Tuesday, July 17, 2012

Pneumatic Jack in the Box, Part 1

This year's new prop is a large Jack in the Box - a two foot cube, powered by the Arduino microcontroller. It will have an Insteon InlineLinc relay module inside so that the prop can be controlled with a hand-held remote or an Insteon motion sensor. When the Arduino sees that the InlineLinc has been activated, it will execute the following sequence of actions:
  1. Turn on a spotlight aimed at the prop so people pay attention to it
  2. Spin crank handle (powered by motor) while playing a sound effect
  3. Open the top lid
  4. Pop up a large scary clown head
  5. Play a sound effect while moving the clown's lips with a servo
  6. Lower the head
  7. Close the lid
  8. Turn off the light

View Arduino Code
Jack in the Box overhead view
View overhead plan

The first sound effect will be the second-to-last bar of "Pop Goes the Weasel." I will be using a pitch-bended version of a music box version of this song. The second sound effect will be a clown voice humming and mocking the final bar of the song.

For me the hardest part of this project is the mechanism that will raise the head. I am going to try using the accordion linkage concept from Animatronics: Guide to Holiday Displays. First I had to model the accordion design in Excel using some trigonometry to determine what length each linkage needs to be and how many levels are required in order for a 12" clown head to rest below the lid when the accordion is collapsed and extend a bit above the lid when the accordion is extended. I then made two accordions out of flat aluminum bar stock I purchased at Home Depot.

One of the challenges of using the accordion linkage is that one of the two legs on both the bottom and top need to slide horizontally relative to the the other leg, which is mounted in a fixed position. I'm going to try using small drawer slides for this.


Building the accordion linkage (no narration)
Overview of pneumatic components
Final accordion mechanism, test with small cylinder
Correct cylinder for accordion
Acrylic electronics chassis and first Arduino test (featured below)

This is a multi-disciplinary project that is proving to be quite challenging. It involves:
  • Woodworking
  • Electronics
  • Arduino
  • Pneumatics
  • Aluminum machining (cutting, drilling, sanding, tapping)
  • Acrylic / Plexiglas (cutting, drilling, gluing)
  • "Painting by numbers"
  • Servos
  • Sound recording and editing
Continue to: Pneumatic Jack in the Box, Part 2

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