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Thread: Newbie questions about laser show

  1. #1
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    Smile Newbie questions about laser show

    I have a couple of questions in regards to laser show world.

    What is 30Kpps or 40Kpps means in the real world? Does it simply translates to more points that can be drawn in a single frame and nothing more; hence richer graphics ?

    Which of these scanners is better? DT-40 or SCANPRO30 from lasershowparts? Anyone knows the ups and downs of these units?

    What's the minimum modulation required for laser driver in order to be able to scan at 20Kpps, 30Kpps and 40Kpps? And what's the difference between TTL and analogue modulation when it comes to laser show? No differences? Both do blanking as required?

    Lastly, does anyone here has any experience with laser modules from extremelasers? Are they any good?

    Sorry if I asked too many questions. Did I mention I'm a newbie ?

    Thanks guys.

  2. #2
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    Quote Originally Posted by VaThInK
    What is 30Kpps or 40Kpps means in the real world? Does it simply translates to more points that can be drawn in a single frame and nothing more; hence richer graphics.
    Yep. That's basically it. Though *sometimes* a set of scanners that can run all the way to 40kpps will be able to scan a pattern at 30kpps with a wider scan angle than a set of scanners that are only rated for 30kpps. But not always.
    Which of these scanners is better? DT-40 or SCANPRO30 from lasershowparts? Anyone knows the ups and downs of these units?
    I'm in the process of doing a review of exactly these two sets of scanners, plus another set as well. But it will be a couple weeks before I've got all the data pulled together. I'll be looking at things like image quality, scan speed, scan angle, and mirror efficiency. Bottom line, they are both nice scanners.
    What's the minimum modulation required for laser driver in order to be able to scan at 20Kpps, 30Kpps and 40Kpps?
    This is a total crap-shoot because different manufacturers rate their modulation speeds differently. As a general rule, you can get by with 10Khz blanking for 20Kpps graphics, and you want 20Khz (or better yet 30Khz or more) for 30Kpps graphics. But, again, this is not an absolute rule because it depends on the way the manufacturer rates the modulation. Bottom line, get the fastest modulation you can find, though there's no need to go beyond 50Khz. (This is what the Maxyz modules are rated for.)
    And what's the difference between TTL and analogue modulation when it comes to laser show?
    TTL means on or off only. So for an RGB projector, you only have 7 possible color combinations. (Well, 8 actually, if you count black as a color.)

    Analog means you can vary the intensity of the laser from completely off to full power. Thus you get a *huge* range of colors that you can produce. You are limited by only 2 things: 1) the wavelengths of the lasers in your projectors set a hard limit on the color chart that you can't go beyond, and 2) the resolution of your controller's digital to analog converter for the color signal... an 8 bit controller will give you 16 million colors, which is more than you'll ever need.

    Obviously, analog blanking is preferred. But you'll normally pay a 10-30% price premium to get analog blanking. (It's worth it!)
    Lastly, does anyone here has any experience with laser modules from extremelasers? Are they any good?
    I have no direct experience with them, but I seem to remember reading about a few people that had problems. I know they sell a lot of modded pointers, which doesn't put them really high on my list to begin with.

    There should be a couple threads here on PhotonLexicon that talk about them; search around a bit and I'm sure you'll find them. Then too, maybe someone else here will chime in with their personal experience.

    Adam

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    Thank you very much Adam for the great explanations. Everything make more sense now. I definitely will be waiting for your review mate. I have no doubt it'll be a great one too .

    Do you know where could I find information on how to build an analogue modulated laser driver module by any chance? I've searched on Google without any luck so far. I'm planning to make a red lab unit on my own, but I might be forced to buy one instead if my effort proved to be unsuccessful in the future. I'm also looking for a heatsinked LD housing similar to maxyz modules, but no luck as well . Thanks again mate.

    Cheers.

  4. #4
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    Building your own analog driver is tricky. It's easy to blow the diode. You've got to have an absolute maxium current limit from your current control output stage, and then you add your modulation after that. Trouble is, you can't have any capacitance in the modulation stage or you risk blowing the diode when you ramp up. (Diode death is caused by excessive optical power at the output face and happens nearly instantaneously, so you absolutely can't have a current surge above maximum, even if it's for the briefest of moments.)

    Here's a thread that talks about a couple options. But be careful; it's really easy to blow a diode...

    RE: heat sinks - several people here have had good luck cutting large power resistors in half and using the case as a heat sink. Browse through this thread for more info...

    Adam

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    Thumbs up to you Adam. I'm refraining myself from designing my own laser diode driver for now as it sounds too risky for my liking . The likelihood of me killing LDs is too high if I decided to have a go at it, especially since I don't have electronics engineering background as well. However, I'm learning a lot from that thread and I'm gonna build some of the laser diode drivers mentioned in that thread instead. Sounds good enough .

    With the heatsink for LDs, I didn't even know that resistor also comes in a package like that . Never seen one or even heard about it. I guess I have to source them from overseas. What kinda wattage do you think would be perfect for my purpose? 25W? 50W? 100W? My LD housing is 12mm in diameter.

    Thanks for your help mate.

    Cheers.

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    I don't know ; I've never actually built a diode housing out of a resistor before. But several others here have done so. Might want to have a look at some of the pictures in that thread and pick one that you like... PM the guy that built it and ask him which resistor he used... (If memory serves, there was a "colorful" discussion about how to get the guts of the resistor out... One solution involved over-current and a somewhat explosive ending!)

    Adam

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    Quote Originally Posted by VaThInK View Post
    I'm also looking for a heatsinked LD housing similar to maxyz modules, but no luck as well .
    No need to worry about a heatsink. Since you'll be pumping close to an Amp through each 16X DVD diode, they'll never live long enough to get hot.

    LOL... this is Bimmerboy from CPF. Couldn't resist the tease.

    BTW, I just responded to your recent intellectual challenges to me over there.
    Alas, poor diode. I fried him well.

  8. #8
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    Thanks heaps Adam for your help so far. I really appreciate it. Cheers mate.

    Quote Originally Posted by PNjunction View Post
    No need to worry about a heatsink. Since you'll be pumping close to an Amp through each 16X DVD diode, they'll never live long enough to get hot.
    Relax, an Amp is just too much for the LDs. Even with TEC it would only last for hours. No good for long term usage. 600mA is the sweet spot .

    LOL... this is Bimmerboy from CPF. Couldn't resist the tease.

    BTW, I just responded to your recent intellectual challenges to me over there.
    It's been taken care of .
    Last edited by VaThInK; 08-08-2007 at 08:14.

  9. #9
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    Quote Originally Posted by VaThInK View Post
    It's been taken care of .
    You're joking, right? You haven't directly addressed a single question in your debate with me, nor even made sense in the attempt.

    However, it's my mistake for not restricting the discussion to CPF, and giving you a poke here.

    If this little exchange has piqued anyone's curiosity, here's the link. My involvement begins at post #46.

    DVD burners that rock for diodes.
    Alas, poor diode. I fried him well.

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