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Strobing LED bulb (not supposed to strobe)


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Posted

Throwing this out there for any EE's.  At my church, I recently replaced all of our 110 60 watt candelabra bulbs with 5.5 watt Philips true color bulbs that turn orange like incandescent does when dimmed.  I also put in Insteon switches for everything (since now we don't have a gazillion watts on each switch).  The bulbs look beautiful, better in fact than incandescent because the "filament" is much larger the light is softer on the eyes when you look directly at them, much more candle like.

Anyway, in one of the back areas there are 4 bulbs on an Insteon switch that would blink rapidly, like a strobe light.  I came to discover that a coat closet light was also on the same circuit and appears to be the source of the issue.  This light is a ceiling fixture with like a hundred small white leds on a panel.  I found that when you turn the Insteon switch on (and it may happen with dumb switches too, not sure), the closet light doesn't come on and the other leds strobe.  If I mess with the other bulbs, unscrew, rescrew, or giggle the closet light fixture, the closet comes on and the others stop strobing.  What the heck is going on?  All I can figure is some sort of harmonic oscillation is going on between the power sources of the different lights.  Probably going to replace the closet light, but still I am a bit baffled as to how this is happening.

Second curious thing, Philips led bulbs on two hanging fixtures cause noise on the sound system (60 hz hum).  These hanging lights are at the chanter stands and there is a mic wire woven down the chain along with the power wire.  It appears that the led's put noise on the power wire that is getting on to the mic wire as they run parallel to each other for about 5 feet.  I had to switch those back to incandescent.  Just isn't worth the tiny electricity savings to try and shield that wire.  Unless someone has an easy fix.

 

Happy New Year

Posted

I find mixing LEDs with one incandescent provides enough stable load to fix any dimmer I have used so far. The dimmer electronics and the LED bulb loading seems to be the problem and a very small load to fill in the zero crossing gaps that LED PSUs do not draw usually causes the dimer to stabilise.

The trouble is finding a spot for an incandescent bulb that doesn;t appear very odd. Middle bulb (or every second bulb) of a chandelier, or smoked / antiqued glass bulb covers can usually hide the differences enough to work.

Posted

I've used that trick with the one incandescant a few times.  Especially when I used cheap Costco leds a few years ago.  Down low they would have real issues.  Better Leds have come down in price and have been another way to solve the issue.

 

Posted

@larryllix @sjenkins  I'm pretty sure this has nothing to do with the dimmer.  I have about a dozen of the same insteon dimmers controlling the same philips bulbs on different circuits without issue.  I also had the same dimmer controlling this circuit when it was that closet led (unknown brand) with incandescent candelabra bulbs and it didn't do anything weird.  This appears to be something related to the combination of these two different leds.  And then jiggling the closet led made it stop.  Perhaps there is a poor contact when it was wired in (I didn't remove the closet led fixture).  But even so, why would that make it strobe?  I don't understand the electronics that could make this happen.  Or maybe the combo of the Insteon dimmer, the closet led, and the philips led.  It is very weird how it full out strobes.  This is not a flicker, this is a full on/off rapid strobe.

Posted

With some leds down low I will have strobing like you are talking about related to the Insteon communications over the power lines. Could perhaps be your issue.


SeJ

Posted
1 hour ago, apostolakisl said:

@larryllix @sjenkins  I'm pretty sure this has nothing to do with the dimmer.  I have about a dozen of the same insteon dimmers controlling the same philips bulbs on different circuits without issue.  I also had the same dimmer controlling this circuit when it was that closet led (unknown brand) with incandescent candelabra bulbs and it didn't do anything weird.  This appears to be something related to the combination of these two different leds.  And then jiggling the closet led made it stop.  Perhaps there is a poor contact when it was wired in (I didn't remove the closet led fixture).  But even so, why would that make it strobe?  I don't understand the electronics that could make this happen.  Or maybe the combo of the Insteon dimmer, the closet led, and the philips led.  It is very weird how it full out strobes.  This is not a flicker, this is a full on/off rapid strobe.

If bulbs strobed against each other on full 120vac they wouldn't be found or sold anywhere. It takes a dimmer to cause this to happen. With intermittent or low current supplies one bulb will charge up it's PSU and then the LED will turn n. This drops the voltage to the other bulb and it shuts off. Once the PSU caps are charged up the current drops, the voltage from the dimmer rises and the second bulb does the same thing.

Of course this is only theoretical, but turning the dimmer higher usually stops this effect, or using a linear load in parallel to the LED bulbs, usually stops it also, as it stabilises the dimmer circuitry detection of current, and likely absorbs some counterEMF oscillation from the wiring inductance coupled with the PSU caps.

There are devices to parallel LED bulbs that can be installed inside the fixture box. I believe they must be only capacitors as they cannot draw and real power or the socket would overheat.

Previously I saw LED bulbs with a small load built into the bulbs but haven;t seen anything like that for a long time. Then colour match and dimming linearity wouldn't match between brands, likely.

Posted
1 hour ago, sjenkins said:

With some leds down low I will have strobing like you are talking about related to the Insteon communications over the power lines. Could perhaps be your issue.


SeJ

Not like that at all.  This is full out strobe and it doesn't matter if it is bright or dim.  It just strobes brighter or dimmer.  It is continuous.  When it starts, it keeps going until you shut it off or if I unscrew a light bulb and screw it back in it might stop too.  Also I noticed if a jiggle the ceiling fixture in the closet it might stop it.

Posted
2 minutes ago, larryllix said:

If bulbs strobed against each other on full 120vac they wouldn't be found or sold anywhere. It takes a dimmer to cause this to happen. With intermittent or low current supplies one bulb will charge up it's PSU and then the LED will turn n. This drops the voltage to the other bulb and it shuts off. Once the PSU caps are charged up the current drops, the voltage from the dimmer rises and the second bulb does the same thing.

Of course this is only theoretical, but turning the dimmer higher usually stops this effect, or using a linear load in parallel to the LED bulbs, usually stops it also, as it stabilises the dimmer circuitry detection of current, and likely absorbs some counterEMF oscillation from the wiring inductance coupled with the PSU caps.

There are devices to parallel LED bulbs that can be installed inside the fixture box. I believe they must be only capacitors as they cannot draw and real power or the socket would overheat.

Previously I saw LED bulbs with a small load built into the bulbs but haven;t seen anything like that for a long time. Then colour match and dimming linearity wouldn't match between brands, likely.

As per a response that I was writing while you were writing this.  The brightness is not related.  It does it at any brightness and I can even change the brightness while it is strobing and it just strobes brighter or dimmer.  I also swapped out bulbs that were working perfectly on other Insteon switches and the problem stayed with the installation location, not with the bulb.  Also, I changed out the insteon switch and it still was doing it.  The unique thing here is that ? brand of ceiling fixture in the closet.  I think I may just need to replace it.

Posted (edited)
5 minutes ago, apostolakisl said:

Not like that at all.  This is full out strobe and it doesn't matter if it is bright or dim.  It just strobes brighter or dimmer.  It is continuous.  When it starts, it keeps going until you shut it off or if I unscrew a light bulb and screw it back in it might stop too.  Also I noticed if a jiggle the ceiling fixture in the closet it might stop it.

If you bypass the dimmer for full powerline voltage and they still do it then the bulbs are defective and hopeless.

....or maybe the wiring/socket connections?

Edited by larryllix
Posted
16 minutes ago, larryllix said:

If you bypass the dimmer for full powerline voltage and they still do it then the bulbs are defective and hopeless.

....or maybe the wiring/socket connections?

I thought maybe the wiring/socket.  So I took down the candelabra and redid the wire nuts and I cleaned the sockets with steel wool.  Same issue.  Need to take down the closet led.  I really believe that this is the culprit, but I don't understand how it is the culprit.  It would also make more sense if it did it 100% of the time.  But the fact that it might be totally fine, then just randomly start doing it, and then I jiggle things and it stops.

Posted (edited)
9 minutes ago, apostolakisl said:

I thought maybe the wiring/socket.  So I took down the candelabra and redid the wire nuts and I cleaned the sockets with steel wool.  Same issue.  Need to take down the closet led.  I really believe that this is the culprit, but I don't understand how it is the culprit.  It would also make more sense if it did it 100% of the time.  But the fact that it might be totally fine, then just randomly start doing it, and then I jiggle things and it stops.

The "jiggle" thing has to be the main factor. The loose connection should be upstream to the bulb parallel point, so that the bulbs can interact with a high impedance supply connection. With a low impedance connection (solid 120vac) bulbs should never interact, no matter what. This indicates, to me, there is a connection problem upstream (supply side) from where the bulbs split ways in the wiring.

Edited by larryllix
Posted
1 hour ago, larryllix said:

The "jiggle" thing has to be the main factor. The loose connection should be upstream to the bulb parallel point, so that the bulbs can interact with a high impedance supply connection. With a low impedance connection (solid 120vac) bulbs should never interact, no matter what. This indicates, to me, there is a connection problem upstream (supply side) from where the bulbs split ways in the wiring.

I suspect you may be right and that it is the closet ceiling fixture.  Hopefully it is easy to pull down.

Posted
3 hours ago, apostolakisl said:

I suspect you may be right and that it is the closet ceiling fixture.  Hopefully it is easy to pull down.

ewwwww....and it sounds like a high ceiling too. How many bulbs in the fixture?

Need scaffolding? Work safely!

Posted

OK, so I screwed up.  I was futzing with the wires and managed to accidentally short to ground which of course fried the triac.  It just stays on full bright.  Otherwise, the switch does all the normal Insteon stuff.  I have extras, but with short supplies, I was wondering if anyone knew if it was a simple component swap out or should I just move that switch to a non-load location?

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