Problem with DR700 LED ?

About 6 months ago I thought I would try out some LED lights in replacing a downlight..

So I have 1 channel on a 8 channel dimmer that drives two down lights (each on its own transformer), so replaced one of the MR16 down lights with a DR700 replacement.

Its worked well since, and seriously considering moving them all across after a successful trial.

Just now, I am sitting under the LED sown light and noticed it was glowing... checked my switches and its not on, went to the dimmer, and the channel is not being lit up.

Turned the light on, and it works, it dims, but turn it off, and the light remains on, although the status light on the dimmer says its off.

For now - I have just turned power off to the dimmer, until I am in a better mood to check it out. Any clues on where to look first ? Replace transformer ? Check wiring at dimmer ? change channels ?
What would you be investigating ? I don't want to be spending all day on this - damn it I have better things to do than fault rectify the issue !

Thanks

 

There is a small amount of current that leaks past the power electronics of most dimmers. Efficient light sources often glow dimly when the dimmer is 'OFF'.
If your lamps always glowed a bit but you didn't notice it before, that sounds quite normal for low-cost LED solutions. If the lamps definitely did not glow before but do now, I suspect a capacitor at the input of the lamp circuit has failed. This is not too surprising as the C-Bus 8 channel dimmer is a phase-cut type and there may be a spike of current every mains half-cycle as a result. Some capacitors can be damaged by such current spikes.

In either case, you can add a small capacitor across the lamp circuit to bypass the "offstate leakage" current of the dimmer if you are so inclined, or alternatively find another LED lamp that is designed to cope with this issue (good quality LED lamps would be designed with this in mind)

 

Thanks Don

Yep aware of residual current on a dimmer - but I can assure you I have never seen this occur on this circuit / led - it sits right above me for 4 hours a night, and is mostly in its off state.

Interestingly, I turned power off, and left it off for a few hours while I was out for dinner tonight - came home, turned power back on and it is no longer glowing... Lets see what happens tomorrow.

I thought the Brightstar DR700 was a half decent LED fitting - certainly not a cheap chinese item... The sooner I cut the holes larger and replace the MR16 with GU10 Leds the better I will be I guess.

 

Hi Impact
Any LED module squashed into the form of a Gu10 or MR16 halogen lamp is most likely to have serious compromises in performance.
What you want is a Purpose designed LED module in Luminaire and driver. There are many good ones out there, but just as many dodgy ones.
The clipsal range is decent, as are the Osram, Barricade, and the five versions from Gerard Lighting. All these dim nicely and will give you 2-3 x more light than a Gu10 or MR16 product.

 

I too have an issue just like this one, on my plate at present.
I have situation where the client's gone and literally changed over all halogen for CLA 240V SMD LED fittings, throughout.

I understand the incompatibility vis a vis LED drivers and phase cut dimming. Is it fair to assume that the C-Bus Universal Dimmer would solve this issue, with the use of trailing edge dimming?

Another issue I'm somewhat concerned about is minimum loads on the dimming channels. There are instances where control groups have only 1 such fitting connected. Is there a "dummy load" type unit that can be purchased, that loads up the dimmer output stage, as required?

As a side note, when the client complained about this to the vendor, her response was to simply lower the programmed maximum output of the dimmer to around 30% which should make the problem go away.
Ahhh... Ignorance is bliss..!!

 

No, you cannot assume that. The LED lamps need to be designed for dimming in the first place. Because there are no standards for this thing you need to contact the LED lamp manufacturer to find out what dimmers it is compatible with. With unknown or no-name brand LED lamps your chance of dimming compatibility with any dimmer is extremely slim, regardless of the type of dimmer.

 

why LED?

While peoples quest to save energy (or $) is commendable, I think all too often they are misguided with *LED* euphoria.

So why did they choose these? I suspect the lighting shop "highly recommended" them, with no consideration of the controls. If they had consulted yourself or another professional they could have avoided this scenario.

So if they have a sophisticated C-Bus control system, you'd probably make better savings using/improving/upgrading the functions. If you have single lamp situations, they are likely to be low usage areas. Really for areas like under-stairs storage, toilets, pantry's that are only likely to be on momentarily a halogen lamp is ideal. You are better to change the controls to a timer or install a PIR to ensure the light is not left on.