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> Seriously, is it normal for LCDs to get warm during operation?
If they have a backlight, yes, because LEDs and CCFLs are only about 10%
efficient at converting electrical energy to visible light. A typical
monitor might need around 5W of backlighting power, most of that is
converted to heat.
> ...is 50 N a lot?
About 5 kg. Significantly higher than the force you usually use to
write/press with.
> Heee, do you remember the old laptops with the blue/purple monochrome
> LCDs? Where if you touched the screen, the whole picture rippled slightly?
They still do, if you don't have any protection on the front. My two
monitors and my laptop screen here certainly do.
> [Actually, our photocopier has a display like that. And I think it needs a
> screen saver, cos some of the controls are well burnt into it! I didn't
> think LCDs could "burn" like that?]
They can if you don't keep the average voltage across each pixel exactly
zero volts. A bad/cheap driving circuit can easily allow enough of a DC
voltage to start to screw things up after years of operation. However
usually the burn-in is not permanent, and disappears after some period (can
be up to an hour or so with very slow displays). Must admit I don't know
the details because the displays we work on are not allowed to have any
visible burn-in at all.
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>> Seriously, is it normal for LCDs to get warm during operation?
>
> If they have a backlight, yes, because LEDs and CCFLs are only about 10%
> efficient at converting electrical energy to visible light. A typical
> monitor might need around 5W of backlighting power, most of that is
> converted to heat.
the bottom?
>> ...is 50 N a lot?
>
> About 5 kg. Significantly higher than the force you usually use to
> write/press with.
5 Kg? Yeah, that is quite a bit... [Hmm, I wonder how much a human arm
weighs?]
>> Heee, do you remember the old laptops with the blue/purple monochrome
>> LCDs? Where if you touched the screen, the whole picture rippled
>> slightly?
>
> They still do, if you don't have any protection on the front. My two
> monitors and my laptop screen here certainly do.
*pokes it* Oh yeah, mine too. :-)
But it's not blue and purple. It's real colour. Even *our* equipment
isn't *that* ancient. ;-)
>> [Actually, our photocopier has a display like that. And I think it
>> needs a screen saver, cos some of the controls are well burnt into it!
>> I didn't think LCDs could "burn" like that?]
>
> They can if you don't keep the average voltage across each pixel exactly
> zero volts. A bad/cheap driving circuit can easily allow enough of a DC
> voltage to start to screw things up after years of operation. However
> usually the burn-in is not permanent, and disappears after some period
> (can be up to an hour or so with very slow displays). Must admit I
> don't know the details because the displays we work on are not allowed
> to have any visible burn-in at all.
Well, it *is* a 2-year old photocopier. And it runs 24/7. (Although
actually after a while it goes into a power-save mode where IIRC the LCD
shuts down too.) That's a touch-sensitive display, come to think of it.
But it doesn't ripple all that much... hmm.
I wonder... If you wanted to go all mad-scientist, how hard would it be
to concoct a chemical which forms a vaguely-functional LCD?
[NB. I once tried to make an oscilator at school. The damn thing never
actually produced any sound. It did, however, heat up the two power
transistors with remarkable efficiency - I would never have believed
that 9V was enough to burn your finger on...]
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible <voi### [at] dev null> wrote:
> I love the way not knowing about differential calculus is perfectly
> acceptable, but not knowing about English literature gets you labelled
> as some kind of idiot. As if English literature is somehow "more
> important" than differential calculus...
In context, it is, in fact. That's because literature is much more
related to the culture around you (which, in the end, is closely related
to socializing between people), while differential calculus isn't.
Humans are cultural and social beings and literature is one of the
best forms of learning and expressing about it. That's why it's usually
considered a good thing for your education to read a lot.
--
- Warp
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Invisible <voi### [at] devnull> wrote:
> ...is 50 N a lot?
Again we have to teach you about something you should know, especially
given that you are a technical nerd.
To get a grasp of what 50 Newtons means, it may be easiest to convert
them to kiloponds.
1 kilopond is the force exerted by Earth's gravity on one kilogram of
mass. In other words, assume you hold a 1 kg object on your hand, and
think how much force it applies to your hand downwards. That's 1 kp.
50 Newtons is approximately equal to 5.1 kiloponds. In other words,
it's the force you feel applied to your hand when you hold a 5.1 kg object.
--
- Warp
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> the bottom?
Most likely just because heat rises :-) Don't know where the LEDs are on
your LCD, or it may even be a CCFL in there...
> But it doesn't ripple all that much... hmm.
That's because it has a touch screen on the front of it - not as easy to
distort the actual LCD.
> I wonder... If you wanted to go all mad-scientist, how hard would it be to
> concoct a chemical which forms a vaguely-functional LCD?
Read the first few parts of:
http://en.wikipedia.org/wiki/Liquid_crystal
It's relatively easy to get a "functional" liquid crystal nowadays, the
extremely hard bit is creating one that works over a wide temperature range,
gives a high contrast ratio, has a fast switching time, etc.
> [NB. I once tried to make an oscilator at school. The damn thing never
> actually produced any sound. It did, however, heat up the two power
> transistors with remarkable efficiency - I would never have believed that
> 9V was enough to burn your finger on...]
I tried to make a simple AM transmitter, my first design transmitted about
5cm. I then proceeded to make the supply voltage higher and higher (in the
end I think I had 5 or 6 30V supplies in series) and eventually I made it
transmit about 3 metres while probably using half of the school's power :-)
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>> ...is 50 N a lot?
>
> Again we have to teach you about something you should know, especially
> given that you are a technical nerd.
I just figured that somebody who's used to dealing with such units on a
regular basis would have a more intuitive grasp of what is or isn't a
large force.
Of course 1 N is the force required to induce an acceleration of 1 m/s^2
on a mass of 1 Kg. But how much *is* that in real-world terms?
> 50 Newtons is approximately equal to 5.1 kiloponds. In other words,
> it's the force you feel applied to your hand when you hold a 5.1 kg object.
So... a reasonably large force to be pressing something with. ;-)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On Tue, 17 Jun 2008 14:53:59 +0100, Invisible <voi### [at] devnull> wrote:
>As if English literature is somehow "more
>important" than differential calculus...
Warp said it all.
It's the way of the world.
[A well known Restoration comedy. Written by William Congreve, an
English playwright.]
:P
--
Regards
Stephen
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>> I love the way not knowing about differential calculus is perfectly
>> acceptable, but not knowing about English literature gets you labelled
>> as some kind of idiot. As if English literature is somehow "more
>> important" than differential calculus...
>
> In context, it is, in fact. That's because literature is much more
> related to the culture around you (which, in the end, is closely related
> to socializing between people), while differential calculus isn't.
>
> Humans are cultural and social beings and literature is one of the
> best forms of learning and expressing about it. That's why it's usually
> considered a good thing for your education to read a lot.
Hmm... Clearly it's going to take me a while to wrap my brain around
this concept...
Presumably this is why all schoolchildren [in the UK at least] have
Shakespear inflicted upon them as a mandatory component of their
education. I still can't figure out what good it's supposed to do.
Certainly I can understand the importance of social interaction. But
"culture" always seemed to me to involve lots of pretensious people
standing around whaffling something incomprehensible about a bend lump
of metal painted green or something...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible <voi### [at] devnull> wrote:
> Presumably this is why all schoolchildren [in the UK at least] have
> Shakespear inflicted upon them as a mandatory component of their
> education. I still can't figure out what good it's supposed to do.
It's good because it's an expression of social culture.
> Certainly I can understand the importance of social interaction. But
> "culture" always seemed to me to involve lots of pretensious people
> standing around whaffling something incomprehensible about a bend lump
> of metal painted green or something...
You have a twisted notion of the term "culture". Culture is much more
mundane than that.
For example, if someone greets you, you greet back. That's part of
your culture.
--
- Warp
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Invisible <voi### [at] devnull> wrote:
> >> ...is 50 N a lot?
> >
> > Again we have to teach you about something you should know, especially
> > given that you are a technical nerd.
> I just figured that somebody who's used to dealing with such units on a
> regular basis would have a more intuitive grasp of what is or isn't a
> large force.
I didn't have any idea whatsoever "how much" 50 N is, but basic education
helped me in figuring it out. I knew that Newtons and kiloponds both measure
the same thing (force), and that a kilopond is a much more intuitive unit,
so the logical step was to convert the Newtons to kiloponds, and from there
imagine a real-life situation where such force would apply (in this case,
holding a 5-kilogram object on your hand).
--
- Warp
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