Sky & Telescope - July 2024 - 73

bright amber LED. I've collected a ton
of random electrical parts over the
years, so I just went with stuff I had on
hand: a 1K ohm Linear Piher thumbwheel
pot, a simple on/off rocker
switch, a half-watt resistor (overkill),
and a 9,000 millicandela amber LED
(probably overkill as well).
The pot is the dimmer, and the
75-ohm resistor limits the current.
If the pot's resistance goes to zero on
one end of its range, the AAA batteries
can deliver more than the LED's safe
current of 20 milliamps, so you need to
add some resistance in series with the
LED. A little experimentation showed
me that 75 ohms kept the current to
about 12 milliamps, which made the
LED plenty bright but was well within
safe range.
Everything gets wired in series. You
can arrange the components in any
order so long as they make an electrical
loop. Make sure you test the circuit first
to confirm you've got the polarity right
going to the LED (the long leg is positive)
and have the pot's action increase
brightness in the direction you find
natural. (For me, I roll the thumbwheel
forward to make it brighter.)
Figure out how everything is going
to fit, then start cutting holes in the
project box. To make the rectangular
slots, I drilled small holes inside the
lines, then cut between the holes with
a box knife and filed the edges smooth.
For the pot, I angled the edges of the
hole to accommodate its curved barrel
and cut notches for the thumbwheel.
I scuffed up the inside of the box and
glued the pot into place with Shoe Goo
(making sure not to glue the thumbwheel!).
The switch snaps into place.
The LED just wedges into a hole drilled
a smidgen tight. My LED had bright
and dim spots, so I frosted its dome
with 400-grit sandpaper. Now its light
is as even as you could ask for. And I do
indeed think it works better than red
for preserving my night vision.
That's pretty much the flashlight.
Snap the cover on and go out observing!
¢ Contributing Editor JERRY OLTION
thinks no project is too small to be fun.
Find these and much more at skyandtelescope.org/community
sk yand tele scope .o r g * JULY 2024 73
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Sky & Telescope - July 2024

Table of Contents for the Digital Edition of Sky & Telescope - July 2024

Contents
Sky & Telescope - July 2024 - Cover1
Sky & Telescope - July 2024 - Cover2
Sky & Telescope - July 2024 - 1
Sky & Telescope - July 2024 - Contents
Sky & Telescope - July 2024 - 3
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Sky & Telescope - July 2024 - Cover3
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