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Thread: 200mW 650NM Laser from 18X DVD Writer

  1. #1
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    Default 200mW 650NM Laser from 18X DVD Writer

    Hi everyone, this is my first post here. A couple of weeks ago I trashed three 18X DVD writers in trying to make a reliable switching mode power supply to drive one of these diodes from one or two AA cells. I've now got it all working and it's quite impressive seeing it cost around $60 to make and has worked reliably now for many hours. Has anyone else here had success with the LD out of a DVD writer here yet? I'm now trying to cram everything into a very tiny case which won't be too much bigger than a keyring pointer.

  2. #2
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    Yep I have destroyed a few Lite-on DVDRW drives for the diodes. I have not used battery power but instead have emulated the driver from a green module for power. I have measured (with lasercheck) 216mW @ a shade over 300mA - must get round to doing a proper profile. I had one of these in my small projector with 100mW green G120 scanners and analogue modulation. Driven by mamba black the results were great.http://www.stanwax.plus.com/laser/ryg1.jpg and http://www.stanwax.plus.com/laser/ryg2.jpg are pix of it in action.
    This head has now been stripped to be set up with my SP168 whitelight and I am planning on rebuilding it with x2 red diodes combined with the green and eventually blue. I have much machining work to do once i sort out the diode lensing, which im looking at at the moment.
    Why do you describe your driver as switching mode? Surely from batteries you just need to (properly) limit the current as the chances of getting noise spikes is virtually non existent. In fact making a switcher is very likely to give you spikes or noise that could kill the diode. 2xAA will provide enough volts - (only just if they are Ni-Mh).

    Pix would be good....

    Rob

  3. #3
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    Welcome to the forums Rob.
    I'm not too far away from you, I live in Kearsley just outside Farnworth.
    I served my apprenticeship with British Nuclear Fuels at Risley.

    The rest of the pictures on your site are quite impressive too.
    What is the DAC that you have built?

    Jim

  4. #4
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    Hi Jimbo
    thanks 4 the welcome - have on the odd occasion lurked here and as I've been in dialouge with the forum admin over some scanners I thought it was about time i joined. :?
    Anyway....the dac is a 5 channel one based on ad7524 convertors. There ia a lot of dac chips out there but I saw some multi channel dacs with 4 channels and thought it a waste to have 8 channels and waste 3 so i plumbed for that one. Plus the output stages were originally to be quad op amps but it would have been a tw*t to track so I went for 5 dual op amps (lm1458) instaed and it worked out a treat. It also has 4 74ls chips, gates, flip flop, and a 3 to 8 line decoder. The board was my first attempt at a home brew double sider and it turned out ace. I got spot on alignment first time with very careful uv exposure of the board. Anyway I could rabbit on all night - As for images there are more here
    http://www.stanwax.fotopic.net/c662316.html and I have bucket loads of them on my hdd
    Must upload some recent pix to fotopic as I have taken some belters recently inc the full size pic of my avatar.

    Rob

  5. #5
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    Is the avatar projected onto somebody's face or something?

    Jim

  6. #6
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    yeah my ugly mug
    looks much better when seen at a decent size. (the pic that is)

    R

  7. #7
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    Just saw your post/pics Stanwax, and I must say I'm always amazed at how much more sensitive our eyes are to green light than all other frequencies, in particular the red portion of the visible spectrum.


    When you say "I am planning on rebuilding it with x2 red diodes" do you mean you will optically combine the output of two diodes to create a single beam?


    I have used a switcher for good reason, and that is because I want to make a very small and high power pointer which can also make use of ALL the energy in the batteries, whether they be NI-MH or just alkaline. The diode I'm using is out of a Samsung/Toshiba 18X writer (It comes in a plastic package and is not hermetically sealed) and has a forward voltage of approximately 3V @ 250mA. Even two AA cells in series combined with a low-dropout linear regulator would be lucky to make the diode reach threshold current (43mA), and even if it did, it wouldn't be for too long before the voltage drop would cause the regulator to dropout. Even three cells in series is inadequate when you consider that an alkaline battery is said to be depleted when it's voltage drops to 0.7V. So this is why I have chosen a boost regulator topology with a current feedback loop. Current ripple is only a few hundred uA so I think my LD should remain happy for quite some time.


    I'll try and get some photo's of what I've cobbled together for you to see.

  8. #8
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    Oh, and I failed to mention the boost converter chip I've chosen is rather impressive, as it can still drive my LD with an input voltage all the way down to 0.65V! I initially designed the circuit to drive a single Cree LED (the best flux output per mW input currently available) as a light for my bike but doubles as a good LD driver.

  9. #9
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    Yep I am hoping to optically combine 2 diodes. Up to now my experiments have proved fruitless as the total combined power is only slightly above a sinle output and not worth the extra hassle - but I have a few more ideas to try yet . I will keep you all posted.

    Now I understand why you are using a 'switcher' and it makes sense. From your initial post it looked like you were just doing it for the hell of it - which seem a bit ott.

    So what is this boost convertor chip? And I certainly look forward to the images of your exploits

    Rob

  10. #10
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    Rob;

    How were you combining the beams? Because it certainly is possible to use a polarizing beam-splitting cube to combine two beams into a single beam of roughly double the power. (Minus a few percent for optical losses through the cube, of course.) The crucial step is getting the polarization angles of the two lasers positioned exatly 90 degrees to each other.

    Here are some examples showing the layout and the resulting beam with the lasers on. (Thanks to Liteglow for posting the pics in the PhotonLexicon gallery that I linked to!)

    Adam

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