Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,329   Posts: 1,537,179   Online: 821
      
Page 1 of 3 123 LastLast
Results 1 to 10 of 22
  1. #1
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845

    Cold light with a Gralab timer?

    I've just gotten a Gralab Model 300 darkroom timer for a good price, but note after receiving it that the data plate shows: 750 W, 6 Amps, 3 Amps "T". I presume "T" refers to the timer switched circuit. I plan to use it to switch a Zone VI cold light in my Omega D2.

    I'm a little concerned at this low rating, since the inductive load of a cold light gives it a very high startup draw relative to its steady state condition, as well as making it prone to arcing on switch contacts when switched off. I don't know the rating of the Zone IV unit I have, though, and it doesn't seem to have a data plate.

    Based on the size of the tube, it can't draw much more than 20 W; if that's the case, even allowing for 10x rating to handle startup load and inductive cutoff, the Gralab's relay should be fine. However, I don't know if the cold cathode tubes used in cold lights are really comparable to the common fluorescent lights I'm more familiar with; the light is bright, but not any brighter than a 15W fluorescent desk lamp I have here.

    So, my concern is, will I be overloading anything running the cold light from this darkroom timer? The heater circuit for the cold light will, of course, bypass the timer to remain on during the entire printing session.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  2. #2

    Join Date
    Sep 2002
    Location
    Boston, MA
    Shooter
    Multi Format
    Posts
    970
    Images
    3
    Donald, I have a Aristo cold light Head on my Omega D2. I did the same thing checking to see if my timer would be OK. The only warning from Aristo was to make sure your solid state timer can handle inductive loads. I would think that a mechanical timer with a rating like yours should be OK. The smaller relays in solid state timers may be under rated. Mine was designed with the possibility of cold light heads and can handle it.

    I don't know if the Aristo is similar to Zone VI... maybe someone else can add to this.

    --John

  3. #3

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Years ago I had an Aristo head on a D2 with a Gralab 550. I built up a relay circuit to handle the load. I figured that the relay was cheaper then burning out timer relay contacts.

    I let the timer switch the relay coil voltage and let the new supplemental relay contacts handle the cold light.

  4. #4

    Join Date
    Feb 2003
    Location
    Hudson, New York
    Shooter
    8x10 Format
    Posts
    171
    I've tried it and it eventually fried the microswitch in the timer. I had to switch to one of the Beseler digital timers which has worked flawlessly.
    Paul Hamann

  5. #5

    Join Date
    Nov 2004
    Location
    Italia
    Shooter
    Multi Format
    Posts
    4,680
    http://www.dimco-gray.com/gralab/Cat..._300.asp?m=300

    Max Lamp Load: 600W

    Max Resistive Load: 1200W

    Maybe drop the company an email?

  6. #6

    Join Date
    Jan 2005
    Location
    Downers Grove Illinois
    Posts
    1,051
    Aristo makes a contactor to isolate the timer from the cold light to solve potential problems. I use is in addition to the dimmer they make.

  7. #7

    Join Date
    Dec 2002
    Shooter
    Large Format
    Posts
    6,242
    Building a relay circuit is quite simple if someone wants to do so. A simple 20 amp double pole normally open relay with 120 VAC coil, a little bit of wire, an enclosure, and terminals are all that are required.

    1. Install a male plug on one end of #16/3 SJ wire from the enlarging timer enlarger output and attach the other end to the new relay coil.

    2. Install a male plug to # 12/3 SJ cord to the common poles of the relay.

    3. Install #12/3 SJ cord with a female plug to the normally open poles of the relay.

    4. Install the green ground wire from the SJ cord to the enclosure chassis.

    5. Plug your cold light into the female outlet installed in step #3

    6. Plug the male plug installed in step #2 into a 120VAC power supply.

    7. Install the relay into the enclosure.

    This relay will handle over 2000 watts.

    All of the parts are available from a HVAC supplier such as Johnstone Supply or WW Grainger. Total cost of all parts should be approximately $18-$25

  8. #8
    lee
    lee is offline
    lee's Avatar
    Join Date
    Nov 2002
    Location
    Fort Worth TX
    Shooter
    8x10 Format
    Posts
    2,913
    Images
    8
    I dont think there is anything in this electro-mechanical timer to blow with the cold light. This is not the timer I would pick to use with an enlarger but sometimes we must do what we must do.

    lee\c

  9. #9
    craigclu's Avatar
    Join Date
    Sep 2002
    Location
    NW Wisconsin, USA
    Shooter
    Multi Format
    Posts
    766
    Donald... I used my Gralab 300 with an Aristo rig for 10+ years without seeing any problems. I still use the timer for some things and it continues working fine.
    Craig Schroeder

  10. #10

    Join Date
    Mar 2005
    Location
    Seattle
    Shooter
    8x10 Format
    Posts
    1,212
    Images
    47
    I used a greylab 300 with a 5x7 arisogrid for 15 years. No one told me it wouldn't work ok. I didn't tell the timer or light , so they didn't know either.

Page 1 of 3 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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