3 – Light Controller Module for Photosensitive Synthesizer

The project is still firmly in progress.  This page will be updated as work is completed. As it stands, it’s more of a journal of errors and ideas.

The idea for this project was formed after playing around with the photosensitive synthesizer. I realized that due to the implementation of the photocells, it was nearly impossible to get reliably consistent sound out of it in a demonstration, much less during a gig. The photocells require a sort of calibration in order to become properly responsive, and sometimes the unit doesn’t receive enough light to produce audible tones, even in a room that could be considered ‘normally’ lit. Also, we realized pretty quickly that pulsing a light near one of the photocells produced some interesting effects, and that the color of the light made a difference. With that in mind, I decided that it would be easier in the long run to build a light source with a variable color and completely adjustable flashing rate than to cobble together (and carry around) an assortment of items that blinked and glowed.

I forgot to take a 'before' picture, but this is practically identical.

I had an old tape drive that I’d previously gutted for components, and had been itching to use the case for another project. It’s really over-sized for this particular application, but after some consideration, I decided that it would be a good enclosure because the ample size would allow me to build another synth of some sort and fit it in the same case, along with any effects, a/c power supplies, etc. that I may decide to add down the line.

For the light itself, I wanted to be able to produce a full range of color, all the way up the spectrum to white, so I went with an RGB LED. It’s actually three separate LEDs in one, with a common power lead and one pin for each color. The advantage of this is that all three LEDs can be illuminated at the same time to make a white light, or, with some switches and potentiometers, can be used in any combination and adjusted to produce a wide range of colored light.

4 pin RGB LED

While trying to decide how to mount the light, I toyed with the idea of using a cheap USB gooseneck ‘flex light,’ which would be perfect: it’s small, adjustable, stays put and would even allow me to put a USB port on the unit for easy connection and mounting. Since USB uses four wires, all I had to do was remove the LED on the end, and solder my four pin RGB into place. In theory. In reality, inspection of the USB connector revealed only two pins (which, in hindsight, I should have realized beforehand: the LED they used only needed two leads, why would they go to the trouble of running the normal four wires?). Damn. Determined to make it work, I removed the USB connector to gain access to the presumably hollow gooseneck tube, which turned out to be filled with some sort of semi-hardened foam insulation. Double damn. Shelving the idea for the moment, I set about finding a replacement flexible gooseneck, which turned out to be more frustrating than I’d hoped.

  • After looking high and low, I found a seller online that cranks them out in bulk and sells them as low as $15, which isn’t terrible, but it was high enough to place it squarely in ‘last resort’ territory. I wasn’t really looking to spend more on the gooseneck than most of the parts combined.
  • Later, on a clearance rack at a local Office Depot (for $5!) I found a flex-neck desk lamp which, by all appearances, was ideal. When I got home, my wife liked it, and I’ve been forbidden from gutting it. D’oh.
  • Hallelujah.

    Finally, I stumbled across a broken combustible gas detector whose sensor was mounted on the end of a shiny flexible gooseneck tube, which turned out to be completely hollow, except for the wires already running through it.

The tape drive enclosure I used had two parallel ports on the back, for being connected in-line between the computer and the printer. With the hardware figuratively scooped out like so much pumpkin goop from a burgeoning jack-o-lantern, the ports were left empty, and their niche turned out to be a perfect place to mount the cylindrical base of the gooseneck (seen at bottom left on the manufacturer’s picture of the salvaged detector). The ends of the cylindrical base are actually screwed into the base itself, by fairly long threads, so it was simple to temporarily tension-mount the assembly by placing the base in the niche on the back of the tape drive case, then expanding the base until it was held firmly. This worked quite well as a temporary solution, during wiring and assembly.

Sometime during the hunt for a gooseneck (damn, I’m tired of that word, now), I picked up some RGB LEDs from Tanner, and tested them out. Turns out, the only kind they have (at least, at this time) are common anode, while the kind I had researched online is common cathode, where all three LEDs share the same negative connection.

In a common cathode design, power runs in through the positive of the Red, Green and Blue separately, then out through a fourth (negative) lead. In a common anode design, the power flows in through a lead, then goes out through either the red, green or blue. This is a problem for two reasons:

  1. Since the leads for each light are cathode, the power can only be adjusted for all three lights equally, which seemed to be the biggest issue, until I realized that…
  2. Only one LED can be on at a time. This design of LED could be red OR green OR blue, to varying intensity, but nothing else without using pulse width modulation, which is a whole other can of worms and entirely too much trouble to implement in this case. (Not to mention, using PWM on an RGB LED is just entirely too many acronyms for one sentence.)

So, again, I tried to figure out how I could make this work with what I had on hand. Looking at the gooseneck, I realized that the hollow was large enough to accommodate a small bundle of wires, so I got the idea to try using an array of 3 RGB LEDs, with controls to adjust the color and intensity of each one. A less elegant solution, but a solution nonetheless. I set about running wires through it, and ended up fitting ten, which was just shy of the twelve (3 anode, 3 red, 3 green, 3 blue) I needed for this to work, so again… damnit.

The irritating part of this is that before realizing that the triple light array wasn’t in the cards, I got impatient and set about mounting the controls in the enclosure, which was… not bright. So now, I’ve got four knobs, a toggle switch, eight push buttons, and five indicator LEDs on a box, with a scorpion-tail silver gooseneck coming from the back. It is a pretty interesting conversation piece, don’t get me wrong, but until I decide exactly what I’m going to do with it, and draw out exactly how it’s to be done, I’m not touching it. It’s growing increasingly likely that I’ll start from scratch with a small enclosure, and just try to figure out something to do with the current case, and its controls.

[Later, I’ll upload some pictures of the… erm… scorpion-tailed box, in its current state.]

Design ideas going forward:

  • Simplicity. No modular design. No room for expansion. A device that emits a light with controls to adjust color, toggle flashing, and control rate of flash. In a small form factor. I could have already had one made, but I’m oddly hesitant to order parts online. There’s just something about the immediacy of picking up components, and driving home with ideas racing through your head that’s so much more satisfying. Granted, the damned thing could be long done by now had I ordered parts instead of sourcing them locally, so I’ll get over this particular hang up soon, and get on with it.
  • I’ve been playing with the idea of integrating a digital metronome instead of a DIY 555 timer circuit to control the flashing. Pros: exact BPM with digital readout, subdivision of ‘measures’ with optional accents. Cons: output stops while adjustments are being made preventing on-the-fly tempo changes, a tempo knob would be preferable to the up/down buttons on both metronomes I currently own.
  • I considered a third setting for the light (the first two being ON and FLASHING), which would be sound-responsive. It wouldn’t be too hard to implement, and if I used a wired remote microphone, it could be set to react to the bass drum without much difficulty. I may revisit the idea, but it seems right now like it would have more novelty value than actual use.
  • I also thought about adding a percussive trigger, that could be played like a drum. It would work, but I don’t know that the results would be worthwhile. Besides, if I want that, I’ll use electronic drums.

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