Odd Lights

[securespark]

Saw these this morning in a cafe in Salford Royal.
I don't know if the picture shows it well, but the pendant lights hanging over the counter had CFL candles in. The odd thing was that it seemed that the furthest one away from the camera was brightest and the nearest one dimmest, with a gradual reduction in between. I wondered what would cause this. I immediately thought of volt drop but that would be unlikely, I concluded.

I know it's difficult to see, but all those lamps are actually lit: it just doesn't look like it!

 

[Spark123]

Polarised or louvred shades?

 

[securespark]

The shades are just Kilner jars, adapted into light fittings.

I'm referring to the pendant lights mounted on discs on the dropped box section over the counter.

 

[JohnW2]

Do I take it that it's not just an 'optical illusion' - did you try looking at them 'from the other end'?

Kind Regards, John

 

[securespark]

Mmm, yes.

The brightness of each does not appear to alter when you move round the room.

 

[JohnW2]

Mmm, yes. The brightness of each does not appear to alter when you move round the room.

Oh wll - it was just a thought! Simple answers are most often correct, so I would suspect that there are just differences between the lamps/bulbs - and either a coincidence that they appear to get gradually brighter from left to right or, perhaps, someone arranged them that way (so as to look less odd) when they realised that they were different?

Kind Regards, John

 

[winston1]

I immediately thought of volt drop but that would be unlikely, I concluded.

CFL lamps have internal switch mode power supplies which give a constant wattage over a wide voltage range.
So, defiantly unlikely.

 

[333rocky333]

Maybe its the glass jar shades doing it and like john says they have aranged them to look more even

 

[eveares]

Maybe the dimmest was replaced the longest amount of time ago and were all replaced one at a time in sequence OR what Jhon said and they arranged them in order of apparent brightness deliberately?

Doubt they would be accidentally wired in series, as amusing they even work (likely wouldn't work) you would have the brightest on the outsides and the dimmest in the middle due to the AC nature right??

 

[JohnW2]

Doubt they would be accidentally wired in series, as amusing they even work (likely wouldn't work) you would

Six CFLs wired in series simply wouldn't work - at 230V, they'd get less than 40V each.

... have the brightest on the outsides and the dimmest in the middle due to the AC nature right??

Even if they would work in series (e.g. if the supply voltage were 1200V or so, I don't really understand that comment!

Kind Regards, John

 

[eveares]

Six CFLs wired in series simply wouldn't work - at 230V, they'd get less than 40V each.

That's what I was suggesting, at what voltage would a CFL fail and go out?

Even if they would work in series (e.g. if the supply voltage were 1200V or so, I don't really understand that comment!

If you have 4 x 3v bulbs connected to a 12v battrey, the bulb wired to the positive terminal of the battery would be the brightest right?

Now swap the positive and negative terminals over on the battery, and the dimmest bulb (now on the positive side) would become the brightest right?

Now swap the negative and positive terminals over 100 times a second and you would have a 50hz AC square wave right?

See where I am going, with AC you would have the apparent lowest voltage in the middle of the circuit and the highest peak to peak voltage at the beginning and end of the circuit what are constantly swapping back and forth?

 

[JohnW2]

Even if they would work in series (e.g. if the supply voltage were 1200V or so, I don't really understand that comment!

If you have 4 x 3v bulbs connected to a 12v battrey, the bulb wired to the positive terminal of the battery would be the brightest right?

Errr, no. Assuming thy were identical bulbs, each would have 3V across it, so all would be as bright as one another.

Now .... Now swap the negative and positive terminals over 100 times a second ... See where I am going?

You're going in a totally wrong direction because you are starting with a totally incorrect assumption (see above).

Kind Regards, John

 

[bernardgreen]

The lamps will be fading from dark to bright several thousand times a second at the frequency of the electronic ballast. ( the same as old fashioned fluorescents do at 50 Hz ).

If the camera shutter was fast then the variation might be due to the lamps all being on different points on the fading up and down cycle at the instant the photo was taken.

 

[JohnW2]

The lamps will be fading from dark to bright several thousand times a second at the frequency of the electronic ballast. ( the same as old fashioned fluorescents do at 50 Hz ). ... If the camera shutter was fast then the variation might be due to the lamps all being on different points on the fading up and down cycle at the instant the photo was taken.

I assume that secure noticed this phenomenon with his eyes (which would smooth out all those fluctuations) before he decided to photograph it! Also, it would need an incredibly fast shutter (probably 1/10,000 sec or less) to invoke the effect you describe at the frequencies involved (assuming freq ≥10kHz).

Kind Regards, John

 

[ban-all-sheds]

you would have the brightest on the outsides and the dimmest in the middle due to the AC nature right??

If you have 4 x 3v bulbs connected to a 12v battrey, the bulb wired to the positive terminal of the battery would be the brightest right?

Now swap the positive and negative terminals over on the battery, and the dimmest bulb (now on the positive side) would become the brightest right?

You have some of the most bizarre ideas about electricity I've ever encountered.

Truly astonishing.

Please don't ever give anybody any advice about anything on this forum again.