White LED appropriate for illumination?
in [Design]
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From: Don Klipstein on 13 Feb 2010 23:37 In article <hl5j9d$fkm$1(a)news.eternal-september.org>, Ban wrote: > >"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >news:slrnhnchm9.588.don(a)manx.misty.com... <SNIP to here to edit for space> >> The datasheet is at: The W42180 datasheet link in: >> >> http://www.acriche.com/en/product/prd/zpowerLEDp4.asp >> >> U rank is supposed to achieve minimum 91 typically 100 lumens at 350 >> mA with heatsinkable surface of the "LED emitter" (what gets attached to >> a heatsink or a "star board") at 25 C. >> >> At this point, I like to see a bucking switching current regulator >> supplying 300 mA, with typical LED power consumption .96 to maybe .98 >> watt, and power consumption of the LED and regulator circuit combined >> maybe 1.2 watt, likely producing a goodly 80 lumens. Four alkaline AA >> cells in series should power this successfully for 6-7 hours, possibly 8 >> hours. >> >> 80 lumens, even if radiated in a manner very slightly less directional >> than lambertian, is good for 60-67 lux at 2 feet. >> >> I would prefer a few hundred lux - fair chance reasonably obtainable by >> experimenting with convex lenses, especially ones with lower f ratio. >> >> - Don Klipstein (don(a)misty.com) > >The tube I suggested puts out 250lm and apart from that is a line source >which doesn't get shielded that easily as a point source. Makes a difference >when turning the pages, with a LED, where yuo have to press down the paper >to avoid those ugly shades. So basically you would need two of your LEDs to >have a similar illumination. The OP was asking for a light to be used from 2 feet away. What fluorescent are you talking about - the 6 watt F6T5? (6 watts, 295 initial lumens, 230 design lumens) The F4T5? (4 watts, 135 initial lumens, 95 design lumens, and light emitting portion of the length about 3-3.5 inches long) A 3.5 inch line source from 2 feet away will have nearly as much of the shading you mention as a point source will. -- - Don Klipstein (don(a)misty.com)
From: Ban on 14 Feb 2010 08:48 "Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag news:slrnhnevg2.7tr.don(a)manx.misty.com... > In article <hl5j9d$fkm$1(a)news.eternal-september.org>, Ban wrote: >> >>"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >>news:slrnhnchm9.588.don(a)manx.misty.com... > > <SNIP to here to edit for space> > >>> The datasheet is at: The W42180 datasheet link in: >>> >>> http://www.acriche.com/en/product/prd/zpowerLEDp4.asp >>> >>> U rank is supposed to achieve minimum 91 typically 100 lumens at 350 >>> mA with heatsinkable surface of the "LED emitter" (what gets attached to >>> a heatsink or a "star board") at 25 C. >>> >>> At this point, I like to see a bucking switching current regulator >>> supplying 300 mA, with typical LED power consumption .96 to maybe .98 >>> watt, and power consumption of the LED and regulator circuit combined >>> maybe 1.2 watt, likely producing a goodly 80 lumens. Four alkaline AA >>> cells in series should power this successfully for 6-7 hours, possibly 8 >>> hours. >>> >>> 80 lumens, even if radiated in a manner very slightly less directional >>> than lambertian, is good for 60-67 lux at 2 feet. >>> >>> I would prefer a few hundred lux - fair chance reasonably obtainable by >>> experimenting with convex lenses, especially ones with lower f ratio. >>> >>> - Don Klipstein (don(a)misty.com) >> >>The tube I suggested puts out 250lm and apart from that is a line source >>which doesn't get shielded that easily as a point source. Makes a >>difference >>when turning the pages, with a LED, where yuo have to press down the paper >>to avoid those ugly shades. So basically you would need two of your LEDs >>to >>have a similar illumination. > > The OP was asking for a light to be used from 2 feet away. What > fluorescent are you talking about - the 6 watt F6T5? (6 watts, 295 > initial lumens, 230 design lumens) > > The F4T5? (4 watts, 135 initial lumens, 95 design lumens, and light > emitting portion of the length about 3-3.5 inches long) > A 3.5 inch line source from 2 feet away will have nearly as much of the > shading you mention as a point source will. > I had a look Osram L8W/540 Ban
From: Don Klipstein on 14 Feb 2010 12:27 In article <hl8v02$bs$1(a)news.eternal-september.org>, Ban wrote: > >"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >news:slrnhnevg2.7tr.don(a)manx.misty.com... >> In article <hl5j9d$fkm$1(a)news.eternal-september.org>, Ban wrote: >>> >>>"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >>>news:slrnhnchm9.588.don(a)manx.misty.com... >> >> <SNIP to here to edit for space> >> >>>> The datasheet is at: The W42180 datasheet link in: >>>> >>>> http://www.acriche.com/en/product/prd/zpowerLEDp4.asp >>>> >>>> U rank is supposed to achieve minimum 91 typically 100 lumens at 350 >>>> mA with heatsinkable surface of the "LED emitter" (what gets attached to >>>> a heatsink or a "star board") at 25 C. >>>> >>>> At this point, I like to see a bucking switching current regulator >>>> supplying 300 mA, with typical LED power consumption .96 to maybe .98 >>>> watt, and power consumption of the LED and regulator circuit combined >>>> maybe 1.2 watt, likely producing a goodly 80 lumens. Four alkaline AA >>>> cells in series should power this successfully for 6-7 hours, possibly 8 >>>> hours. >>>> >>>> 80 lumens, even if radiated in a manner very slightly less directional >>>> than lambertian, is good for 60-67 lux at 2 feet. >>>> >>>> I would prefer a few hundred lux - fair chance reasonably obtainable by >>>> experimenting with convex lenses, especially ones with lower f ratio. >>>> >>>> - Don Klipstein (don(a)misty.com) >>> >>>The tube I suggested puts out 250lm and apart from that is a line source >>>which doesn't get shielded that easily as a point source. Makes a >>>difference >>>when turning the pages, with a LED, where yuo have to press down the paper >>>to avoid those ugly shades. So basically you would need two of your LEDs >>>to >>>have a similar illumination. >> >> The OP was asking for a light to be used from 2 feet away. What >> fluorescent are you talking about - the 6 watt F6T5? (6 watts, 295 >> initial lumens, 230 design lumens) >> >> The F4T5? (4 watts, 135 initial lumens, 95 design lumens, and light >> emitting portion of the length about 3-3.5 inches long) >> A 3.5 inch line source from 2 feet away will have nearly as much of the >> shading you mention as a point source will. >> > >I had a look Osram L8W/540 I tried web searching for that one, and can't find it. Are you sure it's not an L 8 W /640? (Apparently equivalent or nearly equivalent to F8T5/CW) I can believe 250 lumens from underpowering that lamp at 5 watts. (I just checked my Philips catalog just now - F8T5/CW at 8 watts produces 400 lumens initial, 300 design. The L 8 W /640 achieves 385 initial lumens with 8 watts.) A 250 lumen line source, over a 100% reflective planar reflector, produces 50.7 candela, good for 136 lux at 2 feet. A lambertan emitter with no optics at all achieves that illumination with 159 lumens, maybe 180 considering that style LED often has radiation pattern a little less directional than lambertian. Two of those Seoul Semiconductor W42180-U1 will achieve 180 lumens at about 1.1 watts apiece. The efficiency of inexpensive and easy driver circuits for fluorescents and for LEDs powered from batteries is another reason why I would go with LED. - Don Klipstein (don(a)misty.com)
From: Ban on 14 Feb 2010 12:57 "Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag news:slrnhngciq.qd1.don(a)manx.misty.com... > In article <hl8v02$bs$1(a)news.eternal-september.org>, Ban wrote: >> >>"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >>news:slrnhnevg2.7tr.don(a)manx.misty.com... >>> In article <hl5j9d$fkm$1(a)news.eternal-september.org>, Ban wrote: >>>> >>>>"Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >>>>news:slrnhnchm9.588.don(a)manx.misty.com... >>> >>> <SNIP to here to edit for space> >>> >>>>> The datasheet is at: The W42180 datasheet link in: >>>>> >>>>> http://www.acriche.com/en/product/prd/zpowerLEDp4.asp >>>>> >>>>> U rank is supposed to achieve minimum 91 typically 100 lumens at 350 >>>>> mA with heatsinkable surface of the "LED emitter" (what gets attached >>>>> to >>>>> a heatsink or a "star board") at 25 C. >>>>> >>>>> At this point, I like to see a bucking switching current regulator >>>>> supplying 300 mA, with typical LED power consumption .96 to maybe .98 >>>>> watt, and power consumption of the LED and regulator circuit combined >>>>> maybe 1.2 watt, likely producing a goodly 80 lumens. Four alkaline AA >>>>> cells in series should power this successfully for 6-7 hours, possibly >>>>> 8 >>>>> hours. >>>>> >>>>> 80 lumens, even if radiated in a manner very slightly less >>>>> directional >>>>> than lambertian, is good for 60-67 lux at 2 feet. >>>>> >>>>> I would prefer a few hundred lux - fair chance reasonably obtainable >>>>> by >>>>> experimenting with convex lenses, especially ones with lower f ratio. >>>>> >>>>> - Don Klipstein (don(a)misty.com) >>>> >>>>The tube I suggested puts out 250lm and apart from that is a line source >>>>which doesn't get shielded that easily as a point source. Makes a >>>>difference >>>>when turning the pages, with a LED, where yuo have to press down the >>>>paper >>>>to avoid those ugly shades. So basically you would need two of your LEDs >>>>to >>>>have a similar illumination. >>> >>> The OP was asking for a light to be used from 2 feet away. What >>> fluorescent are you talking about - the 6 watt F6T5? (6 watts, 295 >>> initial lumens, 230 design lumens) >>> >>> The F4T5? (4 watts, 135 initial lumens, 95 design lumens, and light >>> emitting portion of the length about 3-3.5 inches long) >>> A 3.5 inch line source from 2 feet away will have nearly as much of the >>> shading you mention as a point source will. >>> >> >>I had a look Osram L8W/540 > > I tried web searching for that one, and can't find it. Are you sure > it's not an L 8 W /640? (Apparently equivalent or nearly equivalent to > F8T5/CW) > > I can believe 250 lumens from underpowering that lamp at 5 watts. > > (I just checked my Philips catalog just now - F8T5/CW at 8 watts > produces 400 lumens initial, 300 design. The L 8 W /640 achieves 385 > initial lumens with 8 watts.) > > A 250 lumen line source, over a 100% reflective planar reflector, > produces 50.7 candela, good for 136 lux at 2 feet. > > A lambertan emitter with no optics at all achieves that illumination > with 159 lumens, maybe 180 considering that style LED often has radiation > pattern a little less directional than lambertian. Two of those Seoul > Semiconductor W42180-U1 will achieve 180 lumens at about 1.1 watts apiece. > > The efficiency of inexpensive and easy driver circuits for fluorescents > and for LEDs powered from batteries is another reason why I would go with > LED. > I have it very often in use to illuminate my keyboard, when the room light is dimmed. It is in a camping light and works from 6 NiCad D-cells. So the batteries are kept alive by frequent use. I like it because the long tube doesn't make shadows and I often have to look up something in books. My distance is around 30 cms only. I also have a flashlight with a 3W LED, but it is too blueish and the reflection from the paper blinds my eyes. The /540 is right, maybe an older model, bought it almost 8years ago. cool white is written on it as well. ciao Ban
From: Robert Baer on 15 Feb 2010 06:43
Don Klipstein wrote: > In article <hl8v02$bs$1(a)news.eternal-september.org>, Ban wrote: >> "Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >> news:slrnhnevg2.7tr.don(a)manx.misty.com... >>> In article <hl5j9d$fkm$1(a)news.eternal-september.org>, Ban wrote: >>>> "Don Klipstein" <don(a)manx.misty.com> schrieb im Newsbeitrag >>>> news:slrnhnchm9.588.don(a)manx.misty.com... >>> <SNIP to here to edit for space> >>> >>>>> The datasheet is at: The W42180 datasheet link in: >>>>> >>>>> http://www.acriche.com/en/product/prd/zpowerLEDp4.asp >>>>> >>>>> U rank is supposed to achieve minimum 91 typically 100 lumens at 350 >>>>> mA with heatsinkable surface of the "LED emitter" (what gets attached to >>>>> a heatsink or a "star board") at 25 C. >>>>> >>>>> At this point, I like to see a bucking switching current regulator >>>>> supplying 300 mA, with typical LED power consumption .96 to maybe .98 >>>>> watt, and power consumption of the LED and regulator circuit combined >>>>> maybe 1.2 watt, likely producing a goodly 80 lumens. Four alkaline AA >>>>> cells in series should power this successfully for 6-7 hours, possibly 8 >>>>> hours. >>>>> >>>>> 80 lumens, even if radiated in a manner very slightly less directional >>>>> than lambertian, is good for 60-67 lux at 2 feet. >>>>> >>>>> I would prefer a few hundred lux - fair chance reasonably obtainable by >>>>> experimenting with convex lenses, especially ones with lower f ratio. >>>>> >>>>> - Don Klipstein (don(a)misty.com) >>>> The tube I suggested puts out 250lm and apart from that is a line source >>>> which doesn't get shielded that easily as a point source. Makes a >>>> difference >>>> when turning the pages, with a LED, where yuo have to press down the paper >>>> to avoid those ugly shades. So basically you would need two of your LEDs >>>> to >>>> have a similar illumination. >>> The OP was asking for a light to be used from 2 feet away. What >>> fluorescent are you talking about - the 6 watt F6T5? (6 watts, 295 >>> initial lumens, 230 design lumens) >>> >>> The F4T5? (4 watts, 135 initial lumens, 95 design lumens, and light >>> emitting portion of the length about 3-3.5 inches long) >>> A 3.5 inch line source from 2 feet away will have nearly as much of the >>> shading you mention as a point source will. >>> >> I had a look Osram L8W/540 > > I tried web searching for that one, and can't find it. Are you sure > it's not an L 8 W /640? (Apparently equivalent or nearly equivalent to > F8T5/CW) > > I can believe 250 lumens from underpowering that lamp at 5 watts. > > (I just checked my Philips catalog just now - F8T5/CW at 8 watts > produces 400 lumens initial, 300 design. The L 8 W /640 achieves 385 > initial lumens with 8 watts.) > > A 250 lumen line source, over a 100% reflective planar reflector, > produces 50.7 candela, good for 136 lux at 2 feet. > > A lambertan emitter with no optics at all achieves that illumination > with 159 lumens, maybe 180 considering that style LED often has radiation > pattern a little less directional than lambertian. Two of those Seoul > Semiconductor W42180-U1 will achieve 180 lumens at about 1.1 watts apiece. > > The efficiency of inexpensive and easy driver circuits for fluorescents > and for LEDs powered from batteries is another reason why I would go with > LED. > > - Don Klipstein (don(a)misty.com) Ghaa..lumens, candela, lux, candlepower, percent efficiency, and who knows what else (watts per steradian?)! Seems every maker uses a different "standard" not only for different LEDs they make, but also different than other makers. What are the relationships and the conversions? My basic questions concerning a given LED would be how bright is it - can i depend on the number given to tell one is brighter than another at the same drive (seems the answer is NO). |