Page 1 of 3 123 LastLast
Results 1 to 10 of 30

Thread: projector building: setting max driver current question

  1. #1
    Join Date
    Oct 2016
    Posts
    209

    Default projector building: setting max driver current question

    I noticed when I set the current for my diode to say 1.6A when it is connected to a constant 5V source for the signal and then run my projector through ILDA with a RIYA DAC, the most this DAC tells to draw is 1A. And the laser output is lowered approporiately.
    So, should I be setting my diode driver current while connected to a DAC instead?

    With DAC I used LSX and set all the blanking and extra points to 0 and set the point count on my graphic to max (40 kpps ) and it wouldn't get any brighter. But the max brightness is 30% less than with a constant 5V signal source.

  2. #2
    Join Date
    Oct 2016
    Posts
    209

    Default

    Bump.
    To add to this the housings get much cooler like this which again hints the diodes are underperforming with a DAC instead of a constant 5V signal.

  3. #3
    Join Date
    Feb 2007
    Location
    Fort Mill, SC USA
    Posts
    1,507

    Default

    LSX has a galvo resonance safety feature built into it that ensures a minimum number of points are displayed. This minimum number varies by DAC and by projection speed. The difference between your frame (plus any added points defined in your optimization settings) and this 'minimum number of points' are blank points, thus you not getting a higher modulation value to your driver.

    I don't know what DAC you are using, but you can do an ILDA export to see exactly how many total points there are and how many blank points were added. As general guidance though, the Etherdream DAC requires 100 total points per 10KPPS - so you need 400 points minimum (again after added points defined by your optimization settings) for 40KPPS. You still won't get to a modulation of 5.0V no matter what you do, but you should be able to something akin to 4.8V.

    -David
    "Help, help, I'm being repressed!"

  4. #4
    Join Date
    Oct 2016
    Posts
    209

    Default

    RIYA Lite is what I use

  5. #5
    Join Date
    Oct 2016
    Posts
    209

    Default

    So to answer the question, I need to change the current trimpot position again while DAC is connected and max number of points is being displayed to get the max out of my diodes?
    My projector doesn't have a "constant 5V mode" and only has an ILDA port so sounds like I'm losing brightness pointlessly right now.

  6. #6
    Join Date
    Feb 2007
    Location
    Fort Mill, SC USA
    Posts
    1,507

    Default

    No, you set your target max current with on +5V on the modulation input as you described originally. You will likely never achieve 5V with ILDA input from any software package, so you won't get quite the same output as you had when you set your current. (There is an exception to this rule by incorporating a DZ colour board into your projector, but let's not go into this right now.)

    My prior advice was how to create LSX ILDA frames that will get you close to max modulation output. Again, adding more points up to 100 points per 10Kpps display speed (with all of the caveats described in my prior post) will result in the 'brightest' possible output.

    -David
    "Help, help, I'm being repressed!"

  7. #7
    Join Date
    Oct 2016
    Posts
    209

    Default

    Okay, maybe I'm not getting it, but what's the point of setting a current which provides the desired max stable power output via a signal source which is higher than any DAC in the world will reach? Right now it seems to me like we are setting the max power current but will only ever use max 96% of it. Like 4-5% isn't much but when I lose so much from bounce mirrors, dichros and scanner mirrors combined I'm at least curious why I should give away another 4% or more for this. Sorry if I'm being dumb and you already explained this.

  8. #8
    Join Date
    Feb 2007
    Location
    Fort Mill, SC USA
    Posts
    1,507

    Default

    I think the majority of us consider this ~a safety margin to counter for driver spikes and such. You can try to push your diodes harder by upping the current a tiny bit or by getting the DZ colour board that I mentioned earlier.

    <Edit> In addition, if you are pushing your diodes near their stable limit, the difference in current for that last 4% of modulation voltage is going to result in very little difference in mW output as you are nearing the peak of the output curve. </Edit>
    "Help, help, I'm being repressed!"

  9. #9
    Join Date
    Oct 2016
    Posts
    209

    Default

    That DZ color board thing sounds like it does exactly what increasing the current would do, sounds like it just increases the modulation voltage to peak at 5 instead of 4.something.

    I'm not really pushing my diodes to their curve peak where more current actually causes drop in power, but I want to push them closer to the peak where my housings can't keep them at a stable low temp anymore. That's a bit different. Unless I'm projecting a graphic (logo or something) where one of the colors is always there I can't think how in a beam show or graphic show I'd ever reach the testing levels where I have the diode in constant on mode for hours straight. So basically if they don't overheat then they probably have very little chance of overheating in practice. Now if I was overdriving them that would be a different thing where a moment of current spike just above what I had set could destroy the diode.

  10. #10
    Join Date
    Mar 2010
    Location
    Raleigh, NC
    Posts
    2,292

    Default

    Quote Originally Posted by dkumpula View Post
    You will likely never achieve 5V with ILDA input from any software package, so you won't get quite the same output as you had when you set your current.
    I can't speak for other software, but with Spaghetti you can achieve max output by simply turning the minimum value of all lasers to max. This forces them to run at full power even when blanked.

Posting Permissions

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