Why are LED lights constantly failing?

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Arthur

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A friend has several LED lights on his front stoep. 220V bayonet bulb replacement type. They stay on 24x7. However, his LED lights have a very short lifespan, sometimes just a few months. LEDs should have an excellent MTBF, but these are much worse than regular filament globes. Anyone have any idea what could be causing them to fail? What should we be looking at?
 
Arthur said:
A friend has several LED lights on his front stoep. 220V bayonet bulb replacement type. They stay on 24x7. However, his LED lights have a very short lifespan, sometimes just a few months. LEDs should have an excellent MTBF, but these are much worse than regular filament globes. Anyone have any idea what could be causing them to fail? What should we be looking at?
Click to expand...

Spikes in the electricity supply?
 
Could be. But he's rather peplexed as to why the LEDs are failing more often than the filament bulbs on the patio, which are on only at night. Could be that being on 24x7 means they get more exposure to spikes than night-only lights. The more common problem in his area, apparently, is under-voltage, sometimes down to 190V, he says. Is this an issue?
 
Arthur said:
Could be. But he's rather peplexed as to why the LEDs are failing more often than the filament bulbs on the patio, which are on only at night. Could be that being on 24x7 means they get more exposure to spikes than night-only lights. The more common problem in his area, apparently, is under-voltage, sometimes down to 190V, he says. Is this an issue?
Click to expand...

To be honest I don't know for sure, but I would gather that rapid cycling of the LED or its circuitry would cause it to fail sooner.

Perhaps the patio is exposed to extremes of temperature and humidity. That could also be it or maybe it's multifactorial.
 
Suspect wrong voltage. Maybe the LED's are getting too much voltage?

Might be that the assembler made a mistake with the calculations and put in incorrect resistors etc.

We also use a LED light for the children's room, and it's been working for more than a month now.
 
Don't LED's burn out really quickly if you dont have some sort of a resistor connected to them in series??? I read this somewhere. Busy thinking about installing some for when the power is out, read they can burn out very quickly if you don't set them up right.
 
You say on the patio, so my question is:

1) Are these LED bulbs rated for outdoor use? (moisture, heat)
2) Are they suitable for an enclosed fitting. (heat)

LED's will only fail due to heat. Whether that is because they are in a hot, enclosed fitting, a hot day or because of excessive voltage is what you need to figure out.
 
My question is why are they on 27/7?

I asked the chief/cook and bottlewasher for the answer to your question, and here is his reply:


I think Gaz (reply no 10) hit it on the head. Those are the most likely reasons for failure.

Not knowing the exact bulb and its technical specifications it is difficult to say which could cause the problem.

Under-voltage generally does not cause problems. However if the area is prone to under-voltage then there will also be over-voltage situations (these will be shorter in duration). And if the bulbs do not cater for over-voltage then it will be toast. It is always good to have the upper voltage end in the region of 265V / 275V as it protects the bulb from spikes.

An incandescent will just glow brighter with higher voltage and will have a somewhat reduced life span. By how much is not certain. Electronic lights (such as LEDs) will just pop once the voltage exceeds the upper limit.
 
Again. Loose connections would cause failure.
It will cause under voltage aswell as higher current being drawn through the bulb.
Its the most common fault.
 
What do you mean by failing. Do they fail to light altogether or is their brightness suddenly reduced?

LEDs do require a current limiting resistor to keep the current within the rated spec. High power LED's require proper driver circuitry to keep them going properly. It isn't the voltage "across" LEDs that determines their brightness its the current.

Generally most LED lights will most likely use LED's that are pretty much similar and possibly from the same manufacturer. What separates the men from the boys is the circuitry driving the LED. With the high power LED's like those 1W ones in torches there are only a few manufacturers.

As LED's fail they start to fade, if the current is too high they can fry and go dead. Differnent situations call different types of failures.

The really cheap and simple way of allowing a LED to light up is to use just a series resistor and that works as long as the voltage stays relatively constant, like when you are using a battery.

However for illumination from the mains you have harmonics, spikes, brown outs etc to deal with so the driver/controller circuitry has to keep the current through the LED's constant.

Needless to say you get good and bad designs. Some of the better designs can become complex but will protect your LEDs from ugly things that happen on your Eskom line.

Now before you go and blame Eskom or the supplier of your LED's, its possible that the products were tested overseas in environments that weren't as noisy. And you can't blame Eskom for the noise on your power line caused by PC's etc.

Its also good to go and look at where you are situated. Are you in or close to an industrial area. Is there anyone around you or at your home using machinery. And of course do you have a lot of PC's. Because all of these things can contribute towards harmonics which is like noisy spikes which can give susecptable circuitry a hard time.

LED lighting is still relatively new in SA so the body of knowledge is still growing with time all these bugs will be ironed out.
 
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