PDA

View Full Version : LED interference.


GreenLight
08-15-2011, 10:06 AM
I have just recently begun integrating LED into my lighting designs. So far so good, I have only incorporated a few jobs with LED but the end result has been satisfying. Ultimately I am leaning towards hard selling LED much more with each job, even with the lacking long term data and field history.

My question is about LED interference. I know very little about it, but have heard it discussed as something that can occur with garage doors,etc. Are there any suggestions from more experienced LED users on how to avoid interference? Has it been an issue that you encounter very often or more of an abnormality? Overall im just hoping for an understandable breakdown of what to be aware of and how to avoid the pitfalls. All help is greatly appreciated.

The Lighting Geek
08-15-2011, 01:48 PM
I have just recently begun integrating LED into my lighting designs. So far so good, I have only incorporated a few jobs with LED but the end result has been satisfying. Ultimately I am leaning towards hard selling LED much more with each job, even with the lacking long term data and field history.

My question is about LED interference. I know very little about it, but have heard it discussed as something that can occur with garage doors,etc. Are there any suggestions from more experienced LED users on how to avoid interference? Has it been an issue that you encounter very often or more of an abnormality? Overall im just hoping for an understandable breakdown of what to be aware of and how to avoid the pitfalls. All help is greatly appreciated.

I have never heard or experienced any kind of LED interference.

steveparrott
08-15-2011, 06:55 PM
EMI, or electro-magnetic interference, is a very real concern in LED installations.

It results when certain LED driver components radiate and/or conduct high frequency energy. Radiated EMI (the type that radiates outside the light source) is more important for landscape lighting than is conducted EMI (the type that passes back through the system via wires).

Radiated EMI of sufficient strength and at the right frequency can interfere with wireless devices that operate at, or near, or are harmonic with, these frequences. Garage door openers are one such device that can be affected. There have been many instances of LED's interfering with these openers.

In commercial installations, LED EMI can interfere with wireless communications.

If an LED is interfering with a garage door opener or other wireless device, there are five solutions.

1. Change the power supply (from the transformer) from AC to DC. It is the components that convert AC to DC that contribute most to EMI.
2. Relocate the LED to a distance that does not interfere.
3. Replace the LED with one that has EMI filtering or reduction.
4. Use lower power (lower lumens) LED's - the higher the forward vloltage, the higher the EMI.
5. Replace the LED with incandescent.

How to tell if an LED has effective EMI filtering or reduction? It qualifies for emmision standard: FCC Class B Conducted and Radiated.

If an LED spec does not show this rating, then it may or may not radiate problematic EMI.

Retrofit LED lamps are prime candidates for EMI problems for the following reasons:

1. Grounding an LED circuit is the best way to control EMI. Well designed integrated LED's provide a ground connection to the driver assembly. Retrofits can not do that.

2. EMI reduction components are relatively expensive and require customized engineering. Very inexpensive retrofits are unlikely to have these components.

3. EMI reduction is easier to achieve when active components are spaced apart and strategically positioned. Many retrofits cram components into a very cramped space.

GreenLight
08-20-2011, 12:24 PM
Thank you Steve, extremely detailed analysis and stuff I certainly didn't know.