# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Heath Hezzanith question
From: Greg R_
Date: 2007 Oct 22, 21:38 -0700

```--- 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
>
>
>
>
>
>
>
> __________________________________________________
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>

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