Kitchen lighting

[Lime]

If a meter jumps by 6000 units, either it was misread or is faulty. Or perhaps nothing but cinders remains of the house.

:lol: :lol: :lol: :lol: :lol:

Another good one!

 

[NT]

>>There seems to be a good deal of confusion in this thread so far.

> I thought we'd finally cleared it all up . . .

And I didnt, and dont.


>>An incandescent lamp at half brightness is consuming most of full power, not half. Lamp... no I've not got it on this computer but IIRC Light_Output is proportional to Power_consumed to the power of about 13. IOW nothing remotely like a linear relationship. Dimming incandescents is the worst way to reduce brightness.

>Dimming a lamp is, by definition, the best way to reduce brightness

Its not the best way to reduce brightness of a light fitting or room lighting scheme. You're using the wrong definition. The best way to reduce lighting brightness is to switch on a lower power lamp instead, or switch on less lamps.


>>- I guess you mean it's not necessarily the most power-efficient method (pedantic, I know).

maybe more unclear than pedantic


>> Domestic meters read watts not VA.

> We'd agreed that.

Yes, but given what else had been agreed


>> The colour temperature of an incandescent bulb shifts a lot with dimming. To see the difference, put 220v and 240v bulbs side by side on 240v. Or a 40w bulb and a dimmed 150w set to same light output.

> MdB had already made that point quite clearly.

If you think about what happens as a lamp dims, ie why it dims, you'll realise that CCT shifts over a range of very roughly 2:1, which is a very wide variation. The point about the large size of the variation wasnt made AFAIK.


>> Normal dimmers dont produce reactive loads, v and i always stay in phase.

> We went through that discussion and concluded

Yes, I know what you concluded, and why it was wrong.


> V and I do go out of phase as a result of this harmonic distortion.

no


> So I'm not sure where the outstanding confusion lies.

I understand that. Dont make the mistake of thinking everyone else at the same level of knowledge as you are. I may be fairly uninformed on some topics, but not this one.


NT

 

[MdB]

V and I do go out of phase as a result of this harmonic distortion.

no

Err... Yes

A dimmer that is switched on during the first and third quadratures and off the second and fourth powering a resistive load will phase shift the current relative to the voltage by about 30 degs (ish). I can either do the sums for you (a Fourier transform of the waveform) or sell you a piece of equipment that will allow you to measure it.

Note: The voltage and current seen by the resistive load will be in phase but the voltage and current powering the load and dimmer combination will not be. This is probably where the mistake is being made.

(oh and yes, I did design all those bits of kit - its a pity they are not as interesting to look at the stuff that Biff makes...)

 

[biffvernon]

Well I've got a dimmer switch but the plastic knob broke and fell off so I made a wooden one.

 

[Penners]

Well I've got a dimmer switch but the plastic knob broke and fell off so I made a wooden one.

But does it only work with wooden light bulbs?

 

[MdB]

Well I've got a dimmer switch but the plastic knob broke and fell off so I made a wooden one.

But does it only work with wooden light bulbs?

Edit - hmm. Embedded image doesn't seem to work. Here is a direct link http://www.worth1000.com/entries/243000/243178JOQn_w.jpg

 

[Flyfisher]

>Dimming a lamp is, by definition, the best way to reduce brightness

Its not the best way to reduce brightness of a light fitting or room lighting scheme. You're using the wrong definition. The best way to reduce lighting brightness is to switch on a lower power lamp instead, or switch on less lamps.

I thought my 'pendantic' aside would indicate the fact that I had my tongue firmly in my cheek with that comment, i.e. of course 'dimming' reduces 'brightness' although obviously there anre many different ways of achieving this. My apologies for not being clearer :roll:

>> Normal dimmers dont produce reactive loads, v and i always stay in phase.

> We went through that discussion and concluded

Yes, I know what you concluded, and why it was wrong.


> V and I do go out of phase as a result of this harmonic distortion.

no


> So I'm not sure where the outstanding confusion lies.

I understand that. Dont make the mistake of thinking everyone else at the same level of knowledge as you are. I may be fairly uninformed on some topics, but not this one.

It's great that you're well informed on this topic as it gives us a chance to learn, which is the point of discussion isn't it? But it is not helpful to just say 'no' without any explanation.

Err... Yes

A dimmer that is switched on during the first and third quadratures and off the second and fourth powering a resistive load will phase shift the current relative to the voltage by about 30 degs (ish). I can either do the sums for you (a Fourier transform of the waveform) or sell you a piece of equipment that will allow you to measure it.

Note: The voltage and current seen by the resistive load will be in phase but the voltage and current powering the load and dimmer combination will not be. This is probably where the mistake is being made.

Perhaps MdB's post explains where the confusion lies on this point?

Disagree, by all means, but it would be helpful for us to know why.

 

[Penners]

A dimmer that is switched on during the first and third quadratures and off the second and fourth powering a resistive load will phase shift the current relative to the voltage by about 30 degs (ish).

I never have this problem.

I rely on a simple left-handed snib valve agitator to ramp the offline doobriferkin, sufficient to overcome the tensiary effect of the floggle-toggle.

 

[Nemesis]

We modify ours by way of a nurdelsnooper valve.

 

[Andrew Bodenham]

Meanwhile, back in our period properties....

 

[Nemesis]

We light the rushlights.

 

[Penners]

We modify ours by way of a nurdelsnooper valve.

Well just don't tell your insurance company.

Your premium will go sky-high.

 

[Flyfisher]

I never have this problem.

I rely on a simple left-handed snib valve agitator to ramp the offline doobriferkin, sufficient to overcome the tensiary effect of the floggle-toggle.

At least you gave an explanation :wink:

 

[Penners]

At least you gave an explanation

I knew you'd understand it, Flyfisher.


I wish I did.

 

[Gervase]

We just have a little man who does.
Does what, exactly, is anyone's guess, but at least he does...

 

[Flyfisher]

At least you gave an explanation

I knew you'd understand it, Flyfisher.

I don't recall saying I understood it, I was just thanking you for explaining it

 

[NT]

If this forum were a bit more conservation-minded, dimming the lights would mean adjusting the sliding rheostat to reduce the current through the Nernst lamp fed from the 100v supply brought in on bare steel wires.

But you're all so modern....


NT

 

[Nemesis]

I'm off to light the oil lamp. It's a luxury but what the hell...

 

[Gervase]

Oil lamp? On a weekday? Coo, 'ark at Lady Muck.
For us it's fork 'andles (with apologies to Ronnie Barker)

 

[Nemesis]

Oil lamp? On a weekday? Coo, 'ark at Lady Muck.
For us it's fork 'andles (with apologies to Ronnie Barker)

I was being pretentious. I admit to smelly rushlights and bed soon.