LED lights wearing out, loosing efficiency: relevant to second hand

[Keith_]

Hi Folks,

I am new to lighting (came from sound), but occasionally I am asked for lights too (outdoor shows*), so I thought I would start getting a basic outdoor light set together. On a small budget, I have always preferred quality s/h over cheep new. Recent exerience teaches me this does not apply well to LED lights. After some disappointment, I have been reading: https://www.digikey.com/en/articles/understanding-the-cause-of-fading-in-high-brightness-leds

and linked pages. I am here to get the opinion of lighting experts regarding aging and used equipment in this area.

Many thanks.

* E.g. I did sound for a set of local choirs in a town square on a winter evening and there was no lighting, so they were not best presented.

[timsabre]

In my experience LED lighting is quite prone to total or partial failures, but fading/loss of brightness is not noticeable for basic lighting.

The place where you notice it is if you are mixing particular colours with fixtures of different age ... e.g. if you mix a deep purple with lots of blue and a little bit of red, an old fixture will have lost a bit of brightness on the red so the purple will look a different colour compared to a new fixture. But if you have fixtures of different brands (or even different batches of the same brand) they are different anyway so really, it's not much of an issue.

For typical basic use e.g. white or saturated colours, you will not notice it.

My advice would be to buy fixtures from known brands because you will be able to get spares then when the inevitable failures occur. I've got some cheapy LEDJ fixtures and have had a couple of power supply module failures but a quick call to the UK distributor Prolight has had replacement parts in a couple of days.

 

So what recent experience have you had?

Edited June 14, 2023 by timsabre

[Don Allen]

Another thing to be aware of with outdoor LED use is overheating will damage LED's. Some fixtures have thermal protection built in, so will reduce output power until they cool down. If you are using fixtures without thermal protection, do not use them in direct sunlight on hot days, wait until they are in shade or it is dusk and you will notice them. I am in Perth, Western Australia where we do shows in 40C+ days. You may have concerns for cold weather, such as condensation ?

[musht]

Going Dark Emitting Diode, D.E.D. is most common failure mode.

Either failure of single diode or joint in string or PSU failure.

Fading requires the PSU/driver to live long enough.

Large chunk of degradation is in first 1500 hours then slowly to 70%s at 50K hours, in extended testing in manufacturer marketing dept,er, labs.

LED efficiency has leapt over last few years, even cheap is going to be bright, nice but dim for well made gear of yesteryear, like 5+ years ago...

Choir in town square, mebbe battery video lights?

[Keith_]

Thanks chaps.

Mushi roughly corroborated what the technical document I linked to was saying, though perhaps older technology would have deteriorated faster. 50k hours is roughly on all night every night for a bit over 11 years, which would tally with outdoor lights that might have started service, e.g. illuminating a building, in 2011. Judging by the (high quality, but old) units I bought, that is not impossible. I take it, though, that modern LEDs from a reputable manufacturer should be fine for many years of service (as long as they don't get battered about).  Don makes a point also corroborating the document - overheating reduces lifespan and unfortunately the mode of slow degeneration tends to increase heat in the diode leading to a viscious circle. I agree with Timesabres point about good quality and spare parts - it's one of the reasons I prefer good s/h over cheep new.

Any more comments?

[DrV]

13 hours ago, Keith_ said:

Any more comments?

I'd add that the LEDs themselves are not the only components which wear out. Almost all LED fixtures will use a switch mode power supply. This uses electrolytic capacitors and these have a specified life. This life depends on factors such as how close to their rated voltage they are run and their operating temperature. In a cheap fixture the design may be such that they are running nearer to these limits than in an expensive one so the life of the caps may be the limiting factor.

[Keith_]

Good point, DrV. Electrolytics recently featured in the Sound Forum - zero ohm - and could indeed be an issue. Though in this case I doubt that explains the same rate of decline in all the lamps at once, I will open them up and have a look. The PSUs may be at fault because I notice the lamps do not draw their rated power (not even close). They are from a very good manufacturer, though.

[musht]

10 years ago ,100 lumens /watt was top end ,exotic level, performance LEDs.

Now 100l/W be bottom bin brightness.

Then add in degradation.

 

 

[DrV]

PSU faults due to worn out caps tend to be less subtle than just reducing output voltage or current. I just mentioned them because you were talking about second hand fixtures.

[sandall]

7 hours ago, DrV said:

I'd add that the LEDs themselves are not the only components which wear out.

Chatting to a couple of people involved in making high-end fixtures recently I got the impression that the LEDs themselves may well last for how many tens of thousands of hours the manufacturers wish to claim, but in cheaper units the drivers, being cut to the bone, probably won't outlast their tungsten equivalents. Well-made fixtures CAN last - the lamps in the original news set at BH have been running 24/7 for 9 years & are still within 90% of brightness & original colour.

[Don Allen]

A lot of schools that I go to do not bother to turn their LED fixtures off so they run 24/7 without any use of the LED emitters, so the PSU appears to be the weak link.