Led Lighting issues

Here is an interesting problem. I have never had any issues at my place with the OSRAM lamps I mentioned above but my friend tried it out and his place caused them to flicker 2 of the 4 LED's outputs at a very low output.

Not having seen anything like this before I can only assume this is what everyone is talking about.

I seem to be the last person to come to the realisation that there is some cause for concern.

My CBUS is the first generation DIN 8-channel dimmers and his is the original black CBUS and the later CBUS2 dimmers.

 

You should see almost no difference in dimming performance between the different DIN dimmers. The dimmer part is the same for units with both the teal or purple covers, with the caveat that there was some evolution of the design over time.

Shimmering at low light levels or flickering when the dimmer channel is off are just two of the many issues that need to be considered when dimming LEDs. Like many emerging markets, you really do get what you pay for at the moment.

It would be interesting to know if the OSRAM flickering was observed on either the DIN dimmer or the black D750 dimmer at your friend's house.

 

Hi Newman,

I mean to say that both of this systems (old and new) flicker at power off. At 0% they flicker.

How do I get around that ?

Mine are 100% stable.

 

Hi Tobex
How many lamps has he got per channel compared to yours?
Or could it be just a faulty lamp?

 

You need to have something shunt the EMC bleed current past the lamps. The easiest thing is an appropriately-rated capacitor, but you need to stay under the 300nF limit on DIN Leading Edge dimmers. I forget what the limit is for the black box dimmers. If the OSRAM's are 47nF each (for example) and you have 4, that leaves you 112nF of capacitance that you can add in parallel with the load. It might just be enough.

If you can find out what the input capacitance of the OSRAM lamps is (if you send me one, I can check this for you) then that will be key in determining if a bypass capacitor will be effective in suppressing the flicker.

If you can move them to a Trailing Edge dimmer then you can just add a Clipsal 31CAP in parallel with the load as there is no capacitance limit. You would probably want to test their performance on Trailing Edge dimmers prior to committing to buying a Universal Dimmer though.

You can wire another type of load in parallel with these. For example, you could mount a 15W indicator bulb up in the ceiling cavity somewhere, however when it blows the flickering will return.

You can try wiring the dimmer channel in series with a relay channel and just give them the same group address, if you have a relay spare.

You are just lucky that yours don't flicker. You could do a swap with your mates to see if the problem persists to confirm/disprove this. Internally the electronics may be trying to run, but just not enough to make the LEDs light up. To test if this is the case, simply pull the lamp out and check if it's warm (after being off for an extended period). If it's warm, it's dissipating power.

 

This is what I plan to do since the LED Osram lamps are all from the same batch.

* Check all earth connections

* Check polarity on all loads (see if the Live and Neutral are all wired the same).

I personally dont understand why mine is running so smoothly.

 

In my installation there was 3 lamps per channel but after the installation of LED I now have 6 LED lamps on one channel.

In his installation there are 4-5 lamps per channel according to which room it was. We both have GU10 halolgens from the beginning.

 

This could be just enough to make a difference. As you increase the number of lamps on a circuit, the amount of bleed current through each lamp decreases proportionally. As a quick test you can try to disconnect your lamps, one by one, and watch for any signs of flickering in the off state on the remaining lamps.

 

How I did my conversion was that whenever a globe burned out I replaced it with 1 LED lamp. As luck would have it I blew 3 lamps in one month so I ended up with 3 lamps on one channel for several weeks then I changed it some time later. So I incrementally added LED one at a time till it was all LED then I did the other 3 in one time much later and joined them physically. In my case I had LED in parallel with halogen for some time.

So when I tried the same in my friends house I saw behaviour I didnt see in my house. I think it has to be polarity and earthing issues.

Is there a way I can run a test so that I can determine what the issue is ? Do you want me to uncouple all of the halogen globes and go one at a time with LED ?

 

If you have 1 halogen lamp in parallel with the LED lamps you will not see the flickering issue. This is because the bleed current will go through the halogen lamp instead of the LED lamps.

The only way to know for sure is to isolate which lamps are on a single dimmer channel, remove all the globes and then add the LED lamps one by one. I'd be very suprised if you didn't see any flickering in the off state with only a single OSRAM lamp connected to the dimmer channel.

 

I never had a just one LED on my channels without other loads. In both cases there were either additional halogens or multiple LED.

In my case no flickering. In my friends house .... problems.

 

I managed to figure out what was so special about my Osram LED lights that made them work perfectly.

First of all I tried to put in the globe only at my friends house into an existing Phillips GU10 fitting. It flickered when it was switched off.

Later I decided to pull the light fittings out of the ceiling to check polarity and earth to see what is going on. I found all of the existing lamps were fitted perfectly.

I replaced one of the older fittings with a complete lamp and fitting and like magic it was flawless . It appears that the OSRAM GU10 lampholder is different and that it contains a PCB which helps the operation of the fitting on leading and trailing edge and/or CBUS. Even when I operated only 1 LED (and nothing else) on a load. No issues.

When installing OSRAM GU10 LED lights into C-BUS I recommend installing the whole fitting not just the globe.

 

Hi Tobex
I never would have looked for that.
Thanks for passing it on.