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Thread: Back then...this is what we did...

  1. #91
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    Quote Originally Posted by TheHermit View Post
    Thanks for the pointer, Steve. Interesting reading, most of which I'm familiar with, after 10 years of ion laser R&D + show experience. I've already built the rest of my 3 projector system, but only need a circuit to convert audio signals into ILDA standards, cause I'm critically lacking in the analog electronics lobe of my grey matter. But, I can twiddle knobs purdy good. Of course, that was way back in the day, long before the rheumatism set in. CBD helps with that, too.
    Lasermaster1977 is graciously being very helpful for achieving my goals.
    Nevertheless, I have no doubt that RTFMin' the pdf's will help in that respect.
    BR
    😎
    @TheHermit: This or a variation of this circuit may help you to convert audio signals to ILDA standards. I just posted it today in another thread on PLF as well. (Question about X and Y differential ILDA signals) If the DC offset 10K input and the 50K variable resistor are eliminated entirely then the circuit becomes a single-ended (unbalanced) inverting amp with a gain of 2 (change the gain via Rf to suit your needs), the output which becomes the input to the final ILDA differential (balanced) outputs for X & Y. Shown here are X and Y channel circuitry.


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    Last edited by lasermaster1977; 10-29-2022 at 16:13.
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  2. #92
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    Default Life is like a box of chocolates...

    Here is an update to this thread, related to my mentioning back at the beginning of this thread when I first added computer DAC generated imagery to my analog console capabilities. Computer generated imagery was for both abstract and real world line drawings.

    On July 1, a few days ago, I heard from an old friend, Mike. He had some laser related articles he wanted to mail me. It turned out to be some 35mm color slides I had sent him in August of 1979 of the first computer graphics images I had created with his help. My jaw dropped when I saw these slides. And if I ever had other copies of these slides in the past, they had long disappeared!

    Mike, a good friend of my brother, and my brother designed my first DAC card for use with my first Apple II Rev. 0 computer. Mike worked for Motorola and his job was to figure out cool things to do with Rockwell's new 6500 series CPUs. When I approached my brother to help me find a solution for digital graphics, it was Mike who suggested that I buy an Apple II and use it for this purpose since it had I/O expansion slots and used the 6502 CPU. Mike did the digital design of my 1st XY DAC card while my brother did the analog design (op amp circuits). Mike also wrote the binary DAC driver along with several simple BASIC programs for entering, modifying, listing X,Y coordinates of images and together they debugged this first hardware/software project.

    It was delivered to me in June or July of '79. I could draw via the DACs ANY image I wanted provided it used less than 127 XY coordinates! Wow! What freedom, right? I started learning to use this new technology straight away. By then I had also acquired one floppy disk drive for the Apple II for Mike to use during development and to store his programs to.

    Forgive me if I've mentioned what follows in other threads, but even though I now had a nifty 8-bit, 1MHz computer with up to 48K of DRAM AND Integer Basic. To create an image I had to use blue grid paper with 1" major divisions and .1" minor divisions (but in order to minimize grid paper size we mentally subdivided the .1" squares in half for .05" true minor divisions) to draw out my desired image shapes with pencil and eraser. My maximum useable grid size was 254 squares x 254 squares, roughly a one foot square piece of paper.

    The first image I drew was the scripted word "Laser", which was about 4 inches tall and 8 or so inches wide. We then had to determine the best beam path sequence to follow from the start of the word to its end as well as considering any retrace lines. At this time, beam blanking was just a dream. Next looked where the pencil drawn lines of the word "Laser" crossed XY grid intersections, marked that intersection with a pencil dot then counted the XY minor grid lines along the X and Y axes to derive XY coordinate values between 1 and 127, and wrote on another piece of paper 1. 40,64, etc. It was tedious for sure. The first Byte of the image was the image point count, followed by "n" number of XY pairs where n<=127. Images were loaded into memory from floppy drive storage on 256 Byte boundaries with a key code assigned to each image loaded. I could load up to 10 images, 10!

    At the time, I only had GSI G115 open-loop scanners, so this is how the first laser rendered computer DAC image looked at about 3-7 fps, scanned on the dome of a 40 foot diameter planetarium. The dome aluminum panels had small hole perforations for acoustic transparency as there were four audio speakers behind the dome. The red laser beam penetrated some of these holes and hit the inner dome ceiling that was about 3 feet from the dome's true screen. This resulted in a dim offset image ghost seen in the photo.

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    This Kodachrome 64 slide image was taken sometime in Aug 1979. And this had to have been just prior to my first commercial, product reveal gig that also happened in August '79.
    Notice at the end of the "r" you can see the "inductive ringing" inherent in the open-loop galvos at the start of a "Step" response.

    People from the Weedeater company in Houston had seen my Dallas planetarium laser shows and hired me to help with a new product reveal for their executives and wholesalers at a hotel ballroom in Houston at the end of August 1979. I was to draw the outline of their new XR model two-cycle nylon weed whacker on a blacked out stage, black background, just slightly larger than the real thing. Its engine housing was green plastic so naturally we used the green line of my mixed gas laser for this. Again, the image was done in 127 XY points and scanned at around 3-7 fps. This was a good example of how frame-rate flicker added to the dramatic reveal, since in a fairly darkened ballroom the green beam seemed akin to a laser light sword action. The laser effect only lasted a few second then a spot light came on illuminated the new weed whacker where the laser scan had just happened. ...and the crowd roared!

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    I mean...yeah the images aren't perfect but pretty darn good for open-loop scanners of that day.

    [I did a few minor edits today for better readability.]
    Last edited by lasermaster1977; 07-08-2024 at 16:03.
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  3. #93
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    Default Thanks Laserman1977

    Thanks for sharing your awesome story and memories.
    Iím sure it took some time to jot that down and wanted to let you know I appreciate it and found it very interesting and inspiring. I am sure others do as well!

  4. #94
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    Quote Originally Posted by lasermaster1977 View Post
    Mike, a good friend of my brother, and my brother designed my first DAC card for use with my first Apple II Rev. 0 computer. Mike worked for Motorola and his job was to figure out cool things to do with Motorola's new 6500 series CPUs.
    Thanks for the post. I love historical recounts of successful use of lasers back in the days when that was difficult and expensive. Am I correct though, you mean MOS and not Motorola?

  5. #95
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    Quote Originally Posted by Greg View Post
    Thanks for the post. I love historical recounts of successful use of lasers back in the days when that was difficult and expensive. Am I correct though, you mean MOS and not Motorola?
    Glad you caught my error. I meant Rockwell's new 6500 CPU series. Correction made. (MOS was the chip technology used ;-), correction MOS Technology who designed the 6502 was made up of many of the same Motorola engineers that designed the 6800 CPU. The 6502 was a simplified and cheaper version of the 6800...see https://en.wikipedia.org/wiki/MOS_Technology_6502)
    Last edited by lasermaster1977; 07-08-2024 at 18:23.
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