This is a fun device that's very simple to make.

I put mine in a pumpkin for Halloween. I also added an IR motion sensor, sound, and Twitter.
You can follow the victim count on Twitter by following: hackolantern

Step 1: Materials Checklist

Items needed:

- Arduino microcontroller
- A couple cans of Silly String (it's no fun with just one can!)
- Wire coathanger
- Standard sized servo (I used a 39g servo)
- Zip ties
- Basic tools (I'm not going to list everything. You're smart, surely you'll figure it out.)

Step 2: Mark, Measure, and Cut

Take the cap off the Silly String. Measure and mark the cutout locations.

You might be able to use my measurements in the images below, but your brand of Silly String may have different dimensions. Good luck.

Step 3: Bendy / Twisty

Bend your coathanger to resemble the image below. This will act as the trigger.

Step 4: Mount Servo

Run the zip tie through the top holes, and attach the servo.

**Important**
The trigger should be adjusted to fit YOUR can of Silly String. With my setup, the internal bend is horizontal when the outside lever rests all the way against the servo. This allows for the servo to make a full 90 degree rotation without applying any stress to the other components.

Step 5: Example Code

This code is pretty stupid, but it will give you an idea of how to start.

** I used the SoftwareServo.h library only because the standard servo.h library and the VirtualWire.h library don't get along. If you want to use the standard servo library, it works just fine, but you'll have to whip up your own code (it shouldn't be too hard).

Download the sketch anyway, and take a look.

The other sketches on here, SillStringShooter2.pde and Hackolantern_Tweet.pde, is the actual code I used for my pumpkin. Enjoy!