A couple of weeks ago I wrote about a semester-long project the students in my project planning class are working on: an interactive workshop for a regional Indiana Thespians Festival we’ll be hosting at Purdue in December. The students have been plugging away at the project off and on all semester. (They recently admitted that they had strayed wildly from the project calendar they’d generated for the project—conveniently, we’re in the midst of talking about tracking progress and developing methods for controlling time, money, and scope variance, all of which the project suffers from at the moment!) Last night, the two students who took on the “scenic control system” aspect of the project finally got to play with some of the equipment they’re hoping to use.

Here’s the idea for the scenic control system: two different “players” will have the opportunity to each control a four-string, large-scale marionette suspended from a box truss in our black box theatre. The movement of the puppet will be created using long-stroke pneumatic cylinders; the cylinders will be controlled using directional control valves which are in turn controlled by a PLC. The PLC gets input from the volunteer workshop players through the use of—of all things—DDR (or Dance Dance Revolution) gaming pads. (If you don’t have any idea what that means—or if you want a chuckle—check out this video: http://www.youtube.com/watch?v=4yk-ESYl7Bc)

A DDR pad is essentially a 3’x3’ mat with 10 “button” areas: on each for left, right, up, down; one each for up-left, up-right, down-left, down-right; and a “start” and “back” button. The idea was that workshop participants could step on the up, down, left, and right buttons on a DDR pad, and control the motion of the legs and arms of the puppet: “up” might make the right arm lift (and the left arm drop), while “down” might reverse this motion; “left” and “right” might then control the legs in a similar fashion.

Of course, the students had no idea how they might make this happen: how do the buttons work? Would they need to create some kind of adaptor to get the signal from the Xbox-style connector and somehow convert it to the low-voltage discrete (i.e., “on” or “off”) signals the PLC could understand? There was only one way to find out: cut one open.

When they cut the DDR pad open, they discovered that the controller was ridiculously more simple than they had imagined. Under the top layer of fabric was a thin layer of plastic on which was adhered a super-thin series of conductive ribbons in a kind of mesh in the area of each button; each of these ribbons connected together into one common, wide ribbon that ran back to a circuit board. Just under the bottom layer of fabric was another thin layer of plastic on which was adhered more super-thin conductive ribbons in a kind of webbed area in the location of the button; each of these ran back to separate terminals on the circuit board. Between the two layers of plastic was a thin (1/16” thick) layer of non-conductive soft foam that had a series of holes cut into it in the area of each button. When a button was stepped on—wherever it was stepped on—some of the webs on each layer of plastic made contact through the holes in the foam, creating a circuit. (You can see this in the first few photos below.)

The students realized pretty quickly realized that the circuit board did little more than take the state of each button (i.e., circuit “on” or circuit “off”) and convert it into data that the Xbox could understand. Since the PLC they were using was nowhere near as smart as the Xbox input—that is to say, the PLC only understands “on” or “off” itself, they determined they could bypass the circuit board entirely. By supplying DC voltage to the ends of the ribbon conductors, and connecting these to the PLC inputs, they had a simple and effective way of taking information from the player (i.e., “down” pressed) and get it into the PLC. From there, it is a simple matter of writing the appropriate ladder logic for the PLC to turn relay outputs on and off, causing the pneumatic valves to shift, the cylinders to move, and consequently the puppet to “dance.”

I wrote last January about the learning and teaching possibilities of home-brew electronics. A project like this one is only one step away from what I was writing about in that post: now that these students can visualize how the buttons transmit “data” (in the form of really, really slow transitions from on to off—at least from an electronics perspective), understanding how connecting these leads to a microcontroller instead of a PLC can get information into a more-easily-programmed control device (and one whose form factor is like, 1/1000 the size). Plug all this into an Arduino, say, connected to a Mac running Max/MSP with QLab and a MIDI output, and you’ve got yourself a way of using the DDR pad to control everything from video to audio to lighting cues and moving scenery.

The best part of this whole thing? Watching these two students have one of those awesome “a ha” moments—you know the ones, where a student suddenly puts a bunch of previously disconnected pieces, thoughts, and ideas together, and realized that they fit like this massive puzzle, and their whole perspective on the world twists just like that. Possibilities opened up—new directions and ideas seemed more possible. More importantly, they were obviously much less intimidated by the “mysterious electronics” and much more confident in their understanding of how “data” works—that tricky, hard-to-comprehend stream of “on” and “off” that makes our digital world go around.

Find more photos like this on TheatreFace