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#4488217 - 08/14/17 09:38 AM Strobe Effect with Decorative LED Candelabra Bulbs
Rhymingmechanic Offline


Registered: 08/13/04
Posts: 1325
Loc: VA
I have replaced most of the normal bulbs in my house with LEDs. But one of our most-used fixtures is a 5-bulb chandelier, currently running 40-watt halogen bulbs. I finally broke down and tried the 60-watt equivalent filament bulbs from Wal-Mart.

The light was really impressive--just as bright and the same color as the one remaining halogen (the LEDs came in a 4-pack). BUT--something about it seemed a little off. I chalked it up to dirty eyeglasses until after supper. When I wiped off the table, there was an obvious "strobe" effect as I moved the sponge back and forth. I'm pretty sure no good would come from spending a lot of time under those bulbs. sick

The bulbs arenít flickering in a noticeable way, and none of my full-size LED bulbs do this. The chandelier is on a dimmer, but the new bulbs did the same thing in two different ceiling fans, one with a dimmer and one without. A little google research tells me that cheaper internal electronics can cause this strobe effect.

So finally, hereís my questionóHas anyone here found a filament-type, decorative candelabra-base bulb that doesnít strobe? Thanks in advance for your ideas.

Iím talking about bulbs that look like this, not the ones that are solid on the bottom third:

[img]https://i5.walmartimages.com/asr/453f8c1...mp;odnBg=FFFFFF[/img]

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#4488225 - 08/14/17 09:47 AM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
LEDs run on DC and follow the waveform which feeds them. What they are getting is half a 60 cycle sine wave, not pure DC. The filament in a standard bulb gets current from both directions of the 60 cycle AC which doubles the blinking speed and makes it harder to see. In addition the filament retains heat and continues to glow in the "dead spot" where the current is changing directions. LEDs run on pure DC don't have the problem, but that would make them a more complicated device to build as a filament replacement, as a pure DC power supply would have to be built into each bulb. Dimming an LED is tricky because they are either on or off, no filament to keep glowing on retained heat so they are often pulsed, to dim them they are made to stay off for a greater time and the brain/eye relationship sees this as a dimmer output. It also contributes to the strobe effect.


Edited by HerrStig (08/14/17 09:54 AM)

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#4488230 - 08/14/17 09:50 AM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
Danno Offline


Registered: 10/07/12
Posts: 1990
Loc: Northern Ontario, Canada
I found these at Costco, they work well and no strobe effect as far as I can tell.

https://www.amazon.ca/Luminus-Dimmable-E...s=luminus+elite
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#4488243 - 08/14/17 10:07 AM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
My dining room light fixture holds 8 bulbs.
The sockets are wired together under an access cover on the bottom.

I changed the wiring "Phase" of four alternating sockets - the problem went away. 4 lights are on when the other 4 are off (60 cycles per second).

There used to be a drop-in rectifier available for incandescents called a "bulb life extender". I think all it was was a simple diode, but a full wave bridge rectifier would be IDEAL

http://powerdisc.com/about-powerdisc/
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#4488254 - 08/14/17 10:19 AM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
tmorris1 Offline


Registered: 07/15/03
Posts: 2364
Loc: MN
Get a new dimmer. I had horrible flicker and buzzing until I changed to a new dimmer that was supposed to work better with LED lighting.

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#4488453 - 08/14/17 02:52 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
DeepFriar Offline


Registered: 10/31/13
Posts: 1367
Loc: Georgia
I started noticing the flickering in auto test videos where, I guess, the shutter is accentuating the effect. I haven't noticed it at home yet.

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#4488463 - 08/14/17 03:10 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
LoneRanger Offline


Registered: 07/02/07
Posts: 4058
Loc: Midwest USA
Toxic light. Just kidding, but I agree, the effects of long term exposure to hyper strobing micro strobing whatever you want to call it from LED light sources is not fully known or even well studied, but hey we have to save the environment so to he1l with our brains. Bring on the strobe effect and roll those neurology dice.
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#4488465 - 08/14/17 03:13 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
Kawiguy454 Offline


Registered: 06/01/15
Posts: 579
Loc: Arizona
HerrStig is right on the money... The diodes only half rectify AC so the strobing is a known problem. Some of the better ones are now phasing the leds in paralell circuits as someone else pointed out. Inductors and capacitors can also be used to further phase shift as well to make the light output less "Switchy".
The way to test a cheapo bulb is to plug it into an extenion cord and wave it back and forth in low/no light. the blinking effect is very obvious doing this.

A standard dimmer has a SCR "Chopper" in it to cut off the AC wave to dim a bulb that can exacerbate the strobing of LED's. A LED friendly dimmer cures that issue.


Edited by Kawiguy454 (08/14/17 03:18 PM)

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#4488497 - 08/14/17 04:00 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
eljefino Offline


Registered: 06/15/03
Posts: 32635
Loc: ME
My xmas lights do this but none of my edison base "I'm a legit light bulb" replacements do. In fact many take 1/2 second to turn off just like a glowing incandescent would.

I have a CREE UPC 849665012153 candelabra that claims dimmability though I haven't tried it. Under full power it performs fine.

I lived under CFLs for a decade and these LEDs are way better on the eyeballs, saving the 1/2 wave xmas lights.

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#4488515 - 08/14/17 04:26 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
Rhymingmechanic Offline


Registered: 08/13/04
Posts: 1325
Loc: VA
Will an old dimmer cause problems at full power? I'm not concerned with dimming, but with getting lots of light without burning 2-300 watts.

The chandelier, with 4 LEDs and one halogen, dimmed normally. A second fixture buzzed at full power with 3 or 2 of 3 LEDs, and didn't dim the LEDs at all--they stayed at full brightness and then went dark about halfway. The strobe effect was still evident in a third fixture with no dimmer switch, so at least some of the problem would seem to be the bulbs themselves.

This is a rented house, so I don't want to change dimmers or dig into the wiring. If it was mine, I would replace the candelabra fixtures completely.

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#4488521 - 08/14/17 04:30 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
Rhymingmechanic Offline


Registered: 08/13/04
Posts: 1325
Loc: VA
Eljefino, is that one of the bulbs that's only clear on the top? One requirement here is that the bulbs can't be "ugly."

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#4488529 - 08/14/17 04:39 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
LoneRanger Offline


Registered: 07/02/07
Posts: 4058
Loc: Midwest USA
Why can't they just keep making incandescent bulbs?
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#4488584 - 08/14/17 05:53 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Rhymingmechanic]
eljefino Offline


Registered: 06/15/03
Posts: 32635
Loc: ME
Originally Posted By: Rhymingmechanic
Eljefino, is that one of the bulbs that's only clear on the top? One requirement here is that the bulbs can't be "ugly."


They're ugly! I use them for the candelabra base in a frosted glass fixture. The fixture is pretty cool and fits the room well, and my options in candelabra are limited.

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#4488602 - 08/14/17 06:21 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Linctex]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
Originally Posted By: Linctex
My dining room light fixture holds 8 bulbs.
The sockets are wired together under an access cover on the bottom.

I changed the wiring "Phase" of four alternating sockets - the problem went away. 4 lights are on when the other 4 are off (60 cycles per second).

There used to be a drop-in rectifier available for incandescents called a "bulb life extender". I think all it was was a simple diode, but a full wave bridge rectifier would be IDEAL

http://powerdisc.com/about-powerdisc/

I remember those "life extenders" but could never figure out what they accomplished. (This is arcane stuff for an oil website). I do recall discussions about DC power for the filaments of old tube type "Hi Fi" gear and a suggestions that the tubes didn't last as long on DC. DC was supposed to reduce hum but there are simpler ways to do it.
I's sure there's room in the base of a standard "medium base" LED lamp for a filtered power supply but in the small bulbs used for decorative purposes or nightlights there isn't much.

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#4488672 - 08/14/17 07:34 PM Re: Strobe Effect with Decorative LED Candelabra Bulbs [Re: Linctex]
danez_yoda Offline


Registered: 07/18/09
Posts: 464
Loc: texas
Originally Posted By: Linctex
My dining room light fixture holds 8 bulbs.
The sockets are wired together under an access cover on the bottom.

I changed the wiring "Phase" of four alternating sockets - the problem went away. 4 lights are on when the other 4 are off (60 cycles per second).

There used to be a drop-in rectifier available for incandescents called a "bulb life extender". I think all it was was a simple diode, but a full wave bridge rectifier would be IDEAL

http://powerdisc.com/about-powerdisc/



EE here.

Ive been toying with adding a full wave rectifier to my 6 light chandelier. Linctex's approach of swapping the phase on alternating pairs is pretty cool. The only mild concern is that the screw base is usually ground and low voltage compared to neutral (metal structure of chandelier.) This could be a shock hazard when changing the bulbs.

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