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Thread: The first post of a novice :)

  1. #1
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    Default The first post of a novice :)

    Hi guys,

    I've been hanging around for a bit reading a lot, picking up lots of great suggestions and realizing mistakes I've made .

    Anyways, I've been messing around with increasingly powerful (but still puny) lasers over the past few years and recently acquired an RGY laser from the good old Chinese Department Store.

    Its guts are a 100mw 532nm TTL... manufacturer unknown, a 300mw 650nm CNI diode TTL-- the ugly big beam one, and one of lasershowparts' SCANECO10K scanner kits.

    It also came with iShow, oh what fun.

    Well, I purchased an FB3 last week and it just rocks, but of course, I totally have the bug to upgrade everything... obviously we don't see in green, red and yellow alone. soooo...

    I put in a (I thought) really low bid on a CNI 473nm 100mw unit from extremelasers on ebay yesterday, and won for $750! I know it's a TTL -- but I've contacted them to see how much to upgrade - hopefully they'll follow the 10% rule, otherwise, I seem to have read that I can likely contact CNI and get a new driver with analog for a reasonable price, and still have a decent blue at a good price.

    Anyways, I'm in need of advice as far as incorporating the blue beam into my projector, and just any other advice you can give. I'm definitely planning on replacing the other two lasers as well, as money permits. For now, I guess I'll at least have analog blue, hopefully, and can go from there.

    Oh... and I want to upgrade the scanners, too, so recommendations on those are appreciated as well. I spent several hours on Saturday tuning them according to instructions I found here, and have them pretty well dialed in, able to cleanly display the ILDA pattern at 12k at around 15 degrees, plus do reasonably well on the other two test patterns as well, but I'd like to upgrade those as well. If someone is interested in my current scanset, please let me know!

    Thanks in advance for all your help!
    Will

  2. #2
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    Default

    Hi Will

    welcome to PL ... sounds as if you have done lots of research to me,

    Be warned

    YOU ARE NOW ADDICTED

    there is no turning back

    have fun .... Karl

  3. #3
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    Jan 2006
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    Smile Welcome, Will!

    Hi Will;

    Welcome to PhotonLexicon. Hope you like it here! With regard to upgrading your blue to analog, I don't know how much success you'll have. The last time I remember someone wanting to upgrade like that, the surcharge was closer to 30%, not 10%. But maybe you'll get lucky.

    As for adding blue to your projector, all you need is a reflect blue, pass green and red dichro. These are readily available from Edmund optics, OneStopLaserShop.com, or even from Bridge at LaserWave (he's also member here on PL). In fact, I believe Mliptack (Max) is acting as a US distributor for LaserWave products; he and Bridge managed to work out a deal... So you might want to check the group buy forum and see if you can get in on one of the deals there. (If you buy the mount for the dichro at the same time you buy the dichro, you'll save money.)

    Where are you located, BTW?

    Adam

  4. #4
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    Knoxville, TN & Huntsville, AL, USA
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    RUN, while you can still get away!!

    Oh, wait - too late, looks like you are already on your way to being neck-deep in it, just like most of the rest of us on this forum!!

    Welcome aboard - you found a GREAT place get the info you need to support the hobby, business, obsession - whatever you want to call it! The wealth of knowledge that is openly shared on this forum is phenomenal, and frequently includes postings by not just hobbyists, but some of the top names in the laser show and laser manufacturing industries! AND, it doesn't cost a penny!! (Until you start looking at the group buy section )

    I've only been on this forum for about a year now, and it's taken me from very little hands-on knowledge ("Dude - cool laser pointer!"), to many helpful suggestions towards building my first laser projector (950mw RGB, in progress...). And, unlike many other hobby-related open forums, I've seen very little "flaming" or "newbie bashing" going on here - most of it has been very friendly encouragement and advice! In fact, the only reason I've achieved "Senior" status here is because I've asked SO many questions along the way, and I don't think a single one has gone unanswered!!

    Again, welcome aboard - and be sure to post pictures when you start your project!!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  5. #5
    Join Date
    Apr 2008
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    26

    Talking

    Hi again guys,

    Thanks for the great welcome already!

    So to answer a few of the questions, I'm actually in Milwaukee, WI - and I have seen the group buy on dichros and mounts from Max, who is also a Milwaukeean. I'm really hoping to meet up with him sometime soon.

    So if the cost of upgrading the 473nm unit to analog is ridiculous through extremelasers - what about using Norm's Driver? I've become thoroughly confused reading several posts that say analog modulating TTL lasers doesn't work well (what is jellybeaning, anyways?) But then several people including norm himself use the driver with medium power DPSSs and say they work great. I'm thinking for $70 I could do all three and not have to fuss with anything else. I'm thinking there's no way it's that simple, but please, tell me it is!!

    Also, any recommendations on scanners? I'd like to get some that I can rely on for a nice long time. And - do people still make beamtables, or is that a thing of the past?

    Backstory... While I was in college I had a buddy who worked at a laser show company that was based out of Milwaukee -- called Laser Force (I think they are long gone now, sadly). I actually helped tech a few of their shows (Monster Truck Rallys... lol) and they had this 3w (as I recall) greenie with a 3-phase chiller with a massive beam table and a scan head. After crawling round catwalks and focusing mirrors for a few hours, the result was nothing short of spectacular.

    Anywho... thanks again and I look forward to lots of fun (and money well spent!)

  6. #6
    Join Date
    Feb 2007
    Location
    Delaware USA
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    Default

    Wow, Laser Force out of business That Sucks. They had a really good
    animator that worked there and they produced some great shows.

  7. #7
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    Apr 2008
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    Default

    I did some digging and it seems that one of the two guys now works at Cambridge. The other is now working for another laser display company called Image Engineering.

    Oh, by the way - extremelasers wanted $400 to upgrade the 100mw blue to analog blanking. L... O... L... They did, however, ship it out within a few hours after I paid, which is nice.

    Anyways, I emailed Norm and am going to buy 3 driver kits for a whopping $70 instead. Hopefully they work well!

  8. #8
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    Cool

    Quote Originally Posted by will_ko View Post
    So if the cost of upgrading the 473nm unit to analog is ridiculous through extremelasers - what about using Norm's Driver?
    I don't think Norm's driver is designed to run a DPSS laser.?. Sure, you can power the pump diode with it, but the problem is that you *also* need to power the TEC circuits, and I don't think his driver has any peltier driver outputs. (I could be wrong, but I don't remember Norm's driver having this...)

    Thermal control over the lasing crystal as well as the frequency doubling crystal is *crucial* in a 473 nm laser. If you don't control the temperature very accurately, it will lead to jellybeaning.
    I've become thoroughly confused reading several posts that say analog modulating TTL lasers doesn't work well (what is jellybeaning, anyways?)
    Nice lead-in! Jellybeaning, or modulation-induced power loss, is a phenomenon that is unique to DPSS lasers. Essentially, it means that the laser doesn't always turn on at full power, especially when you are turning it on and off really fast. This is related to thermal effects in the head. It manifests as streaks and dim lines in your images. If you are displaying a series of parallel white lines, for example, you may notice that the begining of the line is red, then after a while it turns to yellow, and eventually it becomes white. This is because the red diode turns on immediately, while the green laser takes a few hundred microseconds longer to reach full power, and finally the blue laser takes even longer to reach full power.

    It's an annoying trait of DPSS lasers, and one that has not yet been fully eradicated. The faster you try to modulate the laser, the more apparent the power loss will be, and the worse your images will look. Some lasers are better than others, but all DPSS lasers exhibit this problem to some extent.
    But then several people including norm himself use the driver with medium power DPSSs and say they work great.
    It may be that they're using Norm's driver to drive the pump diode and then keeping the existing Peltier cooling circuit from the original power supply. Or perhaps Norm's driver has changed since I last looked at it, and he's incorporated a TEC driver now. I dunno...

    But you're going to need to power those peltier coolers somehow, and it would be best to have a feed-forward control on them so they will respond in kind as the pump diode power goes up and down with the modulation signal.

    I've ready a few posts here where members have tweaked the TEC circuit on generic chinese DPSS power supplies to get better performance; might want to look into those posts (or ask Stanwax) for more info about it.
    Also, any recommendations on scanners? I'd like to get some that I can rely on for a nice long time.
    Lots of people here are running the DT-40 pro scanners, and they seem to be OK. They're less expensive, but they do offer a lot of bang for the buck. On the other hand, LaserShowParts.com sells the ScanPro 30 scanners for a little more money, but they offer larger mirrors, better cables, and seem to be *very* durable. They also have a new ScanPro 40 scan set that looks awesome, though I haven't had a chance to personally review them yet. (Will probably have a set to play with here in another month or so.) Have a look at their website and see what your budget will allow.

    If you're on a really tight budget, and especially if you're primarily interested in beams only, then consider the ScanPro 20's, also from LaserShowParts.com. They're just $250, yet they *really* perform well. Of course, you can't get 30K out of them, so complicated graphics will flicker a lot, but the images are otherwise just as good as faster scanners.

    And, of course, the Cambridge 6210's (or 6215's if you want to run 60K) are the cat's meow. But they're 2 1/2 times more expensive than anything I've mentioned above... Still, they're the gold standard against which everything else is compared to.
    And - do people still make beamtables, or is that a thing of the past?
    Some people still do, and it *is* an interesting effect. Having the beams eminate from different places is a cool effect that can't be recreated by a set of galvos. Lots of people use GM-20's to accomplish this, though there are other actuators that will work just as well. As far as building a beam-rail into your rig, well - it all depends on how much money you want to spend on your projector!

    If you are available over the weekend of August 15th through the 17th, I strongly encourage you to make a road trip to Newton, North Carolina to attend the 2nd annual South Eastern Laser Enthusiast's Meeting. (SELEM 2008) Friday evening we have a dinner party and drinks, then Saturday and Sunday we spend the entire day (and evening) geeking out with all sorts of laser gear in a 500 seat auditorium that we have all to ourselves. We'll have multiple RGB projectors(7 to 10), a couple medium size argons, and at least one old-school beam table.

    Search through the forums here and you'll find tons of info about SELEM. But believe me, for someone that's just getting started, it's both a *fantastic* learning opportunity as well as the best "laser vacation" you'll ever have. Need a photon fix? This is it... You'll be inspired by the equipment you see, and more importantly you'll get to meet the people that built it and ask them how they did it. (We all love to talk about our gear!)

    Adam

  9. #9
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    Apr 2008
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    Default

    Hey Adam,

    Wow, thanks for the comments. I've forwarded them on to Norm as well to see if he can shed some light.

    So here lies all my confusion, summarized perfectly!

    What I understand from your post is that we'd need to be able to know the laser's thermal response to any given power output, know the optimal thermal condition for it, then know how hard to drive the TECs to keep it there, right? And the system would compensate based on the signal it was getting from the blanking input, rather than the photodiode output, right?

    Chuckle... and how precise of control are we talking about here? a few degrees +/-, or a few hundredths of a degree? How predictable is the diode's thermal response, and how linear is a TEC's output? I guess I could do some testing once I receive Norm's kits.

    And, is this how the matched analog drivers respond to the problem? It seems like *a lot* of engineering for an additional 10% of the purchase price. Or I could be just totally confused again!

    Thanks as always! Oh - and I'm blocking my calendar now!
    Will

  10. #10
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    Cool

    Quote Originally Posted by will_ko View Post
    we'd need to be able to know the laser's thermal response to any given power output, know the optimal thermal condition for it, then know how hard to drive the TECs to keep it there, right?
    Well, this is probably unrealistic, but if you were going to design a TEC circuit from scratch, you would first need to know the optimal temperature for the lasing crystal and the doubling crystal. Then you would run the laser at, say 25% power and see how far away from those ideal temps you are. Now adjust your TEC circuit to get back to where you need to be. Then ramp up the power to 50% and see how far off you are again. Then check it at 75%, and finally at 100%.

    If you do this, you'll find is that the temperature differences will not be linear as power increases. You may discover that the difference between 50% and 100% is very small, but from 50% to zero you have *huge* thermal changes. So the best bet is to tune your TEC circuit to maintain optimal temperature at some midpoint on the power curve. If you want to get fancy, you can incorporate the modulation signal into the TEC circuit to try to ramp up the TEC power as the pump diode power changes, but tuning this feed-forward circuit will be tricky.

    And, of course, this assumes that you have access to the laser cavity in the first place! So unless you're working on a truly "home-built" laser, you may have to settle for a single setting on the TEC circuit that functions as a happy medium and just leave it there. (Though there is nothing preventing you from incorporating a feed-forward control scheme and then tuning it by hand using empiricle results... Tweak it up or down while watching the beam until you minimize the jellybeaning.) Also, a simmer circuit helps a lot. (More on this below)
    And the system would compensate based on the signal it was getting from the blanking input, rather than the photodiode output, right?
    Assuming you had a photodiode output you could use that signal as well. Either one will give you a way to predict the thermal conditions in the head. (If you wait for an actual temperature shift, you'll be too late.)
    and how precise of control are we talking about here? a few degrees +/-, or a few hundredths of a degree?
    The efficiency of the doubling process is affected by temperature changes of several degrees, but you can get intra-cavity problems due to thermal effects even with changes of less than one degree (due to expansion and contraction). As for the suppression of competing lines in the lasing crystal - I know this is also temperature dependent, but I don't know the span involved.
    How predictable is the diode's thermal response, and how linear is a TEC's output? I guess I could do some testing once I receive Norm's kits.
    I really don't know. Stanwax may have more info on this topic. See this thread and this one for more info. It appears that Rob has an idea for a circuit that is giving better results. (Rob, care to elaborate?)
    And, is this how the matched analog drivers respond to the problem?
    Truthfully, no. Most analog drivers are tweaked to a certain point that is mid-way in the thermal curve. Good ones might keep the pump diode "simmering" at some current level that is below lasing threshold to minimize thermal effects when the laser turns on. (This would be a good feature to include in your design if you can.) The really good drivers incorporate feed-forward control of the TEC based on the modulation input.

    Having said all that, most DPSS blue lasers exhibit *some* jellybeaning. Blue lasers are a lot more sensitive to thermal effects than green ones though.
    It seems like *a lot* of engineering for an additional 10% of the purchase price.
    In my experience, it's closer to a 30% upcharge for analog blanking on a DPSS blue laser. DPSS *green* lasers can normally be upgraded to analog for around 10%, however.
    Oh - and I'm blocking my calendar now!
    You won't be disappointed!

    Adam

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