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LDC for Dummies? (I dont get how they work)

It seems the older I get th further away I become from technology. Sometimes I think we're locked into the generation in which we became a legal adult. In my case, that would be the late 1960s.

Give me an old tube device and I can make it do most anything. The early transistor devices came pretty naturally too, but getting into some of the later devices with chips, some things became fuzzy, and whenever mathematic formulas were added, I was lost. Math was my worst subject in high school, the minute they went beyond basic math, and began talking algebra and geometry, I was lost, and at one point, my math teachers suggested that I leave the math classes and take more shop classes which I always did good with.

Anyhow, I can tell you how a CRT works with no problem, but I've never understood LCD in the least. I spent hours going over articles on Wikipedia and a few others. All of them tend to go over my head. Seems there are multiple methods of using these liquid cystals, but what they dont say, is which method is used in today's LCD tv sets, monitors, cellphones, etc. Then these articles begin using math and wording that I've never heard. In the end, I was quickly lost!!!

What I did learn, is that there are layers. The front glass or plastic covering, a layer of color filters based on the 3 primary colors, a rear layer, and somewhere in between all of this is this liquid stuff. Then, somehow this liquid is moved by a magnetic field behind that rear layer. How that is achieved, I dont understand. Finally, there is a florescent bulb behind the entire screen, which is what lights it up.

This leaves me with many questions.

Here are some of them.

  1. Why is it called a Liquid Crystal DIODE? (Where is the diode and what does it do).

  1. What is the Liquid Crystal substance made of? Is it a chemical, crushed quartz rock mixed with oil, or what? The concept of crystal to me is a solid, made of rock, or man made glass. How can it also be a liquid?

  2. How is the magnetic field created behind the screen, and how does it move these crystals? This would indicate that the crystals contain iron particles.

  1. How does the florescent light behind the screen become pixels, and how are they directed to the right color filter?

  2. What are the color filters? Colored plastic strips, or what?

  1. Since it's a liquid, how come it dont freeze in winter? I've left my cellphone in the car in subzero weather and it still works (even though the batteries seem to lose power fast).

There are other things I dont understand, but these are the main ones....

Is there an actual LCD For Dummies book or some articles on the web written for us old farts whose brains just dont seem to follow these highly technical articles such as the one on Wikipedia, which I read at least 3 times, more in some parts, and just could not grasp it.

Some days I wish I could just go back to the good old days of vacuum tubes and wax coated capacitors, soldered to terminal strips. Hell, I can still recall the numbers on the most commonly used tubes without using any books. That's the problem with technology advancing too rapidly. It makes us old guys FEEL old. And I'm one who fights that feeling all the way. Maybe I should toss all the electronics in the trash, and stick with my building tools and farm machinery. I can still swing a hammer and use a saw, and drive a tractor, and dont have to use words I never heard before or do advanced math to use that stuff. And I may as well say it..... Whoever invented the battery operated hammer, is insane and should shove it up their a$$. (I just saw one of them at the building supply store)...... Ummmmmm, isn't that the reason we have muscles? Or maybe it's just us old guys who still have muscles, and the young ones only have push button fingers and their brains only think in formulas, but none of them could understand how to operate a hand saw or milk a cow!!!!

Reply to
tangerine3
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There are a bunch of variations, but the most basic system has three color subpixels for each system pixel. There are two polarizers with a twisted material in between. An electric field causes the material to twist or untwist so that the polarized light follows the twist and can be either passed or blocked by the other filter. White light goes in and color comes out depending on which of the subpixels is energized to what level through the color filters on the front. There are a whole lot of very important subtleties in that process.

I never saw one in operation, but back in the day, there was a system for secure computing on an airplane or other close-quarters. It removed the front filter and put it in your glasses. Everybody else just saw a white screen.

Reply to
mike

snipped-for-privacy@toyotamail.com schrieb:

Hello,

you should read this first:

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LCDs dont use magnetic fields, they use electric fields.

Bye

Reply to
Uwe Hercksen

ron

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gives a bit more detail about what liquid crystals do - basically rotate the phase of polarisation of polarised light when oriented by a electric field - and how they do it - basically by being long and skinny.

I had to learn about them when they first got to be commercially interesting, back in 1975, when I was working for Kent Instruments in Luton, around when they were taken over by Brown Boveri, now ABB.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

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When working with super bright cockpit displays, the company physicist gave me the following simplistic description which helped me picture what is going on.

It all begins with a floating long molecule [think of a piece of rice] When placed in liquid, these molecules preferentially like to stack on top each other sideways, but not quite line up. each time one is added it slightly rotates 10 degrees. When you have 10 molecules, the stack has rotated 90 degrees. Ok now make certain the liquid is only 10 molecules deep, or thick, by capturing between two panels, Ensure that thickness across the whole panel by placing tiny spacer balls distributed between the two panels. The TOP panel is transparent but polarized in ONE direction. The BOTTOM panel is transparent and polarized at 90 degrees direction to the top panel.

Light coming through from the bottom becomes polarized, then it starts following these miracle 'stacked' molecules and the light's polarization follows them, gets rotated 90 degrees so by the time you're at the top panel, the light is all lined up to come out the top panel! One important, and often missed point. Someone somehow found that during polishing, microscratches left in the panels make the first molecule touching that surface to physically lay in those 'grooves'. Thus, by matching polarization to the polishing direction, the molecules preferentially start in the right position!

So the whole basis is a little stack of molecules laying on their sides that slowly rotate 90 degrees, like a fan of playing cards, so the light can go from the back, be polarized, and as the light progresses up through the liqud step by step rotate that polarization until it lines up with the top plate and out the light comes!

Now knowing that basic principle, put three dot color filters [many molecules large] and at each dot place electrodes. Put voltage on the electrodes and the molecules no longer stay stacked, they start standing on their ends! Oops no more rotation to the light coming up through and you get darkness at that electrode. The strength of the field determines how disruptive to the amount of light that can get through, Now you have gray scale on each color dot.

Verify this description by pressing on the screen and watch how everything changes as you change how many molcules can get stacked in between the plates.

He said that the liquid and molecules all come from one source in Japan.

Of interest, the flatest, most reflective surface is Gortex fiber! Stuff is something like 99% reflective and completely dispersive, no specular reflections at all.

There are probably a lot of over simplifications to the description but the images they instilled certainly helped me to understand LCD's.

Reply to
Robert Macy

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gives a bit more detail about what liquid crystals do - basically rotate the phase of polarisation of polarised light when oriented by a electric field - and how they do it - basically by being long and skinny.

I had to learn about them when they first got to be commercially interesting, back in 1975, when I was working for Kent Instruments in Luton, around when they were taken over by Brown Boveri, now ABB.

-- Bill Sloman, Nijmegen

OMG if you worked for Kent Instruments in 1975 you must have had dealings with the company I worked for which got taken over by them- Micro Computer Systems in Woking. We pioneered CNC controllers.... in conjunction with Herbert Machine tools and Boehringer,Germany.

Reply to
TTman

No. I just did analog electronic design, plus occasional bits of mixed analog-digital (with CMOS, which has only just become cheap). I did have a foundation subscription by Byte, but only because my future wife was in Boston at the time, and thought - correctly - that it was my kind of thing.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

  • The device acts like an LED - a diode, made of a solid material called liquid crystal due to its properties. Remember, glass is a liquid.
  • Glass is a liquid. Some plastics can have a crystalline structure, some with properties like that of a liquid (refer back to glass).
  • Doubt magnetic field; restate "electric field".

  • The light is an attempt to give uniform illumination to the liquid crystal pixels.
  • Yep.

  • Solid-looking liquids like glass do not freeze.
Reply to
Robert Baer

VERY interesting article. To quote and comment on part of it: >The legend usually appears in any of the following forms:

  • That was nicely discounted, BUT please note that glass is used in telescopes, most particularly in large reflectors, and a great deal of practical engineering is done to mitigate the effects of glass flow. Refer to the Palomar and Lick observatories.
  • Reasonable statement, seems this was not discounted too well.
  • It seems to me that this was not discounted.
  • Note (again) that a great deal of practical engineering is done to mitigate the effects of glass flow. Refer to the Palomar and Lick observatories.
Reply to
Robert Baer

amorphous sulphur has no crystaline structure either, but it does have structute, Penrose tilings have no tesselations but still have order.

no evidence they evperience any flow, only bending.

--
?? 100% natural

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Reply to
Jasen Betts

Not to mention glassy metals.

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Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

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