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 Post subject: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 4:33 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Watsonville, CA, US
I made some under cabinet lighting for my shop with an LED strip.

https://www.lightingever.com/led-strip- ... htness=863

The 5A 12V DC supply provided makes nasty RFI. Other wall warts and a 12V battery run the lights and do no make the RF hash. The other wall warts have insufficient capacity an overheat .

How do I figure out if a supply will cause RFI when shopping for the replacement?


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 4:47 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Detroit, MI USA
Switching type supplies which are nearly always the only thing available as original equipment with anything you buy today are notorious for RFI.

Linear/analog types are much quieter, and usually easier to modify to further reduce RFI when necessary.

One big issue would be finding one that can be disassembled in case you needed to do that.

Another big issue is that a linear/analog type supply at that voltage and current rating is going to be large and heavy.

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 6:00 am 
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Joined: Jul Thu 29, 2010 5:35 am
Posts: 929
Location: Simonton, Texas
I put under counter LED lights in my kitchen when we redid the counters after our house flooded last year.

I bought 3 extra so I would have spares if one ever went out. when I was redoing my radio room I

thought about putting a couple on the work bench. I took a transistor radio into the kitchen and put

it up near the LED lights and there was a lot of static coming off the lights so I ditched that idea and

went with incandescent in the radio room. Oh well!

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 5:03 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Watsonville, CA, US
I further searched my place and found a power supply for an old CPAP machine. It is the full 5A and 12VDC. No noise at all.

I was thinking of replacing the overhead T12 florescents with LED strips. I guess I'll find quite power supplies before I do that. As I look at power supplies I see 24VDC is common. If I wire two 12VDC 5A LED strips in series will the 24VDC 5A supply have sufficient current? Sorry, my OHM's law visualization is shaky.


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 5:22 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9231
Location: Santa Rosa, CA
Quote:
I was thinking of replacing the overhead T12 florescents with LED strips. I guess I'll find quite power supplies before I do that. As I look at power supplies I see 24VDC is common. If I wire two 12VDC 5A LED strips in series will the 24VDC 5A supply have sufficient current? Sorry, my OHM's law visualization is shaky.


Should be OK, but not much margin. Can you actually wire them in series or do they need a ground connection?

Note: most any small power supply you can buy readily will be a switch-mode design. It's economical, small, and efficient. The down-side is that many such supplies are designed without much concern about RFI problems.

Rich


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Mon 05, 2018 11:09 pm 
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Joined: Apr Thu 21, 2011 2:00 am
Posts: 3266
Location: Georgia, 30236
I've had to pick out likely power supplies to replace noisy OEM units and I have had the best luck with units having a current rating higher than the OEM unit and a power supply carrying a well known and trustworthy manufacturers' name. I also try to go with relatively new supplies. You can usually tell by how ratty they look. I can find likely prospects at thrift stores and Ebay.

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 1:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Watsonville, CA, US
That is what I was thinking, bring a radio to the second hand store and try them.

Also many supplies sold do not even claim to be FCC certified . It is printed on the label if they are, and you believe the label to be real.


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 1:06 am 
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Location: Georgia, 30236
If you get one that was supplied by a good manufacturer to power their products, they are usually quiet, as long they aren't running at max capacity.

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 2:12 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Watsonville, CA, US
I looked at the power supplies that came with the LED strips. They do not have any FCC compliant logo. For 5-bucks more I found compliant units from another vendor. I wrote a review on amazon point out they are selling non compliant power supplies and explained why that is a problem. I'll throw these in the trash and buy better units.

Isn't it illegal to sell them in the first place?

I am very frustrated by being sold garbage and being outright defrauded. Not just this but other high dollar purchases. It happens way to often.


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 3:47 am 
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Location: Georgia, 30236
Who will prosecute?

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 4:24 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12497
Location: Omak,wa,usa
Hello 19&41
Who will prosecute? I agree there is so much garbage being sold nowdays
I don't think they really care because they arwe getting their cut

Anyway far as a powersupply I would use a old linear supply used to power cb or radio from 12 volts
and those are getting hard to find to i blame the whole green movement


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 5:17 am 
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Location: Georgia, 30236
It's aggravating. On the one hand, inexpensive products, on the other hand, those same products generating RFI. No one wants to complain. I have gotten about 6 powered devices, 3 came with supplies that generated hash, that I had to replace.

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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 4:37 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 18604
Location: Warner Robins, GA
Scot Armstrong wrote:
I was thinking of replacing the overhead T12 florescents with LED strips. I guess I'll find quite power supplies before I do that. As I look at power supplies I see 24VDC is common. If I wire two 12VDC 5A LED strips in series will the 24VDC 5A supply have sufficient current? Sorry, my OHM's law visualization is shaky.


Before you go through all the trouble look for the FEIT 4' LED replacement tubes sold at Lowe's. You just disconnect power from the ballast and wire in the power wire from the LED replacement and install the bulbs in the holders.

Those produce no RFI whatsoever that I can detect. My dad's shop is full of them. Two fixtures he leaves on nearly 18 hours a day 7 days a week and they have worked reliably for nearly 2 years.

Had the occasion to open one up and the first board where the power wire connects I thought was a capacitor dropper, but when the LED strip wouldn't come out I found the LED power supply in the other end cap and that first board with a few caps and inductors is the RFI filter.


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 4:47 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1488
Location: Watsonville, CA, US
LED fluorescent tube replacements...Holy Smokes! Just loose the ballasts?

Those got cheap. The price would be similar to my plan to use two $10 16' strips and a single driver. I was going to use a two 1x4x8' pieces of painted wood and stick the strips to it. That would get screwed to the ceiling.


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 Post subject: Re: RFI LED Powersupply
PostPosted: Feb Tue 06, 2018 5:50 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 18604
Location: Warner Robins, GA
Think this is the one I used.

https://www.lowes.com/pd/Feit-Electric- ... b/50261265


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