Has anyone heard of LED's emitting a frequency band that interferes with the radio controls of garage door openers?
A comment attached to this article seems to indicate so.
hmmm...interesting. Here you go. It seems that the control circuit to maintain the light's efficiency and long life generates radio emissions. The government control technically states that they should be between 30 and 300 MHZ. Most garage door remotes are 288(Liftmaster/Craftsman), 309, & 360(Genie/Overhead Door) MHZ. All within the range when tolerances are considered.
The regulation relies on manufacturers A.) knowing that they must control the frequency emission and B.) The honor system in making sure a product meets the requirements.
One wonders if the engineers who designed the control circuit ever even considered it to be a problem.
I Installed LED lighting in my garage and my 315 Mhz garage door remote(s) stopped working. It took me 3 days to troubleshoot and find this site/blog to finally test with the LED lights 'ON' my remote(s) would not communicate with my Chamberlain HD900D Whisper garage door opener but when I turned the LED lights 'OFF' remotes worked. I removed the LED bulbs and all is well
Something else just occurred to me regarding this situation in the article linked in the original post. When I was in the door industry, we had a mystery in the market here as well as only a few other select markets. Looking back at my note here, I wonder why I didn't mention it.
I believe it was 2005-the US military began to install proprietary communication systems at select bases. We had a few bases in our area, and we had customers who would complain-naturally the complaints came most often from customers with new installations or recent service calls complaining of the problem occurring only after we were there; but there were others as well.
The military communication system was installed in vehicles that traveled the area-for example, from one base to the next, or in conducting business in the local market in support of the base operation. The system would interfere in very random ways-either during the testing/evaluation phase or during operation when the vehicles were on the road. And then the interference would stop. It was very inconsistent as well-for example, it could interfere with one door in a house, and not the other.
So, we would get the call of a problem, go out, and everything was fine. Hundreds of times over many months and customers would act as if we were idiots or crooks for not fixing the problem. It took a while for the factory reps to A.) Believe us and B.) Connect the dots with-initially- just 2 other markets in the country. C.) Acknowledge the problem. Since the FCC grants licenses to private entities and assigns bandwidths, the garage door market has used a certain bandwidth range-since, I think, the 1960's. That range went unaffected for years, but the US Military holds a trump card and can just do as they wish; so they chose a bandwidth for the new system, and said nothing to the garage door industry. This wreaked havoc in our market and several others in the country before Washington decided to start to listen.
Not so remarkably I suppose, while we had figured out what the problem was, it didn't come full circle until one market was affected-yup---Metro DC. Once the Generals, Reps & Senators had trouble with their garage doors, the Pentagon began to talk to the industry. I do not recall how it was eventually solved, if ever in a complete way although the problem did seem to settle down after that.
So, the moral of the story is-don't trust the government or conventional wisdom. As it relates to this-it could be military interference. I wonder what the new domestic drones will be using as they come on line. Radio pollution is certainly a possibility-this example is just one case, but there are so many radio based systems now, it is probably going to be a recurring problem. Aren't Wii games radio based rather than IR like TV remotes? Don't immediately assume your newly installed LED's are the problem; timing of your installation may be sheer coincidence even if your customer doesn't want to believe it.
There's a technique for driving LEDs called pulse width modulation (PWM). It turns them on and off more than 15 times a second. Doing so saves electricity because you're only lighting the LED for half the time. It works because of persistance of vision.
PWM can cause radio interference. However, it seems odd to me that a whole neighborhood's garage door openers would be affected. I suspect something else is going on in the article you cite.
Radio or RF spectrum is like valueable real estate closely monitored and regulated by the FCC. Garage door openeners, RC cars, etc. and other similar devices fall under the "license free spectrum or bands" meaning anyone can use these frequencies without any close FCC oversight or specific license requirement which are needed for commerical use, ie radio, public safety, etc...These devices are low powered so the range is very limited. Garage door openers can be triggered by any number of devices that can generate a rf signal, intential or otherwise. Better quantiy recievers will filter these unwanted signals and in spite of the "digital codes" used it is possible to trigger an opener. Spurious RF interference generated from any number of devices can cause all sorts of problems- even a well designed cell phone can generate signals outside the cellular frequencies- think airline policy of shutting off your phone before takeoff.
Can a 120v.LED bulbgenerate onwanted RF signal to trigger a garage opener nearby- any RF engineer will say yes...A whole block of openers??? very unlikely The power supply switching circuits in the bulb in my opinion would be insufficient to generate the RF power needed.
One note-I addressed this just a moment ago above. But the garage door industry had the "rolling code technology" in place for quite some time when the military interference occurred. Even with a 1 in a billion chance of someone grabbing your code, it happened with the system.
I recall an issue a few years ago with openers in many homes that were close to airports. I don't recall the details, but something to check into for a possible solution.
It's not just garage door openers. A bit of web searching will show numerous instances of RF interference caused by LEDs. The more informative articles are written by Ham radio operators, who actually know something about Radio Frequency Interference. The circuit that drives the light emitting element can product RFI. It's not difficult to design the circuitry to eliminate this interference, but like everything else, cheaper sells better, and cheaper means cutting corners. (Remember those really terrible CFLs that flickered and burned out early, back when CFLs were first introduced?)
As LEDs become more common, we'll hear more about problems with RFI. The solution is not giving up on LEDs, it's insisting that products that make it to market work properly. Requiring the FCC enforce it's regulatory duties would help. Over time, these things will get sorted out. Meanwhile, I'd suggest avoiding the cheapest LEDs -- there's a reason why they cost less. (Often, their light isn't very good, either!)
LEDs are pulsed on/off to get the maximum light from them while avoiding overheating. To run them on DC, they would need to be dimmer to keep from overheating. One can see this on/off cycle when using a laser pointer, too. Just scan quickly across a wall with a laser pointer and note the on/off cycling. As Joel pointed out, it's the persistence within our eyes that sees a bright light but not the brief off-cycle for cooling purposes.
Bring a handheld AM/FM radio to the store next time. Tune it between stations and use it as an RF detector. The AM band will pick up the 60 Hz of the line frequency, but should also pick up other strong RF signals such as those generated by a poorly designed LED circuit. Because of the high slew rate of the switching circuit, the tuning of the radio should be irrelevant.
If the RF noise from the LED lights is going through the AC lines, clamp a Radio Shack ferrite choke (# 273-105) on the lines near the source of the noise. If you put the cheap LED lamp into the garage door opener light socket, you may have a challenge eliminating interference. In that case, using a quality LED lamp as others suggested is your best recourse.