Page 85 - 15 Dangerously Mad Projects for the Evil Genius

64 15 Dangerously Mad Projects for the Evil Genius

“ring-pull” type so there are no sharp edges at the Figure 5-28 shows the hole with the diffuser
top. You will need to make a hole in the can for the behind it. A hit on any part of the diffuser will
laser beam to enter. trigger the can jumper. To disguise the hole, you
Put the board into the can and mark a position could glue the label back on. A label with some
directly opposite the phototransistor. Drill a hole white in the pattern would be ideal so that a hole
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there about ⁄4 inch (6mm) in diameter. Now, tape a could be cut in the label over the location of the
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pad of the packing material about 1 ⁄2" 1" over hole on the can.
the hole using Scotch tape (Figure 5-26). It now just remains to fit everything into the can
Without the packing material as a diffuser, the and test the can jumper. The battery sticks out
laser would pass straight through the hole and only perpendicular to the board and takes up most of
the width of the can. This will keep the bottom of
activate the can if a direct hit was scored on the
the board in place.
phototransistor. With the packing material in place,
the laser illuminates the material, which then lights The top of the board is held in place with
up the entire can, triggering the phototransistor. adhesive putty (see Figure 5-29).
You can see this effect in Figure 5-27.
We now need to make the lid of the can (Figure
5-30). Using the rim of the can as a guide, trace
the outline onto strong card and cut it out. If one
side of the card is black, that is a bonus, but not
essential. The lid needs to be a snug fit so it stays
in place inside the rim of the can and holds the

Figure 5-26 Fitting the diffuser

Figure 5-27 The diffuser being illuminated by
the laser Figure 5-28 The hole in the can