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LED Lighting (350 mA). Is there any standard for # of LEDs is a string?
nctnico:
--- Quote from: Benta on August 13, 2022, 09:03:43 pm ---
--- Quote from: nctnico on August 13, 2022, 08:45:14 pm ---To be sure: I'm writing about 60 milli-Watt = 0.06W!
--- End quote ---
I understand fully what you're writing.
But I've designed 150 W Class-AB amps and 20 W Class-A amps. Thermal management of 6.7 W is easy.
You keep on harping on this. Why? A standard 0.3 W resistor won't even get a little warm at 0.06 W.
--- End quote ---
Because some LEDs will fail without proper heatsinking even at power levels that look like you don't need to care about at all. You can't compare a resistor with a ceramic substrate with a LED that is mostly plastic. All in all: it is not 'harping on', it is sharing practical experience. But my remark about thermal design was aimed at T3sl4co1l. I got the impression that you missed the m for milli.
Benta:
--- Quote from: Zero999 on August 13, 2022, 09:09:35 pm ---Calculations putting the worst case into everything will often result in over-engineering, which might be acceptable in safety critical applications, but otherwise counterproductive.
--- End quote ---
Somehow, this is evolving a bit into a Pub discussion, which I like... but we should rather meet there ;)
! won't rub your nose in British car manufacturing that used your approach vs. "German over engineering". It's history.
You take a Pint, I'll take a Mass.
Cheers. ;)
Zero999:
--- Quote from: Benta on August 13, 2022, 09:41:46 pm ---
--- Quote from: Zero999 on August 13, 2022, 09:09:35 pm ---Calculations putting the worst case into everything will often result in over-engineering, which might be acceptable in safety critical applications, but otherwise counterproductive.
--- End quote ---
Somehow, this is evolving a bit into a Pub discussion, which I like... but we should rather meet there ;)
! won't rub your nose into British car manufacturing that used your approach vs. "German over engineering". It's history.
You take a Pint, I'll take a Mass.
Cheers. ;)
--- End quote ---
German over-engineering didn't win the war. :P
How many of these are you going to make? Your original post says you're using second hand power supplies. I doubt it needs to meet stringent quality assurance. It's definitely feasible to just measure the forward voltages.
Kjelt:
--- Quote from: Benta on August 13, 2022, 09:41:46 pm ---! won't rub your nose in British car manufacturing that used your approach vs. "German over engineering". It's history.
--- End quote ---
Uhum the most reliable cars remain the japanese cars, some german cars being very unreliable. Just google it :)
T3sl4co1l:
--- Quote from: nctnico on August 13, 2022, 09:17:09 pm ---
--- Quote from: Benta on August 13, 2022, 09:03:43 pm ---You keep on harping on this. Why? A standard 0.3 W resistor won't even get a little warm at 0.06 W.
--- End quote ---
Because some LEDs will fail without proper heatsinking even at power levels that look like you don't need to care about at all. You can't compare a resistor with a ceramic substrate with a LED that is mostly plastic. All in all: it is not 'harping on', it is sharing practical experience. But my remark about thermal design was aimed at T3sl4co1l. I got the impression that you missed the m for milli.
--- End quote ---
Indeed, a recent project I had to use 0402 white and green LEDs for indication, and had no room for even much trace width to keep them cool. They ended up multiplexed at fairly modest intensity though (partly for matching intensity with the much dimmer red LEDs, partly didn't need full intensity anyway) so it's probably fine. 4-layer board as well, but that really isn't going to help as much as you'd want when the component width is barely more than the laminate thickness (well, something like that anyways; would be neat to get some measurements to see by how much!).
Tim
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