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Thread: CYGN-B

  1. #491
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    Get a decent 50W soldering pencil with an adjustable power base. I turn mine down to a bit over 3 out of 10 on the dial. It's just hot enough to melt fine solder. If you don't want to buy a whole new setup, an inline light dimmer will work.

    I have been doing this since 2005 and I've sent kits and complete LaserBoy DACs to every continent on Earth except Antarctica. Many people use them professionally.

    I have more pc boards if you need.

    Yes. The recent Akron police shooting was absolutely horrible. Nothing justifies what they did.

    About 9 years ago my 28 year old nephew was shot 4 times and died while working at a McDonald's within walking distance of my house in a failed robbery. In that situation, the police were exemplary. The murderer gave himself up after 10 days because he figured he would get about 8 years and get out early. He got 31 years to life with no possibly of parole.

    I just hide in my basement and make art.

    James.
    Last edited by james; 07-12-2022 at 08:51.
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  2. #492
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    Quote Originally Posted by buffo View Post
    Yes, exactly.

    Likewise, any decent ILDA splitter will have a differential receiver as the first stage. This yields a single-ended output, which is usually fed into a gain and offset adjust amp before going to the output stage, where the signal must be re-converted back to differential before being sent on to the projector. All in the name of noise reduction.

    In fairness, the output of a differential receiver can be bipolar (centered on zero) or biased to be entirely positive (and centered on some positive voltage based on the position offset). But yeah, bipolar is more typical.

    Adam
    Thanks for answering my question and the info about ILDA splitters, which I would have assumed to be nothing more than a bunch of 'Y' connections and DB25 connectors.
    Tried daisy chaining an el cheapo projector to the in/out ILDA connectors on the OPT projector, but it wouldn't allow it.
    It auto detects the ILDA connection and switches to the show card's imagery if nothing is connected. The el cheapo 'ILDA' has common grounds for RGB (4 wires) + x/y differential (4 wires). So it uses a DB25 to RJ45 adapter with a CAT5 cable running to another RJ45 to DB25 at the projector. |-(
    BR

  3. #493
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    Holy shit dude. I have done nothing but offer to help you.
    Creator of LaserBoy!
    LaserBoy is free and runs in Windows, MacOS and Linux (including Raspberry Pi!).
    Download LaserBoy!
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    All software has a learning curve usually proportional to its capabilities and unique features. Pointing with a mouse is in no way easier than tapping a key.

  4. #494
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    I never saw your request to accept my offer to return the kits. I had no idea. I asked you if you wanted to do a bit more research before you even bought them. I even tried to explain what and how to measure the DAC you wanted to use.
    Last edited by james; 07-12-2022 at 13:29.
    Creator of LaserBoy!
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    All software has a learning curve usually proportional to its capabilities and unique features. Pointing with a mouse is in no way easier than tapping a key.

  5. #495
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    Quote Originally Posted by TheHermit View Post
    Thank you for chiming in on this subject that is currently bewildering me. Guess I need to stop worrying about breaking non-existent torsion bars and manufacturing problems within my imagination. Your hands on experience with modern galvos trumps that, for sure.
    I assumed that the differential inputs of the galvo drivers required + & - signals, otherwise there would be an offset between Gnd on one input and the signal on the other. Am I misunderstanding something?
    On the other hand, I planned to use single ended 0-5VDC for RGB, as Greg has mentioned.
    Thanks for your advice, Lasermaster1977. I'm seeing several different circuit designs from others, which is very confusing for the average pseudo-tekkie. Had hoped to find only one 'best' design within the community after all these years.
    I'd really like to get over this hurdle and move on to completing the rest of the system.
    Sorry for my late response but for some reason I've not been receiving email notifications of the additional comments on this thread.

    Open or closed-loop galvo power driver outputs are usually bipolar, like an audio speaker power amp. They are usually just single ended, push-pull power drive amplifiers. At least in the old days.

    To use a further audio analogy, audio line outputs can be single-ended or balanced. At audio line levels (-10 to 0dbm typically or pk-to-pk voltages levels of .7 - 1v) noise is usually not an issue when using shielded cables where cable lengths are a few feet to 25 feet.
    Microphone levels are far lower (-50-60 dbm) and high quality mic pre-amps will have balanced, low-level inputs to the pre-amp for best noise immunity.

    So for best noise immunity and long, line level cable runs having balanced line drivers insures good noise immunity, and any capacitive or inductive noise that is picked up while the signal is in transit is usually canceled out by the balanced line.


    ILDA inputs can be either single-ended or double-ended (balanced). When the Ground of a single-ended line input signal is tied to the ILDA minus connector for either axis, the trade-off for doing so is that the scanner output swing is half what it would be compared to a double-ended or balanced line input.

    My current "hobbyist" setup between the output of my XY DAC's single-ended to double-ended line level signal "mixer/modulators" sends the final line-level XY signals to the ILDA Input connector on the projector through a 10 foot long, unshielded flat ribbon cable with no problems. My RGB outputs are 0-5v single-ended just like Greg's, running through the same 25 pin flat-ribbon cable.
    ________________________________
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  6. #496
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    Quote Originally Posted by Greg View Post
    lasermaster1977: Yes, the two IC2 stages are exactly what I used, except the 10Ks are 22Ks, the rails are +-15, and I don't have the 5K. I don't see it's purpose. However, there's lots I don't know.
    The 5K resistor on the + input of an inverting op-amp circuit is always equivalent parallel resistance between the feedback resistor and the effective parallel resistance off input resistor(s), if and only if you want to minimize the DC offset errors generated at the op-amp's output. When using op-amps for current to voltage conversion on DAC outputs I recommend using 1% resistors, otherwise 5% are usually good enough for our kind of needs.

    Doing so helps minimize chasing and nulling out DC offset errors that propagate through an end-to-end circuit that ultimate is used to feed scan driver inputs or ILDA inputs.

    To save time, money and keep circuitry simple this method is often discarded.
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  7. #497
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    Quote Originally Posted by lasermaster1977 View Post
    Sorry for my late response but for some reason I've not been receiving email notifications of the additional comments on this thread.
    No prob. Perhaps you haven't noticed this at the bottom of your PL emails:
    "There may also be other replies, but you will not receive any more notifications until you visit the forum again.

    All the best,
    Photonlexicon Laser Forum"

    Open or closed-loop galvo power driver outputs are usually bipolar, like an audio speaker power amp. They are usually just single ended, push-pull power drive amplifiers. At least in the old days.
    Glad to know another laserist, who still remembers open loop GS124 'scanners'. TBH, I always purchased their scan amps and left the electronics to the gurus back in the day, but I covered everything else regarding overall system design, mfr'g projection heads, optical mounts, doing shows, installations, & toilet cleaning.
    Prior to lasers, I was a machinist and tool & die maker in the aircraft industry, supporting Northrop's F-18 assembly line. Then I saw Laserium.
    When the HR gal @ Laser Images told me that there would be an entry exam, I assumed that she meant on lasers. So, I read a laser book, then failed because the test was only on basic electronics. But, she said everything else on my app looked fine.
    So, I asked my boss to lay me off from Northrop and took a semester of basic electronics crash courses at the local JC. HR gal phoned me up in between semesters to check on my status.
    "Well, I've been taking electronics classes and have decided to become an electronics engineer, instead."
    "That's really unusual," she replied. "Most of our electronics guys would rather be laserists. Would you please hold for a minute, while I take another call"
    "OMG, she's right!" I thought, while sitting on hold. "I could spend the next 6 years getting a degree and end up back in a factory testing PCBs."
    So, when she returned, I said that I'd like to take the exam again to see how I do.
    3 months later, Dave Cooper and I were flying to London.
    Funny ole world, ain't it?
    Anyway, 2 years later, silly me thought there was a higher level of fame and fortune as a freelancer, until '88. I ended up being a PC tech until I retired in 2015 and became a wannabe maker, connecting IoT devices to Arduino MCUs with copper string. The moment I discovered the Teensy and realized it's potential, but still didn't have enough coding smarts.
    Now, 34 years later, I've returned to lasers, picked up that Teensy MCU and started building my own laser systems, again.
    Just finished testing my 1st op amp circuit, to convert the 0-3.2 p-p outputs from the Teensy's audio DACs to differential bipolar outputs, -5/+5 V p-p. WooHoo!
    Next challenge, learn kicad & have JLCPCB consolidate it all onto a single PCB.
    Upload everything to Github, drop a How-to DIY video, and let the community run with it wherever they please.... or not.

    ILDA inputs can be either single-ended or double-ended (balanced
    Thank you for taking the time to explain. After your previous advice, I RTFMed differential circuits and now have a better understanding of what you're saying.
    When the Ground of a single-ended line input signal is tied to the ILDA minus connector for either axis, the trade-off for doing so is that the scanner output swing is half what it would be compared to a double-ended or balanced line input.
    So, over short distances, I can lose the second stage with the inverted output and double the gain of the 1st stage to achieve the same results. But, the 0-3.2 V p-p output from the DAC still needs the offset corrected in the 1st stage, as well for a balanced bipolar signal.
    My current "hobbyist" setup between the output of my XY DAC's single-ended to double-ended line level signal "mixer/modulators" sends the final line-level XY signals to the ILDA Input connector on the projector through a 10 foot long, unshielded flat ribbon cable with no problems.
    Within my living room, I'm already covering most of the distance to the Teensy Synth, with a 20ft USB cable anyway. The ILDA cable is another 10ft. Model II will have the Teensy Synth inside a lumia projector (salvaged & repurposed el cheapo RGB laser projector components) to utilize more GPIO outputs, but it will still have the ILDA output to the image projector.
    Teensy Laser Synth + MIDI controller + touchscreen GUI + multi track DAW + dual 3 watt RGB projectors + multiport RGB lumina projector >= 1/2 Laserium projector, right? ;-)

    My RGB outputs are 0-5v single-ended just like Greg's, running through the same 25 pin flat-ribbon cable.
    Same here. A single TL084 with some resistors should do the trick. Are you using Zener diodes or anything to limit the 5 V to protect the LDs against early burnout?

    Anyway, enough of my babbling. Enjoying the chat. Not many of us still around.
    Are you still doing shows?
    BR
    Last edited by TheHermit; 07-30-2022 at 16:09.

  8. #498
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    Quote Originally Posted by TheHermit View Post
    No prob. Perhaps you haven't noticed this at the bottom of your PL emails:
    "There may also be other replies, but you will not receive any more notifications until you visit the forum again.
    I don't believe I've ever seen that but it now explains a lot! Thanks for that.


    Quote Originally Posted by TheHermit View Post
    Glad to know another laserist, who still remembers open loop GS124 'scanners'. TBH, I always purchased their scan amps and left the electronics to the gurus back in the day, but I covered everything else regarding overall system design, mfr'g projection heads, optical mounts, doing shows, installations, & toilet cleaning.
    I too like reminiscing with old timer laserists. I started with GS115's, without knowing much other than basic electronics and op-amp circuitry, I built my own open-loop drivers using the Fairchild u719 power op-amp using plus & minus 12v 1amp regulators (7812, 7912). The 719 had its own built-in 1amp current limiting circuitry. I was so reluctant to build a bi-polar, multi-amp unregulated power supply as the voltage regulator inputs for the 8 drive amps for RYGB scan pairs that I used 8 2amp Triad step-down transformers, each with their own bridge rectifier and 2000uF electrolytic filter caps. These scan drive amps & PSUs worked without any failures for over 10 years.


    What a great story on how you became a Laserium laserist! I'm looking forward to seeing your Teensy results. I have several project priorities before I can devote time to my Teensy "exploring".

    Quote Originally Posted by TheHermit View Post
    Same here. A single TL084 with some resistors should do the trick. Are you using Zener diodes or anything to limit the 5 V to protect the LDs against early burnout?
    Speaking of Greg's circuit, that OPA188 op amp with a 20 V p-p bipolar output looks like a perfect solution for the galvo signals... provided that it's centering feature doesn't allow beam positions to drift towards the center. Waiting for his feedback, before purchasing some.

    Anyway, enough of my babbling. Enjoying the chat. Not many of us still around.
    Are you still doing shows?
    BR
    I've not yet implemented analog RGB blanking (not convinced that it is a must have) and still use 2-1/2 556 dual timers chips for RGB TTL line drivers and count on the Chinese projectors LD protection circuitry.
    Greg's circuit will do just fine in providing stable DC offset.
    No, my last professional shows were done in the years 1986, 87 and 88. I now just spend time doing graphic design & choreography just for fun and pleasure. I bought a pair of DT40 scanners w/drive amps for my own RGB projector build but I've not had time to do a build yet. I've been having too much fun updating one of my old professional Apple II/IIe laser graphics software and images to support RGB and hardware to mix & modulate XY outputs feeding the ILDA projector inputs.

    I did do some freelance laser shows on weekends at a live band venue in an old theater in the late 90's or early 2000's, but it was just for fun, for no money.

    Right now I'm writing some conversion software to convert some old (several hundred) Apple II/IIe 2D images to ILDA format for an old Apple IIe colleague.

    Cheers,
    Last edited by lasermaster1977; 07-13-2022 at 17:15.
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  9. #499
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    Single ended or differential drive to scanner amps can in fact produce the same peak to peak voltage swing. It's simply a matter of the difference between the inverting and non inverting input signals. +5V minus -5V is 10V. Just like +10V minus zero (ground) is also 10V. Both the inverting and non inverting signals swing from negative voltage to positive voltage with respect to ground. They are just out of phase. The level of the input signals is the difference between the two. That's why it is necessary to use a differential power supply for the op-amps. So even a single ended op-amp can swing just as negative as positive. The peak to peak limit of the op-amp is slightly less than the positive and negative power supply. Using the +9/-9V DC/DC converter to power the op-amps can result in a peak to peak swing of over +7/-7V. If you need more than that, you have to use a +12/-12V supply. I chose the +9/-9V version because it draws less power from USB even if the op-amp gains are set the same. Power is power.

    .
    Last edited by james; 07-13-2022 at 17:09.
    Creator of LaserBoy!
    LaserBoy is free and runs in Windows, MacOS and Linux (including Raspberry Pi!).
    Download LaserBoy!
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    Ask me about my LaserBoy Correction Amp Kit for sale!
    All software has a learning curve usually proportional to its capabilities and unique features. Pointing with a mouse is in no way easier than tapping a key.

  10. #500
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    Quote Originally Posted by james View Post
    Single ended or differential drive to scanner amps can in fact produce the same peak to peak voltage swing. It's simply a matter of the difference between the inverting and non inverting input signals. +5V minus -5V is 10V. Just like +10V minus zero (ground) is also 10V. Both the inverting and non inverting signals swing from negative voltage to positive voltage with respect to ground. The level of the input signals is the difference between the two. That why it is necessary to use a differential power supply for the op-amps.
    One situation where you lose half the signal is when you drive a differential output into a single ended input. There's nothing to connect the minus output to, and you get just half the signal via ground. The one place where differential is a true must is on the receiving end of the scanners, even when the drive is single ended.
    It also offers a convenient way to flip polarity.

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