Progressive Assembly: Behind the Scenes

Today we officially launch The Capulet (wireless DC dimmer), a small unit that wirelessly controls 6 DC dimming channels, powered by anything from a 3.7V single cell LiPo battery to a 12V brick of 8 AA batteries. We produced the above video, in collaboration with Geeksdanz, to show off a little of what it can do.

Go watch the video if you haven’t already, and then continue below for the spoilers and technical details of how we made it happen.

Ellen is in a black unitard, with EL Wire wrapped around her and sewn onto the costume. We’re using a 2.2Ah 7.4V 2-cell LiPo battery pack for power, Cool Neon’s Blue Fish drivers to drive the 5 channels of EL Wire, and 12 white Lilypad LEDs on the 6th channel. Ellen’s lighting concept has basic limb isolation — one channel each for her left arm, right arm, left leg, and right leg, and a fifth channel for her torso.

First we made a belt out of some stretchy black fabric, with a pouch inside for the battery and electronics:

The biggest component was the block of EL drivers, followed by the battery; the Capulet was tiny by comparison. We used electrical tape to bind everything into a solid pack – the pack slid into the pouch, which was then attached around Ellen’s waist. For tech, we used safety pins; for the taping we actually stitched her in to keep everything firmly in place.

The blue EL wire around the torso was also stitched on, which (like the pack) was a bit of a problem: we couldn’t get Ellen out of the costume without taking it apart. It was fine for this one-off video, but for a repeat performance, we came up with a system of velcro that should hold the wire in place without requiring it to be sewn on each time.

For Ellen, the day of filming consisted of about 4 hours of standing around in a cold studio while she got sewn into her costume, followed by about 2 hours of dancing.

Dimming EL Wire

EL Wire drivers are perhaps one of the least well-documented bits of electronics I’ve tried to interface with. Different combinations of wire and drivers (even the same model of driver) will respond differently to dimming.

There are two basic ways to dim EL Wire: you can take the high voltage AC signal output from the inverter and chop it up with a TRIAC, or you can dim the DC input to the inverter. In our book we talk about doing it with a TRIAC, and in the test circuits we built for the book, it looked like it worked very well. For this product, we did some more testing and discovered that in many cases, the EL Wire will flicker terribly when the output of the inverter is dimmed. Additionally, some inverters will cause high voltage spikes internally that can cause damage to the inverter if they do not have a load attached; this means that when the costume is all dark, the EL inverter may be frying itself. Most inverters are rated for a range of wire lengths — the ones we’re using are rated for 5 to 35 feet. If you connect a smaller load, you risk damaging the inverter. Additionally, as you connect more load to the driver, the overall string gets dimmer. This had the potential to cause strange effects as more channels came on, so we decided to avoid dimming using the TRIAC method.

Instead, we went with dimming the input to the EL inverters. To smooth the output a bit, we added a 100uF capacitor, and to prevent noise from making it back into the dimmer (a problem we identified on some, but not all, of the EL inverters), we added a flyback diode — specifically, a 1N4001. There is some flicker visible on the video at very low levels, but that’s just a video artifact, as it wasn’t noticeable to the naked eye.

(Look for a downloadable update to the EL Wire section of our book in the next few weeks!)

Controlling Everything

Because we were only controlling the costume lighting and not interfacing to anything else DMX-controlled, we ended up directly controlling the Capulet from Processing. Processing is a programming language built on top of Java that makes it easy to incorporate multimedia and interactivity. We could have generated the entire show on a lighting console, or with various sequencing tools, but a previous project we’d done using Processing to output DMX worked very well, so we chose that route. A slight modification to the software, and we were able to use the computer in place of a Trinculo’s Attic Wireless Base Station.

Processing’s audio library has a function that returns the current millisecond position during playback; this allowed us to sync the lighting timing to the music, even when we slowed down the playback while teching the show.

For the improv section (starting at 2:45 in the video), we assigned computer keys to act as bump-decay buttons, letting us improvise both the dancing and the lighting.

Syncing it All Up

In the behind-the-scenes video, you’ll notice that there’s an additional audio and lighting cue before the dance actually starts. This is 2 measures of 4/4 tempo, with a lighting pulse on the last beat before the piece starts. This helped us in several ways:

  • Ellen knew exactly when the music would start, so she could start the choreography on cue.
  • It gave us a short delay between pressing play and the start of the piece, which was handy if one person needed to hit play and also run a light board or watch the camera angles.
  • The LED flash gave us a visual indication that the computer-Capulet link was working.
  • The beats gave us audio to sync to when we replaced the in-camera audio with a clean recording of the piece.
  • The LED flash gave us a frame-lock so we could sync up different video recordings, in order to do a multi-camera shoot without timecode

We actually shot several angles of the dance (in different takes — we cheated), but without a background for frame of reference, it was simply too confusing when the shots changed from one angle to the other. Instead, we stuck with a single angle for the whole video, which gives the audience the full effect of how the lighting and choreography truly are working in tandem.

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