Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18

Thread: Lightspace Pluto II - Red laser module partial failure (637nm, quad module)

  1. #11
    Join Date
    Dec 2008
    Location
    veenwouden
    Posts
    2,577

    Default

    Hmmm. That sounds like a driver issue, not a problem with the diode. It's possible that you just need a new driver. Although if you did replace the driver, you'd have to guess at the current setting.
    If you have a well designed driver you have an 1 ohm resistor where you can measure the voltage accross is which is a value for the current. Single mode sharps needs a max of 240ma if i remember it correctly. So if its a driver issue only that would make it allot easier. But usually with these projectors its not only the driver but also the diodes that need to be replaced. But after the replacement and a new driver its bassically brand new.


    Interested in 6-12W RGB projectors with low divergence? Contact me by PM!

  2. #12
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,489,370

    Default

    Quote Originally Posted by edison View Post
    If you have a well designed driver you have an 1 ohm resistor where you can measure the voltage accross is which is a value for the current.
    I agree that a series resistor on the output for current-sensing is a common feature of many drivers (it's also referred to as a current shunt resistor).

    However, in my experience it's far more common to find a .1 ohm resistor, not a 1 ohm resistor. It really depends on the maximum current rating of the driver though. If the maximum output current is 500 mA, then a 1 ohm resistor would only need to dissipate 1/2 watt of heat at full current, which isn't much of a problem. But if the maximum current is 5 amps, now you're talking about 5 watts of heat on that current-sensing resistor, which could be a problem. True, there are sand-filled resistors that can handle that much heat, but they are big, heavy, and not very precise.

    The other problem with high-power resistors is that most of them are wire-wound resistors. This is a BIG problem for a laser diode driver circuit! It's absolutely crucial that this current-sensing resistor be completely NON-INDUCTIVE, because the resistor is in series with the diode. Any inductance in the output circuit will create dangerous current spikes that can destroy the laser diode. This is the problem that plagued the final production run of Dr Lava's Flexmod P3 drivers; the pick-and-place firm that was assembling the drivers decided to substitute a wire-wound resistor for the thick-film resistor that was specified in the design, and they never told anyone about this change. The added inductance of the wire-wound resistor was enough to create deadly over-current spikes.

    Single mode sharps needs a max of 240ma if i remember it correctly.
    Is that the diode that Lightspace used in the Pluto II projector? I know that the early models only had something like 400 mw of red, but later models bumped that up to ~ 650 mw or so. So if they were using the Sharp GH0631 diode, that would make sense.

    Makes me wonder if they had separate drivers for each diode, or if they just ganged them all together on a single driver (hopefully in parallel with a current balancing resistor on each one). Considering the strange artifacts that Swami was talking about when fading to black, it would seem that it just about has to be running a single driver for all diodes...

    Regarding that "dotted pattern" artifact, I have to say that I've never noticed that on any of my Pluto II projectors. Chris, is there a particular pattern I can display that will consistently show this artifact? I've got one of my Pluto IIs set up in the living room at the moment (it's hooked up to my Radiator), so it would be easy to test. Wondering if this is a problem on all Pluto IIs, or if it might be limited to the earlier models only.

    Adam

  3. #13
    Join Date
    Apr 2008
    Location
    DC/VA metro area
    Posts
    402

    Default

    Quote Originally Posted by buffo View Post
    The modules from OptLaser are quite affordable, but you are correct: they don't have the tight beam divergence that the Lightspace modules have. Although I have only played with their higher-power modules; I can't really speak to the divergence on their 2-4 watt units.

    I remember that Mike Muhler bought a few of the 4 watt all-in-one RGB modules from Goldenstar a few years ago and installed them in some home-built projectors he had. I thought the output looked pretty good when he brought one to SELEM in 2019, especially considering that he only paid like $500 (including shipping) for those modules back then. So that might be another option...

    Adam
    Any idea if the Goldenstar modules were the fiber coupled ones that they are advertising now? Or any reports on how those do? I assume the fire all the lasers into fiber then clean up the output from there. Spec sheets say 1mrad divergence. But some of the larger ones advertise large beam profiles similar to to non-fiber ones, so maybe they just copied over the ad copy from one to the other and forgot to edit. Not sure.
    Modern and Retro laser show hobbyist
    Pangolin QM16, QM32, Beyond Advanced, LSX, ADAT
    LS Pluto II x 2, custom build x 1
    http://lasershowwiki.757.org for my all encompassing laser show wiki.

  4. #14
    Join Date
    Dec 2008
    Location
    veenwouden
    Posts
    2,577

    Default

    fibre means it has a FAC lens build into the diode itself. With some additional lenses you can correct the beam in both axis.


    Interested in 6-12W RGB projectors with low divergence? Contact me by PM!

  5. #15
    Join Date
    Jan 2006
    Location
    Charleston, SC
    Posts
    2,147,489,370

    Smile

    Quote Originally Posted by telmnstr View Post
    Any idea if the Goldenstar modules were the fiber coupled ones that they are advertising now
    I don't know of any fiber-coupled laser modules from Goldenstar.

    As Edison pointed out above, "fiber laser" is a marketing term that is often used to describe a high power, multimode diode that has a strand of optical fiber bonded directly to the emitter face. This fiber strand acts as a cylindrical lens, expanding the fast axis of the beam before it enters the primary collimating lens. If everything is spaced out correctly, then downstream of the primary aspheric collimating lens you should have a more-or-less square beam profile with no further optical correction needed. It's a quick and dirty method to get fairly decent beam characteristics out of a multimode diode without all the cost, complexity, and optical losses that you'd otherwise have with a dedicated set of secondary correction optics downstream of the primary collimating lens.

    This arrangement is nothing like a fiber-coupled laser, however. In a fiber-coupled laser, the light travels through the fiber along it's length. But in a "fiber laser", the light travels across the diameter of the fiber in a direction that is perpendicular to the length of the fiber.

    Perhaps it would be more correct to refer to the Goldenstar modules as "fiber-corrected", but even that could still mislead some people. The problem is that when you say "fiber", most folks immediately think about a fiber launch - including all the complex positioning and focusing adjustments. But there's nothing magical about passing a beam of light down the length of an optical fiber, at least not in terms of collimation or divergence anyway.

    Adam

    PS: The idea of using optical fiber as a cylindrical lens is also evident in an old-school laser effect. There were a few knock-offs of the famous "Machida" diffraction grating, and one of them used multiple strands of bare (no cladding) optical fiber laid adjacent to each other like a bunch of toothpicks. This created an interference pattern that was expanded to nearly 175 degrees, creating hundreds of tiny beams in a very wide fan. Here's a picture of the grating, and another picture of the results:



  6. #16
    mixedgas's Avatar
    mixedgas is online now Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,703

    Default

    I have a "fiber corrected" Goldstar 5W RGB module. . I'm impressed. I'm impressed with the three tiny deep burns on my drywall for 12-14 feet away from a stationary spot, one from red, one from green, one from blue . I bought mine from their US dealer.. He can probably get you a red only module. He is also stocking the diodes in the US for repairs, but I have no idea how they will work with older external optics.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  7. #17
    Join Date
    Apr 2008
    Location
    DC/VA metro area
    Posts
    402

    Default

    Quote Originally Posted by mixedgas View Post
    I have a "fiber corrected" Goldstar 5W RGB module. . I'm impressed. I'm impressed with the three tiny deep burns on my drywall for 12-14 feet away from a stationary spot, one from red, one from green, one from blue . I bought mine from their US dealer.. He can probably get you a red only module. He is also stocking the diodes in the US for repairs, but I have no idea how they will work with older external optics.

    Steve
    Are you saying it's good or that the alignment was way off and a single modulation on caused 3 separate holes?

    If it is good, do the beams line up very well? Like the red, blue and green beams sit on top of each other really nicely so the color coverage is even?
    Modern and Retro laser show hobbyist
    Pangolin QM16, QM32, Beyond Advanced, LSX, ADAT
    LS Pluto II x 2, custom build x 1
    http://lasershowwiki.757.org for my all encompassing laser show wiki.

  8. #18
    Join Date
    Apr 2008
    Location
    DC/VA metro area
    Posts
    402

    Default Follow up so far

    Okay, so I shipped my red back to lightspace hoping they would take care of me well. Well, $260 is their price (so far) for replacing the 3 dead red diodes + shipping back + customs. I am going to push for 4, and maybe see if they can throw in some free extra red diodes for repairs.

    I was super excited and all ready to pull trigger on 3 of the Opt Lasers 5 watt RGB modules, upgrade two Pluto II's to 5 watts and build out a 3rd projector I have parts for. But then at the last minute I asked for spec sheet.

    The Opt 5 watt RGB module is 3.5mm x 6mm beam output at aperture. Too big to fit on the mirrors well on my scanners I think? Facebook response was that the output is kind of a line. The 10 watt RGB module isn't far off in beam specs (4mm x 6mm I think) but that is understandable. Opt is offering cheap 4 watt machines and the replies are that by spec the diodes seem to be over driven pretty hard?

    I guess I am going to pay Lightspace the money to get my stuff back and running but not really thrilled. If it was $160 shipped or something I wouldn't care but the idea that I could easily see failures in future due to the driver being flawed... Maybe I can ask for a few extra reds so I can repair the other one when it dies.

    If anyone knows the actual flaw in the driver and if there is a fix, that would be good knowledge for all.

    - Ethan
    Modern and Retro laser show hobbyist
    Pangolin QM16, QM32, Beyond Advanced, LSX, ADAT
    LS Pluto II x 2, custom build x 1
    http://lasershowwiki.757.org for my all encompassing laser show wiki.

Posting Permissions

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