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ARCHIVED FORUM -- April 2007 to March 2012

This is the first Archived Forum which was active between 17th April 2007 and 1st March February 2012


Latest post 11-21-2011 12:34 PM by GoldenDays. 5 replies.
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  • 11-09-2011 10:00 AM

    LC2 use problem with LED flexible strip - Help needed


    I am currently replacing some of my current lighting with LED devices and I’m facing a few problems with the use of my LC2s.


    I would appreciate if someone that has faced a similar problem can help providing a solution for the problem (Scenario 2) I describe below.


    Scenario 1

    230V AC Line transformer (suitable for LED lighting) providing 12V DC up to 30W  to 12V DC 2.2W LED bulb

    -          No problem with LC2 switching ON/OFF the lamp (LC2 assigned to Lamp # 8 and LC2 was NOT part of any Local Light Picture or Link Light Picture. LC2 programmed as Low Energy Lighting device)


    Scenario 2

    230V AC Line transformer (suitable for LED lighting) providing 12V DC up to 30W to a 12V 24W SMD LED Flexible strip

    -          No problem with LC2 switching ON/OFF the LED strip (LC2 assigned to Lamp #8 and LC2 was NOT part of any Local Light Picture or Link Light Picture. LC2 programmed as Low Energy Lighting device)

    -          Problem with LC2 AFTER switching OFF the LED strip. The LED strip receives a burst of energy every few seconds. The line transformer is the same that works fine with the LED bulb. Replaced the line transformer with a new one but behaviour is the same.


    Feeding the LED line transformer directly from a 230V AC power outlet through a manual switch (No LC2 used):

    -          No problem with the ON/OFF operation of the LED flexible strip.



    -          The problem is NOT with the line transformer

    -          The problem is with the LC2 keeping sending pulses even in OFF operation. These pulses are persistent enough for the LED strip to detect them. However the LED bulb does NOT react in the same manner since the bulb does not shows these bursts of energy.


    I know that some common light dimmers in order to control intensity send pulses at different rates according to the type of mains frequency (50Hz or 60Hz).

    Frequency used in LEDS that are dimmable is higher (around 300).

    The LC2 most probably uses those pulses for dimming. But I was assuming that in a simple ON/OFF situation (like when the LC2 is programmed for Low Energy Lighting devices) the DIM function of the LC2 was not active. Apparently it is since the bursts are received by the LED strip when the LC2 is in the OFF position , or am I missing here something?

    Your comments are most welcome!





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  • 11-10-2011 4:40 AM In reply to

    • Step1
    • Top 75 Contributor
    • Joined on 07-06-2008
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    Re: LC2 use problem with LED flexible strip - Help needed

    I assume this transformer is electronic i.e. switched-mode? does it say something like 90 - 250v 50/60hz on the label? If so it will be the issue. Try using a traditional suitably rated, regulated power supply instead and this should work fine.


  • 11-10-2011 6:41 AM In reply to

    Re: LC2 use problem with LED flexible strip - Help needed

    Hi Olli,

    Thank you for your answer and suggestion provided. In fact I use a LED driver 170-260VAC 50/60Hz as per photo below.

    I am not using a traditional transformer because after contacting several suppliers and reading several articles on dimmers they are not suitable for LEDs. May be I am wrong but please have a look at the following article ( , as an example, where it is said:

    Non-dimmable CFL or LED lamps must never be connected to a dimmed circuit - even if the dimmer is set to full power. While not apparent, the current drawn by the lamp circuit can increase dramatically (5 times or more), and can pose a fire risk as well as reduce the life of the lamp electronics.

    Even commercial dimmers that do maintain an accurate zero-crossing reference should not be used with CFL or LED lamps, or any other "capacitor input power supply" load. In one installation that I know personally, the end user had close to 100% failures of LED tube lights connected through a commercial dimmer. The normal failure rate is closer to 1%, but the suppliers of the dimmer chose to argue.

    The only difference between their installation and all others is the dimmer, therefore it can only be the dimmer causing the failures. Strangely, both the end user and the dimmer supplier seemed to have a problem with this simple concept.


    And in the ‘DC Dimmers’ section of that article it says:

    For dimming LED lamps, we don't use a filter, and the switching frequency can be kept low enough to minimise radio frequency interference. Around 300Hz works very well, and although the LEDs will switch fully on and off 300 times each second, our eyes cannot see the flicker rate as it is much too high. Lamp flicker is a hot topic in some areas, but provided it is well above the maximum visible rate there should be no problems. Normally, anything above 50 flashes/second is considered to be well above our persistence of vision threshold (many references are available on the Net).

    May be I am wrong but I seems that I am using the right transformer for LED lighting, and that the problem I am facing originates before it (i.e. at the LC2 lighting switch that I intend to use as a simple switch and NOT as a dimmer). Do you agree with this?

    The reason I am reluctant to replace the LC2 by a simple ON/OFF switch is aesthetical (it is in a decorated wall/room as part of a set with other LC2s – see examples below).


    Kind regards.



  • 11-11-2011 7:11 AM In reply to

    Re: LC2 use problem with LED flexible strip - Help needed

    This is just an update to my previous posts here.

    I found some good information on the Internet about LED operation. Basically, “even when a LED lamp is completely disconnected on one side, it can still glow.

    If the switch is situated between the neutral line of mains and the lamp, there will be a 60Hz voltage difference between the conductive parts of your fixture and the surroundings. These surroundings have a potential (earth) close to the neutral line of your mains supply.

    There is a small parasitic capacitance between the wires of the lamp and the surroundings. This will conduct a small current. This current will not flow through the return line of your mains, and is not detected by a Watt-O-meter. A LED lamps needs very little current to start emitting light.”

    So I decided to make an experiment by connecting only two LED bulbs, or alternatively one LED bulb and one incandescent bulb to the same LC2 circuit. In the alternative scenario the load was definitively higher due to the fact that I was using a 100W incandescent bulb.”

    The results achieved were the following:

    1)     Connecting a single or two identical 7-watt each LED bulbs to the B&O LC2 Lighting Switch produces the same results : both bulbs ignore ON/OFF actions of the switch and flicker at the same time;

    2)     Connecting one 7-watt LED bulb and one 100W standard resistive incandescent bulb to the B&O LC2 Lighting Switch produces the expected results: the ON/OFF action performs accordingly. The only drawback is that the 7-watt LED bulb emits a strong permanent buzz.

    (I confirmed that - with the switch in the ON position and both bulbs lit – as soon as I start unscrewing the incandescent bulb the 7-watt LED bulb starts flickering).

    So from the above it is clear that an additional resistive load is required in the circuit for the LED bulbs to perform well by “ignoring” the presence of the disruptive small energy.

    At this stage I would give consideration to additional alternatives on the LC2 side. However, since I am ignorant on the technical details of the LC2 and don’t know where to download a technical manual may be someone here that is technically skilled can provide me with answers to the following three questions:

    1)     Where is the switch action placed on the LC2:  on the phase (mains) or in the neutral wire?

    2)     If on the phase, can this be changed to the neutral by simply symmetrically exchanging the leads in the terminal screws of the LC2 (i.e. P1 to P2 & P3 to P4, and vice versa)? Any impact on the programmable functions of the LC2 (assignment of lamp number, etc.)?

    3)     Can be the LC2 modified (and how) in order to act as double pole switch and disconnect both phase and neutral when in the OFF status?

    I hope to find as usual good inputs on this forum.

    Many thanks to all!


  • 11-21-2011 11:00 AM In reply to

    Re: LC2 use problem with LED flexible strip - Help needed

    Did you manage to get some answers to these as I have a similar issue?

  • 11-21-2011 12:34 PM In reply to

    Re: LC2 use problem with LED flexible strip - Help needed


    Unfortunately I got so far no help from any member of this forum.

    I will wait a couple of weeks more. If no answer to my last 3 questions is given I will have to take some risk and will try to exchange the wire connection.

    The whole thing could be unrepairable afterwards, but since I have no technical information about the LC2 there are few alternatives. I will post later the result of my "adventures"!

    Best wishes



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