Constant current source from a single LiPo cell at 5A

Discussion in 'The Projects Forum' started by newhobby, Feb 23, 2015.

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  1. newhobby

    Thread Starter New Member

    Mar 26, 2014
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    Hi,
    I need help identifying a constant current source circuit to power a laser diode at about 5A from a single LiPo cell.
    The Vf of the diode is about 1.9V.
    I'm not interested in off-the-shelf stuff. I'd like to build it from scratch.
    Is requesting help for specific chip selection something I can do or it is against the rules?
    Thanks,
    RI
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Last edited: Feb 23, 2015
  3. newhobby

    Thread Starter New Member

    Mar 26, 2014
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    The cell is 3.7V nominal and I'll have it limited to a range from 3.2 to 4.2V
    I'd rather have a switching circuit because this is for a handheld application and dissipating the resistor on top of the diode is going to be a task on its own.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What are you trying to do with a 10 Watt handheld laser?
    A few miliwatt can already be dangerous.

    Please read this page:
    http://www.repairfaq.org/sam/lasersaf.htm

    Bertus
     
  5. newhobby

    Thread Starter New Member

    Mar 26, 2014
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    Yes, except it is a 5W diode.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    5 Ampere X 1.9 Volts = 9.5 Watt.
    Do you have a specsheet of the laser diode?
    AGAIN what are you trying to do with the laser?

    In my job we use that kind of laser to burn clean the source of a massa spectrometer.
    It heats up the source to about 500 C.
    It is NOT something to play with.

    Bertus
     
  7. crutschow

    Expert

    Mar 14, 2008
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    I agree with bertus. You don't want to be playing with a hand-help 10W (or even 5W) laser diode. Either one can put an eye out instantly and/or rapidly burn a nice hole into you.
     
  8. newhobby

    Thread Starter New Member

    Mar 26, 2014
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    My laser diodes typically have 50% efficiency :(
    I've already built a benchtop 20W laser device, so I can assure you I know what it is and this isn't going to be for a toy.
    My package is actually a triple 5W diode in three different wavelengths, so I'll have to have either 3 drivers or a way to switch which one I want to fire. That means that size is extremely important. I think there is no way I'll be able to fit 3 drivers in the pcb space I have.
    They are probably not going to be fired at the same time because the battery won't be able to handle the discharge.
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    ...#3 , well your better off getting one ready made from Ebay, good luck.
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    At what are you "firing"?
    Will the beam be confined in a closed surrounding?
    Even reflections can be dangerous.

    Bertus
     
  11. newhobby

    Thread Starter New Member

    Mar 26, 2014
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    This is not for a toy. I'm not interested on eBay stuff.
    This will be a commercial product.
    I'm after some guidance in selecting an IC and possibly a freelance job if necessary. I'm not interested in hearing how dangerous lasers are.
    I already know how dangerous they are and I have been unsuccessful in finding a suitable IC. That's why I'm here.
     
  12. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  13. MrChips

    Moderator

    Oct 2, 2009
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    A handheld 5W laser just doesn't sound right and we don't want to hear about it and possible adverse consequences.
    Hence this thread is closed.
     
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