LEDs for 8x10 scratch built enlarger- is there an update?

[Turner Reich]

A basic question: when I contacted Phillips about the application of Lumiled's they said the LED's wouldn't fit in an enlarger head, like the Beseler 45, because the heat sink was going to be too big. Now I see the boards proposed for the replacement of a diffusion light source for variable contrast printing and they have no heat sinks.

What's the difference in these applications where a heat sink is required for one and not the other? Is it the light output that dictates the use of a heat sink and how is that determined?

I would like to use the same application technique that Henry uses but instead of condensers I would use a Styrofoam light box for a diffusion head.

[Alan Rabe]

Calumet makes an LED based VC enlarger head for their Zone VI Type 2 enlarger. As it is a 5x7 head I have no doubt it can be adapted to just about any enlarger. Downside $1200 bucks.

[rob cruickshank]

A basic question: when I contacted Phillips about the application of Lumiled's they said the LED's wouldn't fit in an enlarger head, like the Beseler 45, because the heat sink was going to be too big. Now I see the boards proposed for the replacement of a diffusion light source for variable contrast printing and they have no heat sinks.

What's the difference in these applications where a heat sink is required for one and not the other? Is it the light output that dictates the use of a heat sink and how is that determined?

I would like to use the same application technique that Henry uses but instead of condensers I would use a Styrofoam light box for a diffusion head.

What determines the requirement for heat sink is the power of the led. Small LEDs such as the ones on the Peggy board, each dissipate roughly 60 milliwatts. While a greater portion of this power is converted into light than in an incandescent bulb, there is still heat to dissipate. In this case the thermal conductivity of the led body is sufficient to keep the device cool without a heat sink. The high power LEDs dissipate approximately one watt. (picture squeezing about 15 of the small LEDS into a space not much bigger than one standard LED) While one watt doesn't seem like a lot, it's quite a bit for such a small device, and that heat has to go somewhere. One could, of course use some kind of active cooling with a fan to reduce the heat sink size, or use heat pipes, as is sometimes done with CPUs and graphics cards in computers.

[Henry Ambrose]

A styrofoam light box would be good, but so would just about anything else white. My enlarger happens to use a condenser so I had to feed it the light it wanted. You do have to take into account the nature of the enlarger you're working with. If yours uses a diffusion light source then you'd want to mimic that with your new LED head.

I don't really know about the heatsink. Mine has a relatively huge heatsink that never even gets warm much less hot. Remember that the LEDs are only on for seconds at a time (other than focusing). Still I suppose a heatsink would provide insurance against leaving it on by mistake. Someone else with more complete knowledge than I might have a comment on that.

(what Rob wrote while I was typing seems reasonable)

[aphexafx]

http://en.wikipedia.org/wiki/LED - a good read

[Turner Reich]

Henry which LEDs are the six you have on your head, can you give me the make and model? Does the same manufacturer have the power supply and heat sink for them as well.

It looks like there might be room for three types for a VC head, RBG or CMY or blue / green / white. Any thoughts about a VC light source. I'd like to make one for an Omega 2 1/4 to start then go up to 8x10 when perfected.

[Henry Ambrose]

I don't know what make and model they are. Huw did the electrical parts and put the magic in the box. There are 3 blue and 3 green. Mine is VC and CE (constant exposure). Meaning that when you change the contrast the exposure remains constant.

Its a bit hard to focus because of the color but on a Focomat that doesn't matter since its autofocus. I suggest you add some white that could be switched separately on for focusing.

Go read this:

http://huws.org.uk/

These 2 links on that page:

5x4 diffuser Lead Head

LED Lit Enlarger

[Turner Reich]

Thank you, I've been over the information on Huws site and I'm no farther along than before. I thought you put together the light source on your Focomat, sorry I must have assumed too much. This I know, it's not a project for the do-it-yourselfer. There is a multitude of electronics and if the exposures are to be consistent some microprocessor programming is necessary and that requires a program engineer. Even with that there are specific design and construction details that have to be followed.

I'm beginning to know how Thomas Edison felt when he tried filament after filament when he was inventing the electric light bulb.

[rob cruickshank]

Thank you, I've been over the information on Huws site and I'm no farther along than before. I thought you put together the light source on your Focomat, sorry I must have assumed too much. This I know, it's not a project for the do-it-yourselfer. There is a multitude of electronics and if the exposures are to be consistent some microprocessor programming is necessary and that requires a program engineer. Even with that there are specific design and construction details that have to be followed.

I'm beginning to know how Thomas Edison felt when he tried filament after filament when he was inventing the electric light bulb.

It's true it's not a beginner project, but it's certainly doable by a dedicated do-it-your-selfer.
There are lots of affordable and fun programming tools out there, it's not like a decade ago when you needed a 1000 dollar development kit to do anything. One approach might be to replace the PIC processor with an Arduino:
http://www.arduino.cc/
which is a very user-friendly environment, and quite capable of doing everything required.

[Albrecht Namatdurer]

I came across these LEDS--LUMILED

http://australia.rs-online.com/web/s...4677604#header

-would anyone care to assess these as suitable for a white light source- i dont intend to complicate the issue by using blue/green LEDS- am determined to follow the dictum of keeping it simple.
And can anyone assist this colourblind clutz as to circuit/design/heatsink requirements?
thanks