Sheldon Destruction?
Yes.
For those on the room.
So Alex, thank you for the last talk today.
Long day already.
Alex is going to talk about e-papers and a shit lot of stuff that I have no fucking clue about.
What it actually means.
But we all thought that it's really amazing, really interesting talk.
And we were all amazed to have that in the energy track.
Thank you.
Go ahead.
Yeah, I'm talking about e-papers.
Maybe you know e-papers like designs on the supermarket.
Like e-book readers.
And my talk is mainly about the type of e-papers you see on the supermarket.
So there's not so much electronics inside.
And normally they cannot display e-gay scales or just limited amount of gays scales.
And yeah.
So why this place matters for energy?
Because we have more more displays.
So that's similar like the last talk.
The devices become cheaper and we are use more more displays.
So we also should think about the power consumption of all this displays.
And we have signature smart meters industrial IoT all this kind of stuff.
And we could use the displays, but there should be a better way.
We could use displays that consume less energy.
But e-papers have some constraints.
Yes, e-papers are also not energy free by default.
They use energy to update.
So it's always thinking about if you have a IoT signage somewhere in your house.
And it's updating a tiny clock in the edge every second.
Then it will wake up every second and use energy.
So it's also thinking about the UI.
How can I use less updates?
Go to sleep faster.
Yes.
But one thing of e-papers is most of them have limited colour and no gays scales.
Or sometimes two gays scales and black and white.
And if you have more colours, then usually they have a much longer update time.
So the update time for a black and white display is in the range of less than a second.
And if you add gays scales, then you come to 10 seconds, 20 seconds.
And then colour displays, you even come to like one minute for an update.
So it's more for only updating the night for a new sign.
Yes.
So how does e-papers work?
The e-papers is built out of small bubbles.
And inside the bubbles are colour particles that are swimming in the liquid.
And usually in the simple ones you have black and white particles.
And their particles are electrically loaded.
So you can move the particles with if you put a voltage on it.
And then you can bring the white particles on the front or the black particles on the front.
You see on this picture microscopic photograph from a e-paper.
The squares are the pixels.
And you see the small bubbles.
And inside of each of these bubbles are hundreds of black and white small particles.
You don't see them on this photo.
And if you go far away, then you only see the rectangle pixels.
And yes, the state of these particles is by stable.
You can let display without power sitting for years.
And it doesn't change.
Yeah.
So how this particles move.
So you bring a voltage field on the pixel.
And then you can move the white and the black pixels.
It depends on the voltage you how fast they move.
Yeah.
And if you reverse the voltage, you come from white to black.
And the other way.
One thing is it's a pure analogue thing.
So if you put voltage on for a longer time, then you will destroy it.
Because the pixel lose their polarity.
And also you have electrosmosis inside the display.
And also the other thing is that viscosity of the fluid changing with the temperature.
So you need to adjust the voltages and the driving times depending on the temperature.
So every display has a temperature sensor inside.
And it adjust the voltages and timings depending on the temperature of the display.
Yeah.
What can we do if you want to have more than black and white?
The first thing you can add RGB color filters on top of it.
So you put like an TFT screen.
You put the color filter over the e-paper.
But the problem is you lose resolution and also you lose contrast.
Because if you have a color filter on it, then on every pixel you only get a small amount of light fluid.
And normally you want to use e-paper displays without the font light.
Otherwise the energy consumption goes up.
The other approach is you can use different colored particles inside the bubbles.
Because the displays are built from a roll that means the small bubbles are produced on a roll of plastic.
And then in a later step put on a display.
You cannot make one small bubbles with red particles and one bubble with green particles.
You have to mix all these particles inside the bubbles.
And then you see the next problem.
We only have two polarities.
So how can we drive more than two kinds of particles?
And the trick is that you make bigger and smaller particles.
So they move faster and slower.
And then if you put the right sequence of voltages on it,
you can move them more or less individually.
But that brings through slow updates.
So that's the cause that you have updates like one minute full color.
So the next thing is now we have this kind of e-paper foil with the colors inside.
How can we make a display on it?
Unlike LCDs or TFTs, we cannot easy multiplex them.
That means you cannot have like lines and columns.
And just drive some line and then move them.
Because our other pixels are affected by the same voltage.
So we need like a back plane for it,
where we are doing the switching.
And usually there is a TFT back plane.
So it's the same TFT back plane as in a TFT.
So it's an area of transistors.
Behind each pixel you have a transistor.
That holds the voltage.
So you can drive millions of pixels.
Yes.
So how does it look like?
It looks similar like this.
You have the driver.
The small bar is the driver.
The small IC that has several thousand of output pins that go into the glass.
And on the other side you have the connector.
And usually you have IC or C or SPI interface,
where you send your pixel data to the display.
Also you see the small bubble there.
That's the connection for the front side of the display.
Because you need you have the TFT back plane on the back side.
You have one single plate of with one voltage against data voltage.
So if you turn it around you see it a bit there.
There is a chip and from here you have all the lines and columns of the display.
And now you have two kind of e-paper displays.
You have e-paper displays with dump driver.
IC is on it.
So you need to supply going to the next line,
sending this voltage on the display,
going to the next line or this kind of stuff.
So you need an external controller.
These kind of displays are usually used in e-book readers.
Because you are much more flexible to and also much faster screen updates with this.
But you need a complicated external IC to do it.
And on all these supermarkets displays you have everything integrated in this IC.
So the whole timing is controlled inside IC.
You have nothing to do with it.
In generates all the voltages you need.
You only have to feed it with 3.3 volt.
And it has a small step up converter inside.
And that's everything for you.
But it's quite limited on the software side.
So you send the image there.
You send the refresh command.
And it even measures the temperature and then doing the magic.
And the interesting thing is, can you hack it?
Can you change the way it does things?
So in the IC there is a waveform that...
Or there are several waveforms depending on the temperature, depending on the color you want.
And usually there are factory programmed inside.
And also usually the manufacturers of the displays they don't want to get you them.
Because yeah, it's not open knowledge.
Yeah, that's a picture of the TFT backplane.
So if you put the e-paper on a microscope, you see the lines and the small bubbles here is the transistor.
And that's the pixel.
So to switch to the display, you need a waveform,
so kind of description, put 70 voltage on the cell for 10 microseconds,
then switch to minus 70 volt.
And then repeat this sometime and then do other magic.
And the idea is, how can we store this with some simple bytes?
So you have one global layer for the backplane.
So you can put only ground on the backplane and switching data.
Trust the pixels, but you can also switch the backplane to get double the voltage.
And then you have waveforms for like black white for grace,
or if it has color for different colors.
So they're the waveform describes how you switch the color.
And inside the normal display, you have like four waveforms,
and then you have 10 sets of these waveforms for 10 different temperature ranges.
And that's stored inside and it looks up the right waveform if you switch to display and then it does the magic.
So how this kind of waveform looks, it looks similar like this.
And every driver does it a bit different.
That's a bit cumbersome if you want to hack it because every display has another driver inside.
And sometimes they have eight groups and sometimes they have only five groups and sometimes the groups are,
you know, ordered way, but you see the general thing is you have like a face air and B.
And you can repeat this several times.
And then you have another two place you can repeat this.
And then you have a repeat counter for the whole block.
And then you have 10 blocks of these.
And so you can describe the voltage form you need to for your display.
So that's another, that's the same thing like before.
And that's the way it's in the storage of the driver.
So you have the first thing is how many times the first block has to be repeated.
Then you have the A and the B and the C in the D block.
And if you can repeat them five times or four times, however you want.
So usually that's kind of code for black white and two gray scales.
It looks like this. And then I wrote some small program that makes the.
So that's the curves that are coming to the to the pixels or the first thing is.
I think it's white and then two gray scales and the black one here.
That's the voltage that are going to the display for one display update.
And then I wrote some small simulator what is means for the display pixel.
And you see here you have the yellow line that's the position or the position I think the particles have just for the white particles.
And you see on the first line the white particles are on the backside.
And then in the middle lines you have two different height and on the last line the white particles are on the top.
And what you also see is the green line the green line is the DC offset.
So one thing is you should never put a long time one polarity on the display because then it will burn in and it will break.
And you see on all this curves on the end of the curve the green line is again to zero.
So if you add all the voltages up over one update, it should always be zero.
So that's also the cause that in most of the time you see inverse picture displayed before and then it's featured to the right display.
So that's the easiest way to accomplish the DC balance because if you always doing like this then you always have DC balance.
If you do like partial updates or fast updates or want to display videos on this then you can also don't do this and just balance over the next pixel.
If you know the last writing of the pixel is white then I can go directly to black I should only not white black the second time.
Yes and what I have done as a demo for here is I take a normal e paper display that only has one or two bits per pixel.
And can only display pictures like the above pixel.
I modified the look so that the look up table so that I can have 16 or 32 device scales and I'm doing this by modifying the look the look up table during the update of the display.
So in the first low I white black and white picture on the display where only the real black pixels are black and all the other pixels are white.
And then I modified the look to display the darkest way and then I sending the picture the all the pixels that are have the darkest way and so on for everything I also have a small video here.
So you see that's the update in the first time it it whites the and then on on this side you see a gray scale.
So it's like a debug thing is and then in the end you have for all the gray scales you can after the talk you can see it in real life it looks much better than under.
Yeah. So what's next? It's still missing the temperature or I'm starting to experiment with it.
So I make some test screens where I write this kind of blocks with four volt with eight volt with nine volt with 17 volt and with different different lengths.
So I can see on 60 volt I get a black nearly on seven and and 20 volt I need a bit more and on 10 volt you even need 60 frames until it gets real black.
So with this kind of data I can modify and accomplish that picture stays the same even if the temperature is changing.
Yeah, what could also be done or what I hope I can do is compress it so in theory I have two bits per pixel so I can write three gray scales per update so it gets faster.
And if that can be done it can also be extended to multicolored paper I've already started to experiment with it but maybe next year.
Yeah, so what what you have to take into account if you do your own load experiments.
Yeah, don't forget there's one setting I don't mention it's the VCOM DC setting because of the TFT backplane the voltage on the on the backside needs to have a kind of offset because all the transistors they're eating a way a bit of voltage so the voltage on the backplane has to be a bit different.
And the voltage on the front side has to don't have DC setting and this DC this voltage is depending on the panel and sometimes it's a problem because the manufacturer don't tell it and on some drivers you cannot read it but there are some tricks you can measure it.
If you have a waveform where you have the same waveform on the front and on the on one of the pixels you can see if the pixel is changing then your DC offset is for and then you can search it and newer drivers they also have a function inside very automatically finds the DC offset.
Yeah, so yes you should avoid permanent DC offset otherwise you burn your displays and yes maybe we can collect more more.
Look up looks and waveform tables together and form an open source knowledge base for driving this kind of displays.
Thank you.
The five years for questions.
Yeah.
Have you tried out the burning in the display?
Yes, it's you can get burned in in about.
The question was if I tried to burn in the display? Yes, it's quite easy I think after 10 minutes for getting to switch off some voltages you can have burn in and it doesn't go away anymore.
How does the the supply chain look for these displays? Is it like one company that or is it one company that makes this place?
And then the other company makes the drivers and the DC integrates it with a display or how does it and which is the biggest one's.
The question is how is the supply chain for the displays? The actual supply chain is that.
Patent holder E ink is manufacturing the foil.
Then you have companies like BOE that are great manufacturers for TFT screens they they're making the TFT back planes and then you have many model factories they combine this to and you have indeed.
Around five or six manufacturers of driver ICs.
But most of the time they are doing this together with E ink.
And there's only one single left company that avoiding the patent of E ink and has a slightly different.
And maybe it will go in the next years because the first E ink patents are no.
Not more valid and expiring and.
The question is if I tried to use waveforms to reduce energy.
The question is if I tried to use waveforms to reduce the energy consumption.
Yes, that was the first thing I have done for commercial project.
It was the trade-off is you shouldn't use gray scales.
And most of the time it's about to get the update faster.
So you can go to sleep faster.
You can do a bit the the integrated voltage generator usually is not that performant.
You can optimize it a bit with a bit better coil and this kind of stuff.
But why aren't the manufacturers doing that directly.
Because the question is why the manufacturer don't do this in the first time.
I think most of the.
This place that you will get and not that optimized there just optimized for it's good enough.
And if you buy five millions of this this place then they will talk it you and then they will optimize it.
It's the same if you want to have fast update then I always have this kind of things.
How maybe you you can set it to 150 degrees external temperature.
And then we have a we have a hidden look up table inside for 150 degrees and then there there is some magic inside but we cannot help you with this.
So that's most of the time.
And I have to feeling that if you are big enough then they're talking directly to it and if you're small enough then you just get.
Good enough this place.
So what.
How many different types of displays and if you try that you are you limited to like a couple of different.
Manufacturers or do you do like nice format one sort of as a refurbished king or displays or anything like that.
The question is how many different displays I have tried.
Yeah I've for for the gray scales I only have this one because it was my my project to try to make like a photo booth.
Most of my displays are coming from one company that has to do something that I.
Working for display company and that's our big supplier for this place and so I'm trying to understand how they work because they don't understand it they just sell it to us.
Yes.
Thank you.