48 N
    > > 122 W
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > > Gary LaPook writes:
    > >
    > >
    > >
    > > Why not use this opportunity to join the 21st century and use a red
    > > LED
    > > (light emitting diode) cheap at Radio Shack, uses almost no current
    > > and
    > > lasts forever?
    > >
    > >
    > >
    > > gl
    > >
    > >
    > >
    > >
    > >
    > > Chuck Taylor wrote:
    > >
    > >
    > >     red nail polish on the bulb or lens.
    > >
    > >
    > >
    > > I use a red felt-tip marker for coloring the bulb on my boat's
    > > compass. It works well. It would likely work also on a sextant
    > light.
    > >  I picked up that trick from a compass repairman at a boat show.
    > >
    > > Chuck Taylor
    > >   48 N
    > > 122 W
    > >
    > >
    > >
    > >
    > >
    > >
    > >
    > > __________________________________________________
    > > Do You Yahoo!?
    > > Tired of spam?  Yahoo! Mail has the best spam protection around
    > > http://mail.yahoo.com
    > > >
    > >
    >
    >
    > >
    >
    
    
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