LED interference

[gar]

160221-1550 EST

tkb:

You are absolutely correct in your analysis, and definitly use 130 V bulbs.


Back to interference:

I have four Kirlan fixtures in my breezeway. Originally I would have used either a 150 or 100 W bulb starting 50 years ago. These did not have a long life and were a nuisance to change. 130 V or long life incandescents were very expensive or not available, and I never set up a reduced source voltage, just lazy. When CFLs came along I started using them. Better life, but poor output vs temperature.

After I got the Feit and tested them, then I put two noisy ones in the breezway. The cold weather light level is much better. Today I decided to test for radio interference. The garage has not had a car in it for possibly 30 years. The breezway is the parking location. Presently is daytime and on my strong WJR 760 kHz signal the Feit did not interfere. Later at night I will try the test again. If I tune to a weak station nearer 1000 kHz, then I get a strong 120 Hz modulated noise that is well above the radio's background noise level and that is correlated with turning on and off the breezway lights. This is not a big problem because the lights are not on normally when I need low background noise.

My breezway is a partial screen room because the ceiling is an expanded metal lath for the plaster. At night there is a noticable signal strength reduction when I pull into the shaded area.

The other two fixtures will get Feits, but I won't buy any more Feits.

Anyone going to LEDs should evaluate a particular light for radio or other interference. I think the FCC needs to look into this problem.

I am going to gradually replace my 8' Slimline fixtures with LEDs. Bulb life has shortened greatly in recent years for fluorescents, and my limited testing on LEDs shows good performance and lower electrical cost. From the start I had put noise filters on all my 8' fixtures, otherwise there was a lot of radio interference. The cheap LED fixtures I have tested do not create RFI.

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[don_resqcapt19]

...
He said that there is no way that an LED would interfere and the LED would last forever.
...

Tell him to go open a box for a Chamberlain opener and read the instructions. I replaced on in my garage last summer and in bold letters the instructions say not to use LED lamps..

NOTEo not use halogen,shortneck, or specialty light bulbs as these may over heat the end panel or light socket.
Do not use LED bulbs as they may reduce the range or performance of your remote controls.

 

[gar]

160222-2350 EST

Last night I did a radio test relative to my breezway Feits, still only two. First I turned off my dimmers in the house because they are major noise sources.

WJR 760 kHz was not bothered by the Feits, but from about 900 to 1100 kHz there was substantuial noise with the characteristic 120 Hz modulation, and a peak signal about 1050 kHz. This is what I would expect based on my bench tests and estimated frequency of oscillation in the middle of the Feit current pulse.

If the rectangular shape of the currrent pulse was a major problem, then I should have detected it in other portions of the AM band. That I did not detect.

,

 

[James L]

160222-2350 EST

Last night I did a radio test relative to my breezway Feits, still only two. First I turned off my dimmers in the house because they are major noise sources.

WJR 760 kHz was not bothered by the Feits, but from about 900 to 1100 kHz there was substantuial noise with the characteristic 120 Hz modulation, and a peak signal about 1050 kHz. This is what I would expect based on my bench tests and estimated frequency of oscillation in the middle of the Feit current pulse.

If the rectangular shape of the currrent pulse was a major problem, then I should have detected it in other portions of the AM band. That I did not detect.

,

I was looking at some Utilitech svrew-in bulbs and noticed a warning that said something to the effect that FCC requires that the bulb cannot cause "harmful" interference, and must accept any interference - even if it creates undesirable performance in the bulb.

 

[mgookin]

I was looking at some Utilitech svrew-in bulbs and noticed a warning that said something to the effect that FCC requires that the bulb cannot cause "harmful" interference, and must accept any interference - even if it creates undesirable performance in the bulb.

That's the FCC Part 15 nomenclature for unintentional radiators.
What it means is that by using it, you agree not to complain that someone else is doing something that's interfering with your ability to use that product.
And further that if your product interferes with something else, you agree to stop using it.
Unintentional radiator testing is done with anything that has a high frequency, such as cpu's & other electrical devices. Your light has a driver in it.

 

[gar]

A different model Feit 9.5 W LED

A different model Feit 9.5 W LED

160229-1016 EST

My son bought 4 Feit 9.6 W LEDs this weekend at Costco, for about $3 ($0.75 each). Supposedly these are dimmable, I did not try that fuction. My test was for RFI.

This bulb has a horrible current waveform with an approximate 50 kHz signal on it. On an AM radio loud at about 550 kHz, and repeats about every 50 kHz as expected, and by around 1100 kHz is not too severe.

Current measurent shunt is three 2.7 ohm carbon comp resistors in series.


The AC line current at 2 mS/major division:





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Time base changed to 20 microsecond per major division to estimate oscillation frequency:





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[mgookin]

Gar:
Have you ever scoped inrush on LED vs. incandescent?
It's my understanding that for LED the magnitude is much greater but for a shorter duration and the waveform is more spiked than curved. I'd be interested to see some real world results.

 

[gadfly56]

I put LED bulbs in my garage door opener. It's a Marantec opener. This unit holds 3 bulbs. I put in 60 watt LED equivalents. All the sudden the remote stopped working consistently. The keypad outside the door stopped working. A lot of intermittent problems. I realized most of the problems were when the lights were on.

I pulled the LED's and went back to A-lamp incandescents. Bingo, problem resolved.

Never had an LED cause interference before, but I'm disappointed I can't save money on my electric bill.

I may try compact fluorescents next. Hopefully the ballast is not as noisy as the LED driver.

I don't know if control circuits for AC and DC are similar, but I discovered by accident that there's some kind of chopper circuit involved. My IT guy was checking out the inside of a desktop and asked to borrow my MagLite. Next thing I hear is an expletive, and I look over and the fan for the power supply isn't moving. Except, we could hear it. So he points the light away from the PS and we see that the fan is spinning fine. Point it back, and it looks frozen again. I'm not surprised that the bulbs are causing interference.

 

[GoldDigger]

I don't know if control circuits for AC and DC are similar, but I discovered by accident that there's some kind of chopper circuit involved. My IT guy was checking out the inside of a desktop and asked to borrow my MagLite. Next thing I hear is an expletive, and I look over and the fan for the power supply isn't moving. Except, we could hear it. So he points the light away from the PS and we see that the fan is spinning fine. Point it back, and it looks frozen again. I'm not surprised that the bulbs are causing interference.

They are often very dissimilar. For a DC drive chopping is the only way to regulate or reduce current without wasting energy in a resistance, With AC you can use phase angle control at 120 Hz. Both can be noisy though.

 

[gadfly56]

They are often very dissimilar. For a DC drive chopping is the only way to regulate or reduce current without wasting energy in a resistance, With AC you can use phase angle control at 120 Hz. Both can be noisy though.

Not to get too far off topic, but if you've got LED under-cabinet lights running off a transformer, they're probably using a chopper circuit?

 

[gar]

160229-1236 EST

mgookin:

I have plotted an incandescent a number of years ago. See photo P3 at my website http://beta-a2.com/EE-photos.html .

For a 100 W bulb turned on at a 120 V RMS sine wave peak the peak current was 16 A vs 1.2 peak at steady state. This can also be calculated from 170/10.2 = 16.7 A. Scale this to 60 W and peak current is 16.7*0.6 = 10 A. RMS of 1.2 peak is 0.85 A, and 120*0.85 = 102 W, adequate check.

You will have to wait a while before I setup to do the LED.

I am doing some experiments with LEDs, but I don't have a good setup at the moment. However, as a preliminary rough statement the 9.5 W LED peak inrush may be less than the 60 W incandescent, and very roughly about the same duration. At the moment I am using a mechanical contact and there is oscillation with large short spikes from contact bounce, but these are really not part of what the bulb electronics produces for inrush.

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[gar]

160201-2134 EST

This post is simply to provide some information about my present test circuit.

The current sensor is an LEM Hall sensor using feedback and a null balancing of the magnetic field. The present tests are with 10 turns thru the sensor window to multiply sensitivity by 10. Very approximate full scale is 10 A peak.

The measured inductance of the 10 turn loop at about 100 kHz is 4 micro Henrys.

Switching of the applied voltage is a mercury wetted contact relay to minimize contact bounce.

In this post two tests were performed using a CD capacitor box. The only explicit load on the switch output was 0.001 ufd or 0.005 ufd plus a small amount of scope probe capacitance.

With the 0.001 capacitor the oscillation was about 2 mHz. Calculated total inductance is about 6.2 microH. With the 0.005 mfd capacitor oscillation was about 760 kHz and calculated inductance about 8.5 microH. Thus, we see more inductance in the larger capacitor as might be expected.


0.001 mfd:


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0.005 mfd:




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Thus, the inductance of the current sensor becomes an error component in the measurement of very short current pulses that needs to be considered.

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[gar]

160302-1114 EST

We have drifted from the OP and I would be interested to know if by changing the bulbs to present CREE bulbs solves the interference problem since I don't see much high frequency stuff in the CREE current. But I do need to a radio test on the CREE.

Back to the diversion.

By accident I shorted the NO contacts on my mercury wetted contact relay, and for the present I am back to a P&B KUP relay. But before the mercury relay failure I did answer a question that is important to the following measurements. A 1 microsecond or thereabouts pulse in both current and voltage is introduced by the current sensor and is to be ignored in our present measurements.

At the present time I obtain a measurement with turn on near a voltage peak by multiple random tries until I get one close to the peak.

Red is voltage, blue is current.



60 W 130 V Ace incandescent:
Peak current about 7.2 A. Peak steady-state about 0.7 A, 0.5 A RMS.





9.5 W (60 W equivalent) 120 V CREE LED, vintage 2013:
Peak current about 5.9 A with a somewhat typical RC charging curve.
The gradual rise to peak is an inductive effect.
This pulse can be described as near maximum peak inrush current. But this peak will vary greatly as a function of the turn-on time in the AC cycle.
Rated RMS steady-state current of 0.078 A.





Expaned time base of the same measurement.




.
.
9.5 W (60 W equivalent) 120 V Feit LED, vintage 2016 Home Depot sale:
Peak inrush current about 0.0 A.
Rated RMS steady-state current of 0.093 A.
Lots of RFI.

 

[gar]

160302-1329 EST

On interference:

Using my Panasonic broadcast to 30 MHz receiver, and a CREE from 2013, or a present one, my obseravations were:

The receiver has an attached antenna coil for the broadcast band, and I used a 2 meter 1/4 wave antenna for all other bands.

With the bulb directly on top of the receiver there is magneticly coup[led noise directed coupled into the set. With the bulb four feet away, but still plugged into the same socket as the receiver, and this magnetically coupled noise is gone on all tested frequencies.

I don't have a screen room.

There was some power line coupling at 15+ MHz that was removed with a Corcom filter.

At 30 MHz there was no RF coupling from 6 ft away.

In a garage door opener is the interference from magnetic coupling or radiation?

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[ELA]

Gar,
.... Did you get an oscilloscope for Christmas :happyyes:

Here is an old capture from an LED bulb with lots of noise. I have a home automation system that is sensitive to interference so I used to test all my led bulbs before installing. I returned this one. Some are good and others not so good.

 

[spark master]

Did I mention it above ??? This thread got too cluttered..

I installed FIET LED's, and now it works fine. I can spend time in my garage, play with my motorized toys. FIET LED's throw off good light. The MAXlites went into the basement.