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Thread: Dimmable LED lightbulbs

  1. #1
    Master
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    Dimmable LED lightbulbs

    Help please.

    I've a couple of lights which operate from (20 year+!) old light switches that have an on/off switch and then a "rotary" dimmer. They work with normal incandescent lightbulbs. I was looking at getting dimmable LED lightbulbs but suspect that the switch and lightbulb technologies are incompatible.

    I'd be grateful for confirmation or otherwise.

    Thanks.

  2. #2
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    The type of lamp socket/base is really important. Do you happen to know what type of lamp you need?


  3. #3
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    Quote Originally Posted by jcm3 View Post
    The type of lamp socket/base is really important. Do you happen to know what type of lamp you need?
    Thanks. Oddly, none of these!

    Just a bog standard (if now old fashioned) bayonet fitting. (Just seen you're in the US so maybe that explains!)

    Wasn't looking at these specific ones but these:

    https://www.toolstation.com/led-gls-...le-lamp/p29167

  4. #4
    Grand Master TheFlyingBanana's Avatar
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    I recently bought a load of these, and they work perfectly on dimmer:

    https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1
    So clever my foot fell off.

  5. #5
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    This "All LED" TRIUMPH 9W lamp is the best performing dimmable B22 base replacement lamp that I know of. There are 3000K and 6000K versions (that refers to the color of the light). You should also know that most LED lamps do not get warmer in color when dimmed, unlike incandescent lamps. They just put out less light. The bottom end, level where the LED no longer puts out any less light, is about 30% on this Triumph lamp.


    http://www.allledgroup.com/image/cat..._DATASHEET.pdf

  6. #6
    You will most likely need a leading/trailing edge dimmer for led bulbs.
    Varilight are my go to brad, not cheap mind.

  7. #7
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    Quote Originally Posted by MrSmith View Post
    You will most likely need a leading/trailing edge dimmer for led bulbs.
    Varilight are my go to brad, not cheap mind.
    Another vote for Varilight dimmers here. We have a few of those for the rooms we have Led lights in and they work really well.

  8. #8
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    Why not just try it? My old dimmer works fine with Led ES bayonet bulbs.

  9. #9

    Dimmable LED lightbulbs

    We moved into our current house almost exactly 5 years ago and I set about replacing the bulbs (the previous owner had paid no attention to maximum wattage in various fittings so they needed replacing!)
    At that time, dimmable led bulbs just didnít seem to exist, or they were very expensive and everything easily available was Ďwarm whiteí. In the last couple of years the technology seems to have moved on and dimmable led bulbs are easy to find at similar prices to the non dimmable ones of 5 years ago. The colour choice also seems much improved. Like others I find Amazon has a decent selection.


    Sent from my iPhone using Tapatalk

  10. #10
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    The quality of the LED driver ("transformer") is vital to the quality of the dimming. The lamps with integral drivers are almost all crap quality built down to a price. They will dim OK at high brightness but getting them down really low never works. The only way is to spend money on decent drivers and LED lamps but this costs a lot more.

  11. #11
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    Had this a while ago and had to change the light switch, an electrician friend basically told me what to get and explained that the resistance in LED bulbs is so low that the old switches simply don't operate properly. Since installing the new switch all works well :-)

  12. #12
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    Quote Originally Posted by Maris View Post
    Why not just try it?
    Because I know nowt about electrics and don't want to pop a bulb that I've just spent £5 on or worse knacker a switch/light fitting or cause other damage/set the house on fire!!

  13. #13
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    Many thanks for all the replies and suggested replacement kit. I'll have to see about getting the switches replaced!

  14. #14
    Grand Master TheFlyingBanana's Avatar
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    Seriously, the ones I linked to work perfectly- even down to very low to no light output level.

    No switches changed, no hassle!
    So clever my foot fell off.

  15. #15
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    Quote Originally Posted by TheFlyingBanana View Post
    Seriously, the ones I linked to work perfectly- even down to very low to no light output level.

    No switches changed, no hassle!

    Thanks. Iíll see if that manufacturer makes a 100W equivalent and see about getting some!

  16. #16
    Master Geralt's Avatar
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    Quote Originally Posted by broxie View Post
    The quality of the LED driver ("transformer") is vital to the quality of the dimming. The lamps with integral drivers are almost all crap quality built down to a price. They will dim OK at high brightness but getting them down really low never works. The only way is to spend money on decent drivers and LED lamps but this costs a lot more.
    I recently changed my kitchen spots to LED (Phillips GU10s) and fitted a new dimmer (Wickes). However, now the spots won't dim below about half way though can turn up full. Suspect the dimmer is the wrong type? Seems there is leading/trailing edge types. What's the difference between these? Any tips appreciated. Ta.

  17. #17
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    Quote Originally Posted by Geralt View Post
    I recently changed my kitchen spots to LED (Phillips GU10s) and fitted a new dimmer (Wickes). However, now the spots won't dim below about half way though can turn up full. Suspect the dimmer is the wrong type? Seems there is leading/trailing edge types. What's the difference between these? Any tips appreciated. Ta.
    Very few LEDs will dim completely to off. Part of the way LEDs are built prevents this. The internal power supply in an LED lamp is typically built to maintain a constant light output, and this design works against the function of a dimmer that throttles the power down that the lamp receives. There are a few fixtures that are built with this in mind, and they are nearly always labelled as 1% dimming, or .1% dimming, fixtures. These typically cost a lot more than a typical LED.

    The way in which the LED power supply interacts with the electronics in a dimmer depends on the construction of both. There are no standards, so many manufacturers provide use case testing to show the results with different products. I have linked an excerpt from a test report for one manufacturer and a specific Philips lamp (Philips
    409904). As you can see, the interaction is also not completely linear, and is totally different from the way incandescent lamps work.

    As far as general types of dimming, there are at least 6.

    The first, a simple Rheostat. Rheostatic dimmers divide the incoming voltage into two rails via a resistor, some of the voltage goes to the lamp, and some is directed away from the lamp. Most of this lost voltage is dissipated as heat. These are rarely used today, and not suitable for use with LED.

    The second type is Triac. A triac is a type of electronic gate, that can latch open and closed really fast, and is able to let very tiny amounts of power through. Most old rotary and slide dimmers are of this type. These dimmers date back to the late 1950's. These dimmers work in an unpredictable fashion with LEDs.

    The 3rd type is PWM. PWM works via a very fast switch, that can stay on for a specified amount of time, letting a specific amount of power through. PWM dimmers are available in two common types, called Leading Edge or Forward Phase, and Trailing Edge or Reverse Phase. These describe the portion of the power wave that they intend to let through. Different LED lamps behave differently when attached to these different types. Many LED manufacturers will specify which type works best with their product.

    The other types are not commonly found in residential applications, and involve separate wired or wireless control signals in addition to power to control the lamp.


  18. #18
    Master Geralt's Avatar
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    Thanks for the comprehensive reply. Sadly can find no info on the Philips UK website regarding suitable dimmers, only that their LEDs 'work with most dimmers'. Suspect I may need a better quality trailing edge dimmer like the Varilight V-Pro. Only one way to find out...!

  19. #19
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    Quote Originally Posted by jcm3 View Post
    Very few LEDs will dim completely to off. Part of the way LEDs are built prevents this. The internal power supply in an LED lamp is typically built to maintain a constant light output, and this design works against the function of a dimmer that throttles the power down that the lamp receives. There are a few fixtures that are built with this in mind, and they are nearly always labelled as 1% dimming, or .1% dimming, fixtures. These typically cost a lot more than a typical LED.

    The way in which the LED power supply interacts with the electronics in a dimmer depends on the construction of both. There are no standards, so many manufacturers provide use case testing to show the results with different products. I have linked an excerpt from a test report for one manufacturer and a specific Philips lamp (Philips
    409904). As you can see, the interaction is also not completely linear, and is totally different from the way incandescent lamps work.

    As far as general types of dimming, there are at least 6.

    The first, a simple Rheostat. Rheostatic dimmers divide the incoming voltage into two rails via a resistor, some of the voltage goes to the lamp, and some is directed away from the lamp. Most of this lost voltage is dissipated as heat. These are rarely used today, and not suitable for use with LED.

    The second type is Triac. A triac is a type of electronic gate, that can latch open and closed really fast, and is able to let very tiny amounts of power through. Most old rotary and slide dimmers are of this type. These dimmers date back to the late 1950's. These dimmers work in an unpredictable fashion with LEDs.

    The 3rd type is PWM. PWM works via a very fast switch, that can stay on for a specified amount of time, letting a specific amount of power through. PWM dimmers are available in two common types, called Leading Edge or Forward Phase, and Trailing Edge or Reverse Phase. These describe the portion of the power wave that they intend to let through. Different LED lamps behave differently when attached to these different types. Many LED manufacturers will specify which type works best with their product.

    The other types are not commonly found in residential applications, and involve separate wired or wireless control signals in addition to power to control the lamp.

    Love a proper explanation - thanks!

  20. #20
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    Quote Originally Posted by Ethos View Post
    Love a proper explanation - thanks!
    How man WISís does it take to change a light bulb? I canít wait until the OP starts thinking about upgrading his TV or car, thats going to be one mega thread.

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