Making the Rube Goldberg box

Let’s make a Rube Goldberg machine that blows a confetti surprise at the end!

Duration: ~1 hour

|Step 1| - Make the chute

Goal: We need a chute to drop a weight down to turn on the fan.
Materials: scrap cardboard, hot glue, scissors

  1. With your scrap cardboard, measure and cut 3 rectangles that are all 10 inches long by 1.5 inches wide.
  2. Hot glue the long edges together to form an open chute, so that your chute mimics a box without its fourth side.
  3. Cut one smaller square, about 1.5 inches by 1.5 inches, and glue it to the bottom of the chute.

Parts for making the chute Parts for making the chute

|Step 2| - Attach your servo

Goal: The servo needs to hold the weight up and release the weight down the chute.
Materials: servo, popsicle sticks, hot glue, cylindrical weight

First, start by opening your servo package. Inside you will probably find multiple extensions for the servo. Choose the one that has only one arm.

Glue the chute together Glue the chute together

Cut 2 inches off a popsicle stick and hot glue it to the servo arm.

Cut the servo stick Cut the servo stick

Hot glue the servo to the right side of the chute. Cut a slit in the cardboard so the servo can rotate in and out.

Attach the servo to the chute Attach the servo to the chute

|Step 3| - Add the pushbutton

Goal: When the weight drops, it will land on the pushbutton that turns on the fan.
Materials: chute, hot glue gun, button

Cut a small triangle in the bottom of the center piece of the chute.

Pushbutton for the bottom of the chute Pushbutton for the bottom of the chute

Slide the pushbutton (facing up) through the triangle hole and glue to the bottom of the chute. Try to keep it centered on the bottom piece.

Glue the pushbutton to the bottom of the chute Glue the pushbutton to the bottom of the chute

Later, the chute is mounted (with a tilt) to have your metal cylinder fall from the top of the servo and roll down the chute. It pushes the pushbutton down when it stops at the bottom.

|Step 4| - Attach your battery case and board

Goal: Attach the Adafruit Circuit Playground Express and battery case to the side of the chute.
Materials: chute, battery pack, Adafruit Circuit Playground Express, hot glue

Use scissors to pry off the clip on the back of your battery pack. Remove any remaining tape too.

Connect the battery pack Connect the battery pack

  1. Hot glue this side of the battery pack (opposite the on/off switch) to the upper left side of the chute.
  2. Hot glue your Adafruit Circuit Playground Express on the other side, right below the switch with the battery connector on top.

Attach the battery pack Attach the battery pack

|Step 5| - Set up the fan

Goal: Wire up the fan and connect its batteries.
Materials: jumper wires, alligator clips, fan, batteries for fan

Note: if the fan you’re using requires multiple batteries (if your fan needs more voltage to run than just one battery) you must connect them in series. To do so, use an alligator clip to connect the positive on one to the negative on the other (white alligator clip). Now one battery will be left with an open (+)(red) and the other with a (-)(green). These are the new power (positive) and ground (negative) terminals.

  1. Find the two wires coming out of your fan. Connect the red one directly to the positive terminal on your battery using an alligator clip.
  2. Connect the black wire to one of the two wires extending from your pushbutton (it doesn’t matter which one).
  3. Connect the other wire from the pushbutton to the negative terminal on the battery.

Connect the fan and batteries Connect the fan and batteries

|Step 6| - Connect the force sensor

Goal: Connect the force sensor so it will start the servo.
Materials: ribbons, force sensor, alligator clips, hot glue

  1. First decorate the force sensor to disguise it. Have fun- be creative! Here we used ribbon bows.
  2. Connect an alligator clip to each of the two connections

force sensor parts Force sensor parts

Connect clips to the force sensor Connect alligator clips to the force sensor

|Step 7| - Connect the servo and force sensor

Goal: Connect the force sensor to operate the servo.
Materials: main chute, alligator clips, force sensor

  1. Connect the black wire from the servo to the GND pin on the board.
  2. Connect the red wire to the 3.3V (power) pin on the board.
  3. Connect the yellow wire to pin A3.
  4. Connect one side of the force sensor to ground.
  5. Connect the other side of the force sensor to pin A1.

Connect the force sensor All the connections

Pin connections on the board Pin connections on the board

Connect the force sensor Tape the wires an clips to the chute

|Step 8| - Assembly

Goal: Put the chute, force sensor, and box together.
Materials: hot glue, electrical tape, scissors, large cardboard box, chute and attachments, popsicle stick

Chute and box next to each other The chute and box ready to go together

First, open up the four corners of one side of the box and glue them out so they extend the box. Open up the back side of the box to make assembly easier, but don’t do anything with it quite yet.

Box opening Box opening

Get the scissors, glue gun, and ruler ready.

Tools for the chute Tools for the chute

Carefully take the chute and place it inside the box. Glue the bottom of the chute to the bottom of the box. Then, take a popsicle stick, glue one side to the top of the chute, and the other to the top of the box. To make sure the weight falls the way you want it to, adjust the angle of the chute if you need to.

Mount the chute in the box Mount the chute in the box

Take the remaining part of the popsicle stick and glue it to the bottom of the chute. This will hold in the weight after it falls.

Remainder of the stick Remainder of the stick

Glue the weight keeper on Glue on the weight keeper stick

Cut a small hole in the side of the box, and pull the wires and force sensor through. Tape the wires in an appropriate place so the decorated force sensor can be centered.

Tape on the force sensor Tape on the force sensor

Glue the fan near the back of the box to leave room for confetti.

Glue on the fan Glue on the fan close to the back

|Step 9| - Decorate!

Goal: Cover the box in tissue paper and hide the wires.
Materials: tissue paper, electrical tape

Use tissue paper to cover the box. For a more discrete look, you can use electrical tape to tidy up the wires.

Decorate the box Decorate!


Congratulations! You have completed the Rube Goldberg prank box make challenge. Now, cut up the leftover tissue paper to make some confetti.

Confetti Get some confetti

Load your prank box with the confetti to get it ready!

Load confetti into box Load the confetti into the box

Ready to do some coding? OK, good…connect the Adafruit Circuit Playground Express to your computer to get started.

NEXT: Code