Lighting – Garage door lights: which cfl bulbs work

garage-doorgarage-door-openerlighting

I discovered yesterday that led bulbs cause RF interference and disrupt the use garage door remotes. While I could look for a low interference led bulb, they are rather expensive. I had some cfl bulbs lying around, so I decided to try to use them.

One weird thing was that one cfl bulb worked, while the other cfls didn’t. This has nothing to do with the light switch. To test this, I turned the light on, and then tried various bulbs.

So the question is, why would this cfl bulb work on a garage door opener socket:

works

While this cfl bulb doesn’t work in a garage door opener socket (I tested it in a lamp and verified it is a functional bulb that lights):

doesn’t work

What is the technical difference between the two that makes the garage door operate with one, but not the other?

Best Answer

How do I detect which bulbs will play well with my garage door opener remote? You find out which radio frequency your remote uses, tune a radio to that frequency, turn on a candidate bulb, and listen.

How do I detect this pre-purchase, say from a product listing on Home Depot's website? You don't. The needs of your garage door opener are poorly documented, and the RF emission band diagrams of random bulbs are not documented at all. Or even consistent enough to document! Nevermind manufacturing inconstencies, nothing keeps an LED marketer from changing internal parts and completely changing the RF frequencies it emits.

Now, about this:

I discovered yesterday that led bulbs cause RF interference and disrupt the use garage door remotes

That's a blanket statement, and it's not true. Here is what is true:

  • High frequency electronic devices tend to emit radio frequency interference on the same frequencies, unless shielded. If on the same frequency as your remote, it will drown out the weak remote signal.
  • CFLs, by nature of their design, must generate high frequency signal which is not practical to shield because it must reach the tube. That frequency does not need to be high enough to interfere with garage doors, but that's cheaper.
  • LEDs natively want 3 volts DC, so no frequency at all. The problem is voltage conversion, most cheaply done by using a high-frequency chopper circuit, the higher the cheaper. This can be shielded, not for free.
  • For the cheapest bottom-shelf consumer bulbs of both types, it's a game of pennies. A shortcut that cuts manufacturing costs by 0.1 cent per unit will tend to be taken.
  • The FCC calls for shielding as part of its Part 15 certification, but this may not be enough to prevent interference. Some cheaper manufacturers fake this certification.

The answer is to redline CFLs immediately, and look for LEDs that have been designed with care to not create this high frequency interference. These will be consciously designed products, and will not benefit from the extreme "optimizing for cheapness" that our Chinese, um, allies are so fond of putting in products marketed to us.

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