LEDs not used below 5-10mA - Page 1
Forum section: electronics / beginners

author: lilmantis
author_rank: Contributor
timestamp: April 15, 2016, 09:56:36 am
content: Hello everyone, I've been looking through some LED datasheets and I have seen in many that the LEDs should not be used below 5mA to 10mA depending on manufacturers. Does anyone know what is the reason for this?

author: lilmantis
author_rank: Contributor
timestamp: April 15, 2016, 09:59:46 am
content: Some examples:http://www.digikey.com/product-detail/en/osram-opto-semiconductors-inc/GW%20JDSMS1.EC-FSFU-5C8E-L1N2/GW%20JDSMS1.EC-FSFU-5C8E-L1N2-ND/4834169http://www.digikey.com/product-detail/en/osram-opto-semiconductors-inc/GW%20JDSMS1.EC-FSFU-5C8E-L1N2/GW%20JDSMS1.EC-FSFU-5C8E-L1N2-ND/4834169

author: Rerouter
author_rank: Super Contributor
timestamp: April 15, 2016, 10:13:08 am
content: I dont understand what you mean, I had a solid look through those datasheets and many of the performance graphs extended to 200uA

author: lilmantis
author_rank: Contributor
timestamp: April 15, 2016, 10:19:55 am
content: The info is at page 15 in the datasheet, on the max. permissible forward current graph.

author: amyk
author_rank: Super Contributor
timestamp: April 15, 2016, 10:40:52 am
content: Probably a "we don't guarantee functionality or any of the specs" thing.

author: MatthewEveritt
author_rank: Unknown
timestamp: April 15, 2016, 10:48:52 am
content: Given that it only appears on that one plot I suspect it really means don't use over about 95C, no matter how much you reduce the current.

author: lilmantis
author_rank: Contributor
timestamp: April 15, 2016, 11:07:28 am
content: The 5mA is specified over 0 to 100 degrees.

author: izx
author_rank: Newbie
timestamp: April 15, 2016, 11:22:10 am
content: Quote from: lilmantis on April 15, 2016, 09:56:36 amImportant to note this isn't a dinkly little If=20mA indicator LED, but a power lighting LED with typical If=120mA. Look at the relative intensity curve on page 13 (reproduced below), and notice that the intensity curve on the Y-axis disappears right around where 5 mA would be on the X-axis. So Osram is saying thattypicallythis LED will have no effective output below If=5mA.Edit: our regular If=20mA LEDs will happily emit light visible to the naked eye down to at least 0.5-1mA in my experienceBTW, dimming lighting LEDs in general is more commonly done with PWM rather than a linear constant current driver.

author: ovnr
author_rank: Frequent Contributor
timestamp: April 15, 2016, 11:22:56 am
content: Definitely "We don't characterize this below 5mA, so you're on your own". Osram datasheets are generally terrible in any event.

author: izx
author_rank: Newbie
timestamp: April 15, 2016, 11:25:28 am
content: Quote from: ovnr on April 15, 2016, 11:22:56 amThe double-Deutsche everywhere REALLY messes up my normal datasheet speed scan routine

author: lilmantis
author_rank: Contributor
timestamp: April 15, 2016, 11:32:36 am
content: I was wondering if there is some effect I haven't heard about for certain LEDs. Anyway it is quite an absolute statement instead of "not caracterized below 5mA".

author: wraper
author_rank: Unknown
timestamp: April 15, 2016, 12:37:23 pm
content: This is a white led for lighting. At the low current, color spectrum will degrade significantly.

author: alank2
author_rank: Super Contributor
timestamp: April 15, 2016, 08:47:01 pm
content: I have found that some LED's require you to throw a lot of current at them and others can light brightly on relatively little current.I've had good luck with these:APT2012CGCKAPT2012SURCK

author: jitter
author_rank: Frequent Contributor
timestamp: April 16, 2016, 06:12:14 am
content: Quote from: lilmantis on April 15, 2016, 11:32:36 am"Do not use below 5 mA." is definitely a statement that doesn't leave any room for (mis)interpretation.Look at the end of the datasheet, one of the notes explains that basically, all values are typical statistical values. In other words: every LED is unique and differs slightly from any other LED of the same type. My educated guess is that below 5 mA, there's way too much variation to be able to specify a statistical value.From the datasheet:Quote

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 16, 2016, 06:52:09 am
content: It means you may see significant brightness variation between parts below the stated current. This is why dimming is done with PWM rather than current control.At very low currents, <1mA for parts specced at 20mA, brightness variations can be huge, even with parts from the same bin.

author: ConKbot
author_rank: Super Contributor
timestamp: April 16, 2016, 01:47:45 pm
content: +1 To what mike says, big variations between LEDs, plus some power LEDs may not even light fully or evenly with too little current. Not talking about multi-chip types either. Some of the Luminus Devices LEDs that run at 9A max, unspecified below 1A, with a warning that it might not even light at 1A. and on candlepowerforums, some folks had issues with this with some multi-mode drivers on the lowest setting.http://www.luminus.com/products/Luminus_SST90_Datasheet.pdf"Special design considerations must be observed for operation under 1A. Please contact Luminus for further information."

author: retrolefty
author_rank: Super Contributor
timestamp: April 16, 2016, 05:47:18 pm
content: Quote from: lilmantis on April 15, 2016, 09:56:36 amI do know that most standard arduino boards use 1Kohm series resistors for the power and pin 13 leds which is below 5 ma and they are still quite bright. So generalizations are of little value, just specific LEDs characterizations.

author: uncle_bob
author_rank: Unknown
timestamp: April 16, 2016, 08:55:04 pm
content: HiSitting here on the shelf, they have zero current flowing. When I unplug the lighting fixture, they have zero current. If "do not use below 5 ma" is taken literally as phrased, then you *must* keep current on them at all times.A far more accurate phrasing would be "you would be stupid to use this below 5 ma" (which is quite correct and a very similar phrase).Bob

author: starphot
author_rank: Contributor
timestamp: April 18, 2016, 09:11:44 pm
content: Bad phrasing. I noticed color shifts/current on those early dinky T-1 3/4 white LEDs, but I don't think that anyone would operate these ones in question below 5 ma anyway. These are for lighting. PWM dimmers are usually used on these anyway. I got similar high current LEDs at the cabin operating off of a 12v solar system with dimmers.Joe