I want to use LED replacements for GU10 lamps in a 4 spot kitchen ceiling unit. Does anyone know how effective these are in terms of light output compared with halogen lamps. I am not using these for cost saving but for effect, however I do want a reasonable light output.
LED spotlights
- Thread starter davecooper
- Start date
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I have some in an extension and I have to say they are not nearly as bright as Halogen. I am told that you can get brighter ones now and as time goes on the output will increase Im sure. Some DIY sheds and wholesalers etc have these on display so you can see for yourself before you buy.
You should be able to compare the light output because the spec will have a rating (e.g. lumens). IMO the ONLY reason to use LEDs is because you only have access to a d.c. supply. If you have a.c. then halogen will always be brighter and cheaper.
B
breezer
Dippy said:
Obviously you dont know about led gu10 replacement lamps that run quite happily on ac
here is one i made earlier
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i have had both the gu10 led lamps and the energy efficient gu10 lamps.
The kelvins are fairly high (ie very blue white light). Almost past daylight lamps.
For the kitchen as in main light (even if there are a few) theres not much light coming out of 'em (the ones i had had 17 or 18 leds)
Now the energy efficient ones are the DB's, im well impressed with them.
Positive:
1. Slightly higher wattage (7w's compared to 2w's for leds)
2. The brightness is greater than the led's
3. they are equivelent to a 35w lamp.
4. Will pay for themselves quickly (well depending on how much you use the light
Negative:
1. light delay when switching them on (ever so slightly )
2. Bigger depth than a normal gu10 (same width)
3. Cost about £6 each.
if you want can take a pic of a led lamp and also a energy efficient one as well to show you the size difference.
The kelvins are fairly high (ie very blue white light). Almost past daylight lamps.
For the kitchen as in main light (even if there are a few) theres not much light coming out of 'em (the ones i had had 17 or 18 leds)
Now the energy efficient ones are the DB's, im well impressed with them.
Positive:
1. Slightly higher wattage (7w's compared to 2w's for leds)
2. The brightness is greater than the led's
3. they are equivelent to a 35w lamp.
4. Will pay for themselves quickly (well depending on how much you use the light
Negative:
1. light delay when switching them on (ever so slightly )
2. Bigger depth than a normal gu10 (same width)
3. Cost about £6 each.
if you want can take a pic of a led lamp and also a energy efficient one as well to show you the size difference.
I stand corrected.
What does concern me though is what the manufacturer's claims for longer life actually mean. I very much doubt that when 1 LED fails, they consider that the whole lamp has failed. More likely they consider that the lamp is operational until the 15th LED has died!
Whilst it might be good to have a lamp that survives individual LED failures, of course it will get dimmer over time.
Also LED expected lifetime is reduced as average temperature rises, so again it would be interesting to know what temperature the manufacturer's tests are done at.
What does concern me though is what the manufacturer's claims for longer life actually mean. I very much doubt that when 1 LED fails, they consider that the whole lamp has failed. More likely they consider that the lamp is operational until the 15th LED has died!
Whilst it might be good to have a lamp that survives individual LED failures, of course it will get dimmer over time.
Also LED expected lifetime is reduced as average temperature rises, so again it would be interesting to know what temperature the manufacturer's tests are done at.
i don't see how supply access has anything to do with it, halogens will run quite happilly on DC and LED modules are widely availible that will run on AC.
halogens get a high light output in a small fitting, they give a very high quality light (high color temperature and near black body spectrum) and they are cheap to purchase BUT thier lumen/watt is only margingally better than normal light bulbs and thier beam patterns mean you tend to end up using a lot of them so you can easilly end up with very high running costs (and in the case of a non grid system either a constantly running generator or very large battery banks).
LEDs aren't quite as good on lumen/watt as flourescents (they are far better than halogens), tend to give worse spectrums but have extremely long life, don't tend to fail suddenly (leds are typically measured in terms of the time it takes them to reach half thier original brightness) are easilly dimmable with the right control logic (the modules you buy as halogen replacements may not be though) and turn on instantly (unlike flourescents). they are great for indicators and possiblly for highlighting but are imo not yet really suitable for main lighting.
As long as you aren't bothered by the flicker (some claim to still have issues with flicker even with the HF fittings) flourescents are the way to go for brightly lighting rooms with low installation and running costs. I've heared (haven't tried myself though) that combining a small incandescent with a large flourescent can make the flicker much less noticeable while still keeping an overally high lumen/watt.
halogens get a high light output in a small fitting, they give a very high quality light (high color temperature and near black body spectrum) and they are cheap to purchase BUT thier lumen/watt is only margingally better than normal light bulbs and thier beam patterns mean you tend to end up using a lot of them so you can easilly end up with very high running costs (and in the case of a non grid system either a constantly running generator or very large battery banks).
LEDs aren't quite as good on lumen/watt as flourescents (they are far better than halogens), tend to give worse spectrums but have extremely long life, don't tend to fail suddenly (leds are typically measured in terms of the time it takes them to reach half thier original brightness) are easilly dimmable with the right control logic (the modules you buy as halogen replacements may not be though) and turn on instantly (unlike flourescents). they are great for indicators and possiblly for highlighting but are imo not yet really suitable for main lighting.
As long as you aren't bothered by the flicker (some claim to still have issues with flicker even with the HF fittings) flourescents are the way to go for brightly lighting rooms with low installation and running costs. I've heared (haven't tried myself though) that combining a small incandescent with a large flourescent can make the flicker much less noticeable while still keeping an overally high lumen/watt.
B
breezer
i am cusrious, can you show an example diagram of how to dim a led? (really good for a project i have in mind)
B
breezer
doesnt work like that
a led "strikes" if you will at a set voltage, below this it wont work, but led dimmers can take it lower that this voltage
(or something like that)
its just that unlike an ordainiry lamp by adding resitance to it (variable pot) doesnt dim it becuse of the way led work, i also believe its only recently they figured out that you can dim a led
a led "strikes" if you will at a set voltage, below this it wont work, but led dimmers can take it lower that this voltage
(or something like that)
its just that unlike an ordainiry lamp by adding resitance to it (variable pot) doesnt dim it becuse of the way led work, i also believe its only recently they figured out that you can dim a led
assuming you are working with raw LEDs (not any kind of module) here is a quick primer on driving them.
brightness mostly correlates to current and LEDs are generally rated by maximum current, you will typically be given a voltage at which this current is achieved, but this is ONLY an estimate and may vary wildly from one LED to the next.
LEDs have the voltage/current profile of a diode, that is a very small change in voltage equates to a very large change in current.
in other words to drive a LED predictablly you need something that approximates a current source, where efficiancy is not a concern (e.g. indicator applications) this is typically done by taking a resistor from the supply voltage (usually 3.3V or 5V as that is what the rest of the electronics run at), varying this resistor will vary the current and hence the brightness despite having little effect on the voltage accross the LED.
in practice however LEDs are not dimmed by varying the current as this is hard to automate. Instead they are dimmed by adjusting the duty cycle of a high frequency (the exact frequency doesn't really matter too much but 1KHZ is probablly about right) waveform.
brightness mostly correlates to current and LEDs are generally rated by maximum current, you will typically be given a voltage at which this current is achieved, but this is ONLY an estimate and may vary wildly from one LED to the next.
LEDs have the voltage/current profile of a diode, that is a very small change in voltage equates to a very large change in current.
in other words to drive a LED predictablly you need something that approximates a current source, where efficiancy is not a concern (e.g. indicator applications) this is typically done by taking a resistor from the supply voltage (usually 3.3V or 5V as that is what the rest of the electronics run at), varying this resistor will vary the current and hence the brightness despite having little effect on the voltage accross the LED.
in practice however LEDs are not dimmed by varying the current as this is hard to automate. Instead they are dimmed by adjusting the duty cycle of a high frequency (the exact frequency doesn't really matter too much but 1KHZ is probablly about right) waveform.
LEDs can be dimmed by a varible resistance to a certain extent, the series resistance pulls the voltage/current curve into more of a linear form than it is nativly, meaning you can control the brightness this way more than you can say by varying the voltage by say changing number of batteries in series to power it
But yes PWM is the elegant way to do it
But yes PWM is the elegant way to do it
B
breezer
this one works (so it says) but it only dims white leds, thats part of the problem, leds having varying "strike voltages" depending on led colour, brand etc
i want one that dims any and is easier
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