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Thread: driver circuit for DVD burner diode laser

  1. #1
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    Default driver circuit for DVD burner diode laser

    Hey everyone;

    I should soon be receiving three 90mw diodes that were ripped out of DVD burners. I'm anxious to see what I can do with that many red photons! However, I am concerned about constructing an appropriate power supply. I'm not interested in tweaking them for the highest possible output, I just want to drive them carefully so they'll live a long life.

    With that in mind, I've been looking through Sam's Laser Faq... I found "Sams laser diode test supply," and it looked like it would be just the thing. I figured I could assemble it on a breadboard with the potentiometers in place, then run the current up slowly until I get to the rated optical output, and finally measure the resistance so when I solder the thing in permanently I can substitute the correct resistors for the pots...

    Does anyone have a better idea, or experience with another circuit that perhaps I should be looking at? (How do you power your diodes?)

    Adam

  2. #2
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    Default

    I also have one of those diodes... the thing is, it's current-regulated. Most of the diode power supplies I've found are designed for diodes with photodiode-feedback, including all of the power supplies with modulation capability...

    In theory you could just use a transistor or logic chip, but I have a feeling that there's more to diode power supply design than that.

  3. #3
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    Eric;

    So your diode has an internal current regulator? Or are you just saying that the power supply has to regulate the current without the benifit of optical feedback?

    I agree that without optical feedback, it's a little harder to control the diode, but I think with a carefully designed current regulator, I could safely power the diode without blowing it up. I might just end up setting the absolute maximum current output of the driver to a level that is slightly below the norm to give me a safety net.

    The circuit linked to in my post above doesn't show any means of modulation, but I would think that a power mosfet would do the job nicely. (Just put the mosfet in series with the output of the current regulator, and use the TTL signal from your controller to switch the mosfet on and off...)

    Am I on the right track here?

    Adam

  4. #4
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    I've got a 90mW that I ripped out of one two or three monthes ago and kind of put in on the back burner...along with so many other projects... but I would like to get it lasing. If you get a working power supply, post the schematics.

  5. #5
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    Default DVD burner laser diode driver circuit

    Will do!

    I spoke with Sam Goldwasser about it and he thought it would be fine, but he also suggested that I ask the folks on alt.lasers (usnet). I'm going to wait until I can post pictures of the diode before I do that though. (Diode should be here early next week)

    Sam also recommended an EU38 from Rothnier, but I can't seem to find anyone that sells them in small lots. (Sam said they go for $10 or so...)

    As for the power mosfet to do modulation, he recommended that I check it with a dummy load first to make sure it doesn't cause the current regulator to freak out.

    Come to think of it, I'm pretty sure Astroguy has a few of these diodes too - I should probably ask him which circuit he used...

    BTW, are you the same CTR that posts on greenlasers.co.uk?

  6. #6
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    Hey Buffo, glad to see you picked up a few of the diodes. I have two of them in pointers I made. I am driving them with the drivers out of green pointers. You can sometimes pick them up cheap when some people try to mod there pointers and fry the diodes. They work great. I just used my laser check to check out put and trimmed the pot until I got 90 mw output. I believe it was pulling around 400 ma. When you get the diode you will see that it has a feed back circuit using a beam splitter to check output. I find that the drivers I am using without feedback are still pretty stable.
    I also got the package you sent me thanks !!
    "Gravity its not just a good idea its the law"

  7. #7
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    Astroguy!

    Thanks for the quick reply...

    So these diodes *DO* have optical feedback? I thought they didn't... My bad! Are the pins on the case labeled as to Cathode, Anode, and feedback? (Well, I assume that the Anode is the case, and is common to both the drive and feedback circuits, right?)

    The EU38 is a driver board for a pointer, but it doesn't support optical feedback. They do sell others at Rothnier that do have feedback circuits though. I might need to look into that further.

    Glad you got the package OK. When you get some time, post some pictures of that line grating in action!

    Adam

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    Buffo, I am not a tech but if you can figure out how to use the driver and feedback circuit that is included with the diode module, please let me know. I could not figure it out. Also there are two diodes included with each module. One is the high powered burner diode and a low powered read diode plus the power senor for feed back control. There will also be a mirror beam splitter and a cube beam splitter and lens.
    "Gravity its not just a good idea its the law"

  9. #9
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    Astroguy;

    When I get the modules I'll take some pictures and post them here. If I can figure out how to use the built-in feedback circuit, I'll post details of that as well.

    I didn't realise that these modules came with the driver intact. If that is the case, then it should be fairly easy to figure out how to power it. (After all, there are only 2 voltages available for a DVD burner... +5 volts and +12 volts.)

    Anyway, I'm going crazy waiting for all these parts to arrive. (Still waiting on the Alphalite too!) But as soon as I get a chance to play with them I should have more information.

    In other news, I finally finished my power supply for the ISOMET AOM... Hooked everything up, only to discover that the damn driver for the AOM needs more than 1.5 amps. (My voltage regulation circuit is based on the LM317, which can't deliver more than 1.5 amps!) ARGH!!!! So now I've got to wire in a big transistor as a pass bank. I've got everything I need except for the high wattage input resistors, so that means waiting another week for stuff from Digikey... (Unless by some miracle Radio Shack carries .3 ohm, 5 watt resistors!)

  10. #10
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    I found anotherone doing some tests with DVD burner diods that might be of value.

    http://24.200.192.31:81/LaserShow/Ga...s/00000292.htm
    You know, I have one simple request. And that is to have sharks with frickin' laser beams attached to their heads!

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