Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,934   Posts: 1,585,600   Online: 647
      
Page 2 of 5 FirstFirst 12345 LastLast
Results 11 to 20 of 49
  1. #11
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    6,394
    Speaking of Wheatstone Bridge, here is a neat little meter circuit from the 16mm Minolta 16QT. Instead of a galvometer in the middle of the bridge there is a differential amplifier. The two bulbs alternate blinking when it is balanced. I'd give this one the award for "Most Elegant Meter Circuit" of the film age.

  2. #12

    Join Date
    Sep 2005
    Location
    Huntington, NY
    Shooter
    35mm
    Posts
    305
    OMG, making it way too complicated. Schotkey diode 1N-6263 in series with the battery. Meter accurate and linear within 1/8th of a stop (after calibration) and since most are shooting print film these days, that "inaccuracy" easily falls within the plus or minus 1.5 stop (or more) latitude of the film. Then there's shutter speed latitude, film asa latitude, f stop latitude, the joker making minimum wage at the drug store pushing the "start" button on the "automatic" machine developing your film. John

  3. #13

    Join Date
    Jan 2004
    Location
    NYC
    Shooter
    Medium Format
    Posts
    1,188
    Well I guess the diode is the way to do it. Nice to come up with a bettter solution though, maybe something a bit more accurate.

    BTW what is the voltage drop on that diode?... most are around 1 volt, how do you conpensate for it?

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  4. #14
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    6,394
    Here is a voltage regulator designed by someone with your same concerns: http://ludens.cl/Electron/mercreg/mercreg.html

  5. #15

    Join Date
    Jan 2004
    Location
    NYC
    Shooter
    Medium Format
    Posts
    1,188
    The size of the transistors alone are way too big for a compartment, even the IC I listed still much smaller but also too big. Although the FX reg is by far the best of em all.

    Do you have any spares to experiment with? Maybe KEH "as is" bin has a busted camera for a few bucks I can glom one out of?

    .
    Anyone can make a Digital print, but only a photographer can make a photograph.

  6. #16

    Join Date
    Sep 2005
    Location
    Huntington, NY
    Shooter
    35mm
    Posts
    305
    Quote Originally Posted by paul ron View Post
    Well I guess the diode is the way to do it. Nice to come up with a bettter solution though, maybe something a bit more accurate.

    BTW what is the voltage drop on that diode?... most are around 1 volt, how do you conpensate for it?

    .
    As stated, any "accuracy" is lost in all the other latitudes. My OM-1/1N meter conversion is on the money at BV15, 12 and 9. at BV6 it's about 1/16th of a stop off. Plenty accurate, and to get more complicated is wasted labor (especially with negative/print film). This is perfect even with slide film. Voltage drop is about .2 volts, so working voltage from a silver oxide 1.55V battery (which is really around 1.6V) is approx. 1.35V. John

  7. #17

    Join Date
    May 2006
    Location
    Aurora, IL
    Shooter
    35mm
    Posts
    1,992
    I never really care about the accuracy of these old cameras' meters but for the sake of it I think may be one can build a battery grip using AA with room (and current) for a rock solid 1.35V supply.

  8. #18

    Join Date
    Jan 2004
    Location
    NYC
    Shooter
    Medium Format
    Posts
    1,188
    Hey Chan that is a great idea, a grip with the regulator buiilt right in.

    I have never used the meter in my OM1MD or any of my 35mm cameras. For some reason they just nbever seemed accurate and were always finiky.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  9. #19
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    6,394
    I had a look at an original circuit board from the FX-3 and it looks like I made a mistake. The Vreg in the diagram is just a test point. The actual regulator is incorporated into the integrated circuit and is not a separate component.

    I think one could make a tiny regulator based on a Zener diode like this: http://hyperphysics.phy-astr.gsu.edu...c/zenereg.html

  10. #20

    Join Date
    Jan 2004
    Location
    NYC
    Shooter
    Medium Format
    Posts
    1,188
    So the Shotky is the best solution for now.. or the regulator in the grip idea.
    Anyone can make a Digital print, but only a photographer can make a photograph.

Page 2 of 5 FirstFirst 12345 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin