LED GLS bulbs

[SillyOldDufferModerator @sillyoldduffer]

Posted by Steve Skelton 1 on 06/07/2020 09:52:09:

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If you are using quality components (ie switches, power supplies (if needed) and LED light units then you should not be experiencing problems. As the current demand for LEDs is significantly lower than was previously used the light switch contacts may be your problem as the currents now being used will not be self-cleaning and will not clean high resistance contacts. As Michael suggested you could try replacing your switches use good clean contact switches. Poor contact switches could be continually arcing at the currents involved.

Steve

Picking up on Steve's point, Robin's first post said: 'I've bought cheapo Wilko bulbs, mid range from Screwfix, pricier Phillips and Osram but they all fail well before the advertised MTBF.'

in my home pretty much the same mixture of fittings have been reliable. As Robin says his all fail I smell a rat. I suggest this isn't about finding a reliable brand, it's about what else might be causing the issue. Old switches arcing is a possibility, as are spikes on the mains, or high volts. (My supply is usually a bit over 240V but I've seen it as high as 253.) Spikes might be due to a defective appliance in the house switching on or off, or it could be external.

If internal, the cause is likely to be something switching a lot of power like night-storage, where the switch or thermostat is worn out and arcing, and the suppression has failed.

Excessive volts can be found for a few quid, but does anyone know of a straightforward way of detecting and tracing spikes?

Dave

Edited By SillyOldDuffer on 06/07/2020 12:36:10

[David JuppParticipant @davidjupp51506]

Straightforward, but not cheap way to detect spikes, dips etc. – a power quality analyser.

I purchased a single phase Fluke analyser on the back of a customer project – it's very impressive and also easy to use. It automatically produces a time stamped log of spikes, dropouts, etc. plus frequency, harmonics. So if you note when (say) a switch was operated – check the log at that time for any disturbances.

You might be lucky and could borrow or rent such a device.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Jupp on 06/07/2020 12:55:24:

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Straightforward, but not cheap way to detect spikes, dips etc. – a power quality analyser.

I purchased a single phase Fluke analyser […] You might be lucky and could borrow or rent such a device.

.

Dave could probably knock one up from a couple of arduino [plural, like sheep?], one for the detector and one for data-logging.

MichaelG.

[Robin GrahamParticipant @robingraham42208]

Thanks for further replies.

Steve – I appreciate your advice concerning using the existing wiring to run a low voltage DC system. After mooting the idea I I had a look for the DC current rating of standard light switches – it seems that MK will not give even a derating figure for their switches, and don't supply any alternative switches certified for DC. This info comes primarily from a thread on BuildHub where the topic is discussed in some detail. You are right – getting it signed off would be a nightmare.

In the light (sorry!) of Steve's comment about the possibility of arcing in the switches, SoD's rat smelling, MichaelG's experiences and my own observation that my stairwell light which burns continuously has lasted a year and still going strong, the switches seem the most likely culprit. That might add up – the house had a 'makeover' a couple of years before we bought it, and I suspect that every expense was spared. The light switches certainly feel 'spongy' compared to the to the industrial-standard jobs I specified for my workshop.

Thanks again for comments – I'm slowly 'doing up' the house so replacement switches will go on the list.

Robin.

PS – one of my favourites is "How many social workers does it take to change a lightbulb?" "None – they convene a working group on 'living with darkness' ". I guess there must be (equally unfair) ones out there about engineers!

R.

Edited By Robin Graham on 07/07/2020 00:58:53

[Ady1Participant @ady1]

Someone in here mentioned that the led itself cones from a silicon wafer which varies in quality, the best in the central zone and diminishing quality towards the edges

The chip industry never really talks about these things at a retail customer level, which bit you are buying sort of thing

[Anonymous]

Posted by Ady1 on 07/07/2020 07:51:01:

Someone in here mentioned that the led itself cones from a silicon wafer which varies in quality, the best in the central zone and diminishing quality towards the edges

Sadly they're wrong. A silicon wafer is a single crystal. Of course there are defects but they are randomly spaced. It's also incorrect to say that LEDs are based on silicon. A modicum of thought will show that the bandgap in silicon isn't large enough to produce visible light. A variety of semiconductors are used, but gallium arsenide and gallium nitride are common.

Andrew

[John HaineParticipant @johnhaine32865]

Generally group III/V compound semiconductors, including Indium and phosphorus depending on colour.

[Frances IoMParticipant @francesiom58905]

Here in the SE there are definitely spikes or missing half cycles on the mains supply – two devices on separate rings seem prone – both have clocks (one a kitchen clock radio + the other a fancy timer to allow recording from the radio – both are now getting on in years) – the spikes occur some time after midnight and before 7am – I suspect some load switching by the supplier

[Michael GilliganParticipant @michaelgilligan61133]

A quick note about about mains light-switches:

I was in ‘Home Bargains’ yesterday, and saw ‘Status’ switches [also widely available elsewhere] dirt-cheap.

No idea what the contacts are like, but mechanically they have a nice crisp action.

… available in single, double, and triple versions __ starting at 99p

MichaelG.

[Oven ManParticipant @ovenman]

I have always been quite skeptical when people have mentioned switches as being responsible for problems, mainly because the usually come from people with little or no electrical knowledge. However after following this thread and reading the various sensible theories I can now see how they could potentially be a problem. It really is amazing the depth of knowledge on this forum, thank you very much. Just off down the Screwfix to pick up some MK switches. MK has always been my go to make since my electrical apprentiship days.

Peter

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Oven Man on 08/07/2020 10:13:40:
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I have always been quite skeptical when people have mentioned switches as being responsible for problems, mainly because the usually come from people with little or no electrical knowledge. However after following this thread and reading the various sensible theories I can now see how they could potentially be a problem.

[…]

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I suspect that this will become increasingly apparent as we use more low-current switching, Peter

… higher currents [unless excessive] serve to self-clean the contacts.

Diodic contact problems are well-understood in Audio and Instrumentation circuits, and I’m sure we have all ‘fixed’ a low-current battery operated device by just cleaning the contacts.

MichaelG.

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