sort-of OT: interference to remote-control systems from fluorescent lighting

I guess I will go out on a limb and say the fluorescent lighting emits every little IR. Some of the UV from the mercury vapor arc will get through the phosphor. Any IR will come from the heating of the glass tube.

Also, the IR would have to match the coded signal that tells the VCR and TV to turn off. Any IR from the light would be steady. The UV would fluctuate 120 times per second.

Pretty slim chance of all that coming together at one time to tell the equipment to shut off.

Paul

Agreed. But it happens. I first observed it with a conventional fluorescent tube.

It's the electronic ballasts and switchers that run the fluorescent lights that are the culprit. Most IR remotes use a 38KHz carrier frequency. They can also be 33-40 or 50-60 KHz but those are uncommon. CCFL lights run between 40-70 KHz. If the frequencies match, you get interference problems.

Oddly, it's not false activation that causes the most complaints. It's the failure to detect a proper signal from the remote that's more common. Put a CCFL light near the TV and try using the remote. You may find that you have to press the buttons a few times in order to get a response, and that the remote range will be impacted. Turn off the CCFL light, and the problem goes away.

Also, plasma TV's belch plenty of IR and various switching frequencies which can affect IR remote receivers. As an added bonus, plasma TV's also belch quite a bit of RFI/EMI, which affects RF remote controls. These are often mistaken as IR interference as some remotes will do both IR and RF.

Aiwa AD 6900 susceptible, a small shroud over the sensor, stopping lamp light from the ceiling direction, stopped the interference

Electronic ballasts are evil for that, on account of their more or less unfiltered 40 kHz switching action. They put out crap that extends out way past 1 MHz.

Try magnetic ballasts if you can. (You can't with CFLs, of course.)

Cheers

Phil Hobbs

It may well be that flourescents put out very ittle IR, but what of the selectivity of the detector ? If the mix of the plastic isn't just right it could admit too much UV or even visible and pick it up as interference.

Of course the odds of it actually hitting a pulse train for a specific function are pretty tall, in fact it may be like hitting the lottery but it its playing maybe 30,000 tickets per second.

My only experience of this was the flourescent light would lock out any r/c use , not erroneous code interpretation. Much like those continuous

On Saturday, September 14, 2013 7:03:58 AM UTC-5, William Sommerwerck wrote :

m fluorescent lighting to interfere with remote-control systems? I've seen this with a Sony VCR. And the Vizio TV in my den shut off twice this mornin g. * (This happens several times a week.) * No, the sleep timer is not enga ged. "We already know the answers -- we just haven't asked the right questi ons." -- Edwin Land

I have seen this a number of times, just turned off the offending light to use the remote.

Don't discount this.

I recently asked a Xeror repair man to share one of the biggest head scratchers with me.

It was CFL or some type of discharge lighting in an office confusing the IR paper path sensors in one of those copier/scanner/do everything beasts. It caused the scanner paper feeder to fault, ever after it was replaced.

Repositioning the machine was the fix.

As the OP, I need to clarify is that this is /exactly/ what I experienced -- /not/ interference preventing my remote-control transmitter from operating, but the fluorescent light sending junk that the TV or VCR interpreted as a valid command.

This happened to me not only with CFLs, but a GE LightStick.

About 25 years ago, within a week of reading an article about fluorescent bulbs overdriving the sensor of remote control devices, I got a call. The remote for vcr had been in for repair, complaint "does not work". I tested it and it worked properly. I was on the phone with the customer and a bit perplexed, out of the blue I ask if had changed any lighting, he said yes, they had put in a fluorescent light. I ask him to shut it off, he did and the remote worked. I ask him if he put a book on the VCR would that shield the light from the vcr receiver. He tested it and that solved his problem. (yes light back on) :-) Mikek

What do RF emissions have to do with an infrared problem? Sunlight reflecting on something shiny, or directly shining on the IR receiver, will mess with the remote functions.

It's not an RF problem specifically.

The electronic ballasts operate at a high switching frequency, and this causes the fluorescent tubes to flicker at this frequency. Some of the tube output is IR.

TV remote controls operate via pulse-modulated IR. The pulse frequency is commonly in the 32 kHz - 40 kHz range. The IR receiver commonly has a bandpass filter after the photodiode/amplifier, in order to pass the correct frequency range and block out the effect of sunlight and low-frequency (e.g. 60 Hz) IR noise.

If a fluorescent light using an electronic ballast is "within view" of the TV remote's IR sensor, and if its switching frequency (and the tube flickering) is within the frequency passband of the IR receiver, then the IR receiver circuit will "see" the tube's output as a strong signal of pulses. If strong enough, it will interfere with the detection of the remote control's IR pulse sequence (which is in the same passband).

I would think the persistence of the fluorescing medium would make an RF excitation invisible.

It pretty well does, except in the closely-spaced emission lines, which respond fast, especially near the ends of the tubes. You can get annoying amounts of crap out past 1.5 MHz, even with carefully chosen interference filters.

See e.g. and

Cheers

Phil Hobbs

Take a small am portable radio and sniff around a fluorescent light fixture with a magnetic ballast, and then do the same thing in the area around any cfl which haall have electronic ballasts, or around a regular fluorescent fixture that has an electronic ballast. See which type of ballast generate s noise up into the AM MHz frequency band.

respond fast, especially near the ends of the tubes. You can get......"

I was thinking along similar lines sorta....

The IR might not really come from the phosphors so much as rom the arc itself. Unless the glass or something filters it there should be some output in those ranges.

Phil, a fluorescent lamp puts out noise well past 4 GHz. I used to use one on the bench to test C-band LNAs and LNBs. Noise sources use gas discharge tubes to produce broadband noise.

That's the blackbody noise of the plasma, though, which is a lot lower than the radiated harmonics of the switching frequency. (Besides, at

Cheers

Phil Hobbs