Published February 14th, 2011 by

Around 1987 I was into my home audio/video system big-time. Between surround, cassette, open-reel, mixers and synthesizers I spent more time wiring than I did using the gear itself. I thought it would be fun to build a matrix router for all my gear. My buddy Dieter, who taught me a lot about analog electronics, had helped me design and build a 16 channel mixing board already so I thought I would tackle this one on my own.

My intended feature list was:

-16×16 matrix of four-channel audio, single channel composite video

-Capability to breakaway any channel

-Touch switch user interface (touch switches were so new and cool back then!)

-Serial interface for computer control

I broke the project up into several boards that were then plugged into a motherboard bus that was contained in a 19″ rackmount case. I’m not sure what became of the front panel/user interface I originally built….that was a few years ago.

The middle board (pictured) was one of two boards that with custom touch-switch circuitry to handle a keyboard of small metal plates arranged as a phone-type keyboard. You typed “Source” “2” “Destination” “5” and that would send input #2 into output #5. This typing was interpreted by the leftmost board (pictured) into a parallel array of data that was used to control the rightmost board–one of several boards that handled the A/V matrix switching. Note the missing chips that were scavenged for later projects!

It worked. A little piezo returned a “click” sound as you touched the metal button/plates giving it a nice “aural feel”. Video quality was weak because analog video circuitry wasn’t my strong point. Audio worked well although bandwidth was weak because of the switching chips I used. I learned a lot about analog circuitry on this. I didn’t take it much further than a few ins and outs….once I realized that the quality wasn’t there it was hard to stay interested.

AV Router

Published February 14th, 2011 by

Back around 1983 I was experimenting with Voice Synthesis in software on a Commodore 64, recording phonemes and playing them back. At the health club I worked in I met a gentleman who was a saleman for the Detroit-based Votrax company that created the SC-01 Voice Synthesizer chip. When he heard I was an electronic hobbyist he graciously gave me an SC-01 chip (which retailed for several hundred dollars as I recall).

I went right to work building a small amplifier/buffering board for this puppy so I could plug it into the parallel port of my C64. I still remember how cool it was to piece together human-sounding voice from that little chip!

Voice Synthesizer

Published February 14th, 2011 by

This one is a bit of a mess, having been scavenged for parts over the years. Originally I built this as a successor to my first 3D digitizing device back in 1990. Unlike the manual method of digitizing that the first model used this was intended to be fully automatic–place an object in range and the digitizer would repeated search out the object until it had enough data to display the wireframe. It used several stepper motors to position various contact pointers until it found the surface of the object and found data. It worked–sometimes. It was only functional on shapes that could be “lathed” or were symmetric around a center axis. I built it as more of an excuse to learn to use stepper motors than anything else and I succeeded with that goal.

DigiPen 2

Published February 14th, 2011 by

Back in 1988 while using Sculpt-3D on the Amiga I wondered if I could digitize 3D objects with a custom hardware device. I constructed this little monster, the DigiPen using hiresolution potentiometers and an analog to digital converter. There were originally four joints in the arm of the pen (I’ve since scavenged some for parts on other projects). You held the pen in your hand and touched the object being digitized. It could “trace” an object in real time into a 3D model using bezier curves or polygons. I used the pots and built a multiplexer to allow me to use only one A/D because I couldn’t afford to have four A/D converters….and pots were a lot cheaper than optical encoders at the time. I learned a lot about multiplexing hardware with this project as well as serial communications and matrix mathematics for 3D.

It worked amazingly well. Originally it had a standalone user interface that I wrote for the Amiga. Later I interfaced it into “Vertex”, the 3D modeling application that I wrote whose source code was subsequently stolen.

Today there are several devices available commercially that perform the same task in higher resolutions.

DigiPen 1