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Thread: It's that time again: LED bulbs - recommendations?

  1. #49
    Senior Member Xlucine's Avatar
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    Re: It's that time again: LED bulbs - recommendations?

    I've used a couple of sainsburys own brand LED bulbs, and haven't had one fail yet. The clear ones make a pretty good stand in for incandescent/halogen bulbs in exposed fittings (only noticeable difference is they take a fraction of a second longer to turn on than halogens, but it's pretty hard to spot unless you look for it)

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    Senior Member watercooled's Avatar
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    Re: It's that time again: LED bulbs - recommendations?

    That does at least suggest they have a proper driver circuit rather than the cheap+nasty method of capacitive dropper or just stringing a load together and hoping for the best (they flicker horribly and don't generally last very long).

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    Re: It's that time again: LED bulbs - recommendations?

    Hi!
    I found these variants [**snip**]. I want to buy some for my garden and make garlands. They will arrive in two days and I will give better review


    URL removed by Admin.

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    Re: It's that time again: LED bulbs - recommendations?

    Quote Originally Posted by Apex View Post
    Just checked and Ikea still do the GU10's but they look to have changed supplier so they arn't the same, for the price i paid i am well happy with them and they are close to the 2700k the box said they where; the new ones i carn't comment on.
    You are right, they have changed.
    So I used to get the 3w frosted bulb. They're now 2.5w and unfrosted. Annoyingly they put it under the same brand name, yet its different.
    I will say £3 for 3 bulbs is mighty good value, so I was happy to take the gamble.
    But it's no where near as good light, I suspect more to the frosting. Looks like I am back to the drawing board as well with the GU10s


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    Re: It's that time again: LED bulbs - recommendations?

    For all those who have LED bulbs that don't last long, check your mains voltage, they are designed to use the Euro standard 230v, although the UK signed up to this the power distribution companies are still running at 240. Now if you have a solar or wind farm feeding the grid in your area the voltage can reach a staggering 260v if they are not set up correctly. You can get your local grid company (not electricity supplier) to check and monitor your voltage and if required they will down step your local transformer to try and get to 230v. I did this and not only save on blown bulbs but also on leccy bills and lengthen the life of all your electrical gear.

    Trust me I'm an engineer.

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    Senior Member watercooled's Avatar
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    Re: It's that time again: LED bulbs - recommendations?

    It depends what sort of circuit they use, and 10V isn't all that significant anyway for supply voltage. For any using any sort of SMPS rather than just stringing them together with a resistor/capacitor (i.e. the rubbish, cheap, flickery ones) it won't make a difference.

    WRT voltage making a difference to other appliances, it depends, hence why 'voltage optimisation' is at times of questionable value. For any purely resistive loads like incandescent lamps, heaters, etc, yes the lower voltage will mean lower instantaneous power, but it's not a free gain - lamps will in many cases be appreciably dimmer as the lumen drop-off for lower voltage is not linear (if anyone is still using incandescents at home) and any thermostatically controlled heaters will simply need to run for longer, and if anything the resistive losses in cables during that time will be higher, though without actually working it out the difference is likely negligible. Stuff like computers, other electronics etc use regulated power supplies and it won't make a jot of difference there. Again if anything, I2R losses in cables supplying them would be marginally higher due to higher current and many SMPS tend to be more efficient at higher voltages anyway. /voltage 'optimisation' rant.

    The voltage rating in the UK is 230V with a tolerance of -6%/+10% precisely because of what you said, no-one went around changing transformer taps when we adopted '230V'. So 216.2 to 253V. If it's within that, good look getting a DNO to do anything.

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    Re: It's that time again: LED bulbs - recommendations?

    "So 216.2 to 253V. If it's within that, good luck getting a DNO to do anything."
    The voltage only has to spike above 253v once and they are obliged by law to investigate, usually putting a recording monitor in, in my case we have a lot of solar and wind turbines locally, on windy days the voltage would go out of spec, due to poor regulation on one or two turbines, they were more than happy to tap down the transformer.
    voltage optimisers can cost upwards of £1500, getting your grid supplier to sort it costs nothing bar a few phone calls.

    As for "computers and other electronics" yes they have regulated supplies but the extra power input has to be dissipated, that will shorten the life of the PSU if nothing else. One prime example is microwave ovens, the magnetron that generates the power can be compromised and lose 20% of it's life due to over voltage. Another is stuff with AC motors (washing machines, driers, dish washers etc.) and their drive capacitors, both can be damaged by over voltage these devises don't normally have the luxury of switched mode PSUs so the voltage to them goes up and can damage circuit boards. LED lamps will not dim noticeably (mine haven't) on an average day the over voltage was about 5%, and they weren't noticeably brighter on the very windy 10%+ days, they just blew then! negating any cost saving, when I pointed this out to the grid supplier I was sent a box of 20 GU10 bulbs, I still have most of them still in the box.

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    Senior Member watercooled's Avatar
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    Re: It's that time again: LED bulbs - recommendations?

    There is no 'extra power input' to be dissipated. Higher voltage results in them drawing less current - they are not linear devices, and nor does a higher voltage within spec reduce life. Properly-designed devices will be capable of dissipating spikes well above spec too. A modern computer power supply can operate worldwide and obviously won't draw twice as much when connected in the UK vs USA. In fact as I said earlier, they tend to be more efficient at higher voltages so draw less power overall.

    Single-phase AC motors (of which there are very many types) would generally only be damaged if the voltage was high enough to break down winding insulation or start/run capacitors which are usually specified *way* above line voltage, amongst other things to protect against failures due to everyday voltage surges. In fact the windings would usually go through an insulation resistance test at roughly double the supply voltage, sometimes known as hi-pot or dielectric strength testing though they're not necessarily the same thing. Washing machines are different again as they're generally three phase motors fed from a variable frequency inverter drive.

    If 5-10% over-voltage is destroying lamps, they're crap lamps, plain and simple. Voltage changes will not vary the brightness of properly regulated LED lamps, but may do so for the very cheap ones fed through resistor/capacitor droppers, however the difference still may not be as obvious as the fairly large difference seen with incandescents.

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    Re: It's that time again: LED bulbs - recommendations?

    Quote Originally Posted by watercooled View Post
    There is no 'extra power input' to be dissipated. Higher voltage results in them drawing less current - they are not linear devices, and nor does a higher voltage within spec reduce life. Properly-designed devices will be capable of dissipating spikes well above spec too. A modern computer power supply can operate worldwide and obviously won't draw twice as much when connected in the UK vs USA. In fact as I said earlier, they tend to be more efficient at higher voltages so draw less power overall.

    Single-phase AC motors (of which there are very many types) would generally only be damaged if the voltage was high enough to break down winding insulation or start/run capacitors which are usually specified *way* above line voltage, amongst other things to protect against failures due to everyday voltage surges. In fact the windings would usually go through an insulation resistance test at roughly double the supply voltage, sometimes known as hi-pot or dielectric strength testing though they're not necessarily the same thing. Washing machines are different again as they're generally three phase motors fed from a variable frequency inverter drive.

    If 5-10% over-voltage is destroying lamps, they're crap lamps, plain and simple. Voltage changes will not vary the brightness of properly regulated LED lamps, but may do so for the very cheap ones fed through resistor/capacitor droppers, however the difference still may not be as obvious as the fairly large difference seen with incandescents.
    Can I remind you of Ohms law, current is proportional to Voltage X Current, then the power law power, Power equals Current X Voltage both physical laws you seem to want to break

    May I remind you again I AM an engineer, with 50 years experience both commercially and as a Naval engineering officer, I have a degree, both in electrical engineering and electronics.

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    Re: It's that time again: LED bulbs - recommendations?

    Sorry but throwing down qualifications doesn't make your previous post correct, but usually makes me shake my head (had that happen a couple of times recently). Yes, your first line of this post is correct, at least when applied to simple DC or purely resistive AC circuits, but also incomplete when it comes to e.g. AC circuits due to reactive (capacitive/inductive) elements (something I'd expect any electrical engineer to be fully aware of). It's also not as simple as just pointing at Ohm's law if you're relating it to a switched mode power supply input power vs voltage? Else I can't think what you're referring to, nor have I ever said otherwise.

    As I said, look up universal power supplies/chargers which are supplied with phones, laptops, etc, they will generally be rated for a wide input voltage from 100-240V. This does not mean, as I believe you're implying, that the power supply runs horribly inefficiently at 240V, drawing the same current and wasting more than 50% of the input power as heat. On the contrary, many such power supplies are in fact more efficient when operated at a higher voltage. The reason for this is due to how switched mode power supplies work. There are different types, but at a simplified level, the first stages involve rectifying the input and feeding it through a regulated inverter - for different input voltages it can be as simple as varying the duty cycle of the PWM circuit feeding the inverter, in order to achieve a stable output voltage.

    A common type of SMPS used for small devices like phone chargers is the flyback converter.

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    The late but legendary peterb - Onward and Upward peterb's Avatar
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    Re: It's that time again: LED bulbs - recommendations?

    Quote Originally Posted by RichMc View Post
    Can I remind you of Ohms law, current is proportional to Voltage X Current, then the power law power, Power equals Current X Voltage both physical laws you seem to want to break

    May I remind you again I AM an engineer, with 50 years experience both commercially and as a Naval engineering officer, I have a degree, both in electrical engineering and electronics.
    But if the lamps have a built on constant current regulator, (remembering that an LED is a non-linear device, so Ohms law is not applicable) changes in voltage will not affect brightness or longevity. If the are poor quality lamps fed with a simple regulator, then they will, as water cooled says) be susceptible to premature failure from power surges.
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    Re: It's that time again: LED bulbs - recommendations?

    Buying the right LED is very different from buying incandescent bulbs. The brightness of LEDs, however, is determined a little differently.

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    Re: It's that time again: LED bulbs - recommendations?

    Looking for PIR Floodlight for garden which is 4m2. What kind of watt should I be looking at, they have all moved to LED now so now sure how good the spread the light. I've seen 10w, 20w, 30w, 40w at Screwfix.

    Also has anyones indoor lights lasted a few years. I'm changing LED bulbs yearly. Not the 25,000 hours quoted on the pack.

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    Re: It's that time again: LED bulbs - recommendations?

    I have had only 1 led bulb pack up in 3 years, in my house I have about 18 led bulbs
    Jon

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    Re: It's that time again: LED bulbs - recommendations?

    Same, we've had LED lamps last several years of sitting room type use, not sure what that works out at in terms of hours. What sort of brands are you using, out of interest?

    I think I've said before but I tend to use B&Q's Diall brand which seem pretty decent for the price and easily available. Some of the properly cheap ones you can get are some horrible capacitive dropper ones with a horrible ~100Hz flicker which you can see as a strobing effect any time you move stuff in the room. I suspect they're the type that people have bad experiences with, with regard to colour quality and life too.

    Did you have a floodlight up in the garden already? Using the wattage of that would be a good starting point. Even a 10W would light it up but it depends how much light you need e.g. enough for putting bins out or to do some sort of work under?

    One last thing, beware of wattage ratings of floodlights on places like ebay, they're often... optimistic?

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