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Can reversing ac polarity of half of the bulbs in a chandelier bring the flickering out of sync (out of phase) so that half of the bulbs are ON while the others are OFF?
I mean the AC polarity of the socket and not the DC terminals of the internal driver circuit I did some experimentation with a 5 w bulb, a testing socket and the phone's camera after removing the defusing cap and zoom to the LEDs but the result was not what I expected : the light was not exactly blinking but moving in a line from side to side and when the socket was flipped instead of reversing direction or just stay the same the light just flicker without the first pattern. Another LED bulbs were not flickering at all but they are too bright and uncomfortable fir indoor. To be honest the flickering is not detectable unless you put some effort to detect it by playing with the camera's anti banding and frame rate settings but I'm afraid it could one day ruin an important video.

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    \$\begingroup\$ No, that will not work. \$\endgroup\$ – Hearth Feb 26 '20 at 15:59
  • \$\begingroup\$ @Hearth But doesn't the fact that it changed its blinking/flickering pattern when reversed means that it will at least partially work? \$\endgroup\$ – Amr Berag Feb 26 '20 at 17:02
  • \$\begingroup\$ @AmrBerag Since LEDs flicker at double mains frequency, flipping the hot and neutral does nothing. You'd need to phase shift one by 90 degrees to do what you want. \$\endgroup\$ – user1850479 Feb 26 '20 at 17:25
  • \$\begingroup\$ If it changes when reversed, that indicates to me that you have a poor-quality LED bulb that uses a half-wave rectifier. This type is substantially more flickery than ones that use full-wave rectifiers. But what you suggest would work on these bulbs. It will not, however, get the flickering to be as low as full-wave-rectified bulbs. \$\endgroup\$ – Hearth Feb 26 '20 at 17:30
  • \$\begingroup\$ @Hearth It has ISO and other certification symbols and the build quality looks and feels good and individual LEDs are labeled D1 D2... but its a cheap bulb at less than one Euro each but it has other echoes I will post a a question about: it causes instant migraine when looked at with the cap remove while a 5 times stronger one doesn't \$\endgroup\$ – Amr Berag Feb 26 '20 at 22:46
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Can reversing ac polarity of half of the bulbs in a chandelier bring the flickering out of sync (out of phase) so that half of the bulbs are ON while the others are OFF?

No. The bulbs will use a full-wave rectifier so that the LEDs are powered on both positive and negative polarity of the mains. The result may be flicker at 100 Hz or 120 Hz depending on whether you are in 50 Hz land or 60 Hz land.

I did some experimentation with a 5 W bulb, a testin socket and the phone's camera after removing the defusing cap and zoom to the LEDs but the result was not what I expected:

I have no idea what a "testin" socket is. If it's a brand name then it should probably be capitalised.

.. the light was not exactly blinking but moving in a line from side to side and when the socket was flipped instead of reversing direction or just stay the same the light just flicker without the first pattern.

There isn't enough information here. Moving from side to side in what? The video? In what orientation was the camera running? What camera, etc.

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  • \$\begingroup\$ A testing socket is a socket used to test if a bulb is good or bad. its usually has two legs but some times 3 to insure correct polarity. A testing socket is also the cheapest thing you can find in a supermarkt or a hardware store. the ones I use have two legs so i can reverse it on the G type outlet that has 240 vac \$\endgroup\$ – Amr Berag Feb 26 '20 at 17:27
  • \$\begingroup\$ OK. The original post said "testin socket". \$\endgroup\$ – Transistor Feb 26 '20 at 17:29
  • \$\begingroup\$ ok that was a typo and the pattern is similar to that of a runway lighting in the trunk of a spaceship in a sci-fi movie more precisely as if a diameter of a circle is shifted right from end to end and when it reaches right edg it starts from the right so that only the leds on that line are on at a given time \$\endgroup\$ – Amr Berag Feb 26 '20 at 17:46
  • \$\begingroup\$ ok that was a typo and the pattern is similar to that of a runway lighting in the trunk of a spaceship in a sci-fi movie more precisely as if a diameter of a circle is shifted right from end to end and when it reaches right edg it starts from the left so that only the leds on that line are on at a given time \$\endgroup\$ – Amr Berag Feb 26 '20 at 22:30
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It sounds like you are using standard household LED light bulbs - in which case playing around with switching the live and neutral wires can lead to a fire, since these household bulbs were designed to the properly wired socket - live on the center, neutral on the threaded metal can (if it's a standard bulb).

If you have flickering in your chandelier, there is an underlying issue that what you are trying to do won't address. Do you have an adjustable brightness switch on that chandelier? If you do, most LED bulbs don't work with that kind of light switch, you need to buy special dimmable LED bulbs.

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  • \$\begingroup\$ There is no flickering visible to the eye but it appears in videos especially when zooming near the bulbs. \$\endgroup\$ – Amr Berag Feb 26 '20 at 16:50
  • \$\begingroup\$ Swapping hot and neutral on a socket won't start a fire, though it is a code violation \$\endgroup\$ – user28910 Feb 26 '20 at 17:04
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    \$\begingroup\$ @user28910 it's not illegal because of fires. It's illegal because of shocking and killing humans. Keep in mind, stunning is lethal when it has knock-on effects such as falling or drowning. \$\endgroup\$ – Harper - Reinstate Monica Feb 26 '20 at 23:46
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No, you must not do that!

Fixtures must be wired so that the shell on the Edison base is neutral, and that must be always-wired. The tip in the bottom center of the socket must be hot, and must be switched.

Unless you are adding a grounding strap, it doesn't matter anyway because the LED bulb has no idea what polarity even is. It cannot distinguish hot from neutral. It is a bird on a wire. Everything is relative: If a bird is sitting on a 9600V 3-phase wire, then the bird is grounded, the other two phase wires are at 9600 volts, and the planet below is at 5540 volts: 9600/sqrt(3).

The root problem is junk bulbs... Or a broke dimmer

You ar not dealing with raw LED components, you are dealing with consumer products made to replace incandescent lights, which happen to use LED as an underlying technology. There is no reason for these products to flicker. It is perfectly achievable to build these that do not; It's just a matter of including an internal DC power supply of sufficient quality to not flicker. Billions of such products succeed at it. So this leaves us two possibilities:

  • You were hoodwinked by cheap junk, or you intentionally bought the cheapest junk. This would reduce your question to "how do I buy cheap junk and have it behave like quality, also my budget is zero because it would defeat the purpose to spend $1 per bulb fixing them when I could just have spent $1 more to get better bulbs in the first place". Or...

  • Unbeknownst to you, there is a dimmer, lighted switch, or some sort of powered switch using the old school "neutral-less" method of powering itself, which connects the device's electronics in series with the bulbs, and relies on the low impedance of an old incandescent bulb. Many LED bulbs do not play well with this method, and this is no reflection on the LED. The nickel test for this is replace one bulb with an incandescent and see if the problem magically goes away.

This latter problem can sometimes be fixed by applying a LUT-MLC or equivalent dummy load in parallel with the light bulb sockets. Otherwise the dimmer or powered device may need to be replaced entirely, and the new one may require a separate neutral wire. This can be a problem in older switch loop installations where only a hot and switched-hot wire come to the switch.

Note you need to use a LUT-MLC or similar equipment that is UL-listed. You are not allowed to dive into the electronic parts bin and fit a capacitor or resistor component that is RU (UL-recognized).

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  • \$\begingroup\$ the even cheaper ones I bought have no flickering at all. But i bought those ibecause they were the only 5w bulbs I found in all nearby stores and i dont want overwhelming brighter bulbs and I live in a place where tax is really low exept for alcohol, tobacco and softdrinks and these bulbs have ISO and more certification logos bought from a store known for not selling junk but who knows most goods are junk nowadays \$\endgroup\$ – Amr Berag Feb 26 '20 at 23:17
  • \$\begingroup\$ The only certs that matter are on the NRTL list (google that). Make sure to check for a dimmer etc. \$\endgroup\$ – Harper - Reinstate Monica Feb 26 '20 at 23:39
  • \$\begingroup\$ Yes I use these dimable lamps as night lights somewhere else becase of the remote controls that comes with these \$\endgroup\$ – Amr Berag Feb 26 '20 at 23:56
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The problem you are seeing with your camera is caused by the relationship between the variation light produced, due to AC frequency or pulse width modulation (PWM) from a dimmer, and the shutter speed of the camera. That's why it isn't noticeable by eye but is on your video.

Although you mention that you have adjustments on your camera that can compensate for banding and by changing the frame rate, this is not an option or is limited in less expensive cameras. You can use a lower frame rate if that provides acceptable quality.

Another option is to improve the lighting, increasing the flicker rate from the power supply or the frequency of the PWM so the shutter effect isn't seen. Or you could go to DC lighting with no dimmer.

In any case I would test the camera settings in whatever lighting situation before shooting something important. If you don't do that you can remove flicker in post-production with a little loss in quality.

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  • \$\begingroup\$ The camera issue doesn't add up. OP has stated wanting less light which contradicts wanting to use this for set lighting e.g. For a youtuber. When you shoot video, you want more light! So it makes more sense that OP is filming to show us the problem, which implies OP had a problem before deciding to shoot video. \$\endgroup\$ – Harper - Reinstate Monica Feb 27 '20 at 0:11
  • \$\begingroup\$ @Harper-ReinstateMonica You are right that this camera answer is unrelated but there was no problem before I decided to use the camera to check if there is a problem. I was going to make a video and photos but that 5w bulb really cooked my head from steering at it \$\endgroup\$ – Amr Berag Feb 27 '20 at 0:30

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