Question tn lcd refresh rates

[tx_rodben]

Hi, i'm new on the forum and if i made some mistake on the rules or the place where the question is done, first i do apologize -its not my intention- and second, pointing me on the right way will be very welcome.

My question is:
I need a tn lcd monochrome dot matrix screen, 128x128 to make a project. The main point is that i need to "mimic" the crt behaviour, so if the screen its 60hz, i want to know if its possible to update each pixel faster, so each cycle, all the pixels are updated, one by one. I know it can be a weird question. Just want to know if there is any trick or technology that can do that. I've read about de duty specs and so on... but at last i can not understand if its possible or no.

Its not about showing an image, its about making in a cycle a pixel by pixel update, so on each step all of them are on black state and just one on white state. Starting on the top left corner and finishing on the down right corner.

Thanks in advance.

 

[Ralston18]

"tn lcd" as in:

https://www.tomshardware.com/reviews/tn-panel-twisted-nematic-definition,5767.html

Feel free to provide another applicable link if and as necessary.

What device will you be using for input to the lcd and what coding language are you using?

More information needed.

 

[Eximo]

Fast Monochrome LCD, probably not that common. These would be mostly for slow, low power displays and probably won't have the characteristics to display, presumably, a demonstration of how LCD refresh cycles work.

128x128 OLED display is probably easier to get, you can choose the monochrome output you want.

https://www.mouser.com/ProductDetail/SparkFun/LCD-15890?qs=xZ/P%2Ba9zWqbpqGFKv5VSsw==

 

[tx_rodben]

"tn lcd" as in:

https://www.tomshardware.com/reviews/tn-panel-twisted-nematic-definition,5767.html

Feel free to provide another applicable link if and as necessary.

What device will you be using for input to the lcd and what coding language are you using?

More information needed.

Hi, first of all, thanks for the answer.

My fisrt choice is to use C and raspberry 3b gpio pins. But can be changed if it can impact overall speed. In fact my question should be wider.

I need help on choosing the correct hw setup to achieve the crt behavior. Also i need that the screen has no controller attatched on the back. It has to be capable of removing the back reflector/mirror.

For each hz the screen must be capable of redraw all pixels one by one. Maybe its not possbile. Dont know.

So OLED is not an option.

Thanks

 

[tx_rodben]

Fast Monochrome LCD, probably not that common. These would be mostly for slow, low power displays and probably won't have the characteristics to display, presumably, a demonstration of how LCD refresh cycles work.

128x128 OLED display is probably easier to get, you can choose the monochrome output you want.

https://www.mouser.com/ProductDetail/SparkFun/LCD-15890?qs=xZ/P%2Ba9zWqbpqGFKv5VSsw==

Thanks for the answer.

OLED is not an option because i need to make it transparent.

Anyway, maybe it is not possible to do what i want because the technology does not allow.

On the other hand, i am open to any kind of hw recommendations for the setup. The only constraint is it has to be an ldc dot matrix screen has to be transflective so it can use backlight.

Thanks

 

[Eximo]

They make transparent OLED panels.

https://www.amazon.com/1-51inch-Transparent-Interfaces-Raspberry-XYGStudy/dp/B0B9F55ZVZ

Might have to look around and see if anyone does a 128x128 panel, might have to go digging on aliexpress or alibaba though.

You can also turn many LCD panels into transparent ones by removing some of the layers. That is a bit risky though, easy to take off the wrong layers and ruin the display.

 

[tx_rodben]

They make transparent OLED panels.

https://www.amazon.com/1-51inch-Transparent-Interfaces-Raspberry-XYGStudy/dp/B0B9F55ZVZ

Might have to look around and see if anyone does a 128x128 panel, might have to go digging on aliexpress or alibaba though.

You can also turn many LCD panels into transparent ones by removing some of the layers. That is a bit risky though, easy to take off the wrong layers and ruin the display.

oh, cool. Didn't know. Thanks, i'll take a look.
Are then, the oled, a good option for my specs?

 

[Eximo]

Your goal isn't clear in my mind unless my guess was correct. But your explanation of the refresh rate didn't really make sense to me.

Up to the drivers(as in hardware, not software drivers) how fast it can go really. If they accept a certain rate of input it is then up to the panel's performance. OLED are pretty much instant on/off since there is no LCD involved. But given these things seem to made for making simple displays and clocks, it is doubtful the drivers are very fast.

 

[tx_rodben]

Your goal isn't clear in my mind unless my guess was correct. But your explanation of the refresh rate didn't really make sense to me.

Up to the drivers(as in hardware, not software drivers) how fast it can go really. If they accept a certain rate of input it is then up to the panel's performance. OLED are pretty much instant on/off since there is no LCD involved. But given these things seem to made for making simple displays and clocks, it is doubtful the drivers are very fast.

Ummm let me try to explain better.

Let's say a green monochrome CRT has 50Hz refresh rate. That means that each frame can be fully drawn 1/50 seconds. But, as a catode ray tube, a frame is drawn with the electron bean impacting on the surface of the screen, line by line each hertz.

Each line is drawn faster than an hertz, lets say if the screen has 512 lines, it takes 1/(50*512) each line.

If we go down to each dot, it takes 1/(50*512*number of horizontal dots).

Reproduce this on an lcd screen 50hz 128x128 , should take 1/(50*128*128).

They are not meant to work as i need, i know, because it can show 50 images per second, so all the pixels can change 50 times per second. 50Hz.
What i need is a white dot to traverl from the first pixel to the last in each cycle having the others on black state, in each hertz so it is like the CRT beam passes through all the screen on each cycle.

If theres no technology that allow me to do that, the software part is not important hahaha

I know maybe its a stupid question, but i need to clarify if its possible... and if it is, pleas, that some one points me to the right technology choice.

I do apoligize as my mother language is not english. If you sitll can not understand me ill try to make some diagrams and use a translator.

Thanks a lot.

 

[Eximo]

CRTs didn't have pixels exactly, just an electron beam hitting a phosphor grid. And yes, the beam tracked at a few dozen kHz, so that it did sweep across the whole screen every cycle. One of the advantages of analog circuits was that it could switch off that fast and not just make the whole screen glow.

LCDs don't do that because they don't need to. There is no singular beam, but a grid of crystals to turn on and off in front of a static backlight (we'll not get into local dimming or strobing)

Now the phosphors couldn't turn off instantly, so they would glow for a time after being energized. To get the visual equivalent you would want to control the brightness I guess.

Command the first pixel to be full on, then the next, but the previous pixel you would run at 90% brightness, and 80%, and so on, so that there is a bit of artificial persistence. But there is no full equivalent way to do this.

Visually people can't see that fast, so I'm not sure what trying to command pixels at a kHz rate would gain you.

 

[tx_rodben]

CRTs didn't have pixels exactly, just an electron beam hitting a phosphor grid. And yes, the beam tracked at a few dozen kHz, so that it did sweep across the whole screen every cycle. One of the advantages of analog circuits was that it could switch off that fast and not just make the whole screen glow.

LCDs don't do that because they don't need to. There is no singular beam, but a grid of crystals to turn on and off in front of a static backlight (we'll not get into local dimming or strobing)

Now the phosphors couldn't turn off instantly, so they would glow for a time after being energized. To get the visual equivalent you would want to control the brightness I guess.

Command the first pixel to be full on, then the next, but the previous pixel you would run at 90% brightness, and 80%, and so on, so that there is a bit of artificial persistence. But there is no full equivalent way to do this.

Visually people can't see that fast, so I'm not sure what trying to command pixels at a kHz rate would gain you.

Can i write you in private so i can comment the project more indepth?
If not, thanks anyway.

 

[tx_rodben]

Making some calculations, what i need is a 3ms response time per pixel. Maybe it does not exist. No OLED, just dot matrix monochrome lcd with backlight capabilities.

 

[tx_rodben]

Thanks to all the replies. i found a better solution for the project PoC.
Cheers.