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The LED weirdness saga continues
Posted by: Buzz
Date: May 13, 2019 05:12PM
About a month ago, I posted about some issues we were having w/ a newly rebuilt hanging lamp. After a few days the cheapie Costco, dimmable 100W equiv, soft white LED bulb started acting up in its new socket. Occasionally it would not go on when the dimmer was slid all the way to full brightness. Sometimes it would take a few tries to go on, others it would go on after jiggling the bulb. Once on, the dimmer would work throughout its range, bud oddly, it would be brightest at about 85% - 90% power, then actually dim a bit at 100%.

I finally swapped the bulb out for an expensive, glass globed, Feit bulb w/ aluminum fins. It goes on immediately upon getting power, and doesn't have to get full power to start up like the cheaper one did. It's (the new Feit) behaving much like the expensive CREE bulb that failed shortly after the hanging lamp's reconstruction. FWIW, the old CREE, and new Feit, are made incredibly similarly.

I'm not sure what my conclusions are, other than that LED's w/ high wattage equiv, and dimmers, just don't naturally play nice together. I'm looking for an explanation that adds some clarity to these situations, so that dimmers can just work w/ dimmable rated LED's. Phillips has some charts online that list which popular dimmers work w/ each of their LED bulbs. This shouldn't be necessary; LED bulbs should just work w/ LED rated dimmers. There's obviously way more to dimmable LED's than just their light that meets our eyes.

We want answers!
Thanks.
==
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Re: The LED weirdness saga continues
Posted by: space-time
Date: May 13, 2019 05:36PM
incandescent bulbs were analog devices, with a well defined voltage-current characteristics. Not really linear, but you can think of it like a dumb resistor. you put more voltage, it takes more current.

the LED bulbs have AC/DC converters that are NOT linear at all. They are more like digital devices. If you increase the voltage by 10%, you don't necessarily use 10% more current. On top of that, dimmers come in many varieties, and usually they work but cutting the voltage ON/OFF faster that the 60 Hz (in fact 120 times per second) you get from outlet. They may keep the voltage ON for only 1/2 that amount (from zero to peak), and shut if off when the voltage drops from peak to zero. You can find details at Wikipedia. Here is a picture. Some LEDS respond to this kind of voltage in different ways.

Here are some links

[www.ledsmagazine.com]







Edited 1 time(s). Last edit at 05/13/2019 05:38PM by space-time.
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Re: The LED weirdness saga continues
Posted by: Buzz
Date: May 13, 2019 07:04PM
Thanks for the linked info, but it's way too smart for me. I liked the part where the guy also stated that LED bulbs just oughta work with dimmers similar to the way incandescent bulbs work. The techy stuff was above my pay grade. I just wanna know the quick and dirty of which dimmable LED bulb to grab.

FWIW, we have a very nice dimmable torchiere floor lamp that played nice with LED's for a few years after converting from incandescents, then stopped dimming, regardless of what LED bulb is used. A couple of local lamp shops would not guarantee that any replacement dimmer they put in would work reliably, and we've only been using a 60W equiv LED in the lamp.

Who'da thunk trying to go green w/ LED's would be so difficult?
==
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Re: The LED weirdness saga continues
Posted by: Yoyodyne ArtWorks
Date: May 13, 2019 08:20PM
Feit has supplanted Lucas as the Prince of Darkness...



Once we place nonhuman animals outside our sphere of moral consideration
and treat them as things we use to satisfy our own desires,
the outcome is predictable.

- Peter Singer
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Re: The LED weirdness saga continues
Posted by: space-time
Date: May 14, 2019 07:48AM
Who'da thunk trying to go green w/ LED's would be so difficult?

it is if you insist on using the same old hardware. it's like trying to use a Tesla Power Train in a 1950's car.
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Re: The LED weirdness saga continues
Posted by: Buzz
Date: May 14, 2019 12:22PM
Quote
space-time
Who'da thunk trying to go green w/ LED's would be so difficult?

it is if you insist on using the same old hardware. it's like trying to use a Tesla Power Train in a 1950's car.

Um, uh..., I want to put the Tesla underpinnings in a 1968 Dodge Charger R/T; I'm not dumb enough to try to put it into a 1950's car..., well, except for maybe a red 1959 Eldorado Biaritz droptop.



And I still want dimmable rated LED bulbs to work with LED rated dimmers.
==
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Re: The LED weirdness saga continues
Posted by: MrNoBody
Date: May 15, 2019 04:33AM
Great explanation space-time!
I used to pull my hair out trying to explain to clients why they couldn't
replace expensive AGM deep-cycle batteries with cheapo L-A batteries in their UPS systems
unless the on-board charger was programmable (most were not) and was correctly re-programmed.

Then there was the guy who thought he could make an cheap analog dimmer into
a motor speed controller...
hot smiley



N39° 39.7234', W075° 33.9788'
...word salad is not a disorder, it is a symptom...

“If you can't explain it to a six year old, you don't understand it yourself.”
-Albert Einstein

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