LCD pixel addressing?

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spinnaker

Joined Oct 29, 2009
7,837
On the way home the other day I got to thinking about those huge LCDs that are so ubiquitous on roadsides today. So I did some searching and found this video.


Nice to get a refresher on something I have probably long forgotten. But what he kind of glosses over is the addressing issue. I realize it uses multiplexing but I would think the address bus of those controllers would still need to be fairly enormous. Does anyone know the typical address bus size of these controllers?

also how do the really large screens work? Do they have multiple CPUs each responsible for their own section?


I find this kind of tech fascinating that someone figured out how to apply it. The CRT seems pretty simple to see how development occurred Someone probably fired an electron beam at a plate. To prove electrons were striking the plate, they coated the plate with phosphor, they then exposed the beam to a magnetic field and the CRT was born.


But LCD. Something so tiny. You have to wonder about thought process that went into the original experimentation.
 

dl324

Joined Mar 30, 2015
9,099
But LCD. Something so tiny. You have to wonder about thought process that went into the original experimentation.
When I was working at HP Labs in the late 70's, HP was experimenting with liquid crystals and we used one as an attenuator in an optical pulse generator prototype we built. The laser diodes and liquid crystals were so developmental that I had to simulate their operation using an HP calculator with a bunch of HI-IB controlled devices until they were actually available.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,837
When I was working at HP Labs in the late 70's, HP was experimenting with liquid crystals and we used one as an attenuator in an optical pulse generator prototype we built. The laser diodes and liquid crystals were so developmental that I had to simulate their operation using an HP calculator with a bunch of HI-IB controlled devices until they were actually available.

But how did they become aware that the crystals had these properties? Was it all discovered with math? Back to the CRT again. I would think anyone with a bit of craftsmanship and some basic knowledge of electricity could easily reinvent a crude CRT. I mean you can see it or envision it working in your minds eye. You can't see a crustal in an LCD. It just amazes me that someone figured a way to apply the tech. And even more amazing someone (actually someones) figured a way to manufacture large displays on a massive scale.
 

dl324

Joined Mar 30, 2015
9,099
I think the concept of polarizing the crystals had already been discovered by the time we started making them. I had an LCD watch back in that timeframe and the display was slow enough that I could watch the segments forming.
 

Raymond Genovese

Joined Mar 5, 2016
1,658
It is an interesting topic and it caught my attention because of a keynote address at a conference that I attended in 2004. It was a Nobel Laureate giving the presentation (1 of 2 such talks that I have had the pleasure of attending). It was Alan J. Heeger and he won the prize a few years earlier for his work with conductive polymers. The talk is still memorable to me for a number of reasons.

First, in about 15 minutes he summarized his work to a *very* eclectic crowd, including holding up a little piece of "special" plastic demonstrating that, under certain conditions, you could put a small charge into polymers and they illuminate. Being neither a chemist nor any kind of physical sciences person, I actually felt like I understood what he was saying (or thought as much) and was taken by how humble and matter-of-fact he was. He mentioned work and colleagues from years earlier.

Second, he went on in the rest of the talk to discuss and show slides of what winning the prize was like. This included signing the book and all kinds of cool things. He conveyed a real sense of humor about learning about so many friends that he had...after winning. It was just an incredible talk and very memorable to me.

To your point, this article includes some background and a timeline (see section 1.1) that gives some idea of the development time line.
 
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