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PHOSPHOR Video Distortion

PHOSPHOR is a MIDI-controllable distortion device for analog video. I made it to create glitchy video projections in sync with Ableton Live.

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There are some very impressive devices out there to create cool glitch art with analog video. I took the schematics of one of my favourite projects, the AVE MOD V2, and added self-made vactrols and a Sparkfun Pro Micro to control the device via USB MIDI. This does not only introduce saveable presets, but also allows for beat-synced analog video projections when performing live music with Ableton Live or similar software.
Like the AVE MOD 2, this distortion device is based on the schematic of the vintage Archer video enhancer.

Some people have asked me for the files of PHOSPHOR's predecessor, the ARCHER. The video circuit of this project is exactly the same. If you don't need the MIDI functionality, you can omit the vactrols and everything below to basically get the ARCHER. Another possibility would be getting the AVE MOD by syntonie.fr, of which the ARCHER was more or less cloned.
In reverse, if you don't want manual controls, you can omit the potentiometers and toggle switches. I would recommend keeping those for calibrations though.

I used both the ARCHER and PHOSPHOR prototypes with PAL analog video hardware and was very happy with the results. It should work with NTSC as well, but couldn't try it myself.
If I find the time, I will upload a version with the SOP version of the IC, since the DIP version is out of production (but can still be sourced relatively well).


Here are some stills that were done with the previous version (identical video circuit). I captured them by recording the ARCHER's video output on a VHS tape, playing it in slow motion on a Sony Wega rear-projection CRT and photographing that with a DSLR.





Phosphor1_1_hardware.zip

KiCAD folder, Gerber files and schematics for the PCB, BOM and vector files for lasercutting the enclosure

Zip Archive - 2.91 MB - 07/01/2019 at 08:47

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Phosphor1_1_software.zip

Arduino and Processing sketches for programming and MIDI-controlled operation

x-zip-compressed - 274.20 kB - 05/01/2019 at 12:30

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PhosphorSMD1_1.zip

UNTESTED KiCad / software files for a variant using the SMD TLC5940PWP since the DIP version is no longer in production.

Zip Archive - 332.04 kB - 05/16/2019 at 13:42

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  • 1 × See BOM file in the hardware folder

View project log

  • 1
    Caution

    USE THIS DEVICE AT YOUR OWN RISK. Using the original software to create and use patches as well as the recommended parts, the unit should use much less current then a usb port can deliver. The video circuitry should be isolated well enough from the controller circuit that is connected to the computer, but I'm not a professional and don't really know what I'm doing. I am not responsible for any damage that could occur while using this device.

  • 2
    Make 20 vactrols

    In order to control the video effects via MIDI, I needed a part that could override the potentiometers. For full effects, I need less than 30 ohms, to switch an effect off completely, a resistance of more than a few kohms would be desirable. I couldn't find a semiconductor solution that really seemed to do the job for a reasonable price and very low-resistance Vactrols like the vtl5c4 are way too expensive. A cheap find on ebay turned out to be a scam. So I decided to make my own vactrols:

    I chose RND components high-power white LEDs for their low cost and brightness. They emit 27000mcd at an angle of 15°. When put directly in front of a GL5506 light-dependant resistor and connected to 5V with a 120 ohm resistor, the LDR reaches a resistance of below 60 Ohms.  Therefore, most of the effect channels of the PHOSPHOR use two vactrols in parallel.

    1 - The LED and LDR are touching each other. A ~12mm long piece of shrink tubing with a diameter of slightly larger than 5mm is placed over the components as shown.
    2 - Heat is applied to shrink the tubing near its ends without shrinking the middle too much to prevent it from blocking the light path (step 3).
    4 - A ~16mm long piece of slightly larger black shrink tubing is again heated mostly near the ends to give the vactrol more stability and keep light from escaping.
    6 - To really encapsulate the vactrol, I put a drop of black nail polish into both openings.

    20 vactrols are needed in total. for each channel one vactrol sits above, another under the board. Exceptions: Just one vactrol each is needed for the fifth and the eighth channel from the left. I suggest to test and measure the vactrols before soldering them in, some of mine had too much resistance and were replaced.

  • 3
    Soldering the components

    Soldering should be pretty clear. Please note that the images in the gallery show my prototype, the silkscreen layer of the available 1.1 gerber files now has all the components labeled and some values changed.

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Discussions

CrysisLTU wrote 12 hours ago point

You're right, everything went through fine and I've got my PCBs. As soon as I gather all the components, I'll built it and report to you. I couldn't source the same spec LEDs, would it still work fine with lower mcd LEDs?

  Are you sure? yes | no

CrysisLTU wrote 09/01/2019 at 18:29 point

Hi,

I am trying to order some PCBs of this project through JLCPCB. However, the through hole version is not recognized, while the SMD version is fine. Not sure what the issue is, but could you check and make sure that the through hole version Gerber files (and the actual KiCad project as well) has all of the correct parameters and configs? Would really love to try this project out.

Thank you.

  Are you sure? yes | no

Joris Wegner wrote 09/01/2019 at 19:41 point

Hello, I just tried again and it worked for me.

  Are you sure? yes | no

CrysisLTU wrote 09/01/2019 at 20:13 point

Could you upload the zip file you are using to upload to JLCPCB? Also, when uploading the SMD version to JLCPCB, the Gerber viewer warns about not having defined edge cuts. I would guess the same warning would be for the through hole variant.

  Are you sure? yes | no

CrysisLTU wrote 09/03/2019 at 19:01 point

Tried again. It works, kind off. The gerber preview at first shows nothing, but when I add everything to the cart, it is properly recognized, albeit without the dimensions. What are the exact dimensions of the PCB?

  Are you sure? yes | no

Joris Wegner wrote 09/04/2019 at 23:59 point

It should work fine, I also got my pcbs from JLC with the exact same gerber files (and maybe the same glitch). The dimensions are 100x100mm.

  Are you sure? yes | no

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