Sound Reactive EL Panel Dimmer (for real this time)

Let me tell you a tale.  8 months and 18 days ago, on March 25, I was sent an email requesting a commissioned piece of electronic clothing similar to my DJ jacket for a musical performer to wear on stage.  I mulled it over for a bit, and came up with the idea of a sound-reactive EL panel dimmer.  Unlike most cheap “sound reactive” stuff that just blinks to music, I wanted my dimmer to allow for a more appealing pulsating effect.

EL panels are just like EL wire except instead of having a phosphorescent insulating tube wrapped around the inner wire in a coaxial pair, it has a sheet of the same material placed between two conductive sheets.  They operate on the same principle: need 100V-ish AC input at


2kHz to light up.  The only difference is that the panel, giving off more light, draws more power.

EL wires, panels, and other materials don’t seem to be generally well understood by the sources provided to me by the internet.  I couldn’t find any good sources explaining how to make a dimmer, so I set out into uncharted water to come up with my own solution.

Almost two months after that email, I had created my first sound-reactive EL panel dimmer.  While it was probably one of the most educational projects I’ve worked on, it was also the biggest disaster I’ve ever blogged about.  The dimmer didn’t work very well.  The panel wasn’t getting bright enough.  I decided not to mail the dimmer to my client and instead try to figure out how to improve it (note the FAQ where it says that I don’t work well with deadlines).  Since then, I’ve been writing a ton of posts detailing my experiments with EL wire: 1, 2, 3, 4, 5, 6, 7

Well, I think I FINALLY HAVE IT!  Okay, it’s not perfect.  There were numerous ugly reworks required to make this work, and it still has some room for improvement, but as a proof of concept, it is totally done.  I will probably only need one more short blog post after this to just show off a rebuilt version without all those ugly reworks.

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Revisiting the EL Panel and the True Meaning of RMS

So, I’ve got a little time before I need to start packing, and I thought it would be well used investigating a theory I had about the EL panel.  It turns out that my theory was wrong, but that might be a good thing.

So as you might recall, I specifically decided to use a 120V square wave to drive my EL panel instead of a 120V sine wave assuming that it wouldn’t make a difference.  Well, there is a very important distinction to be made between these two types of waveforms, and I decided to investigate exactly if and how that disctinction affected my circuit.

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