| The Foton (Minus 1)
Making your own [keychain flashlight name removed]-like miniature
LED flashlight is very simple. You need the following materials:
· Bright white LED.
· 2 flat coin type batteries (3 volts). I used 2025
lithium batteries.
· A 100 ohm resistor (takes the 6V down to ~4V, which
is okay for white LEDs).
· Plastic milk jug or similar plastic material (water
bottles work well). Need curved surfaces.
· Soldering materials or, if you prefer solderless
solutions, smallest possible crimp-type electrical connector.
· Electrical tape.
· A pin, awl or small drill.
Directions:
1. Solder or crimp one lead of the resistor to the positive
(longer) lead on the LED. Make this as short as possible
2. Stack the two batteries positive on negative. Use electrical
tape to hold the batteries together by taping them at the
edges. Make sure to leave a good-sized open spot in the middle
of both the top and bottom surfaces.
3. Test the LED by placing the resistor lead on the (+) side
of the battery stack and the LED leg on the (-) side. The
LED should light brightly.
4. From a rounded corner of the milk jug, cut a circular
piece of plastic about the same size as the batteries. It
will be the "dome switch" for the positive side.
5. Again, from a milk jug corner, cut a round piece like
before, but with a tail on it (tadpole-shaped). The tail will
be your lanyard connection.
6. With the pin, awl or drill, make two small holes about
1/4 to 3/8 inch apart at the top of the domed pieces of plastic.
When the leads of the resistor and LED are threaded through
these holes, they will be elevated off the battery's surface.
7. Bend the leads of the LED/resistor in a kind of a "4"
shape, with the LED at the top point of the 4. The vertical
line of the 4 will be the negative lead of the LED. The angled
part will be the positive LED lead and the resistor. The cross
line will be the free end of the resistor.
8. Thread the resistor lead through the holes of the circular
dome. Thread the negative LED lead through the tadpole-shaped
dome.
9. Position the battery stack (proper polarity) between the
plastic pieces. Adjust the leads as needed. Try it out. Make
sure the leads contact when pressed. If too much pressure
is needed, try cutting some thinner pieces of plastic.
10. Once satisfied with the "switches", trim the
leads and start wrapping the thing with electrical tape in
a criss-cross fashion. Make sure to wrap tightly around the
base of the LED. Leave the tail of the bottom dome unwrapped.
The resistor will leave a little lump on the side of the flashlight.
11. It is not pretty, but it should be functional. Poke,
punch or drill a hole in the tail and connect it to a key
chain. It will not easily trigger accidentally.
I have made several of these and am very happy with their
small size and brightness. The total cost can be as cheap
as 4 or 5 bucks.
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