LED life.

[Dave Plowman (News)]

Have an old audio amp that came with a standard 5mm red LED as a mains on indicator. Fed from one of the 50v rails.

Changed it to a blue opaque type. Just because I prefer the colour. Calculated a new series resistor to 5mA, but it was still far too bright. So just fiddled with it to get it down to an acceptable level.

The LED has failed after a few months use. Fitted a new one. Had bought a packet of 20 from Ebay.

Does it shorten the life of LEDs running them at very low current? Or did I just get poor LEDs for that low cost on Ebay?

[Theo]

If you're buying LEDs from ebay, they're probably no-name Chinese. I have no idea what the quality control on those might be like.

It shouldn't be a problem to run LEDs at low current - unlike 1970s LEDs, most of the current ones are insanely bright if you run them at the rated maximum current, so indicators are frequently under-run.

Theo

[Steve Walker]

I am pretty sure that it is only high currents that destroy them and you can go as low as you like.

SteveW

[tabbypurr]

no.

You might have got rejects or 2nds.

NT

[newshound]

If it is behind an indicator window, can you wire up (say) three in parallel to become failure tolerant?

[Dave Plowman (News)]

What I thought. Although given the very low cost and it not being a critical use, I'll put up with it. Assuming it just to be a rogue one.

I do remember buying some early 'white' ones - when they were pricey - to light a meter, where the original tungsten has a short life. Due to being on for very long periods. And they didn't last well either. More expensive replacements from a reputable source were OK.

Thanks Theo - what I guessed. Just wanted it confirmed.

I recently bought an HDMI four in two out switcher unit with remote control. The LEDs on that are so bright as to be distracting - as it's placed below the screen.

[Dave Plowman (News)]

It is a single one poking out of the fascia. Hence using a diffused type.

[Brian Gaff]

Is the rail regulated? I've not played with the blue/ white ones but are there not two types, one that is indeed blue and another that somehow uses aa uv to make a tiny screen glow? Brian

[Brian Gaff]

No I don't think I've ever had any led file when underrun, unless it was run from a very spiky voltage of some kind. I used to love those high brightness red ones you got very cheap in the old tandy stores. With my failing sight at the time they were great. Brian

[RJH]

On 29/03/2019 14:06, Dave Plowman (News) wrote: snip

Had a similar problem with a wireless charger - you could quite happily read by the light it gave out.

Used a couple of layers of electrical tape over it in the end. I see some enterprising souls are selling 'LED dimming tape' precut to size (that is, small circles). Peak capitalism :-)

[mm0fmf]

The quality control is that cheap Chinese components have already failed real quality testing. Before eBay they would have become landfill.

[tabbypurr]

Usually you can stick another 1 or more behind it.

NT

[Dave Plowman (News)]

No point. It's only a ten minute job to fit a new one.

[tabbypurr]

and a 10 minute 10 second job to fit 2

NT

[Dave Plowman (News)]

Are you saying one diffused type squirting through another would look just the same? Zero transmission losses? Or would I have to experiment with resistor values and drive it harder to get the same effect? Good luck in doing all that in 10 seconds.

[tabbypurr]

LED packs don't cause significant losses at he emitting frequencies. It'd be pretty silly if they did.

NT

[whisky-dave]

I've used black nail varnish in the past.

[Bob Eager]

I use Blu-Tack (I have a very bright blue LED on the 8 port KVM in the office).

The advantage is that you can 'tune' it by making the layer thicker or thinner.

[Dave Plowman (News)]

Now answer my point. ;-)

[whisky-dave]

I guess so, but with nail varnish you can also get it in other colours, including glitter :-). and you get the nice smell ;-) But I also have blue, white and pink blu-tak , so in keeping with LGBTQ I have girl, boy and gender neutral blu-tak.

I also have low noise parcel tape, and some pink masking tape. I just wish I could find some cheap leopard/tiger print versions.