LEDs and reliability

  • #1
sophiecentaur
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Yet again, I am getting furious about the reliability of domestic LEDs. I have been moved to ask for the current views and experience of PF about them. The top of my search list on PF has an old 2012 post of mine, moaning about the same thing. There are some interesting comments from PF on that thread.
All this time later, you would think that they would be more reliable but are they?
There is a particular location in my house where LEDs are particularly vulnerable but I have checked connections in the circuit and I can't put it down to 'fizzing'.
What could possibly be different about that location? Premature death has happened to three different models of LED. (I am miles away from any Radio transmitters.)
I am trying to be Green and I refuse to use yucky CFLs, which make everything(/ body ) look sick.
Any ideas about this? I have used cheap and expensive LEDs (Expensive real can be expensive, too, if you get no more than 6 months of life).
 

Answers and Replies

  • #2
Borek
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Side note, or clarification, or whatever: it is not LEDs (inside the LED lamp) that go belly up. I tried to cut the dead one open, what I found was that the LEDs were OK (I am using them now and then with another source of power), it was the switcher that has died.
 
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  • #3
sophiecentaur
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Side note, or clarification, or whatever: it is not LEDs (inside the LED lamp) that go belly up. I tried to cut the dead one open, what I found was that the LEDs were OK (I am using them now and then with another source of power), it was the switcher that has died.
Was the lamp in question a budget version or an expensive one? I think it's iniquitous and that the companies are riding on the wave of the Green revolution. A switcher for a steady 10 or 15W load should work for EVER!!!
 
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  • #4
Borek
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Bought in IKEA (relatively cheap place) for about €12 (rather expensive compared with other models). But then it is a Polish market, so it can be difficult to translate the price directly.

Actually the switcher was still working - once it started. That required switching the light on many times. Switcher was rated for tens of thousands of on/off cycles, it probably went through no more than 1k.

What I am doing now is I am writing with a permanent marker installation date on the white part below the bulb. So far no bulb ever worked as long as advertised.
 
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  • #5
anorlunda
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So you say that it is not the LED, and not the switcher. What is the failure mode?
 
  • #6
Borek
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Perhaps my English failed me and I wasn't clear - it is the switcher that failed, but its failing mode is that it is still capable of supplying the current when it is in a working mode, it just can't get past the starting procedure.
 
  • #7
Svein
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Perhaps my English failed me and I wasn't clear - it is the switcher that failed, but its failing mode is that it is still capable of supplying the current when it is in a working mode, it just can't get past the starting procedure.
Possibly the startup resistor. Some voltage is needed for the switching circuit to start. It is usually supplied through a 100k resistor or thereabouts.
 
  • #8
anorlunda
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OK, you suspect some electronics that supplies start/run mode to the switcher.

You can't expect a company like IKEA to have the same kind of product engineering and testing as a company like Phillips. IKEA needs the flexibility to switch suppliers if necessary, and when switching they can't take a year or more to investigate and qualify a new supplier. They must depend on the statistics of customer complaints and returns to know when a product they sell is faulty.

LED bulbs at very low prices are sold in bulk on alibaba.com . I presume that they are bought by retailers who know next to nothing about the manufacturers.
Here's an example link to an alibaba ad for LED bulbs, €0,21 ($0.25) each in quantities of 60000 per day.. Use your own imagination to think of who buys them, and what names they stamp on them before sale.

By the way, the alibaba ad also says 2 year manufacturer's warranty. Your LEDs may be covered by the warranty. Lots of luck with that.

You should do your part by returning the failed units to IKEA and ask for a refund.

To avoid trouble in the future, you need to be a more vigilant consumer. Stick to Phillips/Seimens/ABB/Electrolux or other European brands that engineer/manufacture/and test their own products.
 
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  • #9
CWatters
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I've had the LEDs themselves fail in some down lighters. Individual LEDs develop black spots or fail in "strings".

Heat is the main culprit. LEDs run cooler than halogen but are more sensitive to heat.
 
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  • #10
Tom.G
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Here in Southern California, USA, the traffic signals were changed over to LEDs several years ago. For the first few years it was common to see them with several (6 or 8?) of the individual LEDs not lighting, presumably those in a series string. The Highway Departments seem to have found a reliable vendor and now that failure mode is rarely seen.

Good Luck. (and let us know if you find a reliable vendor!)
 
  • #11
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There is a particular location in my house where LEDs are particularly vulnerable ...
Could you please tell us more? Where is that location and how is the failure happening?

The most vulnerable point of the LED bulbs currently in use is the heat management. In theory, everything is designed according to the needs of the LEDs, but at the end the electronics just can't get rid of the waste heat on the available surface, so it heats up. Then it cools down as switched off.

The hot period eats up the capacitors, the cycling eats up the soldering.
 
  • #12
Baluncore
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I see two electrical problems.

1, The environmental temperature. This directly reduces LED light output. High temperatures age the LED, switching semiconductors and the electrolytic capacitors.

2, The starter resistor, as Svein pointed out. Manufacturers ignore the fact that 240VAC is widely used and seem to do their design and testing only for 110VAC. The startup resistor is always across the rectified AC, typically 155 to 350VDC. Resistors are now rarely rated for the high voltages. High voltage rated resistors are more expensive. It is a better investment to make a starter resistor chain from two or more resistors in series. That divides the voltage and heat between resistors.

Like Borek, I write the date of purchase, supplier and invoice number on all new techno-junk products. I have no problem taking things back for a refund or replacement with a different design.
 
  • #13
sophiecentaur
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I see two electrical problems.

1, The environmental temperature. This directly reduces LED light output. High temperatures age the LED, switching semiconductors and the electrolytic capacitors.

2, The starter resistor, as Svein pointed out. Manufacturers ignore the fact that 240VAC is widely used and seem to do their design and testing only for 110VAC. The startup resistor is always across the rectified AC, typically 155 to 350VDC. Resistors are now rarely rated for the high voltages. High voltage rated resistors are more expensive. It is a better investment to make a starter resistor chain from two or more resistors in series. That divides the voltage and heat between resistors.

Like Borek, I write the date of purchase, supplier and invoice number on all new techno-junk products. I have no problem taking things back for a refund or replacement with a different design.
That's all very well but I think you are being far too indulgent with the suppliers. They really should be getting a lot of stick about it and I sometimes feel I am the only person actually wingeing about it. At several pounds a throw, they should last as claimed. ~The aggro of returning a faulty one is a powerful reason to do nothing about it (mea culpa).
What you say about the 240V design is actually quite inexcusable when you think of the level of cleverness involved in the diodes themselves.
What do we want?
Reliability
When do we want it?
NOW!!
 
  • #14
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I can’t help but pull apart prematurely failed LED lights. Those facing downwards (ceiling lights) seem to fail quicker than those mounted facing up - I suspect convection has a role in this.

I tend to buy cheaper ones with capacitive dropper circuits, all with poor heat sinking - LEDs mounted on ally plate but with a plastic body and no heat sink compound. Every failure so far has been a single LED in the series string of 60 or so. These can be snipped out and bridged.

If you can get them apart, they are serviceable. Once you’ve found the bad one with the DMM diode test and bridged out, switch on and measure current through one LED by bridging with an ammeter. Most units are overdriven, ca. 30-40mA.

Aim for 20mA - so divide 20/(measured current in mA) and multiply the resulting factor by the dropper capacitor value. Swap for an appropriate capacitor, check new current and reassemble with a dab of heat sink compound.

This is time-consuming, but far more fun than buying a decent unit and having it boringly work for years.
 
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  • #15
sophiecentaur
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This is time-consuming, but far more fun than buying a decent unit and having it boringly work for years.
Haha. You are incorrigible! :wink:
I have been trying to picture such an arrangement, strung from our living room ceiling in a decorative fitting.
 
  • #16
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Haha. You are incorrigible! :wink:
I have been trying to picture such an arrangement, strung from our living room ceiling in a decorative fitting.
Are you in the UK? Poundland/world. Their £1 LED bulbs can be easily hacked to run at a cool 20mA, and will last (as far as current testing goes) 2 years or more. You’ll need a set of polyester caps 100-570 nF or so. Rated 400V.

The long winter evenings will just fly by.
 
  • #17
Baluncore
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It is hard to provide feedback directly to the design engineers since the manufacturer can be hard to identify from the customer end of an international supply chain. In Australia, the buck stops with the importer. If no one returned faulty products to the retail outlet, there would be no feedback and so no change in the available product or a careless importer.
~The aggro of returning a faulty one is a powerful reason to do nothing about it (mea culpa).
I have no problem returning faulty devices. There is no aggro because I know the consumer law here and I have the record to prove supply. I would find it very difficult to return faulty devices without that recorded information. Maybe you should record more data.
 
  • #18
Borek
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Most units are overdriven, ca. 30-40mA.

Aim for 20mA
We must be talking about different LEDs. LEDs in the lamp I took apart work at over 200 mA (I didn't test them at higher currents), which is not surprising at all. For my model lights I bought Cree SMD mounted diodes rated 350 mA (these ones).
 
  • #19
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We must be talking about different LEDs. LEDs in the lamp I took apart work at over 200 mA (I didn't test them at higher currents), which is not surprising at all. For my model lights I bought Cree SMD mounted diodes rated 350 mA (these ones).
Mine use 60 or so LEDs in series, each with approx. 3V drop to give 180V across the lot. The balance of the 330V recified peak voltage is dropped across the series dropper capacitor.

60 of these running at 20 mA gives about 3.6 W. To get a higher rating, they just overdrive them by increasing the capacitance of the dropper.
 
  • #20
jim hardy
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Isn't it just Swiftian that these high tech monstrosities are mandated on us

when a plain 60 watt incandescent bulb reliably provides both light and heat , a boon to those of us not living in the Sun Belt ?

How did we let Lilliputians get the upper hand ?
 
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  • #21
sophiecentaur
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Isn't it just Swiftian that these high tech monstrosities are mandated on us
That is a bit harsh, I think. LEDs are very expensive at the moment but the low amount of heat they produce is very relevant (it should be, at least) in avoiding overheating of enclosures and contacts. We have all suffered from the bad fish smell of a filament lamp socket in which the spring has become tired and lost its temper, producing an HR contact and damaging heat.
The cost of manufacturing and distributing strong glass envelopes for multiple filament bulbs will never go down but the cost of a single well designed LED for its 'proper' lifetime should mean that LEDs are actually better. The spectrum is amazingly good these days. CFLs on the other hand are the true monstrosities.
Candles have their own special charm . . . . . . .:wink:
 
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  • #22
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Isn't it just Swiftian that these high tech monstrosities are mandated on us

when a plain 60 watt incandescent bulb reliably provides both light and heat , a boon to those of us not living in the Sun Belt ?

How did we let Lilliputians get the upper hand ?
Filament bulbs - simple, cheap, reliable, dimmable, good power factor, good CRI. I think their efficiency should be calculated by factoring in the heat they provide - they’re only really inefficient in warm weather when the heating’s not on.

A case rather like fossil fuels for cars - a discovery that took us so far ahead that greener technology is struggling to be even NEARLY as good as what it replaces, in terms of performance rather than efficiency.
 
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  • #23
CWatters
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I've been buying cheap GU10 LED lamps for perhaps 7 years and found reliability is very hit and miss. When you think you have found a reliable source they change their supplier so you can't buy any more from them without taking another risk. What's happened in my house is that gradually the unreliable ones have failed and been replaced, sometimes two or three times, but gradually I'm accumulating a set that seem to go on and on. The oldest are now at least 5 years old. A few in our bathroom are in totally sealed (IP67) fittings so far from ideal heat wise.

Initially I purchased cheap unbranded LEDs from china because branded bulbs were horribly expensive, however more recently the price has fallen so you can now get relatively cheap branded LED bulbs in DIY stores and I've generally found those reliable (but not always).
 
  • #24
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Good leds, but their accessories are very broken. I have used a bunch of LEDs at home, however unlike the commitment to longevity. Their drivers are very buggy.
 
  • #25
sophiecentaur
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Good leds, but their accessories are very broken. I have used a bunch of LEDs at home, however unlike the commitment to longevity. Their drivers are very buggy.
It's really shocking. They are all shamelessly riding on the Green Wave. It would cost only pence to sort out the peripheral problems.
 

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