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| LED driver at -40degc ambient |
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| Zero999:
--- Quote from: tooki on August 21, 2018, 03:41:52 pm ---Wouldn't one solution be to simply install small thermostatically controlled heaters into the units to always keep them above the critical temperature? --- End quote --- Wouldn't that defeat the main benefit of LED lamps: efficiency? I suppose the heaters could be put on a timer, so they only have to turn on for an hour or so a week, to get the temperature above 15°C. Painting the case black may also help absorb sunlight in the summer to raise its temperature above 15°C, even if the air is cooler. --- Quote from: Ian.M on August 21, 2018, 03:39:40 pm ---It can take a total of a couple of years below -10°C to initially trigger it, so summer temperatures are a key factor as if they reliably get above about 15° C, it will 'reset the clock' on it. That means its got a vanishingly small probability of occurring except in outdoor fixed installations in the high Arctic or above the snow-line, or installation in walk-in freezers etc. Any portable electronics or vehicle is likely to be brought into a shirt-sleeve environment at least annually. If Treez is selling fixed exterior LED lamps to the Alaskan oil industry he probably should worry about it. --- End quote --- What's worse, extreme cold or lack of warmth in summer? His product might not be used in such extreme places as Alaska. There are a few places in the UK which barely get above 15°C in summer, but they don't get much below -10°C in winter. One example is Cairn Gorm, which usually gets below -10°C in winter, but doesn't normally get much above 15°C in summer. https://en.wikipedia.org/wiki/Cairn_Gorm#Climate |
| tooki:
--- Quote from: Hero999 on August 21, 2018, 04:06:11 pm --- --- Quote from: tooki on August 21, 2018, 03:41:52 pm ---Wouldn't one solution be to simply install small thermostatically controlled heaters into the units to always keep them above the critical temperature? --- End quote --- Wouldn't that defeat the main benefit of LED lamps: efficiency? --- End quote --- Absolutely!! It really does beg the question of whether LED is optimal for all situations. --- Quote from: Hero999 on August 21, 2018, 04:06:11 pm ---I suppose the heaters could be put on a timer, so they only have to turn on for an hour or so a week, to get the temperature above 15°C. Painting the case black may also help absorb sunlight in the summer to raise its temperature above 15°C, even if the air is cooler. --- End quote --- Aye. --- Quote from: Ian.M on August 21, 2018, 03:58:11 pm ---Yep. However, running a heater 24/7 isn't going to do you any favours for energy efficiency, especially if your refrigeration plant has to get rid of the waste heat from the small heaters keeping the lights nice and toasty. --- End quote --- Well treez seems to work for a company making street lights, so that's the intended application, I assume. But you'd be right, of course. (I sometimes chuckle when I go past the hot food bar in a US grocery store, throwing off tons of heat into a space that's being refrigerated down aggressively…) |
| Ian.M:
--- Quote from: Hero999 on August 21, 2018, 04:06:11 pm ---What's worse, extreme cold or lack of warmth in summer? --- End quote --- I don't know - if I did, (and had the data to back it up) I could make good money as a low temperature reliability consultant! I also don't have data on how long and how much it needs to be above the transition temperature to reliably convert all grey tin back to white tin. If anyone wants to experiment, put a ziploc bag with a small coil of >99% Sn SnCu solder deep in the freezer, and when its well chilled bend it a few times without letting it warm above zero, then leave it in the freezer and check it weekly. If the paper I linked is reproducible, there's a significant chance you'll have grey tin to play with in a few weeks time. |
| Whales:
--- Quote from: tooki on August 21, 2018, 04:16:34 pm --- --- Quote from: Hero999 on August 21, 2018, 04:06:11 pm --- --- Quote from: tooki on August 21, 2018, 03:41:52 pm ---Wouldn't one solution be to simply install small thermostatically controlled heaters into the units to always keep them above the critical temperature? --- End quote --- Wouldn't that defeat the main benefit of LED lamps: efficiency? --- End quote --- Absolutely!! It really does beg the question of whether LED is optimal for all situations. --- End quote --- Not entirely. LEDs + dedicated heaters can outlast filament bulbs, incans and the likes by large factors (if designed correctly). This might be very important in cold locations if changing the bulbs/units is hard, or it might not be important at all. |
| mzzj:
--- Quote from: Ian.M on August 21, 2018, 03:58:11 pm ---Yep. However, running a heater 24/7 isn't going to do you any favours for energy efficiency, especially if your refrigeration plant has to get rid of the waste heat from the small heaters keeping the lights nice and toasty. Also, this reasonably recent paper is scary: https://www.emeraldinsight.com/doi/full/10.1108/SSMT-10-2013-0027 If their results are reproducible, it looks like the combination of low temperatures, the wrong solder alloy and mechanical stress can induce tin pest *WITHOUT* inoculation by grey tin dust in under a fortnight, which means a massive logistics problem maintaining heated storage so it isn't already compromised when you install it. --- End quote --- Why everyone is fixated about heaters when there is tens of watts of heat coming from the leds itself in the same package? >:D Unless this is a lighting for darkened cryo storage room :-DD I found the same paper about tin rot earlier but it was bit too much accelerated testing again vs real-world probabilities. One point from that paper is that it might be bad idea to tighten any mounting screws over tinned areas of pcb. And I'm not saying that you should ignore tin pest in every case, life supporting equipment on McMurdo station for example.. |
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