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LEDs ... The Good, The Bad, and The Ugly

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Michael Gilligan23/09/2014 16:32:57
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Posted by Neil Wyatt on 22/09/2014 14:50:02:

I was disappointed that two of my Ebay GU10 LED lamps failed early admittedly running about 15 hours a day, (which is why I wanted LEDs).

.

Neil,

I don't think it's the same unit, but have a look at this video.

Personally; I am coming to prefer to supply LEDs via low voltage circuits ... Keeping the Mains side of things somewhere accessible.

MichaelG.

 

Edited By Neil Wyatt on 26/09/2014 17:43:20

OuBallie23/09/2014 19:05:41
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MichaelG,

I haven't invested in any LED lamps, yet, but that video is an eye opener to say the least.

Today finished the mechanical connection of the motor to the FeedRod.

Just need to power up the motor to check all is as it should be, then finish the electrical connections.

Then sort out how to take a video of me taking the Apron off once again, this time to replace the worm gear and Gear Shaft.

Geoff - Just demolished a rib eye, egg and veg. Lekker!

Edited By Neil Wyatt on 26/09/2014 17:43:25

NJH23/09/2014 21:04:21
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Michael

That's a very interesting ( and disturbing!) video.

I have three GU10 fittings in the house each with 4 bulbs. The conventional bulbs lasted a very short time before expiring like flash bulbs! A couple of years ago I therefore took the plunge and purchased 12 x GU10- LED bulbs as replacements. I have experienced no failures with these and light output is still fine. Following your post, however, I quickly went round and checked my bulbs. All these are totally enclosed in a glass envelope and no metal parts are accessible. Big sigh of relief! I think it is another instance of " You pays yer money and makes yer choice" The ones I got were certainly not cheap - but they are fully encapsulated in glass with no accessible " live" parts. I think, in spite of the outlay, I'm probably in pocket now due to the reliability ( and maybe reduced running costs)

Norman

Edited By Neil Wyatt on 26/09/2014 17:43:29

Ed Duffner23/09/2014 22:41:45
840 forum posts
94 photos

If I buy any kind of electrical equipment I always look for the British Standard kite mark and CE mark.

Edited By Neil Wyatt on 26/09/2014 17:43:33

Martin W24/09/2014 00:30:32
921 forum posts
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Ed

If you order direct from China even though they carry a CE mark there is no guarantee that they conform to any of the required EU legislation regarding lamps or whatever the product may be etc., you only have to look at the Chinese companies that have had their approvals rescinded by the EU. However if you buy from a UK seller/importer then they are required by law to ensure that the products comply with the relevant regulations prior to putting them on the market.

This won't necessarily protect you as some small concerns will import directly from China and just assume that as it is CE marked it is OK or may be totally ignorant of or wantonly ignoring the requirements. If in doubt buy from an established source as they have too much to lose.

Cheers

Martin

Edited By Martin W on 24/09/2014 00:32:12

Edited By Neil Wyatt on 26/09/2014 17:43:37

Douglas Johnston24/09/2014 09:42:33
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I have bought a few mains items from China on ebay in the past, but no longer do so after seeing similar problems regarding lack of proper insulation. The items can be very cheap, but is it worth it if they kill you.

Doug

Edited By Neil Wyatt on 26/09/2014 17:43:41

Neil Wyatt24/09/2014 10:47:01
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Michael, that's why I bought lamps that have a glass cover in front of the LEDs. You can get ones without a cover from Ebay, but I doubt whether they have a (genuine) CE mark.

Neil

Edited By Neil Wyatt on 24/09/2014 10:48:00

Edited By Neil Wyatt on 26/09/2014 17:43:46

Andrew Johnston24/09/2014 10:51:00
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Rumour has it that some 'CE' marks are subtly different to the official mark, and stands for 'China Export'.

Regards,

Andrew

Edited By Neil Wyatt on 26/09/2014 17:43:50

Ian P24/09/2014 11:05:30
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Posted by Andrew Johnston on 24/09/2014 10:51:00:

Rumour has it that some 'CE' marks are subtly different to the official mark, and stands for 'China Export'.

Regards,

Andrew

 

Its not a rumour.

I will try an dig out an article I read recently showing the differences in visual appearance of CE and CE marks.

Ian P

 

Edited By Neil Wyatt on 26/09/2014 17:43:54

Michael Gilligan24/09/2014 13:05:49
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Posted by Neil Wyatt on 22/09/2014 14:50:02:

The failure mode was interesting, one LED fails. On the first few starts the lamp flashes, then runs rather dim. After a few time, it just runs dim.

I assume that the 'dead' LED gets a full 240V AC across it and slowly arcs and vapourises until it chars internally and becomes a resistor, allowing the rest of the LEDs to work at reduced current.

.

Neil,

If you are interested in failure modes of LED clusters ... this is worth a look.

MichaeG.

.

P.S. ... I do hope that your stated assumption is not correct..

 

Edited By Neil Wyatt on 26/09/2014 17:43:59

Neil Wyatt24/09/2014 15:24:10
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The 'drive circuit' built into the LED lamps is little more than a bridge rectifier. Hardly sophisticated, but nice to have a noise filter on the input!

led driver.jpg

Back in the early days I heard of a petrol station canopy burnt down due to a cascade failure in a fluorescent replacement LED bar where the failure mode was for the LEDs to go short, rather than high resistance... can you see where this is going?

Neil

 

Edited to correct circuit diagram - again

Edited By Neil Wyatt on 25/09/2014 15:34:22

Edited By Neil Wyatt on 26/09/2014 17:40:39

Martin W24/09/2014 15:49:14
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HI

There is an article here regarding the CE and CE marks on Chinese products.

Martin

Edited By Neil Wyatt on 26/09/2014 17:40:44

Ian P24/09/2014 16:00:14
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Posted by Martin W on 24/09/2014 15:49:14:

HI

There is an article here regarding the CE and CE marks on Chinese products.

Martin

Thanks Martin, you've saved me a job, that's the one I was looking for!

Ian P

Edited By Neil Wyatt on 26/09/2014 17:40:49

Les Jones 124/09/2014 16:04:44
2261 forum posts
156 photos

Hi Neil,
I think your schematic is wrong. I think you will find that the 560K resistor is in parallel with the 560 nF capacitor. Also the 560 nF capacitor will be between one AC input and the bridge rectifier. The capacitors purpose is to limit the current trough the LEDs. It will have a reactance of 1/(2 x pi x f x C) = 1/(2 x 3.142 x 50 x 560 x 10^-9) = 5683 ohms. A capacitor is used rather than a resistor so that no significant amount power is lost (And heat generated.) I think the 560K resistor is just to make sure that the capacitor is discharged when the lamp has been unplugged.

Les.

Edited By Les Jones 1 on 24/09/2014 16:05:28

Edited By Neil Wyatt on 26/09/2014 17:40:54

Ian P24/09/2014 16:27:49
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Posted by Les Jones 1 on 24/09/2014 16:04:44:

Hi Neil,
I think your schematic is wrong. I think you will find that the 560K resistor is in parallel with the 560 nF capacitor. Also the 560 nF capacitor will be between one AC input and the bridge rectifier. The capacitors purpose is to limit the current trough the LEDs. It will have a reactance of 1/(2 x pi x f x C) = 1/(2 x 3.142 x 50 x 560 x 10^-9) = 5683 ohms. A capacitor is used rather than a resistor so that no significant amount power is lost (And heat generated.) I think the 560K resistor is just to make sure that the capacitor is discharged when the lamp has been unplugged.

Les.

Edited By Les Jones 1 on 24/09/2014 16:05:28

I like the last bit Les!

They are obviously very concerned lest somebody get a mild electrical shock from touching the terminals after the bulb has been unplugged. That assumes they are not already dead! Oh, but if they were dead they couldn't unplug it, catch 22.

The circuit does look a bit fishy, I only glanced at first and thought the 2u2 capacitor was the dropper, than I saw the bridge. I find 'Eagle' (I think) schematics not a patch on the diagrams that I grew up on in Wireless World. Having junctions appear in the middle of a single wire for example confuses the eye.

Ian P

 

Edited By Neil Wyatt on 26/09/2014 17:41:07

Les Jones 124/09/2014 16:40:47
2261 forum posts
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Hi Ian,
I agree that the resistor is a bit pointless if this is one of the units mentioned that do not have a glass cover over the PCB with the LEDs on. I also found the You tube video about these lamps amusing. The guy that made it seemed to think that the connections on the front would only be live when it was plugged in one way round. He obviously did not consider the bridge rectifier.

Les.

Edited By Neil Wyatt on 26/09/2014 17:41:12

Neil Wyatt24/09/2014 17:43:20
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Hi Les,

Yes you are right. I thought I could make out where the traces went on that side and didn't check them with a meter.

This is one of the glass fronted bulbs, and C E (not CE) marked too!

Still, I've got 48 decent white LEDs here...

Neil

 

Edited By Neil Wyatt on 24/09/2014 17:53:31

Edited By Neil Wyatt on 26/09/2014 17:41:16

Howard Lewis24/09/2014 22:53:08
6301 forum posts
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On the subject of LED lamps, we got a couple of Chinese ones for our ES standard lamp. Brilliant, but after a while one began to flicker quite rapidly, soon after, so did the other. I suspect that the internal bridge rectifier partially failed so that the LEDS were only seeing half wave DC and so only lit on one half of the cycle.

The replacements, from LIDL, have been trouble free, so far. (as have the other Chinese /E bay ones on the machines in the shop. Maybe they don't run long enough to get really hot?)

Germany 1, China via E bay 0

As already said, ultimately "You get what you pay for"

Howard

Edited By Neil Wyatt on 26/09/2014 17:41:21

Danny M2Z25/09/2014 08:56:04
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963 forum posts
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Posted by Neil Wyatt on 24/09/2014 15:24:10:

Back in the early days I heard of a petrol station canopy burnt down due to a cascade failure in a fluorescent replacement LED bar where the failure mode was for the LEDs to go short, rather than high resistance... can you see where this is going?

I once was driving an Australian Army Land-Rover into a service station in Charleville (QLD) when a musical pinging followed by a gradual darkening of the forecourt announced the arrival of the following vehicle. The driver then became quite aware of the useage of the cord attached to the radio antenna which was affixed to his vehicle.

He got every fluoro tube. The LED versions would have been interesting to watch.

* Danny M *

 

Edited By Neil Wyatt on 26/09/2014 17:41:26

Michael Gilligan25/09/2014 09:09:14
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20289 forum posts
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Posted by Neil Wyatt on 24/09/2014 17:43:20:

Hi Les,

Yes you are right. I thought I could make out where the traces went on that side and didn't check them with a meter.

.

Neil

Just "for the record" it might be helpful if you would please post a corrected schematic.

[Myths and mis-information tend to spread on t'internet]

Thanks

MichaelG.

Edited By Neil Wyatt on 26/09/2014 17:41:29

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