LED lights affecting electronics like TV's

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181124-0723 EST

codetalker:

You are correct that, if the manufacturer is to produce an electrically efficient small current source to drive the LED chips, then higher than normal AC line frequency will be required.

Flicker has more than one meaning. One is periodic and another is random.

A periodic flicker occurs when a movie projector is operated at a low frame rate. I believe one movie standard was 24 frames per second, and this seemed to work well. But when TV started out 30 was a logical value synced to line frequency, but this produced too much flicker, and the interlaced concept was invented. Interlacing raised the rate to 60 frames per second without increasing the bandwidth for the same resolution.

Random flickering is what one sees with a candle flame or a loose intermittent electrical connection.

Both these types of flicker occur with some LED bulbs.

I am not sure that it is necessary to go to pure DC at the LED to eliminate flicker for two reasons.

First, illumination type LEDs use a short wavelength LED, the LED itself is very fast, to excite phosphors of various colors in the visible spectrum. Phosphors have moderately long time constants compared to the exciting LEDs, they are a low pass filter. If the excitation pulse rate is high enough, then the phosphor should provide the DC filtering. So this should take care of the periodic flicker. Further the eye brain combination is a low pass filter.

Second, random flicker is probably a result of other problems than pulse rate. Going to pure DC does not solve this problem. Possibilities are --- loose heat sinks. This is a very long time constant, possibly minutes. --- Others are poor electrical design.

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WarrMann said:
That's not correct.

If you balance the loads in a residential panel (or any multi phase panel for that matter) you can, in theory, have no current on the neutral. Not everything in that panel has to be on 240 for that to happen either.

Example - 10 amps on leg A, and 8.5 amps on leg B. You should get 1.5 amps on the neutral. Now, if you add a 120volt, 1.5 amp load to leg B you will have zero amps on the neutral. That's why neutrals are sometimes sized only for the "unbalanced" loads.


Side note - try recording a crappy LED light in slow motion in your phone. You can almost count the the rise and fall of the sine wave



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You won't capture the high speed switching current with a typical clamp on meter. True RMS meter may give you different result than other clamp meter though, but both are giving you some sort of an average result and not giving you the distortion that a oscilloscope would show you.

codetalker said:
I typed a bit too fast on that answer, I thought they were troubleshooting. Never heard of load balancing with that small of a current.

The answer to load balancing is "never going to happen" with triacs clanking away on the AC line.


Also; Is there a button someplace to edit a post. Thanks
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You only have five or ten minutes after posting to be able to edit. If there is no "edit post" button at the bottom of your post, that time had expired at the time you last refreshed the page. If you haven't refreshed the page and edit time has expired it will return a message telling you that time is expired.

I think this is for good reason. It can get really confusing if you have several replies and then someone comes back and changes what they said early on. If you want to change a spelling error or something not too critical to the conversation in general you can ask a moderator if they will change it for you. Otherwise it is less confusing if you just later post that you made a mistake and "this is what I intended" instead of sneaking back and changing the original and potentially making posts afterward refer to something that is no longer there.
 
What kind of TV? CRT, LED, plasma?

What kind of signal? Over the air, cable TV, streaming?
 
kwired said:
You only have five or ten minutes after posting to be able to edit.
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Thanks, that makes since. I like to be able to go back and fix spelling errors that I find the next day.:)

The LED lighting industry has decided to use phosphors to fill the gaps of no light between the ON/OFF times. The phosphors are materials like tritium. I can't believe what manufacturing/industry will do to save a penny. If they just worked on the electronics design i believe they could make the lights work without adding dangerous materials that fill the landfills. They are heading down the same path as the CFLs.
 
codetalker said:
Thanks, that makes since. I like to be able to go back and fix spelling errors that I find the next day.:)

The LED lighting industry has decided to use phosphors to fill the gaps of no light between the ON/OFF times. The phosphors are materials like tritium.
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Tritium, seriously? Hydrogen with two neutrons? Whatever for?
 
181124-1656 EST

LarryFine:

I did a quick experiment.

First, with a square wave excitation to a ordinary red LED I saw substantial flicker at 20 Hz, and at at 25 Hz the light was steady to me.

Second, I increased the square wave frequency to 200 Hz. With my function generator the frequency changes as I change duty cycle, but the pulse width holds constant.

For the same current drive the brightness dims as the duty cycle decreases. Thus, to some extent the eye brain combination is sensing average power.

This experiment is insufficient to determine if there is a brightness advantage to pulsing the LED with constant input power to the LED. Some time later I will try such an experiment.


codetalker:

Phosphors are used to generate visible light of appropriate frequencies to provide something approximating white or other specific desired colors. It just happens that phosphors also have a moderate time constant and serve as a low pass filter on the AC modulating frequencies.

With present knowlege you won't eliminate phosphors in any of incandescent, fluoresent, or LED light sources.

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gar said:
181124-1656 EST
codetalker:



With present knowlege you won't eliminate phosphors in any of incandescent, fluoresent, or LED light sources.

..
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I was under the impression that typical incandescent bulbs, especially halogen cycle bulbs operating at high temperature, did not need phosphors to produce white light. The black body radiation spectrum is good enough, and phosphors are most useful in converting short wavelength light energy to longer wavelengths. Not needed in your typical incandescent light. Now *filtering out* red end energy can improve the color temperature of tungsten light, but that does not involve phosphors.


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gar said:
181125-2414 EST

GoldDigger:

I am trying to find the reference that had mentioned phosphors in incandescent bulbs. It might have been Philips. But so far I have not found it, but there are many interesting articles, such as https://www.bbc.com/news/science-environment-35284112 . Using the search string --- incandescent bulb efficiency improvement --- I found many interesting sites.

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:thumbsup:
As I said, filtering of the infrared, with refocusing it back at the filament providing even more improvement.
 
This is way over my head. I got lost with the phosphors, infrared, filtering, etc. I respect you all for your knowledge of electronics I don't have. But as for my question, it sounds like separating lighting circuits from receptacle circuits won't help any, is that right ? Thank you.
 
181127-0808 EST

Stevenfyeager:

The definition of the word separating is the hang up.

As you are are using the word separate it means the circuits are on different breakers. So in this use of the word a short on one circuit should not trip the breaker of another circuit.

From an electrical conductivity perspective, if the breakers of two circuits are closed, then current can flow from one circuit to the other. As an example: When I loose electric power I pull my main fuses to disconnect from the power company. Next I connect my portable generator to a circuit. Now that generator connects to all circuits with closed breakers on the same bus. So from a conductivity view all those circuits are connected together.

This is what happens when you have a noise source on one circuit. The noise is the generator and its signal propagates to all connected circuits that are not isolated by a suitable filter. When closed, breakers or fuses, are very nice low impedance paths.

Carrier current signals, such as X10, propagate to all connected circuits. In a split phase system the X10 110 kHz signal usually will not couple from one phase to the other without a bridge, capacitor, between the two phases. However, on one phase of your system your X10 signal may propagate to the same phase of a neighbor on your transformer.

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Stevenfyeager said:
This is way over my head. I got lost with the phosphors, infrared, filtering, etc. I respect you all for your knowledge of electronics I don't have. But as for my question, it sounds like separating lighting circuits from receptacle circuits won't help any, is that right ? Thank you.
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It depends on what is causing the problems. As mentioned two separate branch circuits from same source still have some common components that may affect both individual branch circuits. Simple voltage drop issues will be different when two items are on different branch circuits, but simple voltage drop occurring on the service or feeder conductors will affect both branch circuits. Other "noise" issues gets more complicated.
 
gar said:
181127-0808 EST


This is what happens when you have a noise source on one circuit. The noise is the generator and its signal propagates to all connected circuits that are not isolated by a suitable filter. When closed, breakers or fuses, are very nice low impedance paths.
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True, but wiring does do some filtering just from the impedance of the conductors. I deal with power line data transmission (which is noise from the AC perspective) for residential PV system monitoring, and I know that the farther away, electrically, the receiver is from the transmitter, the less reliable the data is.
 
181127-1145 EST

ggunn:

There is impedance, but from a practical perspective conductive and radiated noise from residential systems is substantial with some light and other sources. In the past, and still the case, in all my 8' Slimline fixtures I have installed a Corcom filter that greatly reduces my RFI problems. This is not practical to do for a 9.5 W LED.

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