UV LED Strip Advice please

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Rolleiflexible said:

There is an easier way. You can buy a pair of 96w UV LED Onforu fixtures for about $60. Mount them side by side and you have an 11x15-inch light. Doubled, 15x22 inches for $125.

I have been using them with a vacuum frame for Kallitypes and my exposure time is 22 seconds. I just bought four more so I can print 22x30 sheets. I can’t say enough good things about these lamps — well-built, reliable, cheap, powerful.

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Would this evenly expose 17x22 ?

bryans_tx said:

Would this evenly expose 17x22 ?

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From a couple of inches distance, I think so, yes, assuming you go for the 15x22 option he mentioned.

Keep in mind as you increase the distance between the light source and the printing frame, you gain some exposure area/size. With LEDs it's less than with tubes and especially metal halide bulbs since the light of LEDs tends to be a little more directional, although most come with a fairly wide angle 105 degree lens fitted onto the die.

As to the metal halide bulb in the machine you might get from your workplace: it's a 400W unit which will do OK for your purpose, but it won't fit in the drawer idea. You'll have to place it at something like 3ft minimum from the printing frame, which is also necessary to keep the print from heating up during longer exposures when printing with processes that are sensitive to this (carbon, gum probably too). The advantage is that a metal halide bulb is a point source, although the practical relevance of this advantage depends a lot on what and how you print - in most alt. process printing it's not reall necessary.

Personally I find metal halide bulbs a little awkward; they take time to heat up, they emit a truckload of heat and light you don't need, their light output tends to reduce as they age (which is more pronounced and happens quicker than with LEDs) and there's the whole distance thing...in your place, I frankly wouldn't recommend that direction. On the other hand, some printers really swear by their metal halide setups - but these are nearly invariably people who have been printing for decades and who are really intimately familiar with and attached to their trusted equipment.

If I built another exposure unit today I'd probably use the pre housed strip LEDs, or something like Sanders linked to. Just use as many as you need. You need to see what times people are getting with the LEDs you are looking at because a little time now could save you an enormous amount of time later.

I built mine about 4 or so years ago before housed LEDs were available. I used the LEDs that came on a roll. I had to buy a few of them of course. These are the ones I used according to Amazon-www.amazon.com/gp/product/B07D7RKJYS

I packed them as tight as I could and offset them by half and wired the strips in parallel I think it is called (positive on one end and negative on the other. All positives connected together and all negs connected together). The biggest pain was all the soldering. I used some pretty heavy gauge solid copper wire I picked up at Home Depot in the scrap section. I also put some computer fans in the end of it and a 12v 30a power source. It was a lot of work. In the end though, I have an exposure unit that is very fast. I get times for cyanotype as fast as 1:30. My times are far less than a friend who has a NuArc plateburner. Compared to the old way of doing it with Fl tubes it just isn't comparable. Those got me like 1/2 hour.

I think the whole thing cost me around $130, but all the parts are cheaper now.

The only thing I would change about it is I wish I had made it bigger. The LED area is something like 16x24 I think since I was shooting for 13" prints. I should have just made it big enough to do 17" prints. I guess there can always be a version II. Here is what it looks like on the inside. You'll also notice that I made it pretty thin. I don't remember the math I did but I wanted the LEDs to be as close as possible and still be even. It worked. I get perfectly even prints.

Nice looking photo of the interior!
enjoyed your galleries as well

That dymax 5000 is one scary animal. Probably a good way to accidentally set the house on fire! the Bulb may very well have many many hours on it, no doubt they were curing some sort of resin/adhesive.
I am better off without it.

LEDs arrived. Much work to do.

So I made a Sun exposure, complete with dang cat hairs. grrr. Cats.
Dill Plant
bad scan on a standard printer with a scanner. LOL

If the cat hairs print crisply, the process is working well

lol

The UV box is built!i
Id post a pic.. but it’s well… like my photos , not exactly professional… haha.
Functional. I may need another oh two maybe three strips. 24x24 takes a lot of them!
I kinda ran out..
It’s ok, I accept my fate lol.
Dang thing pulls 10A at 12v. Luckily I have a honker 30a supply for ham radio!
Yeah it’s almost 2am, dang leg cramp

Cool! Looking forward to your results.

bryans_tx said:

Dang thing pulls 10A at 12v.

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Yeah, it adds up fast. With high-power LEDs, I usually move up to 24V or 48V to keep current down. But 10A is manageable.

Looks like about 4 minutes exposure time for a nice blue. I actually removed a few strips.
As expected some of the strips (eventuality probably all) started coming loose from the painted and sanded wood surface. Re-did those with contact cement. I think that will hold up for a while. That also gave me
the opportunity to re-align and re-space some of the strips.

it may be a mother loves it ugly, though it is colorful. I may just paint on some racing stripes or something..
front door is held on by two Magnets.... I need to add a third at top middle.

"Purple mountain haze majesty"

26 strips, smd5050. Six inches high. I will experiment a bit with height, by adding wood blocks underneath. Bought some 1x1 basswood for that.

PS that black plastic in background... I drape that over bathroom door edges, close door, light tight

Such a crazy way to make images lol.
I’m up to 20 minutes exposure haha

Your help was not wasted