Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
most LEDs come with a 120 degree lens. Assuming light distribution is conical round rather than elliptical, spacing between the rows should match the spacing between the elements on the strips. Otherwise you'd have hot spots. With a meter you should be able to change the distance up and down until you get even light readings. If you are hot above the LED the glass needs to be further and if you are hot between the element move the glass closer.here's a nice timer for anybody looking to try building one of these:http://www.auberins.com/index.php?main_page=product_info&cPath=16&products_id=368(sorry, just found this last night)I think alternating strips of different wavelengths would introduce the effects similar to hot spots as you would have different penetrating and crosslinking ability between the strips. It might be worth contacting a manufacturer in China and asking them to make strips with three different wavelengths on them (5050 strips have LEDs with three sources in each LED and can be made with RGB so it might be possible to put three different wavelengths in each unit. The problem is, all the lower nm LEDs I've seen are significantly lower Wattage than the 395-405nm). from what I can tell, PhotoPolymer emulsions are really liking 340 or so for exposure, so chances are your times would be significantly lower with lower wavelength. See chart from Ulano below: pierre
Quote from: blue moon on June 18, 2014, 08:42:53 AMmost LEDs come with a 120 degree lens. Assuming light distribution is conical round rather than elliptical, spacing between the rows should match the spacing between the elements on the strips. Otherwise you'd have hot spots. With a meter you should be able to change the distance up and down until you get even light readings. If you are hot above the LED the glass needs to be further and if you are hot between the element move the glass closer.here's a nice timer for anybody looking to try building one of these:http://www.auberins.com/index.php?main_page=product_info&cPath=16&products_id=368(sorry, just found this last night)I think alternating strips of different wavelengths would introduce the effects similar to hot spots as you would have different penetrating and crosslinking ability between the strips. It might be worth contacting a manufacturer in China and asking them to make strips with three different wavelengths on them (5050 strips have LEDs with three sources in each LED and can be made with RGB so it might be possible to put three different wavelengths in each unit. The problem is, all the lower nm LEDs I've seen are significantly lower Wattage than the 395-405nm). from what I can tell, PhotoPolymer emulsions are really liking 340 or so for exposure, so chances are your times would be significantly lower with lower wavelength. See chart from Ulano below: pierreYes, most all these strip LED's claim 120 degree lens. I did try to lay them out "square" meaning they'd have equal distance between rows and columns.While I do think a 5050 with 3 different wavelength leds would be the best, I don't think anyone is currently using that setup. In fact, I'd be willing to bet that the starlight uses all the same LED's at the same wavelength. Wouldn't it be easy to tell by reading the resistance value off the strip's resistors? That would net us the voltage to the LED's and give us a good guess that they're all the same. The 395nm range have 270ohm resistors. What's the starlight use?Distance from the glass is definitely something a UV meter might help determine IF its sensor is small/narrow/focused enough to pinpoint a change within a few nudges across the top of the glass when taking readings.When I chose the 395nm range, I used this article from screenweb to form my "opinion" on what range would work best for a cheapie diazo emulsion.If those charted images are accurate, lowering down to a 365nm LED, should yield LONGER diazo times and shorter Photopolymer times, right?
that's funny, as I was looking for that article this morning to reference it and could not find it. It shows the curves for both the penetration and sensitivity unlike the other graphs out there.In a quick recap it states the light should be 360-390 for SBQ and 390-420 for Diazo.I think 365-380-410 would probably be the best to cover all the possibilities. According to the article, you should be golden with the Diazo!Yes, the measuring portion of the UV meter is rather small, about the size of one LED, so you should be able to dial it in rather nicely!pierre
from what I can tell, PhotoPolymer emulsions are really liking 340 or so for exposure, so chances are your times would be significantly lower with lower wavelength. See chart from Ulano below: pierre
Quote from: blue moon on June 18, 2014, 08:42:53 AMfrom what I can tell, PhotoPolymer emulsions are really liking 340 or so for exposure, so chances are your times would be significantly lower with lower wavelength. See chart from Ulano below: pierreAm I reading this wrong or wouldn't the 350nm be just the perfect wavelength for everything? (if you had to pick just one) It hits SBQ at 87%, Fe+++(whatever that is) at 52% (not great but WAY better than 5% that the 405nm hits it at), Diazo at 93% and Diazo/AC (whatever that is) at 70% (again, better than 45% that the 405 hits it at).If you had to pick ONE wavelength what would it be?
Quote from: Gilligan on December 01, 2014, 06:40:23 PMQuote from: blue moon on June 18, 2014, 08:42:53 AMfrom what I can tell, PhotoPolymer emulsions are really liking 340 or so for exposure, so chances are your times would be significantly lower with lower wavelength. See chart from Ulano below: pierreAm I reading this wrong or wouldn't the 350nm be just the perfect wavelength for everything? (if you had to pick just one) It hits SBQ at 87%, Fe+++(whatever that is) at 52% (not great but WAY better than 5% that the 405nm hits it at), Diazo at 93% and Diazo/AC (whatever that is) at 70% (again, better than 45% that the 405 hits it at).If you had to pick ONE wavelength what would it be?that chart is only half of the picture (go figure!). Turns out there is penetration and activation. First one has something to do with how well the light gets through and the other is what light activates the best. They are quite a bit apart and it seem the best spot (in between both) is in the 385 or so range for most emulsions. I'll see if I can dig up the other chart.pierre