Make: Volume 52

DO YOU HAVE A CHILD WHO WORRIES

ABOUT LURKING BEASTS IN HIS OR HER

BEDROOM? Are you weary of inspecting

closets for fanged creatures? Are your

knees sore from examining beneath the bed

for clawed critters?

If so, then the Monster-B-Gone is just the

solution you need to confirm a fiend-free

room for your youngster. Even better, it’s

easy for kids to operate, requiring no adult

supervision.

Just push the button — the swirling

blue lights let your child know a scan of the

surroundings is taking place. Of course, the

blue light combines with a beyond-human-

hearing ultrasonic wave (um, yeah, that’s it),

unpleasant to any monster’s eyes, ears, or

antennae. So any monsters within, say, half a

mile (800 meters) will immediately disperse

and return to their places of origin. When the

light turns green, the room is clean.

If you so choose, the Monster Detector

will occasionally detect a monster — red

alert! — but a subsequent scan will green-

light the room again. Whew. Children,

sleep tight.

BUILD YOUR MONSTER-B-GONE

The Monster-B-Gone is easy to assemble

in a couple of hours, and costs less than

$40. Basic soldering skills are required; an

understanding of simple circuits and basic

electronics is useful, but not necessary if the

steps are carefully followed. A drill press or

handheld electric drill is needed for part of

the assembly.

The NeoPixel LED ring used in this project

can be mounted directly on the top of the

project box, or you can 3D-print an optional

shell for the LED ring. Holes will still need to

be drilled through the top, but the shell gives

the project a more finished look.

Most of the project’s parts can be

purchased from any local electronics

supply store, but a few will need to be

ordered online. You’ll also need an

internet connection to download the free

software used for the Monster-B-Gone’s

microcontroller (an Adafruit Trinket), and

the Monster-B-Gone logo if an adhesive

sticker is desired.

1. PREPARE ELECTRONIC

COMPONENTS

For easier assembly and disassembly, I

typically use a combination of headers

and female jumper wires to connect all

electronics components. The flexible

jumper wires can easily be inserted onto the

headers and pulled off during programming

and testing. For this reason, the first

task I recommend is adding headers to

the Trinket, the NeoPixel Ring, and the

pushbutton.

The 3xAAA battery box also needs its V+

and GND wires cut and trimmed. You can

just solder these trimmed wires directly

to their desired locations, but I prefer to

add female jumper wire ends onto these

exposed wires to make them plug-able too.

The Trinket comes with its own set of

headers. Figure

A

shows the Trinket

sitting on top of 10 non-soldered headers.

To solder them, I used a small breadboard

to hold the headers so the Trinket could be

aligned on top.

Next, add 3 headers to the NeoPixel Ring

(Figure

B

) at the following locations (they’re

labeled on the backside): Power 5V DC,

Power Signal Ground, and Data Input.

Soldering headers to the pushbutton and

the battery box wires isn’t required, but I

really find them easier to work with during

the wiring stage; Figure

C

shows 2 male

headers soldered onto the 2 legs of the

pushbutton. Figure

D

shows the battery

wires with female jumpers soldered on. I

used some shrink tubing to cover up the

solder joint, but electrical tape will work

just as well.

Finally, add a glob of solder to two 3-pin

headers to short them (Figure

E

). These

are used to create shared connections for

5V and GND that are needed for both the

NeoPixel Ring and the Trinket, as well as

a method for plugging the pushbutton into

the circuit. You can wrap the solder glob in

electrical tape, but leave the longer pins

exposed for connecting the jumper wires.

2. 3D-PRINT THE NEOPIXEL SHELL

(OPTIONAL)

If you have access to a 3D printer, you

can print out the mounting shell for the

NeoPixel Ring. Download the STL file for

the shell from the project page at makezine.

com/go/monster-detector. Figure

F

shows

the shell printed in purple.

3. PREPARE THE PROJECT BOX

You’ll need to drill a few holes in the project

box. Carefully place the NeoPixel Ring (with

Anthony Lam

Hep Svadja, Brandon Steen

makezine.com 63

makezine.com/52

A

C

E

B

D

F

NOTE: If you don’t have access to a 3D

printer, services such as ponoko.com,

i.materialize.com, and shapeways.com

will print the shell for you and ship it to

you for a fee.

M52_062-5_Monster_F1.indd 63 6/14/16 12:31 PM