Sunday, October 14, 2012

Pneumatic Jack in the Box, Part 3

To support the mask I built a frame out of perforated metal tape. I basically fit each piece into the mask from the inside, then attached the pieces together with small nuts and bolts. The frame was then screwed into a stand made of three pieces of 1x2 wood left over from the torsion box coffin lid project.

An additional piece of metal tape serves as the "jaw" and tucks neatly into the chin of the mask. I also bent out part of the metal tape to tuck into the nose. There was no need to glue or otherwise attach the mask to the metal perforated tape; the nose and jaw hold quite well on their own.

I attempted to mount the servo to the wood using pieces of rubber to cut down on vibration, but I do not think it helped much. The servo I used, the Hi Tec HS-82MG, uses metal gears and apparently this makes the servo very noisy.

At some point I may try the HS-81 servo which has identical specs to the 82MG except for having nylon gears.

Important: Observe the motion of the servo as it is controlled by the Arduino before attaching the horn and control wire. Make sure you know what position the servo is in (mouth closed or mouth open) before fastening the horn onto the servo and connecting the control wire to the mouth.

The first video below shows the inside of the mask frame.

After attaching the wooden stand to the accordion's top platform, I ran two cables. One regular speaker cable and a separate, shielded servo control cable. The two cables are zip-tied together and run down to the electronics enclosure to connect to the ELK-120 and the Arduino.

The servo control cable is shielded to prevent the servo from responding to stray EMF or interference from the high-level speaker signal. The outer shield connects to the AC chassis ground at the electronics enclosure end of the cable only. Three wires inside the shield are for signal ground, +5VDC from the power supply, and the servo control line from the Arduino.

The final phase was to "dress" the clown so that it didn't just look like a head on a platform. I created a shoulder and neck form out of tape and attached it around the head stand. I then draped black felt and blue satin cloth over the shoulders and attached it at the front and back of the inside of the box.

Finally, the purple frilly lace ruffle for the neck. This conveniently hides any part of the frame or shoulder form from showing as well. This was a little difficult to find, until I realized I could use a child-size tutu. Looks fine.

10/04/12: Clown head with mouth servo
10/13/12: Demonstration of completed Jack-in-the-box halloween prop (featured below)

Start from the beginning: Pneumatic Jack in the Box, Part 1

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