Optical Comparator LED retrofit

.RC.

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Aug 10, 2017
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Awhile ago I picked up an old Kodak optical comparator, the main bulb (6V 100W) was blown and while still available as NOS was quite pricey. I modded and installed a 100W Halogen bulb instead. Fast forward a couple of years it would appear my retrofit was not done wisely as the first lens closest to the bulb has cracked and broken, most likely due to the more heat output.

I am wanting to retrofit a LED light in there. I found an old thread here where a person did a similar thing except on a different machine http://www.candlepowerforums.com/vb/showthread.php?297160-Optical-comparator-light-modification

Here is the patent very similar to the machine I have https://www.google.com.au/patents/US2552238 It shows that the first lens system is a condensor. Here is a machine near identical to mine showing the light throw www.ebay.com/itm/Kodak-14-034-Mod-3...ator-Fixed-Stage-Inspection-Jig-/311862059231

Are there any suggestions for a suitable LED chip to install to replace the halogen light? I do have some new lenses to replace the broken one, but I know LED's throw light differently to incandescent.
 

DrafterDan

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may I suggest presenting us with some clear guidelines? Is the thing that needs the light the small box sitting out front? What are the dimensions we need to work with? Does it have to be a spotlight or diffuse? Are you going to reuse the existing power supply, or does it need to run from the 6v supply?

I've played with optical comparators before, but not to the point of seeing how they were put together.
 

.RC.

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Yes the lamphouse is in the front of the machine. The original bulb is one of these http://www.donsbulbs.com/cgi-bin/r/b.pl/cps|6v|100w|dcmr~ansi.html

It sits behind a condensor lens system that projects light across the part being inspected, into another lens system that magnifies the shadow and projects that onto frosted glass to view.

The ideal situation is to have a point type light source. That is why I need a single chip LED. I really have no idea how powerful a light source I need, but it needs a lot. The Halogen bulb barely lit up the screen, compared to photo's I have seen of other comparators.

I have gone a bought a SST-90 LED, the modern version that can handle up to 18amps input, although the biggest driver I can find is 9 amps. As the machine had been retrofitted with a Halogen light, A computer PSU had been installed to power the halogen light with 12V.

So I have a 12V DC power supply installed in the comparator.
 

.RC.

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I should add that I found two other options.

One being the CREE XHP35, which I believe is a single chip, but slightly larger. The other is a brand new LED that does not seem to be available yet the Lumiled Luxeon V http://www.lumileds.com/products/high-power-leds/luxeon-v but it is 4mmX4mm

I think it is going to be an experiment and see.
 

.RC.

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Well I have all the bits and pieces required to test it out.

Wow the SST-90 puts out some light, and a whole lot of heat as well. At 7amps which is what the driver outputs it puts out enough light, although I would not want much less.

I think in hindsight the best LED to use would be one that has been announced, but does not yet seem to be available to buy. That being the Lumileds Luxeon V. Similar required light output (The SST-90 can be driven up to 18 amps though), smaller single die size again and less amps, so less heat.
 

.RC.

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Thought I might close off this thread with the outcome. After some trials and errors and blowing up an extremely expensive LED I have got the machine fixed.

I am now running a CREE XHP35, which is being slightly overdriven, but it is attached to a decent fan cooled heatsink. All this is held by a 3D printed holder that I designed and printed from ABS.

The LED is driven by a CC buck converter. The old lens system was removed and replaced by a single 50mm aspherical lens from Deal Extreme. It has worked out well. I still think a Luxeon V led will be the most suitable LED but it is not yet available attached to, well anything. Just bare LEDS with no boards are available at this point in time.
 
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