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Thread: Home made blue dpss laser

  1. #31
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    dont you have to hold the blue doubler xtal to like .01 C or better for max blue? Like in type I phase matching ? If not, I'd go for a group buy of casix (or better) Chinese blue parts.

    Steve

  2. #32
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    Quote Originally Posted by mixedgas View Post
    dont you have to hold the blue doubler xtal to like .01 C or better for max blue? Like in type I phase matching ? If not, I'd go for a group buy of casix (or better) Chinese blue parts.

    Steve
    Maybe 0.01C with LBO but now BiBO has come along with its massively wide temperature bandwidth it reduces the required accuracy of the TEC.

    Robin
    Lasers and beer don't mix. After 2 beers I lose coherence.

  3. #33
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    Ok, the hood is up, let's look at that V8.
    Attached Thumbnails Attached Thumbnails 473-1.jpg  

    473-2.jpg  

    473-3.jpg  

    473-4.jpg  

    Lasers and beer don't mix. After 2 beers I lose coherence.

  4. #34
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    And then we applies power!
    Attached Thumbnails Attached Thumbnails 473-5.jpg  

    473-6.jpg  

    473-7.jpg  

    473-8.jpg  

    Lasers and beer don't mix. After 2 beers I lose coherence.

  5. #35
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    Its a CNI then
    same as the one Jimbo replacewd diode on - Jim what did you get out of that - I seem to remember you did get blue out of it again - but how much?

    Rob
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  6. #36
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    Hi Rob,

    Wasn't your 473 a CNI too?
    Did you get round to an analogue mod? - I haven't traced out the entire driver yet.

    Robin
    Lasers and beer don't mix. After 2 beers I lose coherence.

  7. #37
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    yes and yes

    My driver is slightly different from yours - there seems to be 2 types yours is like the one Jim has with an odd shaped board - mine has a rectanular board. Dunno if they are the same electronically - I would expect they will be something like similar.

    Basically what I have done is built a board that has 2 duplicate op amp circuits on that I use as analogue input control. One runs the blue the other my green - as that is also cni and the actual diode drive is the same circuit for both. I always imagined the blue would have something more sophisticated - but I digress.
    On the driver circuit there is a 1.2v zener that is the ref for the LM358. Normally the set point for max current is derived from the 1.2v via a preset pot. To TTL the diode on & off the TTL input goes through one gate of a 7408 the output of which feeds the 1.2v zener via a balast resistor. Not very sophisticated but it works. All I have done is disconected the output of the gate and into it via a 10k, fed the output of my op amp analogue input circuit. I hope you are following this
    The op amp circuit has adjustments for max current - I feed in 5V and adjust so that the volts at the zener just reaches 1.2v. ( I have left the zener in for safety ) Then I ground the input and adjust the threshold pot on my op amp circuit til the laser just goes out. This keeps current in the diode all the time - on my its about 700mA at idle - TTL=0 and then as soon as the input rises the laser kicks in. Its not exactly linear but it works.
    Basically all 3 lasers in my small projector use this same method to control the brightness between 0 and 5v.

    Hope that all makes sense.

    Rob

    PS one thing I have not adjusted is the diode current - mine runs a shade under 2A with 5V input - I have considered going a little higher but dont know the limit of the diode and though I could rebuild I dont fancy killing it just yet. I have tweaked the TEC pots and also changed the caps on the tec drives from 100uF to 10uf to improve the response. The laser is still noisy when being turned on & off but I have reduced the noise and the overall output. I can tweak it higher if its on all the time - ie blanking not used but I get less overall power when blanked this way so have tuned it while using blanking.
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
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    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
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  8. #38
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    Hi Rob,

    Thanks for that. All makes sense. I might try sketching out the CCT for the one I have. There is a spare pot position which I guess would be for offset current if the board was configured for analogue modulation.

    As for diode current a 1.5W 808 would have an operating current of 1.7 / 1.8A or so. My head was taking 1.8A so I guessed it was more likely to be a 2W pump diode - knowing the conservative nature of CNI.
    Your's doing 2A would certainly point to it being a 2W device.
    A 2W device will have a max operating current of 2.5A to 2.8A depending on manufacturer.

    I'm off to push mine a little harder.....

    Robin
    Lasers and beer don't mix. After 2 beers I lose coherence.

  9. #39
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    Quote Originally Posted by uk-laser View Post
    I'm off to push mine a little harder.....
    Fnaar fnaaar

  10. #40
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    that reminds me of a very naughty joke

    Time to jump to a different thread.

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
    -----------------------------------------------------------------------------------------------
    Laserists do it by the nanometre.

    Stanwax Laser is a Corporate Member of Ilda

    Stanwax Laser main distributor of First Contact in UK - like us on Facebook http://www.facebook.com/FirstContactPolymerCleaner
    www.photoniccleaning.co.uk

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