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Thread: Homemade LED light source is working

  1. #1
    Eric Woodbury
    Join Date
    Dec 2003
    Posts
    1,528

    Homemade LED light source is working

    After years of thought and slow construction, my modified Beseler CB-7 (changed from the negative platform up) is newly mounted with a 10x12" LED light source of my own design. For those considering their own, here's what you might expect.

    16 green and 17 royal blue, 1 amp Cree LEDs use about 35 watts. Contrast control is a simple knob that shifts from all green to all blue; half and half in the middle. It is 2 stops brighter than my 12x12" Aristo V54 was and gives a slightly broader contrast range on both ends than the standard #00 to #5 filters (on Ilford MG Fiber Classic). Unit plugs into a standard timer. There is no warm up or tail-off of the light. Evenness appears to be very good, but this required careful design of the diffusers.

    None of the parts for the build is particularly expensive, just lots of them. LEDs were $4/ea. The other items nickel and dime you to death. Time is the biggest expense. My drive electronics are all analog, through-hole style, so that I could build them by hand. If one isn't familiar with op amps, current sources, FETs, and soldering, then this should not be attempted.

    If I were to start again, I would seriously consider using 'super bright' LED tapes of royal blue and green. Power each with an adjustable current supply that is controlled by a potentiometer. Gang the "pots" on a single shaft such that as one increases, the other decreases.
    Besides not having to fiddle with filters, the biggest surprise is how much difference just a tenth of point in contrast can make in a print.
    If you're designing your own and would like to correspond, my email address is ejwoodburyatgmaildotcom. No PMs, please.

    Happy printing in the new year.
    my picture blog
    ejwoodbury.blogspot.com

  2. #2

    Join Date
    Dec 2014
    Location
    Iowa City, Iowa
    Posts
    1,276

    Re: Homemade LED light source is working

    Quote Originally Posted by Eric Woodbury View Post
    After years of thought and slow construction, my modified Beseler CB-7 (changed from the negative platform up) is newly mounted with a 10x12" LED light source of my own design. For those considering their own, here's what you might expect.

    16 green and 17 royal blue, 1 amp Cree LEDs use about 35 watts. Contrast control is a simple knob that shifts from all green to all blue; half and half in the middle. It is 2 stops brighter than my 12x12" Aristo V54 was and gives a slightly broader contrast range on both ends than the standard #00 to #5 filters (on Ilford MG Fiber Classic). Unit plugs into a standard timer. There is no warm up or tail-off of the light. Evenness appears to be very good, but this required careful design of the diffusers.

    None of the parts for the build is particularly expensive, just lots of them. LEDs were $4/ea. The other items nickel and dime you to death. Time is the biggest expense. My drive electronics are all analog, through-hole style, so that I could build them by hand. If one isn't familiar with op amps, current sources, FETs, and soldering, then this should not be attempted.

    If I were to start again, I would seriously consider using 'super bright' LED tapes of royal blue and green. Power each with an adjustable current supply that is controlled by a potentiometer. Gang the "pots" on a single shaft such that as one increases, the other decreases.
    Besides not having to fiddle with filters, the biggest surprise is how much difference just a tenth of point in contrast can make in a print.
    If you're designing your own and would like to correspond, my email address is ejwoodburyatgmaildotcom. No PMs, please.

    Happy printing in the new year.
    Good for you! I may try this sometime, I want RGB for color, not sure I have the brains for it.

  3. #3

    Re: Homemade LED light source is working

    This sounds cool. I have just built a UV LED box for contact printing. I used a 60x40 cm black crate with lid. I ran mains into two separate 80 W LED drivers to separately control the left and light hand side of the box. This ran into a junction box so I could then run UV LED strips soldered in parallel. I ran some test cyanotypes a could of days ago. I was able to contact print negatives in 6 mins (not optimised yet). I also printed off a picture in crappy paper which I then waxed to make semi-translucent and got usable contacts in 20 mins.

    I have considered, as a next project, doing something similar to yourself but with UV LEDs for alternatives processes. This way you could go from any negative to direct print without an intermediate enlarged negative. However, I need to think about the UV opacity of condensers, enlarging lenses etc. I would also need LEDs with higher power and there is the issue of heat output but I could rig in a fan. I am sure I saw something similar in the internet once. I may well drop you a line sometime

  4. #4

    Join Date
    Mar 2005
    Location
    Newbury, Vermont
    Posts
    1,303

    Re: Homemade LED light source is working

    hmmm...I believe that Agfa produces quartz optical plates of some sort (too hard to grind, but you could lay some diffusion material on top side) - and there's always the Hasselblad 105mm (quartz/fluorite) UV-Sonnar to consider (no idea how this would work for enlarging)...if you can find one, and are willing to pay dearly for it!

    But to design and build a through and through, UV-Compatible enlarger? Hey Elon, Bill, Jeff, Mark...how about it?

    Then again...did Durst come close to this at some point - at least with a light source?

  5. #5
    Tin Can's Avatar
    Join Date
    Dec 2011
    Posts
    17,230

    Re: Homemade LED light source is working

    Eric has built an LED 'normal' enlarger lamp to replace the Arista 10X10

    The contact ALT printers want UV

    Very different goals

    I seek Eric's solution, he has responded.

    Thank you, Eric!

    Quote Originally Posted by Eric Woodbury View Post
    After years of thought and slow construction, my modified Beseler CB-7 (changed from the negative platform up) is newly mounted with a 10x12" LED light source of my own design. For those considering their own, here's what you might expect.

    16 green and 17 royal blue, 1 amp Cree LEDs use about 35 watts. Contrast control is a simple knob that shifts from all green to all blue; half and half in the middle. It is 2 stops brighter than my 12x12" Aristo V54 was and gives a slightly broader contrast range on both ends than the standard #00 to #5 filters (on Ilford MG Fiber Classic). Unit plugs into a standard timer. There is no warm up or tail-off of the light. Evenness appears to be very good, but this required careful design of the diffusers.

    None of the parts for the build is particularly expensive, just lots of them. LEDs were $4/ea. The other items nickel and dime you to death. Time is the biggest expense. My drive electronics are all analog, through-hole style, so that I could build them by hand. If one isn't familiar with op amps, current sources, FETs, and soldering, then this should not be attempted.

    If I were to start again, I would seriously consider using 'super bright' LED tapes of royal blue and green. Power each with an adjustable current supply that is controlled by a potentiometer. Gang the "pots" on a single shaft such that as one increases, the other decreases.
    Besides not having to fiddle with filters, the biggest surprise is how much difference just a tenth of point in contrast can make in a print.
    If you're designing your own and would like to correspond, my email address is ejwoodburyatgmaildotcom. No PMs, please.

    Happy printing in the new year.
    image

  6. #6

    Join Date
    Mar 2005
    Location
    Newbury, Vermont
    Posts
    1,303

    Re: Homemade LED light source is working

    My attention has been piqued also...partly because I've been looking at getting into whole plate (6.5x8.5) at some point - and although I already have a very nice Heiland LED VC unit for 5x7, and while this slightly oversized...it would not cover this larger size, and at this point, there is really no way I could afford to purchase yet another Heiland unit...much less an even larger one.

    Mr. (Ms?) Bones allusions to somehow cobbling together what seems like (if I interpret this correctly) an actual UV enlarger...capable of creating direct enlargements from negatives onto, say, platinum/palladium paper - assuming it would also be capable of doing this with exposure times measured in seconds or minutes...as opposed to hours (and hours and hours), and also assuming that the user's body and surrounding darkroom would not be cooked in the process...would be quite a feat I think!

  7. #7

    Join Date
    Jun 2014
    Posts
    1,817

    Re: Homemade LED light source is working

    Eric, nice work. Briefly checked the schematic on your blog; looks like a quite thoroughly engineered solution. I see you're using photodiodes to sense the output of the green & blue leds; is this done to compensate for aging and component drift?
    Can you comment on the purpose of R6, R55, R48 and R24? Where does the flash circuit connect to in the rest of the schematic? I see you're running single supply on the opamps; did you witness any issues with a small offset when M1 is conducting, or do the MCP6002's switch off nicely with In+ held down to GND?
    Also, did you consider using LED drivers such as the MP24894, and/or was there a particular reason not to do this?

  8. #8

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    Mar 2005
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    Newbury, Vermont
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    Re: Homemade LED light source is working

    Schematics...yet another learning curve which I feel too old/encumbered to embrace - but so very useful! Should be a required subject in primary education!

  9. #9

    Join Date
    Jun 2014
    Posts
    1,817

    Re: Homemade LED light source is working

    Quote Originally Posted by Duolab123 View Post
    Good for you! I may try this sometime, I want RGB for color, not sure I have the brains for it.
    It can be done. But it's more challenging than b&w multigrade. Eric's closed loop system (which I assume the photodiodes are meant for) might be useful, although it's not a necessity in my experience.

  10. #10
    Tin Can's Avatar
    Join Date
    Dec 2011
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    17,230

    Re: Homemade LED light source is working

    I taught myself tube radios both receiving and transmitting by age 15, not Ham radio. Pirate Radio. Schematics were easy as the symbols used to be defined in old books.

    My 12 year old hobby was ancient Wire Recorders and a 78 RPM Record cutting machine. Somebody gave me the gear.

    Not my Father, he disapproved any hobby I chose.

    I used to live in libraries always reading a lot of books. Now listen to audiobooks while puttering around my photo studio.
    w
    Quote Originally Posted by John Layton View Post
    Schematics...yet another learning curve which I feel too old/encumbered to embrace - but so very useful! Should be a required subject in primary education!
    image

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