Unbored: The Essential Field Guide to Serious Fun — exclusive excerpt: "Remote-Controlled Water Blaster"

Illustration by Mister Reusch

The following project is excerpted from Unbored: The Essential Field Guide to Serious Fun, by Joshua Glenn and Elizabeth Foy Larsen, designed by Tony Leone, published in October by Bloomsbury.

I wrote the introduction to Unbored, and it is probably the best do-it-yourself and activity book for children I’ve seen. The variety of projects is astounding, and it’s modern and appealing to kids and adults. Many contemporary kids’ activity books are rehashes of the old “Handy Book For Boys and Girls” that aren’t much fun and, in my opinion, not very accurate. If you take a look at those old books, you might come to the same conclusion as me that the authors didn’t make the sail boats, wind carts, truss bridges, and other projects. Unbored, on the other hand, has real projects that were actually tested out. Here’s an example of a real project from Unbored, which was written by my friend, John Edgar Park.

SOAK AND DESTROY: Remote-Controlled Water Blaster

Written and photographed John Edgar Park

Want to keep your brothers, sisters, and friends from breaking into your secret fort to dig through your comic books? Build a remote-controlled motorized water blaster so you can soak them while sneakily savoring the moment from a safe distance!

YOU’LL NEED

• Small Phillips screwdriver

• Wire strippers

• Soldering iron and solder

• Heat-shrink tubing, 1⁄8″ diameter—cut into two 1⁄2″-long sections

• 2 dead AA batteries (to be used as “dummies,” or spacers)

• Electrical tape

• Goggles

• Zip ties

• A 9V battery, and a 9V battery holder; OR (for longer shooting time) 6 AA batteries, and 6-AA battery holder

• Optional: Lighter, and strong string

• Grownup supervision

YOU’LL ALSO NEED

Battery-powered Nerf Super Soaker Thunderstorm. Go ahead and use another motorized blaster, but you may need to modify some steps of these instructions.

Remote-controlled 12V DC relay switch kit, such as the Logisys RM01.

Here’s the plan. We’ll strap the water blaster’s trigger into a permanently pulled position, and insert a remote-controlled relay switch into the power supply. At the push of a remote transmitter’s button, you’ll be able to start and stop the flow of electricity running between the battery and the motor that powers the water blaster’s pump.

HOTWIRE THE BLASTER

First, we’ll splice the relay into the water blaster’s battery circuit. A relay is a switch that is opened and closed by applying an electrical current; the remotecontrolled relay switch can be opened and closed from a distance, by a transmitter. By splicing the relay into the battery circuit, we’ll be able to make the blaster shoot by pressing the transmitter’s “on” button.

1. Open the blaster’s battery cover and remove the battery pack (Figure A). Remove its batteries. On the back of the pack you’ll see two metal tabs; the one connected to the coiled spring is the positive (+) tab, the other is the negative (-) tab.

2. Find the 12V OUT wire on the relay switch (your colors may vary from the photos); it will contact the positive tab. (The GND OUT wire is the “ground,” which will contact the negative tab.) Use the wire strippers to remove 1” of insulation from both of these wires.

3. Cover the positive (+) end of one of the dummy batteries with the exposed  12V OUT wire. Cover the negative (-) end of the other dummy battery with the exposed GND OUT wire. Wrap electrical tape around each battery to hold the wire in place, as shown (Figure B).

4. Insert the positive dummy battery into the blaster’s battery holder; make sure the exposed 12V OUT wire is touching the positive (+) tab (Figure C). Insert the negative dummy battery into the battery holder; make sure the exposed GND OUT wire touches the negative (-) tab.

Now we have a dummy power insert. Stick the dummy power insert into the blaster, and close the cover—allowing the relay switch’s two wires to run out from the top (Figures D). They’ll get lightly pinched by the cover, but it’s OK.

POWER THE RELAY SWITCH

Next, we’ll give the relay switch some power. Put on your goggles, and make sure you’re in a well-ventilated space, because we’re going to use the soldering iron to splice the battery holder and the relay unit together.

1. If necessary, use the wire strippers to remove 1″ of insulation from the battery holder’s red and black wires.

2. Slide a 1⁄2″-long section of heat-shrink tubing over the relay unit’s 12V IN wire, leaving the wire’s stripped end exposed.

3. Twist together the ends of the battery holder’s red voltage wire and the relay unit’s 12V IN wire.

4. Heat the joined wire ends with the tip of your hot soldering iron, then solder them together—by touching a length of solder to the joint (Figure E).

5. When the soldered joint is cool, slide the heatshrink tubing into place over the joint. Using a lighter, or the side of your soldering iron, heat up the tubing so it shrinks. We’ve just insulated the joint, which will help avoid a short circuit if the wires get wet.

6. Repeat the above steps to solder together and insulate the battery holder’s black ground wire and the relay unit’s GND IN wire (Figure F).

TEST THE BLASTER

The circuit is complete! Time to test it.

1. Make sure the relay switch kit’s remote control unit is working.

2. Insert a 9V battery into the 9V battery holder (or, if you used a 6-AA battery holder, insert 6 AA batteries). If the battery holder has an ON/OFF switch, turn it on.

3. Pull the blaster’s trigger—nothing happens yet. Keeping the trigger pulled, press the ON button on the relay switch kit’s remote control unit. The blaster should start firing! Press the remote control unit’s OFF button to stop it (Figure G).

4. Use a zip tie to secure the blaster’s trigger in the pulled position (Figure H). Press the ON button on the relay remote—the blaster should now start firing without your finger on the trigger.

DEPLOY AND DESTROY

Finally, we need to deploy the remote-controlled water blaster.

1. Fill the water blaster’s tank, and insert it into the blaster.

2. Place the blaster somewhere sneaky. In your yard, for example, you could use some strong string to lash the blaster to the side of a fort— or to a tree branch (Figure I).

3. When your victim walks into the blaster’s line of fire, turn the remote control unit on (Figures J & K)! Because the remote works from over 100 feet away, you could even hide indoors.

John Edgar Park is a CG supervisor at Disney-Toon Studios, the host of Make: television, a contributing writer for Make magazine, and the author of Understanding 3D Animation Using Maya. He lives in Los Angeles with his wife and two kids. More info: jpixl.net.

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