Before you assemble the Monster-B-Gone
in the project box, I highly recommend
wiring everything up outside the box and
testing first. Pay careful attention to the
wiring; one misplaced wire could result
in a damaged Trinket or NeoPixel LED, so
double-check all your connections against
the wiring diagram (Figure
Once everything is wired up, flip the
battery box switch to the On position (after
inserting the batteries, of course) and
press and hold the pushbutton (it takes a
few seconds for the Trinket to boot up). You
should see a short animation of spinning
blue lights, followed by the all-green “coast
is clear” lights.
If you’re not seeing any animation, you’ll
want to check all your wiring again. If the
Trinket is powering up (a solid green-yellow
LED stays lit when it’s powered) but the
NeoPixel animation isn’t playing, you’ve
likely got a wire connected to the Trinket
incorrectly. Verify the Data Input header
on the NeoPixel Ring is connected to pin
0 on the Trinket. If you’re still not seeing
any animation, verify you’ve uploaded the
MonsterBGone sketch to the Trinket.
Once you’ve got the animation playing
on the NeoPixel Ring, its time to pull
everything apart and reassemble inside the
project box (Figure
). Wire everything up
as before and use velcro or double-sided
tape to secure the battery box inside the
project box. You might also want to use a
dab of hot glue (in place of tape) to secure
the Trinket to one of the inner walls as well.
Use the project box’s screws to secure the
lid in place.
headers) on the project box lid and make 3
small marks where the headers touch the
lid. Drill a ¼" hole at each mark, then test-
fit the NeoPixel Ring (and shell, if you’re
using it) and ensure the headers fit into the
drilled holes (Figures
If the headers can be reached from
beneath the lid, glue the shell to the project
box lid and set the NeoPixel Ring aside
until final assembly. (If the headers can’t be
reached, you may need to drill the holes a
little larger.)
Next, decide where to place your
pushbutton. I drilled a ½" hole in the left
side of the project box (Figure
), but it
could easily be mounted on the box lid
beneath the location of the NeoPixel Ring.
To program your Trinket, first you must
install the latest Arduino development
environment (IDE), version 1.6.9 at the time
of this writing, and update it to recognize the
Trinket. Adafruit has detailed instructions
for this task at learn.adafruit.com/
introducing-trinket/introduction. Be sure to
follow those steps related to your specific
operating system (Mac or Windows);
Windows users will also need to download
special Trinket drivers.
Once you’ve got your Trinket blinking
using the Flash test program, you’re in good
shape. All you need to do now is replace the
Flash sketch (program) with the modified
Monster-B-Gone sketch. Download the file
MonsterBGone.ino from the project page at
makezine.com/go/monster-detector, open
it in the Arduino IDE, then hit the Upload
button to load it onto the Trinket.
I created my own graphics for the top and
sides and had a local print shop print them
for me on a vinyl sticker sheet. Then Make:
illustrator Brandon Steen came up with
the awesome purple monster design you
see here. You can download the monster
graphic from the project page at makezine.
Where to go from here? An obvious choice
would be to add a sound effect. One easy
way would be to use an inexpensive sound
recording module (such as RadioShack
#2761323). Drill some tiny holes in the
project box, hot-glue the speaker in place,
and wire the module’s Play button directly
to the Monster-B-Gone pushbutton so it
triggers your sound effect.
And I’ve always liked the moving arms on
the “P.K.E. Meter” in the movie Ghostbusters
— a couple small servos could be easily
added, one per side, with holes drilled into
the project box for the shafts. Create an
eye-catching “antenna” for each motor and
you’ve got sound, lights, and motion.
I hope you like the Monster-B-Gone.
Even better, I hope some children will find
peace at night when their parents introduce
them to this useful device. Imagination is
a powerful thing, and giving a child a tool
(and letting them help you make it!) to help
combat an imaginary monster can turn a
parent into an instant hero. Have fun!
Brandon Steen
Download the project code, optional 3D file,
and graphics, and share your build at
Monster Detector
M52_062-5_Monster_F1.indd 64 6/14/16 12:31 PM

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