DIY
CIRCUITS
The Eternal Flame
Build simple, nearly indestructible LED lanterns.
By Steve Hoefer
IF YOU’RE LIKE ME, YOU’RE THE BANE OF
hardware store employees. I wander through
the whole place picking up everything, looking
at possibilities more than parts. Can they help
me find anything? “No thanks,” I answer. What
am I working on? “I don’t know yet,” I say. They
move on, keeping a suspicious eye on me.
Some things just seem useful, even if I can’t
think of how at the moment. One time I found
matched pairs of PVC caps and plugs that
fit together into little airtight pods of various
sizes. For what, I didn’t know — until I wanted
a way to float lit LEDs down a stream.
The result: simple, rugged, floating LED
lanterns that glow for days. They’ve survived
being submerged for a week, frozen, and laundered in the washing machine. I even hit one
with the lawn mower, and it still works. When
they get dirty, just hose them off.
1. Drill the hole for the LED.
Drill a hole in the top center of the cap using
a 2" bit; it’s just under 10mm and will make
a watertight fit for the LED.
Use a drill vise to prevent kickback. To
protect the cap from scratches, you can line
the vise jaws with tape or cut a V in 2 pieces
of scrap wood (Figure A).
2. Prepare the LED.
Cut about ½" (13mm) off the end of each LED
lead, so they’ll fit easily inside the lantern. Use
pliers to bend a small dogleg in the longer,
anode (+) pin. This will keep the shorter, cathode (–) pin from accidentally shorting out the
side of the battery.
Finally, for watertightness, put a single wrap
of thread sealing tape around the base of the
LED (Figure B).
Steve Hoefer
132 Make: makezine.com/30
