I dont understand the wattage of these IR  leds. Please help ! - Page 1
Forum section: electronics / beginners

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: January 20, 2019, 08:24:35 pm
content: I am looking for high power 940nm IR ledsThese ones should be OKhttps://www.aliexpress.com/item/High-Power-LED-Chip-Infrared-850nm-IR-LED-1W-3W-5W-10W-20W-30W-50W-100W/32631733161.html?spm=2114.search0104.3.1.1b93f00dnR6XhD&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10068_319_10892_317_10696_453_10084_454_10083_433_10618_431_10304_10307_10820_10821_537_10302_536_5736111_5736011_10843_10059_10884_10887_100031_321_322_10103-10892,searchweb201603_53,ppcSwitch_0&algo_expid=560ced6f-919e-4910-a845-f853519b784e-0&algo_pvid=560ced6f-919e-4910-a845-f853519b784eBut I dont understand their counts for wattage. In their tablefor example, for 20 w you have forward voltage : 12-14V and Forward current : 600mAIf I count, it makes at max 8.4 W and not 20W. It is the same for all the other 940nm leds, and this is actually what seems to be roughly what is written on the bags ( 10w : 5-6V, 900mA).HOW CAN IT BE ? Which led driver should I use then ?Thanks for any help

author: Benta
author_rank: Super Contributor
timestamp: January 20, 2019, 09:17:23 pm
content: Impressive! Aliexpress offers over-unity energy.There's a reason why I've never bought something from there.

author: glarsson
author_rank: Frequent Contributor
timestamp: January 20, 2019, 09:37:07 pm
content: About the standard difference between standard W and Chinese W when used for LEDs.

author: Benta
author_rank: Super Contributor
timestamp: January 20, 2019, 09:44:21 pm
content: Quote from: glarsson on January 20, 2019, 09:37:07 pmHahaha!Seriously though, perhaps they mean W/sr? But without a radiation pattern, this is useless as well.

author: james_s
author_rank: Super Contributor
timestamp: January 20, 2019, 09:52:37 pm
content: My experience with specs on this sort of random Chinese stuff is they just make something up, you really can't rely on any of the data.

author: westfw
author_rank: Super Contributor
timestamp: January 21, 2019, 06:13:09 am
content: I believe it probably means "this is the same substrate that we fill with white LEDs to yield a 20W (?) aggregate part, only stuffed with IR LEDs instead. Max current remains the same (?) and Vf is lower - isn't that great?"

author: RoGeorge
author_rank: Super Contributor
timestamp: January 21, 2019, 06:31:16 am
content: Those watts means:- this "20W" LED will produce the same amount of light as a 20W incandescent light bulb- the "20W" is unrelated with how much power the LED requires in order to produce the equivalent light of a "20W classical incandescent light bulb". Usually the LED will require less power than a light bulb.Later edit:Sorry, I missed the LEDs here are IR.

author: james_s
author_rank: Super Contributor
timestamp: January 21, 2019, 07:57:29 am
content: That doesn't make any sense for IR LEDs, and even for visible types, I have a lot of 10W and 20W white LEDs that are WAY brighter than 10 or 20W incandescent.

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: January 21, 2019, 08:02:19 am
content: Quote from: westfw on January 21, 2019, 06:13:09 amThis looks like a probable answer. Indeed, for their white leds, there is not this inconsistency. I have asked directly to hte store. They answered very rapidly, but not in a very satisfactory manner. I probably did not went beyond the first level of support.QuoteEven with 700mA, it is only 10W, and not 20W.

author: Towger
author_rank: Super Contributor
timestamp: January 21, 2019, 08:16:47 am
content: Chinese watts. Derate by 50% and a bit more if you want them to last.

author: spec
author_rank: Frequent Contributor
timestamp: January 21, 2019, 11:29:17 am
content: (update #1 2019_01_21)Hi AlcidePiR2Don't try to rationalize specifications for any commercial component/equipment or you will go insane in the brain, just get to the important characteristics. With IR LEDs, they are:input electrical powerIR output powerIR frequencybeam patternlife

author: Zero999
author_rank: Super Contributor
timestamp: January 21, 2019, 11:42:58 am
content: Quote from: spec on January 21, 2019, 11:29:17 amThe second two: lumens and colour temperature are only relevant to visible LEDs. The LED linked to above is infrared so will have a very low output in lumens: near zero.The colour temperature is only relevant to white LEDs. Colour LEDs are normally specified as the dominant wavelength for monochromatic devices and chromacity coordinates.Radiant power output, over the desired bandwidth is what's important for IR LEDs and is also used for LEDs at the far ends of the visible spectrum, which are typically used for other applications than direct illumination.Refer to the papers linked below for more information.http://depts.washington.edu/mictech/optics/me557/Radiometry.pdfhttps://www.thorlabs.de/catalogPages/506.pdf

author: spec
author_rank: Frequent Contributor
timestamp: January 21, 2019, 11:49:23 am
content: Quote from: Zero999 on January 21, 2019, 11:42:58 amYou beat me to it. I was thinking about visible LEDs. Above post amended.All the same, the general message about not trying to rationalize specifications and focusing on the core parameters is the important point.

author: Zero999
author_rank: Super Contributor
timestamp: January 21, 2019, 12:06:10 pm
content: Whoops, I forgot to say that chomacity coordinates are used for LEDs with a non-spectral colour, such as pink, purple, pale green etc. which are made use a deep blue/violet/UV LED and a phosphor coating. Anyway, that's off-topic, as this thread is about an infrared, not a visible LED.

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: January 21, 2019, 12:54:01 pm
content: Obviously, the main parameter here is the forward current.westfy was right, 20W is probably the denomination of the equivalent white led.In this casehttps://www.aliexpress.com/store/product/Chanzon-LED-Bulb-1W-3W-5W-10W-20W-30W-50W-100W-High-Power-Epistar-Chips-COB/1913069_32811656870.html?spm=a2g1y.12024536.productList_699027.pic_0The forward voltage is 30-34V and thus 600mA corresponds to roughly 20W.The equivalent IR leds have a forward voltage of about the half at 12-14V. So the power at 600 mA is 10W, but the seller still name it 20W, as it is the same package.This is certainly not the usual convention.What is funny is the discussion I had with them asking advice for the led driver : They recommend a 10W led driver !see the attached account of our discussion.

author: soldar
author_rank: Super Contributor
timestamp: January 22, 2019, 07:12:06 pm
content: Quote from: james_s on January 20, 2019, 09:52:37 pmReminds me of about 40 years ago when audio systems were all the rage and they would come up with tiny systems claiming to put out hundreds of watts, which was clearly impossible and so they would claim it was not "RMS watts" but "musical watts" which was a totally made-up unit and they could claim whatever they liked.Maybe these LEDs watts are "visual watts".

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2019, 08:38:55 pm
content: Oh they still do that. Somewhere I have a tiny set of amplified PC speakers that proudly proclaim 400 Watts."Peak Modulated Power Output" used to be a very common bogus rating too.

author: glarsson
author_rank: Frequent Contributor
timestamp: January 22, 2019, 08:45:53 pm
content: PMPO = "Peak Music Power Output"

author: james_s
author_rank: Super Contributor
timestamp: January 22, 2019, 11:26:37 pm
content: I've seen both definitions for PMPO. Either way it's a meaningless metric made up by marketers.