2 Replies Latest reply: Nov 7, 2011 5:45 PM by Don Ellingham RSS

Replacing existing Halogen LV Downlighters with "Replacement" LED's - Radio Interference

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Has anyone had experience with and solutions for radio interference when replacing LV (12V AC) Halogen Downlighters with "equivalent" replacement LED's.


I was satisfied with the ambience created by existing halogen downlighter (Philips MASTERLINE ES 45W, 60 degree) powered by dimmable toroidal transformers.  However I wanted a (much) lower power consumption (and heat output) system without completely rewiring the system.  As I was unsure of the light output, colour rendering and beam spread of LED's I sourced a number of different types, power (consumption & mcd values), colour temperature and beam spread (angle), advertised "replacement" LED's e.g. high power CREE, high power LED "clusters", SMD's including Philips MASTER LEDspot 10 & 7W, 36 & 60D, MR16, GI5.3 LV Dimmable 2700 & 3000K 12V AC LED's.


My general findings are that "white" or "daylight" bulbs are "harsher" than the existing Halogens but that a satisfactory ambience can be created by the correct choice of LED source although getting the correct combination of power & beam spread is currently difficult.  SMD's coming closest to the large spread given by the Halogens (certainly greater than the nearest equivalent Philips 7W 60D, which is unavailable in the 10W range).


However a problem has arisen with all the potential solutions.  On replacing the existing halogens radio interference is caused with "hissing" on VHF & complete loss of signal on digital radio.  I have tried using coaxial ferrite "chokes" to solve the problem but this has not been completly sucessful and, despite being the most expensive replacement I tried the Philips LED's 7 & 10W have proved to cause the most interference.


Does anyone have similar experiences?  Is there a (simple) solution without replacing the transformers with a "LED tranformer" or reverting to Halogen lighting?

  • 1. Re: Replacing existing Halogen LV Downlighters with "Replacement" LED's - Radio Interference
    Currently Being Moderated

    Can you tell us the manufacturer and model of the "noisy" luminaires? If they have internal transformers, the make and model of those? If a dimmer is used, the make and model number of that?


    I have seen this before and it can occur for several reasons. If you are using a dimmer to drive the fixtures, and they have power supplies in them, there can be RF noise generated by this combination. It can come from the dimmer, transformer (often an "electronic transformer") or from the lamp if electronic, such as a dimmable CFL or LED. We need to determine all the parts from whatever information you can give us, then go from there.



  • 2. Re: Replacing existing Halogen LV Downlighters with "Replacement" LED's - Radio Interference
    Currently Being Moderated

    I've done a little thinking about this particular issue and it really seems to me that the source of the interferance is much more likely the "solid-state transformer", or power supply IN the luminaire. The frequencies and the power level in the LED are both too low to likely cause problems in VHF frequencies.


    A switching power supply connected to the mains is another story!


    Typically, because of space limitations, the power line filtering is minimal in these devices .And therein lies the biggest issue. Even if the conducted EMI, or ElectroMagnetic Interferance, from the input-end of the power supply is really TINY, the power line in your home or building is a MASSIVE antenna. Depending on whether metal shielding is employed or not, called either EMT or BX here in the US, or if just plastic insulation is allowed such as our "Romex" cable, the problem may be much worse. No shielding really enhances the effectiveness of that "antenna".


    If these power supplies have a metal case to shield radiated noise, they aren't always connected to earth ground, to enable radiated noise shielding, and instead are used as "potting' vessels to hold epoxy. The metal case can then collect then re-radiate the noise, essentially as if it wasn't there.


    So I have s diagnostic suggestion.... In the offending fixture, replace the LED lamps with small halogens. Also make sure you remove the LEDs from the other fixtures that might light off this particular switch or dimmer circuit. Then try the radio test. Turn on that one lamp and if a dimmer is used, run through it's range. If there STILL is noise- it is the transformer. Either way, tell me.


    But don't despair yet...Just try that and report back and we will see if we can help.



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