Page 2 of 6 FirstFirst 123456 LastLast
Results 11 to 20 of 53

Thread: ILDA specs

  1. #11
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,739

    Default

    Hard to say what's the cause -- whether it is purely visual (i.e. in your mind), or the fault of that which is driving the laser, or the laser diode driver. Nothing would be surprising...

    If you scope the input to the laser diode driver and it's nice and square, then you could look at laser output using a photodiode and see if that it equally as square.

    But there sure are a lot of crappy laser diode drivers out there...

  2. #12
    Join Date
    Sep 2014
    Location
    Colorado USA
    Posts
    275

    Default

    Quote Originally Posted by Pangolin View Post
    Hard to say what's the cause -- whether it is purely visual (i.e. in your mind), or the fault of that which is driving the laser, or the laser diode driver. Nothing would be surprising...

    If you scope the input to the laser diode driver and it's nice and square, then you could look at laser output using a photodiode and see if that it equally as square.

    But there sure are a lot of crappy laser diode drivers out there...
    Thanks Bill, done that already, which leads me to know that it is the signal conditioning being presented to the projector's ILDA input connector. An the surge is measurable with a laser power meter, it's not in my mind. The initial "brightness surge" does not occur with the projector laser diode outputs when driven by an EtherDream2 or FB3QS, (and these and my outputs are perfectly square as seen on a scope), only when driven by a perfectly square, TTL derived blanking signals whose peek voltage is adjusted via a TL084 opamp to be at or below the respective diode's near max voltage. I noted these two DAC's max RGB ON voltages, having been adjusted for proper blanking with LSX and QS respectively, and my circuit is replicating these full ON voltages.

    Maybe the difference is that I'm not conditioning the RGB diode blanking singles to swing between near turn-on threshold and near max. on, just 0v to near max. I don't see how this could make a difference, though, could it? I should add I'm only trying to turn each color ON or OFF where ON is near but not at full intensity.

    I'll take a closer look at the EtherDream2 and FB3QS blanking signals.
    ________________________________
    Everything depends on everything else

  3. #13
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,739

    Default

    Just because the laser doesn't exhibit problems when driven by QS doesn't mean it's not a crap laser!

    (Similar to "Just because you're paranoid doesn't mean they're not out to get you" )

    Bill

  4. #14
    Join Date
    Sep 2014
    Location
    Colorado USA
    Posts
    275

    Default

    Quote Originally Posted by Pangolin View Post
    Just because the laser doesn't exhibit problems when driven by QS doesn't mean it's not a crap laser!

    (Similar to "Just because you're paranoid doesn't mean they're not out to get you" )

    Bill
    Ok Bill, you are just forcing me to use logic to diagnose this.
    ________________________________
    Everything depends on everything else

  5. #15
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,739

    Default

    Thor makes a series of "amplified photodiodes". You can find them here:
    https://www.thorlabs.com/navigation.cfm?guide_id=2171

    You connect this to the scope and then compare the driven waveform to the light coming out of the projector. (Of course you must use appropriate filters to attenuate the beam going into the detector to prevent overloading it...)

    This can help you to understand the quality / crappiness of the laser...

    Bill

  6. #16
    Join Date
    Sep 2014
    Location
    Colorado USA
    Posts
    275

    Default

    Quote Originally Posted by Pangolin View Post
    Thor makes a series of "amplified photodiodes". You can find them here:
    https://www.thorlabs.com/navigation.cfm?guide_id=2171

    You connect this to the scope and then compare the driven waveform to the light coming out of the projector. (Of course you must use appropriate filters to attenuate the beam going into the detector to prevent overloading it...)

    This can help you to understand the quality / crappiness of the laser...

    Bill
    Much appreciated. Thanks.
    ________________________________
    Everything depends on everything else

  7. #17
    Join Date
    Jul 2008
    Posts
    441

    Default

    Quote Originally Posted by Pangolin View Post
    In all of our software we prevent permanently holding color signals at 5 volts for safety reasons. (And we would not use a sound board to control a laser, again for safety purposes, but that's a different story... What people do in the privacy of their own home is their business )

    Bill
    As a soundcard geek I'm a bit confused here, please elaborate.
    Last edited by dchammonds; 11-25-2018 at 21:37.
    Once milk has been poured over corn flakes, the clock starts ticking.

  8. #18
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,488,779

    Default

    Sound card DACs do not blank the signal between frames. (In fact, the very concept of "frames" is rather arbitrary, if not irrelevant, when talking about sound card DACS.) However, most commercial laser show hardware will, in fact, blank all the lasers in-between frames.

    The idea is that if you have a system failure, the laser will only stay on as long as it takes to complete the frame. Then it blanks. If the next frame never arrives (due to a software crash, or any other failure, really), the laser stays off. The alternative is a risk of a single, static, full power beam being emitted from the projector when Windows inevitably crashes.

    This is what Bill meant when he said he wouldn't use a sound card to drive a projector "for safety reasons".

    Adam

  9. #19
    Join Date
    Mar 2012
    Location
    Akron, Ohio USA
    Posts
    1,314

    Default

    Speaking from experience with the CM-6206 USB sound device that is a popular choice for sound card DACs, if the driver for the device is left at the default setting of stereo or headphone output, the device will set all the color channels full on! So you need to know this before you power on your laser projector. You have to open the driver applet and set it to either 6 or 8 channel operation mode. You can also edit the ini file that initializes the driver so that it will only operate in 6 or 8 channel mode, so that is no longer an issue.
    Creator of LaserBoy!
    LaserBoy is free and runs in Windows, MacOSX and Linux.
    http://laserboy.org/code/LaserBoy_Current.zip
    http://theamerikans.org/LaserBoy

    http://laserboy.org/formatt/
    Ask me about my LaserBoy Correction Amp Kit for sale!

    Either do or do not do. There is no undo!

  10. #20
    Join Date
    Apr 2006
    Location
    Orlando, FL - USA
    Posts
    1,739

    Default

    Quote Originally Posted by dchammonds View Post
    As a soundcard geek I'm a bit confused here, please elaborate.
    Sound cards are made to drive speakers. If "shit happens", nobody is going to be blinded as a result...

    For example, let's say you make laser software that is driving a sound card. And lets say that Windows decides to "beep", or that some generic sound software decides to output a sound. Although Windows provides the ability to select the default sound card for "beeps", what if something goes wrong? What if the selection doesn't stick, or is forgotten??? After all, we're talking about Microsoft Windows here! In such cases, at best you get scribbles on the wall. At worst, the beam is projected into an audience area...

    I can't speak for the way anybody else designs their laser controllers, but one very important role of *our* software is that it "serializes access to the hardware". It means that it prevents two pieces of laser software from accessing the same laser output controller at the same time. In fact, we've made BEYOND be a kind of arbiter. Now we don't have SDKs that directly access the hardware any more. We have BEYOND. Want to talk to the hardware? Talk to (or actually through) BEYOND! The benefit is that BEYOND is able to prevent "scribbles on the wall" by serializing such hardware access. Another benefit is that right now, people who "talk to BEYOND" are able to use any connected laser hardware (QM2000, FB3, FB4, and in the future other hardware), and so this is a hardware agnostic approach. Another benefit is that BEYOND can effectively apply additional things on top of their input -- for example, additional effects or even safety-related features such as BAM, beam-velocity monitoring, feedback and such... But enough about BEYOND... (I just mentioned this to answer the question why we don't allow direct access to our laser hardware any more...)

    Another thing is that we make our laser hardware to be "fault tolerant". It means that if something goes wrong inside the box, it won't result in an unsafe exposure. For example, if the negative power supply goes away in a sound card (or interface box), good luck holding the color outputs low! (Heck, from what James wrote, good luck holding them low anyway!!!)

    Anyway, there are huge differences between sound cards and the laser controllers manufactured by us (and I hope other laser companies do similar things). But what people use in the privacy of their own homes is their business. Scribbles on their walls or blinded (or at least visually annoyed) pets or family members are not our business. We do hope that people will "drive responsibly" when the sound cards are used with lasers outside the confines of homes...

    Bill

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •