LED Filament lamp teardown - Page 1
Forum section: electronics / general

author: Zero999
author_rank: Super Contributor
timestamp: November 26, 2014, 03:52:28 pm
content: Have you ever seen one of these?They look good!

author: SeanB
author_rank: Super Contributor
timestamp: November 26, 2014, 04:51:08 pm
content: You mean like this one? Dimmed so you can actually see the filament in the lamp along with the whole lamp.

author: fubar.gr
author_rank: Unknown
timestamp: November 26, 2014, 05:58:56 pm
content: Quote from: SeanB on November 26, 2014, 04:51:08 pmThey are not the sameThis is a modern "carbon" filament style bulb. I don't think the filament is actual carbon, I guess it simply uses a longer tungsten filament for more resistance, hence the vintage glow.The other bulb has long shaped LEDs that resemble a filament.

author: SeanB
author_rank: Super Contributor
timestamp: November 26, 2014, 06:14:47 pm
content: I doubt whether being made before 1939 is classed as modern..........The LED lamps are trying to emulate this style.

author: fubar.gr
author_rank: Unknown
timestamp: November 26, 2014, 06:35:40 pm
content: Quote from: SeanB on November 26, 2014, 06:14:47 pmDoh! I thought it was one of these retro style bulbs that are getting quite popularhttps://www.1000bulbs.com/category/antique-light-bulbs/All these are currently made. Shouldn't these be banned along with regular incandescents?

author: Zero999
author_rank: Super Contributor
timestamp: November 26, 2014, 08:54:10 pm
content: I thought incandescents were on their way out anyway apart from in ovens when temperature is an issue?No I'm not talking about incandescents, watch the videos. I mean LED lights which mimic old filament lamps by using standard 5mm LED dies on tiny phosphor substrates.They look like this when lit.And this when offThe yellow phosphor is clearly visible.The filament style LEDs can be purchased separately.http://selectronic.co.uk/360-omni-directional-led-filament/

author: macboy
author_rank: Super Contributor
timestamp: November 26, 2014, 09:10:53 pm
content: I wonder how long these will last without any heatsinking? How hot do those "filaments" get. Even with their higher efficiency, a typical LED lamps will use 7 to 13 W of power, and a lot of that is still heat. Aside from that, I really like these!

author: IanB
author_rank: Super Contributor
timestamp: November 26, 2014, 09:34:23 pm
content: Quote from: macboy on November 26, 2014, 09:10:53 pmIf one assumes the bulb is full of nitrogen there is plenty of convective cooling available by circulating gas currents around the filaments.Let's suppose a 6 W lamp has 96 LED dies, that would be 63 mW per die. At a forward voltage of 3.2 V that would be a current of 20 mA.A normal 5 mm white LED in a plastic package doesn't get at all warm running at 20 mA, so I don't see any heat control issues here.

author: Zero999
author_rank: Super Contributor
timestamp: November 27, 2014, 01:44:45 pm
content: Yes, it does seem like they're filled with a gas to help to dissipate the heat.http://www.designingwithleds.com/novel-led-packaging-adds-filaments-retro-bulbs/http://www.z-light.com.cn/d/file/product/newseries/dengsi/20140217/105lmZR39WWV5C21001.pdfhttp://my.tv.sohu.com/us/214591119/69869468.shtml

author: SeanB
author_rank: Super Contributor
timestamp: November 27, 2014, 04:17:14 pm
content: Quote from: fubar.gr on November 26, 2014, 06:35:40 pmSpecial purpose lamps ( like rough service and oven lamps) are exempt.I have a whole box of these, though half are inside frosted versions, which give out a lovely even light. most made in Germany pre war by Siemens, who I doubt even makes lights any more other than speciality lamps, railway and aircraft lights.

author: blackice504
author_rank: Contributor
timestamp: November 30, 2014, 10:59:00 am
content: Thanks for this i seen them on ebay after i was looking for a part for my friends old school lamp "brass and plastic" bayonet lamp fitting, and got me thinking i wonder if you can get them longer as my friend is into light sabers << MY FRIEND NOT ME. "i don't like star wars" place inside like a small solid tube plastic, maybe get different colour it might look good then again it might not work as people mentioned heat and that thought did cross my mind.Its really cool to know people are trying different things and just think back in the day it was only used as a Status light.I replaced the RED LED on my smd rework station with a blue one as they blue one makes it work better.........Also blue PC fans are cold, Red PC, are fast and hot, Green PC fans you should stay away from that pc as its radioactiveThanks for the tear down links i really enjoyed it mmmmm electric porn.

author: richms
author_rank: Contributor
timestamp: December 02, 2014, 08:02:13 am
content: Have bought a few of them.At low colour temperatures they are quite convincing, but ugly to work under etc.The higher colour temperature ones just look "wrong"Also most of the ones I bought have 100Hz flicker in the output. The only ones that dont have a big ugly white bit between the E27 thread and the glass envelope. The ones that look like a nicer lamp seem to just be rectifying mains thru a dropper and have the resulting long off time as the voltage is below the foward voltage of the long string. When dimmed they get even worse making things look like a strobe light freezing motion.

author: Zero999
author_rank: Super Contributor
timestamp: December 03, 2014, 12:20:33 pm
content: Quote from: richms on December 02, 2014, 08:02:13 amThanks for the feedback. I'm looking for LED lamps so will bear this in mind.

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2015, 06:09:46 pm
content: I bought the following:6W LED Filament Light Bulb Lamp Candle Round Glass Warm White 2700khttp://www.ebay.co.uk/itm/121470375031?_trksid=p2059210.m2749.l2649&var=420409229809&ssPageName=STRK%3AMEBIDX%3AITThe colour temperature is slightly lower than a typical incandescent lamp: more yellowish so good for a lounge or bedroom but not for a workshop or kitchen. They're certainly bright enough, with three 6W bulbs being enough to light a conservatory.There is a bit of flicker but it's only noticeable for fast moving objects, so no good in a room with a model railway but fine for a lounge.

author: IanB
author_rank: Super Contributor
timestamp: January 02, 2015, 06:21:38 pm
content: I'm puzzled by a 240 V lamp with an ES base? From childhood memory nearly all UK lamp fittings used a bayonet cap (except for specialty lamps). Are there more screw fitting lamp sockets around now, or is this not the UK? (Bearing in mind the eBay.co.uk address.)

author: kolbep
author_rank: Frequent Contributor
timestamp: January 02, 2015, 06:56:29 pm
content: E27 bases are used in South Africa,in fact, they seem to be used more than Bayonet Clip bulbs,in the last year I have come across hundreds of fittings with es bulbs, and only about 30 that used bc.the only downside with the es is that your holder has to be wired with live on the center pin (so the thread is not live when you touch it.obviously this cannot be a definate if non-polarised plugs are used...

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2015, 07:21:35 pm
content: Blame the proliferation of the PRC manufacturers. They used an ES base for the USA market, and when they started to do worldwide supply they simply continued using the existing lamp bases they had. There is a slight difference in the socket sizes though, but for most users this is not noticeable, with the E27 socket being slightly deeper from thread start to the centre contact. just means some US made lamps will not light in an E27 socket unless you screw it in very tight.

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2015, 09:52:45 pm
content: Quote from: IanB on January 02, 2015, 06:21:38 pmYes I'm in the UK and bayonet is still the most common fitting.Where I live there are all different sorts of lamp fittings: B22, B15, ES22, ES15, GU10 and MR12. It's ridicules. I think it's because my parents had different rooms wired at different times and the electrician just used a random fitting.The LED filament lamps only seem to be available in ES format for a reasonable price. It's actually cheaper to buy an adaptor and the ES variety than a B22 lamp!On the whole I think ES is inferior because we've had more problems with the incandescent lamp bases welding to the lamp holder. Fortunately now with the LEDs it shouldn't make any difference because they don't get hot.

author: MiataMuc
author_rank: Regular Contributor
timestamp: January 02, 2015, 10:28:46 pm
content: in Germany, ES27 and ES14 are used; the only bajonet-style lamp I know belongs to my aunt; I always thought this lamp to be of italian origin.Modern bulbs in here are usually marked with a 220-240V rating.

author: Corporate666
author_rank: Unknown
timestamp: January 03, 2015, 12:28:21 am
content: Has anyone done a teardown of one of these lamps?I'm very curious how the "filament" is made. Is it a line of small dies along the surface of a metallic bar? Or is it somehow an elongated die with multiple bond wires?It would seem that controlling the phosphor thickness in such a package would have to be a nightmare!

author: artag
author_rank: Super Contributor
timestamp: January 03, 2015, 12:35:28 am
content: UK lamp fittings are usually bayonet, but ES is far from rare - mostly in table lamps and other decoratives rather than ceiling fittings. This is possibly due to importing decorative lamps from mainland europe where ES and SES are the default.

author: sleemanj
author_rank: Super Contributor
timestamp: January 03, 2015, 02:28:40 am
content: Quote from: Corporate666 on January 03, 2015, 12:28:21 amYes, it's a series connection of die (dies?).bigclive has done a few things with filament style leds...Quote from: artag on January 03, 2015, 12:35:28 amHere in NZ, ceiling lights are bayonet, except for recessed downlights which are ES, table lamps are often ES as well (probably because imported from China).

author: TSL
author_rank: Regular Contributor
timestamp: January 03, 2015, 02:40:20 am
content: Quote from: IanB on January 02, 2015, 06:21:38 pmThey're quite popular in Australia too, about 50% of the lights in my house were ES until I swapped all but two for integral LED units. The last two I just haven't go there yet.IKEA lighting is mostly ES.regardsTim

author: Zero999
author_rank: Super Contributor
timestamp: January 03, 2015, 09:09:53 pm
content: Quote from: sleemanj on January 03, 2015, 02:28:40 amThanks for posting those links.They're quite good, considering the simplicity of the circuits.I wonder if the sort with the larger base are better?I've ordered some of these 6W bulbs, which at £3.79 and free postage is a bargain. The others were also 6W but £5 each, including postage.http://www.ebay.co.uk/itm/281407901938?_trksid=p2060778.m2749.l2648&var=580434804439&ssPageName=STRK%3AMEBIDX%3AITThe base appears to be larger too so I hope it has a better driver circuit inside.

author: Howardlong
author_rank: Super Contributor
timestamp: January 03, 2015, 09:31:17 pm
content: Quote from: TSL on January 03, 2015, 02:40:20 amUntil Ikea came to the UK about 30 odd years ago it was all bayonet fitting in domestic lamps, now I'd say bayonet in in the minority, both from the predominance of Ikea screw fit and slightly more recently halogens.

author: Zero999
author_rank: Super Contributor
timestamp: January 04, 2015, 12:27:19 pm
content: Quote from: sleemanj on January 03, 2015, 02:28:40 amIn that video he tears down of a lamp which looks similar to the one I've bought and it has a SM2082B current linear regulator IC inside it. The problem with that is it overheats, causing the thermal protection to kick in which lowers the current and causes light output to fall after the lamp has been lit for a minute.Fortunately the one I've got doesn't seem to have that problem. The base remains cool (much more so than the bulb, even after being turned on for over an hour) and I don't have a light meter but it doesn't seem to dim, when left on for awhile.

author: Zepnat
author_rank: Regular Contributor
timestamp: January 04, 2015, 01:22:07 pm
content: I've been using two of these led filament bulbs for about a month. I think they give a nicer light than the energy efficient bulbs, almost indistinguishable from bulbs of old. And of course instant brightness no warm up. Reliability remains to be proven. Just wish they were cheaper but they are hand made.

author: Zepnat
author_rank: Regular Contributor
timestamp: January 04, 2015, 01:32:27 pm
content: Here is a datasheet on one of the sellers websites they seems to run about 75v at 10mahttp://www.alibaba.com/product-detail/Factory-filament-120-130lm-w-RoHS_60031980095.html

author: Zero999
author_rank: Super Contributor
timestamp: January 04, 2015, 02:16:31 pm
content: They're expensive because each of those filaments contain 28 LED dies, probably similar to those used in standard epoxy 3mm & 5mm LEDs used in torches and as indicators.http://www.with-led.com/led-filament.htmlhttp://www.aliexpress.com/store/product/LED-filament-chip-1W-for-bulb-light-13mA-74-8v-112LM-W-warm-cool-white-Light/528280_1862140831.htmlEach LED filament is rated to just under 1W so they're six in a 6W lamp, giving 6*28 = 168 LED dies in total. I think the price is quite reasonable considering how many LEDs you're getting and the labour involved in assembling it.

author: mikerj
author_rank: Super Contributor
timestamp: January 04, 2015, 08:17:56 pm
content: Quote from: Hero999 on January 02, 2015, 09:52:45 pmThe odd thing is if you go to a supermarket in the UK, the range of ES base lamps is often far greater than the bayonet cap lamps.

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2015, 04:27:07 pm
content: Quote from: Corporate666 on January 03, 2015, 12:28:21 amThe phosphor doesn't seem to be very well controlled.The filaments in the bulbs I have are slightly different colour temperatures when lit. If I turn the bulb round, looking at the light shone on to a white surface, I can see the colour temperature changes, depending on how I rotate the bulb.

author: IanB
author_rank: Super Contributor
timestamp: January 05, 2015, 05:24:23 pm
content: Quote from: Hero999 on January 05, 2015, 04:27:07 pmI saw some examples of these LED filaments a few days ago. I noticed a considerable colour variation between samples, where some were rather more yellow than others. It wasn't clear if this was how they were from new, or whether the original colours might have changed over time.Also, it is worth remembering that the strips have a front side and a back side. The illumination is less bright and of a different colour when viewed from the back. So they are not omnidirectional like a hot wire filament would be.

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2015, 08:14:33 pm
content: Quote from: IanB on January 05, 2015, 05:24:23 pmI bought the bulbs new and they've been like that from day one. It's not that noticeable. I wonder if it will get worse/better as the lamps age?You have a point about the strips having a front and a back which may cause this or be a contributing factor.

author: SeanB
author_rank: Super Contributor
timestamp: January 05, 2015, 08:22:41 pm
content: I would guess the lamps are dipped after assembly in a phosphor stream to coat them, and the mix is diluted to the point where it leaves a thin somewhat even coat. You likely have a long strip with the lamp units clamped in it and then the liquid is poured over as it is over a catch tray, then it air dries and is redone till it is deemed thick enough ( x passes) then it is ovened or left overnight to flash off.Likely the lamps used are bulk bare cases and such bought from a lamp glass manufacturer. Then a quick spot welding and slide the finished lamp into the housing then flame seal, and then vacuum down to flash off the last solvents and then a nitrogen gas fill for heat transfer, while keeping the lamp from oxygen which will degrade it.

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2015, 08:47:24 pm
content: Quote from: SeanB on January 05, 2015, 08:22:41 pmThe phosphor is already on the LED filaments before they're put into the bulb.Here's a video showing them being made in China. What a boring job?It doesn't show them vacuuming the bulbs and backfilling them, perhaps they're just filled with air?

author: SeanB
author_rank: Super Contributor
timestamp: January 06, 2015, 08:08:10 pm
content: The led strips are made and coated, then this video shows them being assembled into lamps. Note that they are using parts of an old automated lamp plant, probably an old European plant that was shipped to China, and there they substituted labour for part of the plant. You do not see the pumping down as it is done on the sealing station, it just looks like they turn the lamp around, then it falls off after the seal, but there it has a quick pump down then a fill of nitrogen at atmospheric pressure ( or slightly below) then it is sealed. you need the depressed pressure for the pinch off seal to work properly. You can see they are using product from a standard lamp plant glass plant, just with 4 leadouts in some cases, or using the support wires as connections.

author: Axk
author_rank: Regular Contributor
timestamp: August 17, 2019, 08:35:15 pm
content: Just bought one of these lamps, E27 socket.What surprised me that it has no low frequency flicker that I can detect and it doesn't appear to have much circuitry in it either, everything fits in the screw.I've measured it with a PIN photodiode connected to an oscilloscope with AC input mode.This same measurement setup does show the 100Hz sinusoidal flicker from regular tungsten bulps.With this LED filament bulp I only see some small pulsations at around 50-100KHz.Wonder how they managed to get rid of the mains pulsations.Edit: it does have a 100Hz component to the flicker but it is very small amplitude, smaller than incandescent lamp's flicker and most of the flicker is this 100KHz high frequency component.

author: Axk
author_rank: Regular Contributor
timestamp: August 17, 2019, 09:21:19 pm
content: It does have a DC-DC converter inside the screw I suppose.I suppose because it only drops it to around 70V it has higher efficiency so the screw can dissipate the heat.Found this teardown of a similar Philips bulp:https://www.youtube.com/watch?v=qstka-42HUM.They even managed to squeeze a small transformer in the screw!

author: StillTrying
author_rank: Super Contributor
timestamp: August 17, 2019, 10:07:12 pm
content: Quote from: Axk on August 17, 2019, 08:35:15 pmIn theory you should get a more accurate wave shape with a 10k to 20k resistor in parallel with the PD, and the scope on DC.I've looked at the light shapes from few light sources here, but not aLED filamentbulb - yet.https://www.eevblog.com/forum/chat/20w-halogen-bulb-viewed-by-a-photodiode/

author: David Hess
author_rank: Super Contributor
timestamp: August 18, 2019, 03:02:10 am
content: Quote from: macboy on November 26, 2014, 09:10:53 pmHandling the power dissipation is a major problem and limits the operating life which is much worse than a properly cooled LED lamp.Quote from: Corporate666 on January 03, 2015, 12:28:21 amThe LEDs are mounted to a high temperature transparent substrate like sapphire so the light is emitted from all sides.