Nuts and Volts - September 2014

This Halloween, you can treat your tricksters to both dessert and a show. This project is easy to solder together and uses common tools to assemble. Best of all, the animations for the Halloween songs can be downloaded for free!

Some of you clever readers are probably thinking that this could be repurposed for Christmas. You would be right! In fact, I designed the electronics to be reused for Halloween and Christmas by swapping out the face front for each holiday. It means less work to leave the decorations up without the homeowner’s association complaining that your decorations are out of season. That means more time for Christmas shopping, making cookies, or caroling, if that’s what you’re in to.

There are two parts to this project: lights and electronics. You get to use both your creativity and your logic, so it’s a right brain/left brain kind of deal.

Lights

The lights are the creative part of this project. I made a pumpkin face, but you can use your imagination to build whatever scary face suits you: monster, ghost, vampire, or politician.

The face has three animated parts: two eyes and one mouth (unless your imagination takes you in a different direction). Each of these animated parts will have six segments that are lit up with LED strips. “Why does the mouth need six segments if I only need open and closed?” you might be asking. The answer has to do with Preston Blair.

Animating a Mouth

Preston Blair was an animator who worked on some of Walt Disney’s early animated movies. He later worked at MGM and Hanna-Barbera. Blair figured out that of all the sounds an English speaker can make, there are only 10 different mouth shapes that are needed in order to produce them. These mouth shapes mimic natural lip movements and make the singing animation look far more realistic.

When you’re doing a lighting animation, however, you want to get as many of those mouth shapes to appear correctly in the least amount of lights. One approach is to use a separate string of LED lights for each mouth shape, but that’s inefficient. The clever part of this project is that I figured out how to get all 10 of Blair’s mouth shapes with only six light segments. This is done by adding or subtracting various shapes in order to make the mouth look natural (Figure 2). Neat, huh? (Yes, I patented this approach. Feel free to use this design for your own personal projects, but you’ll need to contact me if you want to sell a commercial product based on this.)

Planning for the Animated Display

You could put all of the LED strips on one layer of plywood, and I wouldn’t blame you if you did. My approach is to do a little more work to save a lot more time later. The advantage of doing this is reuse of the electronics and half of the construction. The reuse approach will divide the animated display into two major elements: the face front, and the light box to hold the LED strips that create the animation. The light box will be reused, and the face front can be swapped out (Figure 3).

It may be easier to understand this approach if you view the face front and light box from the side (Figure 4). The lights extend past the height of the light box and touch the diffuser directly.

I have a small yard, so the size of the animated display I built is about 2’ x 3’. If you have a bigger yard, you’re welcome to scale up the size. The swappable face front has two parts: a light diffuser and MDF backing. The light diffuser is the same acrylic panel that is typically installed in