Hello:

I am using a KORAD KD3005SP programmable power supply and a DS1000Z digital scope. All of the measurements are contained the two screen shots of my post 1.

"It is just a light bulb", I told myself when this started. Who knew?

I am going to take a little break on this and re-do the experiment. I am going to use a SLA 12V battery for the power source and see about borrowing a AM radio.

(I understand that AM radios receive signals thru the air, rather than the internet and are a good way to detect RFI)

I am going to obtain another package of the same brand of bulb in a few days and have ordered another brand from Amazon.

I would hope that this a benign "problem" and I suspect that it is, but it still rather interesting to me.

Back in the day, I was an senior electronics tech and then an associate manufacturing engineer for a company that made telephone equipment. The time and expense that we invested in passing FCC and UL was considerable. But who knew this is a issue for light bulb manufactures!

Any other thoughts? It would be good if someone could verify this independently.

Give me a week or so and I will give it another go.

 

I'm quite certain the clerk did not "comprehend" the issue. If they did - that would be a rare occurrence and one would have to wonder what they're doing working in a store instead of an electronics company. We understand it because we've been in the industry for many years. Even still, some here actually don't understand (comprehend) the issue.

I'm surprised at MrAl's comment about LED headlights causing AM interference. I never heard of that before. And would not have expected that.

I think it was FM too.

 

Satco 6.5 watt; LED MR16 LED; 5000K; 25' Beam Spread; GU5.3 Base; 12 Volt AC/DC -

As they say a picture is worth a thousand words.

I guess the problem was I was using a cheap product.

I am a little disappointed in True Value Hardware

I try to support local businesses, but I guess I will take even more of my business to Amazon.

 

Not much RF riding on this LED, but some. No where near the one in post 1.

 

Satco 6.5 watt; LED MR16 LED; 5000K; 25' Beam Spread; GU5.3 Base; 12 Volt AC/DC -

As they say a picture is worth a thousand words.

I guess the problem was I was using a cheap product.

I am a little disappointed in True Value Hardware

I try to support local businesses, but I guess I will take even more of my business to Amazon.

What I don't see is the way you have acquired these waveforms.
Post a diagram of the test setup? Where is the scope connected?

 

Y'all won't believe what I stumbled upon: H11 LED bulbs. A set that will fit my truck. Only cost me $1.99. Even if they cheap out - it's worth the very small investment. I'll be putting them on my fog lamps. Plug and play. Last night I was playing with them on the bench. DANG they're bright! Was blinded for several minutes. It will be interesting to see if they're "Noisy". And no, I didn't scope them. I suppose I could do that. Maybe. Meanwhile my neighbor is building a shed. Yes, in this heat! He's as sharp as a fuzzy tennis ball, but I love him. Great guy.

 

My test set up is pretty basic.

I intentionally made the connections fairly sloppy in order to maximize any overriding noise.

Note the scope is displaying is still displaying about 120mVac of noise as opposed to the nearly 10Vpk-pk waveform in post 1

 

The question was posed in post #2, and I ask it again: Was this noise causing any problems, any interference with anything?
AND, was there any information on the packaging that implied any required filtering, or warned about any possible interference??
If that noise is not radiated, but only present on the power wires, then a bit of filtering should be quite adequate.

 

The question was posed in post #2, and I ask it again: Was this noise causing any problems, any interference with anything?
AND, was there any information on the packaging that implied any required filtering, or warned about any possible interference??
If that noise is not radiated, but only present on the power wires, then a bit of filtering should be quite adequate.

You are quite right. I have experienced NO PROBLEMS from this.

I did not want to imply that this product was defective and not in compliance with FCC pt 15. I apologize.
There was a FCC part 15 statement on the product and no notices stating that any filtering is required.

I am reduced to wondering why this product has TEN times the apparent RFI than the two other ones.

I do not think that a customer using these lights would even know that there is an issue, or that a "issue" even exists.

I personally will use the lower "EMI" producing product even if I have to pay a little bit more for them and feel fortunate that I have the means to check them.

Do you not smell even a very small rodent?

 

You are quite right. I have experienced NO PROBLEMS from this.

I did not want to imply that this product was defective and not in compliance with FCC pt 15. I apologize.
There was a FCC part 15 statement on the product and no notices stating that any filtering is required.

I am reduced to wondering why this product has TEN times the apparent RFI than the two other ones.

I do not think that a customer using these lights would even know that there is an issue, or that a "issue" even exists.

I personally will use the lower "EMI" producing product even if I have to pay a little bit more for them and feel fortunate that I have the means to check them.

Do you not smell even a very small rodent?

Presently I doubt that I could smell a dead water buffalo that had been ripening under the hot sun for a few days.
Some products are noisier than others, and a test setup that allows a voltage variation in response to current variations iis creating an issue that may not be valid.
Certainly different products can be different in those specifications that are not claimed. That is true with most semiconductor products, even.

 

All he wanted to know was "Why?" At least that's the gist I get from his comments.

 

The "Why" is that designing a "quiet" switcher supply is a lot more effort than one that is not as quiet. And the components for a quiet supply cost more because there are more of them, which makes the assembly cost more as well.
So really it all gets down to the money and the profit, and also, some designers are much more skilled than others.

 

Just saying my take on the point of the question was why does one display more noise than another. I'd offer an answer but I'd be guessing.

Anyway - whatever.

 

Hi,

Maybe throw a capacitor across it get it over with.
That might actually work.