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Alternative oven interior lamps?
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tooki:

--- Quote from: thm_w on February 25, 2020, 10:35:54 pm ---
--- Quote from: tooki on February 24, 2020, 04:45:48 am ---You realize the only reason we have moved away from incandescent bulbs for general illumination is because they waste 90+% of their energy as heat? And you realize that in an oven, that makes an incandescent bulb essentially 100% efficient? Using ANYTHING else makes zero sense.
--- End quote ---

Yes and no. Microwave ovens have started moving to LED bulbs. Regular ovens will move to LEDs at some point.
Its just a matter of who can figure out how to implement them well (as nihaomike mentioned), design a high temperature LED, or can advertise it as a new unique feature and sell well.

Using a higher efficiency (and therefor brighter, with the same given circuitry and wiring), makes a lot of sense when the lighting in most ovens is quite poor.
Not to mention the downside of a single point source light, if you have it on the top, and have a tray, now all the light to the next level is blocked.

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Ummm... no, I don’t think they will switch any time soon.

There’s no reason to even attempt to make an LED capable of oven temperatures, since an incandescent bulb’s “waste” heat becomes useful heat in an oven. You’d be trading the 100% efficiency of an incandescent bulb, and its high reliability, for LEDs requiring a power supply of some sort, which have proven notoriously unreliable, especially in light fixtures that trap heat. Sure, I’m certain it’s possible to design a reliable, very high-temperature LED power supply, but that’s not going to be cheap. Pursuing LED for ovens is a fool’s errand.

The other issues you mention, like having a single light source, have nothing to do with the type of light source. There’s nothing stopping an appliance maker from putting in multiple incandescent lights instead of one.

That microwave ovens and fridges use LEDs now is irrelevant: those aren’t applications where you want the air inside the cavity to be heated, so it’s just wasted energy. Not so in a regular oven.
BravoV:
Not very sure what I'm talking about, as we all know the front door has those glass layered with the fine metal grill with fine holes, wonder if using the same glass + grill, placed inside as small lighting window which has ordinary "bright" LEDs, instead of specially made high temp LED ?  :-//

Reason of LED's advantage is, the natural white colored light, which will show true color of the food rather than the yellow light of incand. lamp.
tooki:

--- Quote from: BravoV on February 26, 2020, 03:30:43 am ---Reason of LED's advantage is, the natural white colored light, which will show true color of the food rather than the yellow light of incand. lamp.

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:-DD :-DD :-DD :-DD :-DD

You realize that color rendering of food is something that’s very hard to get right with LEDs, whereas incandescent bulbs have superb (technically, perfect) color rendering? People routinely notice that LED fridge lights make the food look ghastly. LEDs have gotten a lot better in this regard, but still cannot fully compete with sunlight and incandescent lamps, both of which are perfect black-body radiators.

The yellow color of oven lights isn’t so much from the bulbs being too yellow, it’s from the baked-on gunk on the lenses.
BravoV:
I guess it depends on own preference isn't it ? For kitchen, I prefer white light, either FL or LED, even its not near natural Sun's natural white, as incand light to me will ruin the food's color.
thermistor-guy:

--- Quote from: tooki on February 26, 2020, 03:38:53 am ---
--- Quote from: BravoV on February 26, 2020, 03:30:43 am ---Reason of LED's advantage is, the natural white colored light, which will show true color of the food rather than the yellow light of incand. lamp.

--- End quote ---

You realize that color rendering of food is something that’s very hard to get right with LEDs, whereas incandescent bulbs have superb (technically, perfect) color rendering? People routinely notice that LED fridge lights make the food look ghastly. LEDs have gotten a lot better in this regard, but still cannot fully compete with sunlight and incandescent lamps, both of which are perfect black-body radiators.
...

--- End quote ---

There is a relatively new white LED technology that uses a violet LED plus three phosphors:

https://www.toshiba-tmat.co.jp/en/case_tri_r/index.htm
http://www.solidstatelightingdesign.com/led-lighting-makers-adopt-seoul-semiconductors-sunlike-series/

The spectrum is close to natural sunlight: CRI Ra score of 99 (ideal is 100), R9 (rendition of reds) of 97 (ideal is 100). They are currently used in art galleries, museums, luxury retail stores.  Some pro athletes are experimenting with them at home, because this type of lighting seems to promote better sleep:

https://journals.sagepub.com/doi/full/10.1177/1477153519828419

and I seem to recall NASA is experimenting with it for the same reason, to help spacecraft crews.

Interestingly enough, consumers, when given a choice, actually prefer colour space coordinates that are a little below the black body locus. See slides 7 and 8 in:

https://www.energystar.gov/sites/default/files/asset/document/Energy%20Star%20webinar%20Presentation%20-%20Ohno%202.pdf

"Below the black body locus" means it has a higher red content than a black body source with the same colour temperature. Red wavelengths are important for displaying food like red fruit and vegetables, and juicy cooked meat.

Who knows, we might come to see three-phosphor white LED lighting in luxury appliances like high-end refrigerators, and maybe one day ovens.
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