Laser Light Show Turned Into Graphical Equalizer

The gold standard for laser light shows during rock concerts is Pink Floyd, with shows famous for visual effects as well as excellent music. Not all of us have the funding necessary to produce such epic tapestries of light and sound, but with a little bit of hardware we can get something close. [James]’s latest project is along these lines: he recently built a laser light graphical equalizer that can be used when his band is playing gigs.

To create the laser lines for the equalizer bands, [James] used a series of mirrors mounted on a spinning shaft. When a laser is projected on the spinning mirrors it creates a line. From there, he needed a way to manage the height of each of the seven lines. He used a series of shrouds with servo motors which can shutter the laser lines to their appropriate height.

The final part of the project came in getting the programming done. The brain of this project is an MSGEQ7 which  takes an audio input signal and splits it into seven frequencies for the equalizer. Each one of the seven frequencies is fed to one of the seven servo-controlled shutters which controls the height of each laser line using an Arduino. This is a great project, and [James] is perhaps well on his way to using lasers for other interesting musical purposes.

23 thoughts on “Laser Light Show Turned Into Graphical Equalizer

  1. This is not an equalizer. It is a display. Equalization is a process done to something like an audio signal. I once saw a pair of rack mounted 31 band equalizers with 62 Knobs in 6 rows not sliders in a graphic pattern.

  2. Spinning mirrors is good and all, but you can buy laser line modules that use a lens to spread the beam out into a line. (which would get around the flicker seen when the camera shutter speed is too fast)

    1. My thought too. Years ago I saw someone built an alarm clock that used a line laser module with the same kind of servo-driven linear aperture mechanism as this thing to project a line on the ceiling whose length corresponded to the amount of time left before the alarm would go off.

  3. While really really cool, I’m bothered by the latency that the mechanical shutters introduce. but the only way I can see of fixing that would be to pulse the laser as he mentioned.

    1. Yes/no. Green lasers are actually an IR laser that hits a crystal that then gets frequency-doubled by another crystal. (It’s actually pretty amazing.) They don’t turn on/off as fast as reds or blues, so if you’re making a light show, you’ll notice green smearing.

      Here, he’s modulating them with servo motors (!?!?) so I would imagine that the green afterglow is nothing in comparison to servo jitter / lag / dead-zone. Tradeoff: it’s awesome to watch the servos fly!

      The “right” way to do this is with an acousto-optic modulator. Times however many beams he’s got = $$$$$.

      1. A way to get around long turn on time delays is to partially bias the diode just under the threshold at which it starts lasing. Not efficient from a power consumption standpoint but it basically primes the diode to allow it to start emitting light quickly enough for things like laser based projector/galvo systems and whatnot. Simple enough to modify a constant current driver to switch between the two currents and a completely off state for safety.

      2. Not really :-) accusto optic modulators are fast enough that he can make his 8 line display with a single laser module. Of course as a fun project – why not using a battery powered laser pointers for a display.

        Of course he needs an x-deflection also, but that is no problem.
        The green DPSS lasers are not that bad although they are not as good as a direct diode laser. It’s not so much a problem of speed, there is no afterglow of this crystals. But changing temperature can lead to some fading or changing overall brightness when the duty cycle of the laser changes. There is some tradeoff between max. power and stability.
        Accusto-optic modulators were mainly used with tube lasers like argon ion. There you could not individually modulate the colors as they came from the same tube (multi mode laser). Also you want to carefully ramp a tube up and down with an arc in it, burning at a power of several kW. to limit thermal stress. The efficiency was phenomenal – less than 1 promille. :-) The strongest light show tubes made 20W of light with an input power of about 45kW. It had a good efficvcieny in generating warm water.

        Even the cheapest laser show galvanometer sets for something like 100€ can do 20k points/second, although not randomly distributed. The are measured with the so-called ILDA test picture and some are intermediate points to take care of sharp corners. So you easily can do that simple picture of 8 lines (16 points) with a good frame rate.

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