Laser Dance Matrix

Status: Complete

Links: Image gallery, Illustrated Construction Guide

This was definitely an interesting project. What began as a simple commission to design and build a dance pad for a client evolved into something quite different. The criteria were simple: make a dancepad that would work on carpet, but did not take up the space of a normal rigid dance pad during storage. After prior in-house experimentation with dancepad construction, the laser dance matrix was already being entertained as an idea for a future project. The first iteration of the laser dance matrix used infrared light emitting diodes and was not actually a laser dance matrix at all. The initial testing of the infrared emitters and sensors appeared quite promising and the decision was made to assemble a working prototype. There were immediate issues with false signal detection on the prototype that were ultimately traced back to an error in the manufacturer's datasheet. Rather than re-order parts and delay the project further, the decision was made to fall back on the laser-based design.

The system was designed to be built around an existing USB game controller to simplify development. The control box of the laser dance matrix not only housed the USB game controller, but an interface that allowed the interruption of the lasers to activate button presses on the controller thereby enabling regular gameplay.

Angle view of the Laser Dance Matrix

The laser based system was not without its problems, however. Attaching the laser diodes to the plastic frame had to be done with the lasers activated for proper alignment. The resulting laser "dot", at a distance of approximately one-meter, was only five millimters in diameter on the target. The target was originally a phototransistor, but it was too

small so a Cadmium Sulfide photocell was later used. A plastic diffuser was placed in front of the cell to effectively increase the target area. Another problem was that epoxy did not readily adhere to the brass housing of the laser diodes, so they were housed in a form-fitting vinyl sleeve to which the epoxy was attached. More information concerning construction of the laser dance matrix can be found in the Illustrated Construction Guide.

Once completed, the prototype functioned quite well even in daylight conditions thanks to extra shielding applied to the CdS sensors. The shielding can be seen in images of the prototype protruding from the frame. The laser dance matrix was built around the same design as its infrared predecessor and both were intended for use with Stepmania which does not use diagonal directions during gameplay, so the shielding would not interfere with the player. The prototype was then delivered to the client.

The story does not end there, oh no. As is customary with many Applied Sciences projects, construction details and experimentations are made freely available. A posting was made to the Stepmania website and from there it was picked up by numerous other online publications including: Hackaday, Engadget, Kotaku and many more. TDMonthly, a trade magazine and website, was one of the few outfits to actually contact Applied Sciences for an interview. Many other websites just made up information and published it. A matter of particular amusement was the people who claimed to have played with the prototype and shared their thoughts about it with others in various forums. Six people used the laser dance matrix before it was accidentally destroyed by the original owner while moving into a new house. In response to the vast amount of misinformation that was being perpetuated, Applied Sciences set up a special web page with actual information about the project. In addition, a survey was conducted on the web page to determine if people were interested in constructing their own laser dance matrix and if Applied Sciences could easily supply parts or kits to that end. Applied Sciences even donated an original prototype PCB to a high school in California, but has not heard what became of it. About that same time several companies contacted Applied Sciences about bringing this product to market. Such an idea was heartily endorsed, but the companies actually had no intention of providing any material assistance and Applied Sciences (unfortunately) is one factory short of having a factory for manufacturing. Primarily, the companies just wanted their names attached to an innovative project, and who can blame them?

In the end, the laser dance matrix prototype worked and was delivered in a semi-timely fashion. More images are available in the gallery. The construction guide is well illustrated and freely available here.