DIY light source for 10X10" enlarger.

Discussion in 'Darkroom Developing and Printing' started by jjs, Apr 9, 2008.

  1. Blue and green are correct. Both emulsions are sensitive to
    blue light and one of the emulsions is sensitized so it will
    also respond to green light.

    The multi-contrast gel filters add red light for better visibility
    when dodging and burning -
    red + blue = magenta
    red + green = yellow

    A proper head would have red, green and blue LEDs - allowing
    it to produce 'white' light for focusing and graded paper,
    magenta and yellow light for VC paper, and red light for
    positioning sensitive materials.

    Ilford MGIV paper is a 3-emulsion paper, the third emulsion
    sensitized for cyan. For best control - especially at low
    contrast grades - the head would also have cyan LEDs.
     
    Nicholas O. Lindan, Apr 10, 2008
    #21
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  2. jjs

    jjs Guest

    Oh, darn. That means I can get off my butt, walk 10 yards and get it right
    now. I'm in the library at this moment.

    Thanks, really, I didn't know he did that. Couldn't hoit! Will do.

    Location/Available: Main Library Main Collection Call #: TR145 .A38 bk.3
    Author: Adams, Ansel, 1902-
    Title: The print / Ansel Adams with the
    collaboration of Robert Baker.
    Edition: 1st pbk. ed.
    Publisher: Boston : Little, Brown, 1998.
    Physical Details: x, 210 p. : ill. ; 25 cm.
    Series Title: ( Ansel Adams photography series ; bk. 03)
    General Note: Includes index.
    Reprint. Originally published: Boston : Little, Brown, 1983.
    Local Note MSF FY00
     
    jjs, Apr 10, 2008
    #22
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  3. jjs

    jjs Guest

    I hope the F-Stop timer can handle the bazillion watts I'm gonna put through
    it with this thing. (Joking)
     
    jjs, Apr 10, 2008
    #23
  4. Fluorescent lamps are one variety of gas-discharge lamp.
    They share their major electrical characteristic - negative
    resistance - with HID/Mercury/Sodium lamps. Negative
    resistance means that as the lamp current increases the
    lamp voltage decreases and thus the current, unless
    limited, quickly rises to near infinity (i.e., a lightning
    bolt discharge). The ballast's purpose is to limit the
    lamp current.

    Graphic arts systems use several types of specialty
    ballasts. Many use a combination of these features:

    o Keep light output constant:

    Regulating ballasts wherein the ballast uses a saturating
    core reactor and works, with the power factor capacitor and
    the lamp, as a ferroresonant regulator.

    o Quickly come up to full brightness:

    Ballasts having a low open circuit voltage
    and a low reactance. This increases the current through
    a cold lamp so that it warms faster. The lamps are
    low voltage/low pressure designs with heavy duty electrodes
    that can withstand the higher current without erosion.

    o Keep the lamp warm so it comes up to full brightness
    instantly:

    Multi-level ballasts wherein the lamp idles at low power
    in a keep warm state with the shutter closed and then
    switches to high power with an open shutter to make the
    exposure. Fan speed is reduced when the lamp is idling
    at low power to keep the lamp at a hot operating temperature.

    This feature is usually combined with the ability to run
    the lamp at several power levels.

    o Extend lamp life, especially where lamps cost many hundreds
    of dollars:

    Very low crest factor (Ipeak/Irms) ballasts than keep the
    electrodes from wearing out. Electrode erosion is roughly
    proportional to the cube of the current.

    I don't know that the Aristo equipment is sophisticated enough
    to use any of the above technologies.

    Crest factor is main difference in the quality of a fluorescent
    ballast. The ballasts in $10 work luminaries have a high
    crest factor, leading to short lamp life and low light output
    for power in. A high quality low crest factor ballast first
    raises the voltage with an auto-transformer and then limits
    the current with either inductive or capacitive reactance.
    Often the some of the ballast reactance is supplied by
    air-gapping or shunting the transformer to increase the leakage
    inductance; often a capacitor is used for ballast reactance
    and leakage inductance is used for power factor correction.
    Additionally, the efficiency of the ballasts of high quality
    ballasts is higher: thicker copper wire in the reactor/transformer
    windings to keep resistive losses low, the prescience of power
    factor correction capacitors and the use of low ESR capacitors.

    For a garage work bench lamp all of this is of little concern:
    the electricity savings of an efficient ballast will never
    pay for its higher initial cost.

    Aristo lamps are low current, high voltage, low pressure
    mercury with a phosphor coating - sort of a hybrid between
    a neon and a fluorescent lamp. The ballast is specific
    to such a lamp and is, I am sure, a high quality low-crest
    factor design.

    If you are designing a cold light head using off-the-shelf
    fluorescents you should look for the highest quality ballasts.
    Long lamp life equates with stable light output.

    The best economical high performance ballast systems, designed
    for office/factory use, aren't applicable to cold-light heads.
    Office lighting systems usually supply a high (and usually
    bizarre - 347 volts anyone?) voltage from a central
    step-up transformer with individual inductive ballasts
    at each lamp. If power factor capacitors are used they
    are often central with the transformer.

    Much more than anyone in r.p.d., including myself, would
    (or should) ever want to know.
     
    Nicholas O. Lindan, Apr 10, 2008
    #24
  5. jjs

    jjs Guest

    Hold on. I don't know anything about electricity. I just got it installed.
    All I know is that it really hurts to stick yer tongue into the light
    sockekt. It makes me ferget things. Like not to do it again.

    So, if I put up to [email protected] into that head and plug it into the F-Stop timer,
    it's going to go up in smoke? What do I do? (Besides do another DIY Electro
    Convulsive Therapy thing.)

    John
     
    jjs, Apr 10, 2008
    #25
  6. jjs

    Ken Hart Guest

    Seriously, are you saying that there is a 100A contactor for the F-stop
    timer? And if so, what sort of enlarger would use a 100A light source?
     
    Ken Hart, Apr 10, 2008
    #26
  7. If only it were so.

    The problem of lamp warming isn't mitigated by a meter - there
    is the same variation in lamp output between metering
    and exposing as there is between pre-warming and exposing.

    A meter will compensate for slow variations due to lamp
    aging, room temperature variation, and seasonal or dinural
    voltage fluctuation.

    A compensating timer/light integrator in combination with
    an enlarging meter is a self-defeating mess: The effect is
    to double the error and to do it in the wrong direction - the
    dimmer the lamp the more overexposed the resulting print.
    If the lamp dims the meter will indicate more exposure
    is needed - the integrator will extend the exposure time
    on it's own to compensate for the dim lamp and as a result
    compensation is applied twice - a 10% dimming of the lamp
    will result in a 10% over exposure to the material.

    The only real solution for cold-light woes is to stabilize
    the light output with either a closed-loop regulated head
    or some means of keeping the lamp at a constant operating/
    idling/off temperature.
     
    Nicholas O. Lindan, Apr 10, 2008
    #27
  8. The standard F-Stop timer can only handle up to 2.3 quintillion watts,
    5A or 300W incandescent - whichever comes first.

    Auxiliary contactors are available for use up to 100 amperes.

    The largest light source we make equipment for is 1 terrawatt @
    100 megamps. https://lasers.llnl.gov/

    --
    Nicholas O. Lindan, Cleveland, Ohio
    Darkroom Automation: F-Stop Timers, Enlarging Meters
    A Unit of Cleveland Engineering Design, LLC
    http://www.darkroomautomation.com/index2.htm
    n o lindan at ix dot netcom dot com
     
    Nicholas O. Lindan, Apr 10, 2008
    #28
  9. Seriously -- if you want to control a 1KW head it
    isn't any problem. You will need an auxilliary
    contactor - a metal box with a relay in it -
    that plugs into the (220V ?) power and the
    timer. You then plug the enlarger into the
    contactor box. Not mine, but:
    http://www.largeformatphotography.info/forum/attachment.php?attachmentid=9893&d=1202624791

    Darkroom Automation can supply contactor boxes
    if you don't want to make your own.

    The situation is the same with all timers.
    Most giant enlargers have their own electronics
    for running the head and the servo motors and also
    have their own timer -- in this case the
    contactor is built into the enlarger's power supply.

    If you have an old HID head or a shuttered head
    then the timer connects to the shutter and the
    lamp power is a non-issue.

    If you are making a custom 1 KW head you may
    find yourself involved in making a power supply
    for it. You would then have a contactor as
    an integral part of the supply.

    If you buy a 1KW stand-alone head it more than
    likely has the contactor built into it or the
    contactor is an integral part of the head 'kit'.

    I am sure you have seen this thread ... Durst 10x10 enlarger:
    http://www.largeformatphotography.info/forum/showthread.php?t=32852
     
    Nicholas O. Lindan, Apr 11, 2008
    #29
  10. jjs

    jjs Guest

    Typo. I meant 100W (see how close @ is to W?)
    I have no idea what that means in Amps.
     
    jjs, Apr 11, 2008
    #30
  11. jjs

    Peter Chant Guest

    Nicholas O. Lindan wrote:

    Ah ha - my confusion answered - so simple when you find out why.
     
    Peter Chant, Apr 11, 2008
    #31
  12. jjs

    jjs Guest

    This one is a mercury contactor for 36$US from McMaster. 20A. Good enough?
    http://www.digoliardi.net/relay_1.gif
     
    jjs, Apr 11, 2008
    #32
  13. Yes. There is a 100A contactor for _any_ timer ... it is
    a separate thing in a separate box, not part of the timer.
    I was being facetious. 20A is all anyone would need.
    See http://www.mcmaster.com/ and search for >> contactor <<.

    The best for this purpose are mercury contactors, but most
    enlargers cheap out and use a relay contactor
     
    Nicholas O. Lindan, Apr 11, 2008
    #33
  14. jjs

    ____ Guest

    Does that mean if the ballast is fried and current is still some how
    going to a tube and one is standing on a aluminum ladder ones kiester is
    in serious jeopardy :)
     
    ____, Apr 11, 2008
    #34
  15. jjs

    Peter Chant Guest

    Peter Chant, Apr 11, 2008
    #35
  16. jjs

    ____ Guest

    And David breath very deeply while using it.
     
    ____, Apr 11, 2008
    #36
  17. jjs

    jjs Guest

    Sorry. That requires a user id and password. I don't go to that place. It's
    full of icky self-congratulary strokers.
    I can build anything that does not use wiring. Regardless, I think I'll wait
    for my smart colleague to come back from Antartica (no kidding) and let him
    do the juice thing.

    Thanks for your help.
    (I did order the F-Stop timer. I've a lot of timers, but not that one. Hope
    it gets BBC.)
     
    jjs, Apr 11, 2008
    #37
  18. jjs

    ____ Guest

    Are you serious about even suggesting 220V for him to use?

    That's just plain nuts.
     
    ____, Apr 11, 2008
    #38
  19. Small correction: 277 volts. (It's printed on lots of ballasts.)
     
    David Nebenzahl, Apr 11, 2008
    #39
  20. 100 Watts is no problem for any timer.
    ~0.83 Amps RMS
     
    Nicholas O. Lindan, Apr 11, 2008
    #40
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