Rebuilding my old analog console

[mixedgas]

THE Pass through zero oscillator stops the rotation as the VCO gets a zero control voltage, then reverses the direction of the phases relative to each other if the control voltage goes negative. So when you slow down and goes through "zero" Hertz, your rotating image stops.. Not the digital way, but the way of Analog. Also all your previous spirograph patterns in the sequence re-appear as you turn the CV back up, but the rotations and changes are reversed visually. So that 5 point star rotating clockwise comes back as a 5 point star rotating counter-clockwise etc.

So a through zero VCO and one other quad VCO results in cool stuff. a Through Zero quadrature VCO can be used for pure analog X,Y. or Z axis bidirectional rotation with fine control and Freeze of the rotation, even if the image being rotated is a vector graphic from a CPU.

Steve

[Greg]

If any child is especially attracted to the laser light and is performing poorly in school, or is well off the beaten path development wise, it might be time for testing and an a IEP, Individual Educational Plan.. Let us just say in 39 years of playing with lasers I've seen an informal correlation between obsession with Coherent Light, and problems in classroom performance. I may or may not fit that description, I will neither confirm nor deny. Most folks I've seen that in have a rough time when younger and it does work out in the end, some ending up with owning corporations or teaching PHDs. It gets outgrown.

What you say here rings true in my case Steve. All through school educators were on my case about performing poorly. The complaint was always lack of effort, not lack of capability. My reason for that was, aside from laziness and reluctance to leave a comfort zone, a profound disinterest in everything forced on students in the way of curriculum. I was obsessed with coherent light and programming in machine language, and nothing else, and there was no overlap between that and school. Combined with that was an intrinsic disdain I felt for the way mathematics was profaned by the education system pre-digesting the subject into idiotic "units" that never revealed the underlying symmetry and beauty of mathematics as a whole. After leaving school I bought a couple of well written textbooks (see photos) and methodically worked through a reasonable amount of the material. The math book was great in the way it began by formally defining what is meant when we say the number one. Everything followed in concentric logical sequences from that until one could begin to see the pattern and how it all fit together.

[Greg]

when we developed our abstract console (the radiator), we added hdmi video output so it can be used in scenarios where it's unsafe to use lasers. that also makes it safe around children. you might consider the same sort of approach.

I hadn't thought of that. Good idea. I was thinking more along the line of housing my old MediaLas galvos and a low power diode in my open air flying architecture style of cardboard boxery.

[Greg]

I'm going to need to read through those posts and see if I can understand what is going on. I'm hoping i can put together the rotation circuit and give it a try. This will take me a few weeks. Need to buy the components.

If you want to build the AD633 circuit you could use the wiring diagram I posted on that thread following laserist's schematic. Just note that in the wiring diagram pins 6 are not grounded which they should be. Otherwise the circuit works great with a 360 degree WW2 era sin / cos potentiometer. I had no idea there was such a thing prior to joining these forums. laserist gave me several of those pots, and I'd be happy to send you one if it would be of use.

If at some point there is a processor in your system, the code for rotations I use is:

// convert rectangular to polar
gMagnitude = sqrt ((gX_CYC * gX_CYC) + (gY_CYC * gY_CYC));
gTheta = atan2 (gY_CYC, gX_CYC); // radians

// convert polar back to rectangular
gX_CYC = (gMagnitude * cos (gTheta));
gY_CYC = (gMagnitude * sin (gTheta));

[ronhip]

Greg,

It was not lost on me that the cover of the circuit analysis book looks to be a laser cycloid of some type... Coincidence? I think not.

Ron

What you say here rings true in my case Steve. All through school educators were on my case about performing poorly. The complaint was always lack of effort, not lack of capability. My reason for that was, aside from laziness and reluctance to leave a comfort zone, a profound disinterest in everything forced on students in the way of curriculum. I was obsessed with coherent light and programming in machine language, and nothing else, and there was no overlap between that and school. Combined with that was an intrinsic disdain I felt for the way mathematics was profaned by the education system pre-digesting the subject into idiotic "units" that never revealed the underlying symmetry and beauty of mathematics as a whole. After leaving school I bought a couple of well written textbooks (see photos) and methodically worked through a reasonable amount of the material. The math book was great in the way it began by formally defining what is meant when we say the number one. Everything followed in concentric logical sequences from that until one could begin to see the pattern and how it all fit together.

[Greg]

The AD633 chip was mentioned a few posts back. I'm just rambling a bit more on the subject. Through the 1990s I built cycloid generating transistor circuits of my own design, but could never get three important functions. The functions were analog quadrature voltage controlled oscillator, amplitude modulation, and analog rotation. Relatively recently, I learned from Brian here on PL how 4 quadrant analog multipliers solve these problems, and from Steve I found out their fascinating history going back to the development of radar.
One point I'll add, the AD633 is costly as chips go, and the ones I bought on ebay were fake.

[Kevint]

Greg. Thanks for the reply.

I'm making some good progress. The 4423's are working very well using teflon caps at 0.015uf with 5Kohm dual pots. I'm ready to hardwire the board. Still working on summing and scan amp details. Once done I'm going to attempt the AD633 rotation circuit.

Just curious has anyone tried using 10 bit digipots with an arduino to control the quadrature oscillator frequencies?

[Kevint]

Ok, back to the AD534 question I posted in a different thread. In my old system and how it is currently breadboarded, the 4423's use op amps to sum the signals. See attached simplified sketch. But in the laser lightshow handbook, those circuits use AD534's to sum the 4423 signals. Due to my limited electronics experience, I don't understand the differences or advantage between both methods. Any insight is welcome. I'm enjoying this new learning experience.

[laserist]

Just get used to thinking TLO84 for all of your summing amp needs. I assume your drawing is simplified, but the sine and cosine signals from the quadrature oscillators should go to independent summing amps. One for x and one for y. Individual gains for each quadrature oscillator are a good idea. As well a a master gain after the summing amps. An inverter on one axis of each quadrature oscillator allows you to switch polarity...

[laserist]

Oh and a symmetry control is really handy. Laserium used dual linear pots which isn't ideal, also a single pot that would ground one or the other summing junction for the CYGN-B it worked, and for master symmetry a dual log antilog pot that was central to the master panel symmetry and gains.