This project is based on the open source platform Arduino. The advantage here is that most (if not all) of the components can be swapped out with cheap alternatives.
1) Arduino Uno
(Adafruit Link) and Arduino Software
Most Arduinos or Arduino alternatives will work here.
2) Protoshield (or breadboard)
The only thing used here is one circuit to the speaker and its corresponding resistor. We liked using the protoshield because it attaches right to our Arduino UNO.
3) 9V Battery 2.1mm plug
This makes life easier. You can also use a wall adaptor, but then you have to bring your wall outside.
4) 1 100 ohm resistor
You only need one of these, and the actual resistance governs how loud your speaker is (so go for 1k or less).
(We purchased all of the above materials from our friends at Adafruit in their Arduino Starter Pack for $65 http://www.adafruit.com/products/68
. If you've never used an Arduino before, it has a ton of replay value, so we'd recommend taking the plunge for a starter kit similar to this one.)
5) 8ohm speaker
This is where creativity comes in. Notice that though the speaker itself is less than a dollar, the shipping puts the total cost at about 14 bucks. We had a little fun here- we disassembled a talking greeting card and found one of these bad boys inside. The cards are available at most dollar stores. Radio Shack sells these speakers cheaply, as well.
6) Accelerometer - MMA7361
Here's another point where we encourage getting creative. We used a MMA7361 - available off Amazon and Ebay for relatively cheap, but chances are if you dig deep you can find a similar model online for under 5 dollars. Wiring and documentation may be a bit different, but what's the fun in a project if it's not challenging?
7) 200 ft of 22 gauge wire (or 8 pieces of 22 gauge wire at 25 ft)
(Radio Shack Link)
24 gague wire works, as well. 20 is starting to get a bit on the thick side. The thinner the wire, the easier it is to fly the kite. There is a tradeoff with the length of wire, as the signal degrades over long distance.
8) Misc odds and ends
b) Soldering Kit
c) Colored electrical tape (for marking wires- colored sharpies will work as well)
d) Bubble wrap 3"x2" (for protection in the event of a not-so-smooth landing)
e) Duct tape (to make the world go round)
f) 9V battery (power the Arduino)
g) Wire stripper (for electrical entertainment)
h) Scissors (because cutting with our teeth is annoying)
i) PC Board
or breadboard (hold the accelerometer in place on the kite)
j) Optional: female headers
if you don't want to solder your accelerometer to your breadboard
k) A windy day (or a car will work in a pinch)
...And last but not least, a kite of your choice! We bought ours for $5 at Five Below. The bigger the kite, the better it will support weight, but some larger kites are more difficult to fly (and more painful to watch crash if you're not experienced).