This is a basic overview of how I built the Bounce Box prototype. The design is not finalized, and these instructions gloss over some details- that said, there aren't any expert-level techniques or ideas here, so if you are new to carpentry, soldering, Makey Makey or Scratch, you or a partner can probably figure out how to get it working. Feel free to contact me if you have questions!
- a few 2x4x96 studs (the low-end stuff that actually measures 1.5" x 3.5")
- 0.5" plywood enough to make two, 21" x 24" rectangles
- ~20 tennis balls (can use balls that are old and not bouncy enough for tennis)
- uninsulated metal screen
- electrical wire
- 2.5" wood screws
- four 1.5" angle brackets (aka corner braces or angle irons)
- saws to cut studs & plywood
- drill gun for screws
- tape measure
- staple gun
- soldering iron
- Makey Makey
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Step 1: Frame Part One
Using 2x4 lumber, narrow side up, construct a frame with an inner rectangle of 24" x 21"
I used 2.5" decking screws for hardware.
The dimensions of the interior rectangle are important to get precise, and interior corners must be square. The outside corners need not be perfect. I left two sides long so the box would be more stable and easier to carry.
Step 2: Frame Part Two
Again from 2x4, cut two pieces at 20" and two at 24"
Arrange them in a rectangle as shown, wide side up.
Place the rectangle on the frame as shown, and screw in place.
Step 3: Frame Part 3
The 2x4's just added in Part 2 will get bumped around during play, and need to be reinforced. Attach an angle brace to each inside corner as shown in the picture.
Step 4: Trampoline
Cut two, 0.5" plywood rectangles at 24" x 21" and check their fit inside the frame. For the box to work as a trampoline, the plywood must fit inside the frame and slide freely up and down without catching or sticking. Trim these plywood rectangles as needed.
Once the plywood pieces are the correct size, use them to sandwich 20-30 tennis balls, and then fit the frame over the sandwich as shown. Climb on and give the box a few test jumps to make sure the trampoline is working smoothly. You can adjust the number of balls you use later on if the spring is too strong or weak.
Step 5: Paint
If you want to paint your bounce box, this is the best stage to do it so the paint will not interfere with the circuitry or action. Big thanks to the youth teachers at the South End Technology Center for their excellent artistry on this one!
Step 6: Laying in Contacts
Now that the box is working mechanically, it's time to create a circuit inside it so it can be used with a Makey Makey. For contacts, I used two strips of wire mesh (like window or gutter screen), and attached these where the top of the plywood sandwich hits the frame. One strip gets stapled to the top sheet of plywood, and the other to the underside of the frame where it overlaps. Depending on how your build came out, there may be spots where plywood makes uneven contact with the frame; be sure to put your mesh strips where they will be in contact when there is no weight on the plywood, or the circuit won't work. On my build, the best spot was the underside of the piece colored green in the diagram.
Disassemble your box, and staple the wire mesh contacts into place. If the staples do not sit flush, tap them in with a hammer.
Step 7: Wiring and Soldering the Frame
Once the wire mesh is stapled in, choose a spot close to the frame wall and solder on a 10-foot length of stranded wire. Secure the wire close to the weld so that it won't rip out if the ends get pulled or stepped on (I used a few staples). Run the wire out of the frame near the corner (if there are no gaps large enough to fit the wire through, drill a small hole).
Step 8: Wiring and Soldering the Plywood Trampoline
On the plywood trampoline, the wire needs to run through a hole in the underside of the wood so it does not interfere with the contacts. Drill a hole through a corner of the plywood under the wire mesh, then insert the end of another 10-foot stranded wire and solder it on. Again, the wire should be secured near the weld to protect it (I partially sunk a few small nails in the underside of the plywood trampoline and wrapped the wire around them a few times).
Now that the wire is attached, replace the trampoline in the frame. Secure the trampoline wire to the frame with duct tape and a nail as shown, making sure to leave enough slack for the trampoline to move up and down.
Step 9: Testing the Wiring
Leaving the box upside down, use a multimeter to test your wires to make sure they complete a circuit when the trampoline is in the "up" position. You may need to gently press on the trampoline to help the contacts, but if the circuit is inconsistent, you may need to redo some of the wiring steps.
Step 10: Tack in the Bottom
Replace the tennis balls and the bottom sheet of plywood. Gently depress the bottom sheet of plywood so it is flush with the bottom or frame, then tack it in place with nails. DO NOT sink these nails all the way in so you can easily open the box again if something needs adjustment.
Step 11: Testing
Once the solder is set, reassemble the box- you're now ready for testing and play! Connect the wires to a Makey Makey or Multimeter to test for conductivity. When there is no weight on the plywood, the mesh contacts should be touching and making a completed circuit through the box. When the plywood is depressed, the contacts move apart and the circuit is broken.
If everything is working, pin the bottom sheet of plywood to the frame with a couple nails so the box can be moved in one piece. I recommend you do not sink the nails all the way down, so they can be easily pulled in case something needs fixing.
For an example project using Scratch, connect the Bounce Box to the Space Bar with a Makey Makey and get jumping.