Making EL Wire Change Color

It’s not a dramatic color shift, but it turns out you can control the hue of EL wire over a narrow range by varying the frequency of the resonating driver circuit. dcroy (upper video) did it back in February using a 555, and Paul Stoffregen (lower video) unknowingly repeated the project recently, having noticed that a single fixed-frequency driver produced slightly different colors in two different lengths of wire. My guess is that EL wire manufacturers strive to minimize this variance, which for many users would count as a defect. But I wonder if you could change the phosphors or otherwise tweak the wire’s design to maximize the frequency-dependent color-shift?