Converted 8x10 dichroic to LED's!

Discussion in 'Darkroom Equipment' started by galyons, Jun 30, 2008.

  1. galyons

    galyons Member

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    Well after about 2 months of toasting $3 Luxeon III LED’s like they were popcorn, I have successfully completed the conversion of a Durst 184/301 head to LED light source.

    Firstly, a big “Thank You” to Huw, whose site and emails helped me to get started. His DeVere 504 conversion was my inspiration. I modified Huw’s layout to accommodate my 10”x10” Durst head and used Luxeon III’s, rather than Luxeon I’s.

    My printing process is pretty much some graded and mostly VC. For VC, I use the split grade technique utilizing a RG Designs StopClock. So my design elements were SoftMax and HardMax as simply as possible. What a joy, no more “spinning the dials” on my color head. Just flip 1 toggle for Soft, green, 1 toggle for Hard & Graded, (blue), both for focusing.

    My previous 8x10 working head, a 1000 watt quartz halogen dichroic, worked very well. Quartz halogen lamps produce most of their light in the red range combined with copious amounts of heat. I was looking for a simpler interface, less heat and less noise, (fans), So the comparison, easy, minimal heat and perhaps, no fan needed.

    What about illumination efficiency? The LED head is 2 ¾ stops FASTER! That makes the LED’s illumination equivalent to my old head with 2750 watts. Think about it. It would take 11 quartz halogen lamps and 2 ¾ time the heat to generate the same hard/soft printing power!

    The Durst head was really a joy as a base platform for the conversion. Lot’s of room in the fan compartment for the 24 volt power source and wiring harness runs. I left the internal fan in place, just in case I need to dissipate some heat faster than my heat sinks alone will accomplish. It has 10x10 and 5x7 mixing boxes that slide in like big drawers. Take the mixing box out and the led panel is readily accessible.

    I am still sorting things out, but the initial testing and process run was very, VERY encouraging.

    I will post more as I get more experience with the new LED head, but so far, I’m sold.

    Cheers,
    Geary
     
  2. jeroldharter

    jeroldharter Member

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    That's great. Please post some pics and more technical details. I wish someone here who knew electronics could make a simple 4x5 LED head with green and blue channels like you mentioned for VC printing that would be adaptable to common enlargers (like my Beseler) for a reasonable cost.
     
  3. df cardwell

    df cardwell Subscriber

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    YES
     
  4. galyons

    galyons Member

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    Jerold,
    Just curious, what would you pay? It is doable for a board kit with power supply to be somewhat universal to the major players, Beseler, Omega, Durst & Devere.

    My cost of materials was around $250, (board, heatsinks, LED's, wiring, resistors, connectors, power supply, switches and boxes.) Not really much of a price differential for 4x5 versus 8x10, but perhaps $30-50 less if one uses Luxeon I or fewer Luxeon III's. If one wanted to go with the ability to vary the LED intensity, that would add another $50-75 cost for the PWM board and pots. So for simple split grade printing, the standard retail distribution that would yield a retail price of $1000-1250. Variable add another $250.

    Unfortunately there is not likely the volume to get out of short run pricing. As an example the Luxeon III's come in small quantity cuts costing, today, nearly $4.82 each or in tape reels of 250 for $3.17

    The board can be pre-made in China, Taiwan or India. For a bit more, south of me in the Silicon Valley at job shops. Power supplies from China. But, again the volume levels will probably not drive the price down significantly from what I paid.

    I would appreciate anyone's thoughts on this. The commercial market has not jumped on this, Philips, (Luxeon) was not all that thrilled at my application for the LED's. But...

    Cheers,
    Geary
     
  5. jeroldharter

    jeroldharter Member

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    I was hoping for about $500 for a basic blue/green 4x5 light source anticipating a very basic but functional unit with minimal gadgetry. That sounds unrealistic. I think that APUG would be a good market, especially with a thorough review and pics. I am sure I could be persuaded to pay more for good aesthetics and a good review.

    Based on your remarks about cost of materials, I think a universal 8x10 light source with some sort of adapter to scale down to 4x5 would be best for most people and might allow for more economy of scale.
     
  6. galyons

    galyons Member

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    Yes, there lies the conundrum. $500 is probably a marketable price, but the margins would be prohibitively thin for traditional resales from manufacturer to wholesaler to retailer. Even selling directly, one must allow costs for development, testing, multi vendor procurement, kit assembly, handling orders, cashiering,packaging, shipping and customer service.

    Scaling down a unit developed for 8x10 maybe a bit problematic, but derating the LED's from Luxeon III's to I's would work. Their physical footprint is the same. Getting a good board that could be thermally attached to a heat sink board would be the critical step and the greatest need for volume to reduce the cost. I handwired my board, the LED's attached with high thermally conductive adhesive to an 0.1625" thick aluminum board with the finned heatsinks attached with the same high thermally conductive adhesive. A good daughterboard with traces would have greatly simplified the assembly and cut my LED losses.

    I agree that APUG and LFF would be the logical target markets. I would be interested in other thoughts, interest and/or perspectives. More to follow....

    Regards,
    Geary
     

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  7. Nick Zentena

    Nick Zentena Member

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    One of the German companies is a making a LED head. But the 8x10 cost is a lot more then $1K IIRC.
     
  8. galyons

    galyons Member

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    Nick, Heiland is making a split grade head. Yes, the price is much higher than $1000, even in 4x5. I had not heard that they had an 8x10, only up to 5x7. The Heiland system is very sophisticated offering substantial presets and manipulation of contrast. They do offer kits for the Durst CLS301 Head!

    My definition of split grade print is far simpler: "varying the exposure time at max hard and max soft to yield the overall and local, (burn/dodge), contrast you desire". The only measuring/calibration test is with your eyes!
    Cheers,
    Geary
     
  9. galyons

    galyons Member

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    The Durst CLS 301 was a great head to convert. There is ample room. The head is well constructed. Each panel can be removed easily for access. The mixing boxes are heavy drawers lined with highly reflective aluminum so the light distribution is very even.

    Also there was no guilt. The CLS 301 really sucked as a 10x10 head since it was designed for the 5x7 138 chassis and fitted, as an economy head for 10x10, to the 184. It only cranked out a whopping 600 watts of quartz halogen light. So it was well under powered for 8x10.

    The basic lighting design is 3 arrays of 6 green Luxeon III LED's, (18) and 2 arrays of 6 royal blue Luxeon III LED's, (12). The power supply is a dual channel 24 volt regulated DC. Each array, per electrical specifications, was terminated to ground with a 1 ohm resister. The array calculated to 1 watt dissipation, but I used 5 watt power resisters. It is cheap insurance.

    So each array looked like this:

    24VDC => +O-+O-+O-+O-+O-+O- 1 ohm 5 watt resister.

    I built color coded wiring harnesses and used terminal blocks to facilitate assemble, testing and repair.

    The LED layout was inspired by Huw, but I slightly modified the layout to better accommodate the 10x10 head. I hand-wired my board, the LED's attached with high thermally conductive adhesive to an 0.1625" thick aluminum board with the finned heatsinks attached with the same high thermally conductive adhesive. A good daughterboard with traces would have greatly simplified the assembly and cut my LED losses.

    I built color coded wiring harnesses and used terminal blocks to facilitate assembly, testing and repair.

    The LED’s were laid out on a 10MM grid. Huw calculated this pattern to provide even illumination for his DeVere 504 5x4 conversion using Luxeon I’s. I used the essential layout with the Luxeon III'x to accommodate both 5x7 and 10x10 mixing boxes on the CLS 301.

    More to follow,
    Geary
     

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  10. Nick Zentena

    Nick Zentena Member

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    Ya that would be fine with me to.
     
  11. Curt

    Curt Subscriber

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    They, Philip's, were not supportive at all when I approached them about my application some time back. "It can't be done in that small of a space, the heat sinks are too large" I'm not sure what the thinking is on there part but I got the message.

    When I receive feedback like that it just makes me more determined to make one for myself.
     
  12. Steve Smith

    Steve Smith Member

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    I occasionally do some work for a local PA hire/Sound Reinforcement company. They have recently branched out into supplying staging and lighting too.

    Some of their lights are LED such as these: http://www.djempire.co.uk/product/prolight-led-par-56-par-can-flood-light-silver

    Ignore the price listed, they can get me one of these for £34 ($68). I am going to get one to experiment with. I think with the right diffusing it would work fine.

    It has arrays of red, green and blue LEDs and is bright enough for stage use so it would easily be bright enough for an enlarger. In stage use it takes the place of a 500 watt incandescent lamp. however, I would say that it equates more to about 300 watts than 500. Obviously, that's in white mode with all three colours on.


    Steve.
     
  13. Steve Smith

    Steve Smith Member

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    Me too. If someone tells me something can't be done or that I can't do it. That's a challenge!


    Steve.
     
  14. RH Designs

    RH Designs Advertiser Advertiser

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    Looks interesting Steve. However, "ordinary" blue LEDs aren't really blue enough for best results - I've only been able to get a maximum grade of about 3.5 with them. The so called "royal blue" ones are better, but less easy to find.
     
  15. Steve Smith

    Steve Smith Member

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    I think I may be able to try this out for free. My friend has a couple of these lights where about six of the green LEDs have stopped working. I expect that they are connected in series in sets of six.

    Grade 3.5 would be o.k for me but not ideal. Is grade 3.5 achieved with the blue LEDs only (no green)?



    Steve.
     
  16. RH Designs

    RH Designs Advertiser Advertiser

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    Yes. I was using single 10W LEDs rather than an array, as I only need to cover 6x7 and they fitted neatly into the mixing box of my LPL 7700. This was a quick experiment which I had to abandon due to time constraints, but I intend to revisit in the future.

    Extreme contrast ranges on Ilford MG4 RC were approx 2.5 stops (ISO(R) 75, grade 3.5) with blue only and about 6 stops (ISO(R) 180, grade 00) with green only.
     
  17. galyons

    galyons Member

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    The saga continues!!!! I bumped the Hard contrast range into Grade 5 by adding 4 1watt, near UV/Violet LED’s, (400nm). (See the grid attached for placement.) I ran step wedges to test the contrast. I used Ilford MGIV RC. Looks like I am getting about ISO 65, so well into Grade 5. (See wedge attachments.)

    VC paper was designed for tungsten light sources and is sensitive to below 400nm wavelengths, that is, sensitive to UV light. Tungsten and fluorescent light are broadband and extend into the UV range. The very tight spectral response of the LED’s requires more thought to the paper sensitivity and contrast range. One of the concerns in using LED’s was the inability to get to Grade 5. The Phillip’s Royal Blue produced the hardest contrast, but, in my tests, only got into the lower Grade 4 range.

    We all must be concerned with using the near UV wavelengths. There are some basic safety procedures to avoid issues. Do not look directly at the lit LED, even for a few moments. The spectrum of these LED’s is very narrow with the peak at 400nm. This is really violet and the short wavelength at which light is normally categorized as “visible” for the human eye. But never forget that you only have 1 pair of eyes and always proceed with due caution

    The Soft Grade is very extended, about ISO 215, Grade 00 with MGIV RC. I will run some tests with non-extended range papers, as well. I am using a 21 step wedge. I would like to try a finer gradation, as I narrow down the spectral response.

    The Hard is now about .5 stops faster than the Soft. I may try to achieve a better balance by removing some of the Royal Blue LED’s. Although the near UV LED’s are not “as powerful” , in wattage, the shorter wavelengths are higher in energy.

    The head is really nice to print with, fast, quiet and cool! The elimination of the fan noise and the head heat is a true joy. I did not realize how much I had “environmentally internalized” all that goes with pouring 1000 watts of mostly heat into the DR.

    I have ordered some small modular boards that use the new SMD Rebel LED’s. This will allow easier scalability. The work continues and the LED budget starts to look like the current US Federal budget!
     

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  18. domaz

    domaz Member

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    Very nice. Did you consider using the Luxeon Star LEDs instead of the bare leds? I find the stars much easier to solder and work with. I hope using the resistor works ok for you. I would be concerned about temperature and voltage fluctations affecting consistency. A simple constant current drive circuit like one of these might be worth it for the piece of mind.
     
  19. jeroldharter

    jeroldharter Member

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    galyons,

    Are you still using this 8x10 light source? How is it going? Just curious.
     
  20. dr5chrome

    dr5chrome Member

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    This is amazing! This is the last thing I thought might be possible:surprised:

    Do you actually get even light and 2.75 more stops.. :confused::surprised:

    I have 2 Durst's, a 138 and a 184.

    dw


     
  21. largeformat pat

    largeformat pat Member

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    This is interesting. I have a L184 with a T12 head. Wouldn't mind variable contrast Do think I could fit it into a box about the size of the t12 head? Or do you think it would be to close?
    Pat
     
  22. Sal Santamaura

    Sal Santamaura Member

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    Note that Geary's profile indicates his last activity here was 2-5-09.
     
  23. CBG

    CBG Member

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    Regardless of the last activity from the OP, the subject of a home-brew LED split grade head keeps nagging at me. I can't think of any reason it should not work. I have considered using the screw in pre wired multi LED "bulbs" that one can just screw into a 120 V source. Green and blue/UV.

    I have been using LEDs from www.superbrightleds.com for split grade contact printing and red LEDs for safelighting.

    I'm not interested in the mechanics of wiring LEDs myself so the simplest screw in household voltage bulbs make sense to me. The work very well for safelights. and the greens and blue/UVs are so bright I have to bounce them off a dark surface to have usefully long printing times. I would like eventually to be able to print large to very large, so intensity is very important to me.

    The bulbs are on this page. www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=/specs/E27-W24.htm
     
  24. BetterSense

    BetterSense Member

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    To the OP. Is this enlarger an 8x10 diffusion type enlarger? So there is a sheet of diffusion material between the LED lights and the negative? About how far from the negative is the LED panel?

    In the future I may wish to make a similar LED head, so your LED layout diagram is very informative. However, there are no units included, so I'm left wondering the scale of the layout. Do the squares have a certain size to them? If it's not too much trouble could you measure across the extreme diagonal blue LEDs?
     

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