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Disposable camera flash

Discussion in 'Electronic Design' started by Dirk Bruere at NeoPax, Sep 22, 2009.

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  1. A somewhat common "disposable camera" flash arrangement has a xenon
    flashtube with impedance characteristic (Ko) of about 11-12 ohms-amps^.5.
    I take this to mean resistance of 1 ohm at 121-144 volts, and .5 ohm at
    242-288 volts.

    The energy storage capacitor is typically charged to 300-330 volts. I
    have a bit of experience suggesting that its impedance is a tenth or two
    of an ohm, and that this flashlamp's arc at that voltage can take 50
    microseconds or more to "get nice and warmed up and cooking" with the
    available voltage and energy storage capacitor.

    This makes me think that the flashlamp's current peaks with voltage
    across it maybe around 225-250 volts with its resistance around .6-.7 ohm,
    which means peak current around 300-400 amps. I would like to say closer
    to 300 or low-300's than 400, after considering effects of resistance and
    inductance of wiring from the energy storage capacitor to the flashlamp.

    I do remember some bit of some rule of thumb that peak current through
    the flashlamp in smaller camera flash units is close to initial energy
    storage capacitor voltage divided by 1 ohm.

    300 to "low-300's" amps times 225-250 volts means peak power around 67
    to 83 kilowatts - though I would like to say anywhere from 55 to 100
    kilowatts with some significant possibility of going outside this range.

    This applies more when the flashlamp is is a compact linear one like the
    ones used in most "disposable camera" flash units, as well as when the
    flashlamp is the small most-popular U-shaped one used in many cheap
    "party strobes".

    I have a few web pages touching onto this:

    http://members.misty.com/~don/samflash.html (mostly by Sam Goldwasser)
    http://members.misty.com/~don/xea.html
    http://members.misty.com/~don/xeguide.html

    http://members.misty.com/~don/xesafe.html (at least look at the modified
    photo of myself, the only photo of myself in my entire website now -
    please know the safety info here and in the above samflash.html,
    xenon strobes involve high voltage and possible other hazards.)

    http://members.misty.com/~don/donflash.html (my xenon "top page")

    - Don Klipstein ()
     
  2. Phil Allison

    Phil Allison Guest

    "Don Klipstein"

    ** Snip rest of this wanker's impenetrable drivel and multiple DEAD links
    !!!

    The electro used in a typical disposable camera flash is 160 uF, charged to
    300V - I have a few here.

    So from: E = 0.5CVsquared - the energy stored is about 7 joules.

    The duration of the flash is close to 1 mS, after which most of the energy
    is lost from the cap.

    So, 6 joules goes west in 1 mS.

    Makes the peak power about 6kW.


    ...... Phil
     
  3. That would be average power

    --
    Dirk

    http://www.transcendence.me.uk/ - Transcendence UK
    http://www.theconsensus.org/ - A UK political party
    http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
     
  4. Phil Allison

    Phil Allison Guest


    ** Close enough to the peak value as well.

    You asinine question has no exact answer.



    ..... Phil
     
  5. More like average around 6 kW, with peak significantlty greater, over
    this millisecond.
    - Don Klipstein ()
     
  6. Phil Allison

    Phil Allison Guest

    "Don Klipstein"


    ** YOU got the simple math TOTALLY WRONG -

    you DROP DEAD STINKING **** !!!




    ......Phil
     
  7. Phil Allison

    Phil Allison Guest

    "Tim Wescott = Criminal Autistic Asshole "



    ** Go DROP FUCKING DEAD

    - you PSYCHOTIC ASININE TROLLING **** !!!




    .... Phil
     
  8. A somewhat common "disposable camera" flash arrangement has a xenon
    flashtube with impedance characteristic (Ko) of about 11-12 ohms-amps^.5.
    I take this to mean resistance of 1 ohm at 121-144 volts, and .5 ohm at
    242-288 volts.

    The energy storage capacitor is typically charged to 300-330 volts. I
    have a bit of experience suggesting that its impedance is a tenth or two
    of an ohm, and that this flashlamp's arc at that voltage can take 50
    microseconds or more to "get nice and warmed up and cooking" with the
    available voltage and energy storage capacitor.

    This makes me think that the flashlamp's current peaks with voltage
    across it maybe around 225-250 volts with its resistance around .6-.7 ohm,
    which means peak current around 300-400 amps. I would like to say closer
    to 300 or low-300's than 400, after considering effects of resistance and
    inductance of wiring from the energy storage capacitor to the flashlamp.[/QUOTE]

    Maybe a bit optimistic. Typical IGBTs for flash service are rated at
    ~150A peak collector current.

    http://documentation.renesas.com/eng/products/transistor/rej03g1201_cy25cah8f.pdf



    Best regards,
    Spehro Pefhany
     
  9. Maybe a bit optimistic. Typical IGBTs for flash service are rated at
    ~150A peak collector current.

    http://documentation.renesas.com/eng/products/transistor/rej03g1201_cy25cah8f.pdf[/QUOTE]

    So ballpark figures are 10J and 50kW?

    --
    Dirk

    http://www.transcendence.me.uk/ - Transcendence UK
    http://www.theconsensus.org/ - A UK political party
    http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
     
  10. Neat little circuit.
    Thanks

    --
    Dirk

    http://www.transcendence.me.uk/ - Transcendence UK
    http://www.theconsensus.org/ - A UK political party
    http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
     
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