LEDs and Dimmer Switch - Trailing Edge, Leading Edge, Something Else, or Not Possible?

17 Oct 2018
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United Kingdom
Usual problem - I bought a set of LED downlighters, and a dimmer switch - but the dimmer doesn't reduce the light level!

The dimmer switch is a BG Nexus 200W Grid Dimmer (SKU: RBNDTR) - Trailing Edge.

The LEDs are 6 x 6W flat panel. Neither seller nor product packaging state compatibility regarding dimming.

For comparison, I've tried an old spare dimmer that's marked "Tungsten only" and the effect is flickering.
Q1. Is this likely to be the dimmer type known as Leading Edge? If not, it might be worth buying a Leading Edge dimmer to test.

Q2. Is it a common problem that absolutely no type of dimmer will work?

Q3. In another thread it's mentioned to try adding a Contact Suppressor. Would eBay item https://www.ebay.co.uk/itm/134276575717 be okay, and where would I connect the pins?

Hoping I can avoid changing the LEDs again - it's currently the third pack of ten I've bought, trying to get the brightness and colour temperature spot on..
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Neither seller nor product packaging state compatibility regarding dimming.
That is the problem.

If you want to dim LEDs, then the LEDs MUST be dimmable. Plenty are not.
You also need a dimmer specifically designed for LEDs, not some old piece intended for tungsten lamps.

The ebay item will achieve nothing.
Ah, the joys of the future. All tungsten (filament) direct powered lamps (no transformers or power supplies between dimmer and lamp) are dimmable so it was never mentioned as a feature. Many LED lamps are not dimmable- if it doesn't say 'dimmable' in the specs then it probably won't dim properly under any circumstances. If it does say dimmable it may well specify a particular brand or type of dimmer that will work. Use that type/brand or risk another unsatisfactory outcome.
Thanks guys, I guess I need the inevitable 4th set of LEDs.

The lights are going down the centre of a hallway ceiling, and unfortunately the joist also runs down the centre. I'd chosen this generic flat panel LED design as they're only a few millimetres thick where they would meet the joist, and the springs would fit either side of the joist.

I need to pause and see if there's an eBay seller with a dimmable version (though so far it seems they're all selling products from the same manufacturer, just in different packing). Otherwise I may need to ditch the dimmer.
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ebay is not an appropriate place to obtain lighting or much else.

If it's not cheapo imported tat, it's factory rejects, customer returns, stolen or all of the above.
As has been suggested the internals of LED lamps vary, a LED is a current dependent device, and it needs some thing to limit to current to a safe level, this could be a simple resistor, capacitor or a complex switch mode power supply, the latter will often allow a huge voltage range, one outside light I fitted was 95 to 250 volt, some of the switch mode power supplies are designed to read the supply, and it uses the clipped wave form to tell it output required, but in the main they correct any average voltage so will not dim, the same devices often remove flicker etc.

So in the main we need to dim or colour correct lamps by telling the drivers inside the lamp what to do, in the main using wifi and internet connection with the so called smart bulbs. This however gets expensive when you have a lot of units.

Also the colour temperature is often adjusted by having two LEDs one at one end and one at other end of range, and changing the power to each to get temperature required. Within the defuser of the bulb this seems to work, but with lighting strip one can often see the two LEDs so does not look that good.

In the main dimming was done to give ambience, and so as one dims the light one wants it to reduce in colour temperature as well, this is not possible with a dimmer switch.

In warmer countries where use of cold lighting made sense, they moved first to CFL and used a 1/3 and 2/3 split to give 3 levels of lighting, since in the UK the heat from a tungsten bulb was not wasted, but allowed use to heat the rooms with infrared light which is nearly instant, allowing us to save energy by only heating air in the room to 18ºC and using infrared so it feels like 20ºC only when room is in use, we moved to cold lighting latter then many other countries. As in winter tungsten is saving more energy than LED, although since electric is more expensive to gas or oil, not money.

I have used the idea in my own house, with a 5 lamp chandelier, the centre lamps and outer lamps independently switched. But also had problems finding bulbs for wife's bedroom, where the local sourced bulbs would not switch off and had a shimmer when on, so had to get some from ebay type sellers, and the bulbs used would have been illegal to sell in UK as not marked with watts or lumen.

I am not really worried about lack of markings, but there can be other problems with non local sourced bulbs which can make them dangerous. One is taking a chance, and you have to accept that, and I have a draw full of new bulbs where after buying found they did not suit, new bulbs so loathed to dump them, but likely I will need to.

The smart route is also not as good as it first looks, although all I have seem to work with google home app, and so with voice commands, to program them in I have 4 apps one for each make of bulb used, once set up they work well, but I have spent an hour just getting the bulb programmed in.

Lucky first ones worked seamlessly or they would have also been the last. I know the problem with dim and bright lights on the landing, what it bright most of the time but dim when using bathroom at night so as not to wake others, I used this lamp-landing_1.jpgand only switch on centre bulb for bathroom visits, but lighting can make the home, and there's no magic formula, main living room we used cabinet lights to supplement main lighting.

On many of my bulbs it says Dimmable via the app or remote control, but shows the Not-for-dimmer-switch.jpgsign for not being dimmable, but others show the sign for being dimmable. There seems to be no real standard, reading the EU rules it must state if not dimmable, but we are not in the EU, the sign 1675077938235.pngit seems does not need to say how it can be dimmed, so is also of little help. Back in the late 80's early 90's dimming switches were the in thing, but today seems they are a remnant of the past. Actually getting up to turn a light switch is too much effort, it's hey google turn living room lights to 60%.
You also need a dimmer specifically designed for LEDs, not some old piece intended for tungsten lamps.

That again depends on the LED's, some LED's are certainly dimmable with a conventional dimmer. I had some LED's which worked perfectly with my then 40 year old dimmers. Since changing the LED's for higher wattage dimmable versions, they would then flicker. New LED compatible dimmers solved that, but not as reliably as the old dimmers worked with the first set of dimmable LED's.
Are these basic White round panel lights, Aurora Enlite sell a range of them and you can buy there dimmable driver that runs them
Are these basic White round panel lights, Aurora Enlite sell a range of them and you can buy there dimmable driver that runs them
Yes they're the basic ultra-flat panel type with separate driver. Does the ability to dim depend on the driver alone, or also the LEDs?

Dimming depends on the power supply / driver. The actual LEDs are unrelated.
As yours is a separate driver, it could be replaced with a dimmable version.
However you may find that a separate driver exceeds the cost of buying a complete new panel with dimmable driver.
As mentioned earlier, I bought sets of flat panels 3 times trying to get the brightness and colour temperature just right (once 3W and twice 6W). So I've just tried swapping a 6W driver with one from the other 6W set (they both have the same power connectors, shown in previous post) ...and it didn't work, not even a flicker.

This is from the set I want to use:


And this is from the other set:


I'm very surprised, and now a bit reluctant to buy dimmable drivers. Is there an obvious reason the swapped driver wouldn't work?

However you may find that a separate driver exceeds the cost of buying a complete new panel with dimmable driver.
Yes I think you're right. I only paid £19 including delivery for 10 x 6W panels & drivers.

My dilemma is that I need this type of ultra-flat panel to fit over joists, and there are plenty of UK eBay sellers, I just can't find any that state their item is dimmable. Well I did find one but I'm sure it's an error, I asked and he didn't reply.
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They are both "constant current" drivers.
One is a 60mA driver (@ 12 to 28Volts dc),
One is a 250mA driver (@45 to 90Volts dc).

Although both 6Watt, they have Very different current outputs that are related to how the LEDs are wired inside.

If you were to buy a replacement, using the first one as an example, you would search for "constant current driver 250mA" and then look for one that is actually dimmable and that is rated about 12 to 28V ( slightly off voltage is okay). I hate doing this as it typically takes far too long.
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You're absolutely right - it took a couple of months tracking down the correct dimmable driver, making sure it was the cheapest option, then waiting for it to arrive from China. For the benefit of anyone else here searching for a solution in the future...

I bought the 6W drivers from this Ali Express listing for just £1.74 each (+35p Tax):

The first order was lost and automatically refunded. I ordered again and it took another 3 weeks to arrive! I checked it allows my LEDs to work with the dimmer switch, then ordered the other 9 I needed. (It seems if you buy more than 2 of anything from this site you're charged shipping, so just make multiple small orders.)

And because the cable connectors are not the right type, I bought the correct connectors from this listing just £2.43 for a set of 10:

It was easy to prise open the driver casings, then swap over the cable connectors with a soldering iron.

I bet it wouldn't have cost the manufacturer significantly more if the drivers supplied with flat panel LEDs were dimmable in the first place.
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