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Thread: DVD drive strip down gallery

  1. #11
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,372

    Default

    Hi Dave try this then

    www.stanwax.plus.com/laser/lddriver2.pdf
    I have manually drawn on this and scanned it so its clear whats been added.
    To calibrate, set the mod input to zero and turn the threshold pot up till the desired point. Then put 5V on mod input and adjust primary pot for max current. I have tried this out and seems to work good. The 8k2 resistor and 1k pot may need to be tweaked if your diode has different characteristics, and of course if you get a spec sheet then you should have a figure for threshold current so you could set the mod input to 5v & main pot for this current and then measure the volts on the wiper and you will know the range you need to be in to get to the point you want.

    Of course the propper way to do this - so the signals dont interfere with each other is to put the threshold pot and the max current pot through op amps to buffer their signals but its probably overkill. That said I may well breadboard this setup to see if it performs any better. Also I will try with the threshold adjust circuit and see how linear the output is. I will post when I have results.

    Robwax (thanks Jim for the new name)

  2. #12
    Join Date
    Aug 2006
    Location
    North West England
    Posts
    1,148

    Default

    Sorry Rob, I was thinking of your first name when I did that reply, I will edit it

    Jim

  3. #13
    Join Date
    Jan 2007
    Location
    Sheepsville, Wales, UK
    Posts
    3,372

    Default

    hey i dont mind
    ive ben called worse and that was by people who like me



    R

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