Alternative oven interior lamps? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: February 23, 2020, 03:29:44 am
content: My oven has three halogen interior lights, they are just the small two-pin "push in" type (12 volt from memory).I'm having to replace them every 2-6 months (presumably because they just get too hot). All that sits between the bulbs and the oven cavity is a plate of glass.Is anyone aware of better quality bulbs that might be able to stand up to the hot conditions and last longer? Alternatively, is there such a thing as an LED replacement for this application?

author: Cyberdragon
author_rank: Super Contributor
timestamp: February 23, 2020, 03:34:02 am
content: LEDs in an oven?*knee slap*

author: Halcyon
author_rank: Unknown
timestamp: February 23, 2020, 03:39:28 am
content: Quote from: Cyberdragon on February 23, 2020, 03:34:02 amI know you can get LEDs rated to high temperatures, typically 120-130 degrees Celsius. I just didn't know if a more specialised technology existed?I didn't think the question was that silly?

author: Rerouter
author_rank: Super Contributor
timestamp: February 23, 2020, 03:40:42 am
content: You stuck with incandescent types unless you want some really horrible crap being let out on whatever your cooking,If the bulb is 12V, then replace it with a bulb 2-4 times the wattage in double the voltage rating, It will last much longer. as the device internally will be operating at a lower voltage.

author: Halcyon
author_rank: Unknown
timestamp: February 23, 2020, 03:44:03 am
content: Quote from: Rerouter on February 23, 2020, 03:40:42 amThanks. That sounds like sensible advice. I'll have to check, it's either 12v or 240v. It's a GY4 type bi-pin base (I don't know if it's actually GY4 or some other variant), but they generally only come in low-voltage versions from what I commonly see.If I increase the wattage though, won't it put more load on the transformer/circuitry?

author: Rerouter
author_rank: Super Contributor
timestamp: February 23, 2020, 04:01:20 am
content: bulbs are not linear so the rule of thumb gets a bit tricky. so lets work on plain resistances as an example12W @ 12V bulb, should be 12 Ohms, so draws about 1A @ 12V48W @ 24V bulb, should be 12 ohms, so draws about 2A @ 24VRun that 48W bulb on 12V and you end up with about 12W of light, but with a greatly over-rated bulb, the light output will probably be under 12W due to the lower temperature, but you can see why my recommendation works.

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 23, 2020, 04:30:06 am
content: I suppose LEDs might be possible if you can distance them from the heat and use optics to bring the light inside. But since the heat from the halogen bulbs isn't wasteful in that application, an easier solution would be to drop the voltage to something like 80% of original. Won't look that much dimmer but will last a lot longer.

author: Andreas
author_rank: Super Contributor
timestamp: February 23, 2020, 06:18:53 am
content: Hello,do you use normal halogen lamps or special 300 degree Celsius resistant halogen oven lamps?https://www.amazon.com/Halogen-oven-lamp-capsule-tolerant/dp/B07CVLLJRX/ref=sr_1_fkmr0_2?keywords=special+halogen+oven+lamp+osram&qid=1582438627&sr=8-2-fkmr0with best regardsAndreas

author: Alti
author_rank: Frequent Contributor
timestamp: February 23, 2020, 07:26:05 am
content: I suggest tweaking with bulb wiring.Put a resistor in series.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 23, 2020, 08:44:21 am
content: I buy oven lamps in pairs, hoping one will last for ages (2 to 5 years) with a backup on hand,or if they are crap, I shop for a another brand and buy a pair of those, and repeat the aboveI keep the packaging on the good ones, and pray I can still get themand pray even harder they came from the same manufacturerI don't think the current LEDs and or their electronics will cope with oven temperatures,especially on a six hour cooking marathon of baked foods, cakes, frozen pizzas, PCB board reflows, 7018 electrode dry outs..That all said, maybe another globe in series somewhere else might work so you have a hope of a dimmer but longer lamp life,assuming the main oven lamp doesn't get 'cooked' anyway

author: jogri
author_rank: Frequent Contributor
timestamp: February 23, 2020, 01:33:22 pm
content: Quote from: Rerouter on February 23, 2020, 03:40:42 amThat would work with normal incandescent bulbs, but i am not sure if halogen lamps would survive that for long as they absolutely need the high temperatures to operate: they rely on the tungsten iodide inside the lamp to deposit onto the hottest part of the lamp (the filament), breaking apart and forming new tungsten on the filament-> it repairs itself.If you run it way below its nominal wattage, i am not sure if this process kicks in enough to counter the normal decay of the filament. It could work, but it could also fail much faster as it is ironically not hot enough for the lamp to operate properly (the oven doesn't make a difference since this process needs over 1200°C).

author: steve30
author_rank: Frequent Contributor
timestamp: February 23, 2020, 05:45:49 pm
content: No recommendations unfortunately, but I'm surprised you have to replace your oven lamps so often. My oven uses a standard tungsten "oven bulb" which usually lasts years.

author: Red Squirrel
author_rank: Super Contributor
timestamp: February 23, 2020, 06:17:09 pm
content: That got me thinking, wonder what IS the alternative? Surely they are going to stop making incandescent bulbs soon, if they haven’t already.

author: coppice
author_rank: Super Contributor
timestamp: February 23, 2020, 06:25:10 pm
content: Quote from: Halcyon on February 23, 2020, 03:29:44 amAre you buying the bulbs that are specially made for ovens? Standard bulbs won't last long, but the specially made ones are usually fine..... unless, perhaps, your oven has poor thermal design.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 24, 2020, 12:14:13 am
content: The sockets can get crusty over time and or not screwed in properly etc so not be making enough full contact with the globe, and or arcing on every start up.I've swapped out a crusty one that also sported a cracked glass dome, been good for a few yearsThey should be checked every few years and spares ordered way before, as parts may never be available again just when you need them

author: Whales
author_rank: Super Contributor
timestamp: February 24, 2020, 01:16:01 am
content: I bought some cheap replacements from eBay a while back, but they blew within a month or so.I suspect that "microwave oven" and "oven" types might be having their terminology blurred by sellers.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: February 24, 2020, 01:39:58 am
content: Quote from: Halcyon on February 23, 2020, 03:29:44 amWhat brand of bulbs are you using? They might be Chinesium specials, designed to fail quickly.My oven uses an incandescent lamp, which has lasted for many years. Recently a service tech replaced the lamp, and I had a look at it before he installed it: Smeg brand, made in Italy, still in production, rated at 300 deg. C (from memory).Oven lamps are exempt from legislation that phase out inefficient lamps with low lm/W, like incandescents and halogens, for practicality. These lamps are still in production.The filament temperature is critical. As a practical matter, for long life, you want as low a colour temperature as you can get.Aircraft incandescent lamps rated at 2E5 hours operate at 2000 Kelvin filament temperature. At 2000 K, tungsten has a vapor pressure that is just measurable - in other words, it's just starting to evaporate. Above 2000K, the evaporation increases dramatically.Another other wear-out mechanism is grain recrystallization. As the filament heats and cools, its grain boundaries reform, and start aligning with each other (instead of interlocking). This makes the filament more fragile - more likely to break because of thermal or mechanical shock. To reduce this effect, long life filaments use Rhenium tungsten which has a higher recrystallization temperature. But these are more expensive - another reason to avoid Chinese "bargains" and go with a geniune spare part from a decent brand.http://www.tlt.co.jp/tlt/english/products/industrial_light/miniature_lamp/catalog/info.htmSo, TL;DR: go for a decent brand and low colour temperature.

author: tooki
author_rank: Super Contributor
timestamp: February 24, 2020, 04:45:48 am
content: Quote from: Halcyon on February 23, 2020, 03:29:44 amYou 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.I do agree with everyone that you must make sure you're using bulbs specifically sold as oven bulbs. Ordinary ones will not stand up to the oven environment. DO NOT run halogen bulbs below their rated voltage, as jogri said. (It's OK to do so part-time, but they need full-wattage operation at least some of the time.)Quote from: Red Squirrel on February 23, 2020, 06:17:09 pmIncandescent is only banned for general lighting. They remain fully legal for decorative and specialty applications.Halogen is a more efficient subtype of incandescent, and is subject to different regulation, which is why they're still widely permissible.This isn't going to change any time soon.Quote from: thermistor-guy on February 24, 2020, 01:39:58 amExcept that this applies only to regular incandescent bulbs, and not to halogen bulbs. They are designed to run at higher temperatures and will fail sooner if they aren't allowed to run properly hot long enough. Since the OP's oven uses a halogen bulb, going for a lower color temp is not advisable. (Not that I recall ever seeing different color temp variants of halogen bulbs. Incandescent yes, but not halogen.)

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: February 25, 2020, 02:06:46 am
content: Quote from: tooki on February 24, 2020, 04:45:48 amNo, it applies to both. Going for a lower colour temperature (strictly, lower filament temperature) is still advisable if you have the choice. Halogens generally run hotter simply because they are designed to be brighter (to a human observer). The filament needs to be hot enough to dissociate the tungsten halide, but the dissociation temperature depends on the halogen fill gas - it can be below 2000 K, in which case you don't need a filament much hotter than 2000K, thereby promoting a long lamp life.

author: james_s
author_rank: Super Contributor
timestamp: February 25, 2020, 03:25:15 am
content: Halogen lamps do indeed fail more quickly if you run them too low. I remember back when those halogen torchier lamps were popular I often saw people leave them on dim for extended periods and the whole "bulb" would turn black in as little as a few hours. You'll probably extend the life if you drop the voltage slightly but if you go down too far it will get shorter. The bulb wall *must* reach sufficient temperature for the halogen cycle to work. The most common cause of short bulb life is cheaply made low quality bulbs. Next is probably a tie between excessive vibration and excessive voltage.There's really no alternative to incandescent for a high temperature application like that except for maybe HID, but that comes with its own set of problems.

author: jogri
author_rank: Frequent Contributor
timestamp: February 25, 2020, 11:08:04 am
content: Quote from: james_s on February 25, 2020, 03:25:15 amHmm, that could also be the cause if the oven fan has aquired an imbalance and isn't shock-mounted properly.

author: Electro Detective
author_rank: Super Contributor
timestamp: February 25, 2020, 09:27:06 pm
content: Fan blades may/will get sticky gunk build up, especially on the back where you can't see it, or get to it easily..and any uneven imbalance and the weight of the gunk will cause vibration and noise,vibrations that don't do heated and or aging or a cheaply made globe filament any favors, halogens even less so.Fans with little or no easy access are a pain to scrape and clean properly without deforming them, but it's either get it doneor blow money on a new one eventually after it has overworked itself to premature motor failure,add the cost of 'mystery globe fails' along the way too..

author: thm_w
author_rank: Super Contributor
timestamp: February 25, 2020, 10:35:54 pm
content: Quote from: tooki on February 24, 2020, 04:45:48 amYes and no. Microwave ovens have started moving to LED bulbs. Regular ovenswillmove 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.

author: james_s
author_rank: Super Contributor
timestamp: February 26, 2020, 12:16:27 am
content: I mean you could do it right now if you really wanted to. The double layer IR coated glass used for the oven door reflects a remarkable amount of heat back inside, the outer face of the glass is usually not too hot to touch while baking. An LED on a fan cooled heatsink behind a coated glass lens would probably be just fine. It would cost considerably more though for questionable gain. The bulb in my oven is the only incandescent lamp I can think of that I still have in service in my house. It's not used enough for energy to be an issue and I think I've had to replace it once in 10 years or so.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: February 26, 2020, 01:17:35 am
content: Quote from: james_s on February 25, 2020, 03:25:15 amThe bulb wall must be hot enough (say over 250 deg. C) so that any condensed tungsten on the wall combines with the fill gas to form tungsten halide. The filament must be hot enough to dissociate the tungsten halide and reduce net evaporation from the filament. But if both constraints are met (i.e. halogen cycle is operating), increasing the filament temperature still further, say to 3400 K, will reduce its life.

author: tooki
author_rank: Super Contributor
timestamp: February 26, 2020, 03:07:53 am
content: Quote from: thm_w on February 25, 2020, 10:35:54 pmUmmm... 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 becomesusefulheat 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.

author: BravoV
author_rank: Super Contributor
timestamp: February 26, 2020, 03:30:43 am
content: 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.

author: tooki
author_rank: Super Contributor
timestamp: February 26, 2020, 03:38:53 am
content: Quote from: BravoV on February 26, 2020, 03:30:43 amYou realize that color rendering of food is something that’sveryhard to get right with LEDs, whereas incandescent bulbs havesuperb(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.

author: BravoV
author_rank: Super Contributor
timestamp: February 26, 2020, 03:43:24 am
content: 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.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: February 26, 2020, 04:49:22 am
content: Quote from: tooki on February 26, 2020, 03:38:53 amThere 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.htmhttp://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/10.1177/1477153519828419and 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.

author: thm_w
author_rank: Super Contributor
timestamp: February 27, 2020, 12:53:27 am
content: Quote from: tooki on February 26, 2020, 03:07:53 amManufacturers do not care about waste heat or efficiency of a bulb. They might care about the energy star rating as that is a required regulation and possible advertising opportunity.A modern oven will have digital circuitry inside, so a 3.3V or a 5V rail will be present that is more than capable of powering an LED via a simple resistor.Never said you should pursue it, but it will happen at some point.QuoteSure there is nothing stopping them putting multiple halogens, but it would cost a lot more than multi-point LED strip, where LEDs are pennies vs. $ per bulb and socket for each one.Its not some huge benefit that the lamp is heating up the oven, its a few watts. If you theoretically could swap in a high temp LED, ok you've lost a few watts of heating power, which you compensate for by upping the heater coil wattage.