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555 Contest Entry: VidiSynth

VidiSynth Pop

The VidiSynth is a circuit with multiple oscillators that are controlled with light sensors attached to a video screen.

Video + Synthesizer = Vidi Synth

The light sensors create interesting and complex sounds based on the intensity of different areas of the screen.  I also learned from experimentation that if the sensors are attached to an LCD screen you get relatively normal square wave tones but if you use a CRT screen (TV or monitor) you get extra noisy and buzzy goodness because of the refresh.

I’ve been tinkering with electronics for just over 2 years and VidiSynth has been a huge part of my learning experience.  It all started with early tinkering with 555 oscillators and my first optical theremin inspired by a video from Michael Una.  From there I came up with the idea for VidiSynth and prototyped it using individual 555s.

That prototype actually required an audio mixer to combine the different channels because I hadn’t yet learned how to mix the signals.  I lived with that prototype for quite a while, even building an interactive project around it for an exhibit at Twin Cities Maker during the annual Minne-Faire. Eventually an Electrical Engineer friend from the hackerspace urged me to evolve it into a PCB for potential sale as a kit.  This opened up whole new areas for me to learn. Fortunately I have a couple of very patient EE friends that were a huge help along the way.

The design was done entirely in Kicad which is a nice tool once you climb a bit of a learning curve.  I eventually worked my way through all the steps of laying out the schematic which involved creating some custom components, mapping the components to footprints (more custom work) and then finally laying out the PCB. Kicad’s autorouting features worked great for my simple design and along the way I learned details about vias, ground plains and trace parameters for power versus signal.  The final step was to learn about all of the various layers that must be sent to the PCB manufacturer and making them all look the way I wanted.  Finally I sent my design off to BatchPCB, ordered the components and waited.

When my PCBs arrived I eagerly populated the first one, and IT WORKED!

The PCB version of the VidiSynth was born.

VidiSynth went through various prototypes before its current incarnation pictured above.  It uses two 556 chips to implement four oscillators, the output of the four oscillators is mixed through a set of resistors into a 1/8” mono jack.  On each oscillator the resistive element that  normally controls frequency is terminated on a terminal block in order to allow different options for controlling the frequency.  This can be achieved with photo-resistors as originally conceived, with potentiometers for more direct control or anything else that allows control of resistance.  You could also add complexity by switching the channels with transistors.

Here is a list of a few interesting ways to use the VidiSynth that I’ve discovered:

1. As originally conceived you can connect photo-resistors randomly to a video screen and play your favorite movie or any old thing you have lying around to get interesting sounds.  Film Noir is particularly dramatic.

2. Pipe the feed from a video camera or do display on a TV or monitor and you have an interactive instrument.  I recently had a conversation about using Skype video conferencing in conjunction with this in order to facilitate a remote performance using VidiSynth.

3. Run all the channels through potentiometers and you can play with drones similar to Casper Electronic’s Drone Lab.

5. I have written a midi driven Processing script that displays grayscale blocks on the screen based on the midi commands.  This allows sequenced control of all 4 channels.  I plan on releasing this in the future once I finalize it.

6. Another method of sequencing I have used is to run a couple channels through Mikey Delp’s Bender Sequencer that was created for sequence circuit bent toys.

The possibilities are endless once you start combining different input methods.  You could even mix multiple VidiSynths for more fun.

Below are a couple video demonstrations of the how VidiSynth can be used.  It’s a fairly simple circuit, but with that simplicity comes a flexibility that allows for some fun experimentation.

Before I move on to the demonstrations, here is a link to the schematic for the project:

VidiSynth Schematic


VidiSynth Demonstration

VidiSynth Build Video

Expanding the VidiSynth Part I

Expanding the VidiSynth Part II

Expanding the VidiSynth Part III

Finally I would like to recognize Paul Sobczak who encouraged me to enter the 555 contest.  He’s a smart and humble guy who is infinitely generous when it comes to inspiring people to do cool things and is always there to lend a helping hand.  Also thanks to my two tremendously smart and helpful friends Mike Hord and Adam Wolf.

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