Author Topic: EEVblog #1044 - LCD Technology Tutorial  (Read 1439 times)

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Online EEVblog

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EEVblog #1044 - LCD Technology Tutorial
« on: December 02, 2017, 11:20:57 AM »
Part 1 in a series of videos on designing a custom LCD display.
This tutorial covers how LCD displays work, the 3 different types of interface (DIP, Elastomeric, Flex), the three different optical types (Reflective, Transflective, and Transmissive), and the two different types of drive (Static vs Dynamic)
Microchip  AN658
http://ww1.microchip.com/downloads/en/AppNotes/00000658B.pdf

« Last Edit: December 02, 2017, 01:30:59 PM by EEVblog »
 
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Offline floobydust

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #1 on: December 02, 2017, 11:56:25 AM »
Link "video unavailable" fixed  :)
Please include low temperature fluids, use them here in the Great White North down to -30C. Needs more drive though, +/-5V and contrast moves around lots with temperature.
« Last Edit: December 06, 2017, 03:24:21 PM by floobydust »
 
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Offline tautech

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #2 on: December 02, 2017, 12:35:40 PM »
Looking forward to the future vids, excellent topic.  :-+
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Offline W2NAP

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #3 on: December 02, 2017, 12:35:48 PM »
hmmm "This video is unavailable."

something is broken.  :scared:
 

Offline rs20

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #4 on: December 02, 2017, 12:55:32 PM »
I think he's correcting a couple of issues; which is awesome -- trading in short-term view stats in order to ensure that he has an awesome, accurate video in perpetuity.
 

Offline wilfred

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #5 on: December 02, 2017, 01:22:01 PM »
I think he's correcting a couple of issues; which is awesome -- trading in short-term view stats in order to ensure that he has an awesome, accurate video in perpetuity.
I'm all for encouraging Dave to make videos with long tail viewing (ie not debunking) but doesn't sacrificing the initial peak viewing seem a high price to pay?

Is it awesome he's correcting some issues, or just you thinking it is awesome?  Maybe I'll agree with the later but where does Dave say he's fixing issues?
 

Online EEVblog

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #6 on: December 02, 2017, 01:31:43 PM »
New upload link working again.
 

Offline wilfred

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #7 on: December 02, 2017, 01:59:55 PM »
Is there going to be a video about driving an LCD display with multi bias voltage levels?
 

Offline SeanB

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #8 on: December 02, 2017, 03:14:32 PM »
Is there going to be a video about driving an LCD display with multi bias voltage levels?

He does mention a few times the next one about LCD will cover that.
 

Offline wilfred

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #9 on: December 02, 2017, 03:38:32 PM »
Is there going to be a video about driving an LCD display with multi bias voltage levels?

He does mention a few times the next one about LCD will cover that.

I didn't hear that. I only heard Dave say that discussion of multi bias level was probably a video in its own right. Not necessarily the same as the next one will be covering that. I interpreted what he said as, this one won't go into that level of detail.

Multi bias levels is something I have found difficult to get my head around so I would like to see it covered. I haven't found a good video on it that I can grasp. If Dave is doing this stuff for his new product then there is no better time to try and get it on the video agenda.
 

Offline unclebob

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #10 on: December 02, 2017, 11:42:34 PM »
Really great tutorial, I can't wait to see the other parts. Thanks a lot.
 

Online EEVblog

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #11 on: December 02, 2017, 11:55:34 PM »
Is there going to be a video about driving an LCD display with multi bias voltage levels?

I don't think that far ahead.
 

Offline jonovid

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #12 on: December 03, 2017, 01:55:29 AM »
Thanks Dave.it's about time! looking forward to next video.  :-+ :-+
what happened when posting the video to YouTube.  :-//
some of us like to fiddle or mod LCD displays for fun.  ;D
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Offline Twoflower

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #13 on: December 03, 2017, 04:33:35 AM »
Very informative as usual  :-+.

But the term "LCD Display" makes me shudder all the time. It's just not a Liquid Crystal Display Display. But as a non native English speaker I should be careful for what I call for :)
 

Offline richnormand

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #14 on: December 03, 2017, 05:24:14 AM »
Nice video Dave. Looking forward to the next one.

Suggestions for followup videos (in addition to added tutorials)

Looking at:
Driving schemes and pitfalls for directly addressed LCDs with standard chips.
Are there standard pinouts/voltages to look for?
Embedded/onboard hardware and software drivers with LCDs to look for (like the Noikia with ARM Cortex drivers combo (Github)

Also of importance for many that have older equipment:
Any way to increase the contrast of LCD panels on older HP, Ithaco, Pace, Canberra and the like. Typically they do not have contrast adjustments and are only readable using a strong light in front of the display now :--.
Any way to regenerate the older LCD to work better, as many of these displays are OEM and not replacable.

Options for adding back lighting to LCDs that did not have provision for that (like some of the retrofits shown on the EEVblog forum)

Keep up the good work. :)

Cheers and thanks.

 

Offline Ertew

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #15 on: December 03, 2017, 08:38:39 AM »
Dave, can You include "silver polarizer" and frontlight in next videos?
 
Transflective LCD have "black polarizer" on both sides and reflector on bottom. Light that doesn't pass are absorbed by polarizer. Silver polarizer (located at bottom of LCD instead of black polarizer and reflector) reflect light that doesn't pass through. In this construction active segments shows light from backlight unit while inactive segments shows light from environment. Results: poor contrast in poor light but excellent both in sunlight and darkness.

Second nice technology are reflective display + frontlight unit. Technology was popular years ago when other types cannot give enough brightness. Photos below shows my ST5111 (reflective) and E52 (transflective). Both with light turned off.

http://forum.bongofish.co.uk/index.php?topic=2561.0 - here are my review of that ST5111 tablet-PC. Sadly all photos are gone.

Any way to regenerate the older LCD to work better, as many of these displays are OEM and not replacable.
Broken LCD cannot be fixed. But broken connectors (common problem) can be easy to fix by replacing zebra rubber or carbon flat flex cable. The most problematic damage are broken conductive tracks on LCD.
« Last Edit: December 03, 2017, 08:45:27 AM by Ertew »
My english is poor, but i try to not make mistakes.
 

Offline Mr. Scram

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #16 on: December 03, 2017, 11:32:10 PM »
I noticed a while back that ultra cheap items, like a 4 dollar multimeter and a calculator, often had very nice high contrast displays even when compared to very expensive multimeters. I wondered about that and I guess this video explains it. No backlight!
 

Online HKJ

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #17 on: December 04, 2017, 07:36:17 AM »
I noticed a while back that ultra cheap items, like a 4 dollar multimeter and a calculator, often had very nice high contrast displays even when compared to very expensive multimeters. I wondered about that and I guess this video explains it. No backlight!

There is also another explanation: Simple display. Simple multiplexing gives better contrast.
 

Offline Peabody

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #18 on: December 04, 2017, 08:42:23 AM »
This discussion brings to mind the fact that the display on my Sharp Carousel microwave oven is getting dimmer with age.  It appears this is a common problem on a lot of such ovens.  Everything still works fine, but you just can't quite read the display anymore.  An odd form of planned obsolescence.

But on closer inspection, the segments are actually lit up, on a black background.  Does that mean it's really an LED display, not LCD?  Well, I guess the backlight could be amber.  There is a bit of polarizer darkening, but not total like my laptop display.  The Youtube videos on this problem refer to Sharp LCD display.  So is it likely there is a fix - short of replacement?

 

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #19 on: December 04, 2017, 09:20:32 AM »
I noticed a while back that ultra cheap items, like a 4 dollar multimeter and a calculator, often had very nice high contrast displays even when compared to very expensive multimeters. I wondered about that and I guess this video explains it. No backlight!

All things being equal, less or no multiplexing = better contrast.
More expensive meters typically have dual display, bargraph etc, that means a lot more segments, more commons, and more multiplexing required.
 

Online coppice

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #20 on: December 04, 2017, 10:42:33 AM »
This discussion brings to mind the fact that the display on my Sharp Carousel microwave oven is getting dimmer with age.  It appears this is a common problem on a lot of such ovens.  Everything still works fine, but you just can't quite read the display anymore.  An odd form of planned obsolescence.

But on closer inspection, the segments are actually lit up, on a black background.  Does that mean it's really an LED display, not LCD?  Well, I guess the backlight could be amber.  There is a bit of polarizer darkening, but not total like my laptop display.  The Youtube videos on this problem refer to Sharp LCD display.  So is it likely there is a fix - short of replacement?
Most older microwave ovens, and even many new ones, use VFDs (Vacuum Flourescent Displays). Like any form of electron tube they do wear with age, and become dimmer. Their lives aren't too bad, though. If you've had the oven 10 years, and its one which displays the time all day long, the display has run for nearly 100k hours. That's not a bad life for a low cost electron gun device.
 

Online coppice

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #21 on: December 04, 2017, 10:48:14 AM »
All things being equal, less or no multiplexing = better contrast.
More expensive meters typically have dual display, bargraph etc, that means a lot more segments, more commons, and more multiplexing required.
History has been largely as you said. 1mux being higher contrast, wider viewing angle and wider temperature range that 2mux, with this pattern going up to 4mux. However, for displays beyond 160 segments (40x4) its getting common to use 6mux or 8mux. Many of these give really good contrast over a wide viewing angle and a reasonable temperature range while running from just 3 volts. To get most 4mux displays to work well over a wide temperature range you need nearer to 4 volts. I don't know what is different about the design of these higher mux panels.
 

Offline Peabody

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #22 on: December 04, 2017, 11:11:55 AM »
Most older microwave ovens, and even many new ones, use VFDs (Vacuum Flourescent Displays). Like any form of electron tube they do wear with age, and become dimmer. Their lives aren't too bad, though. If you've had the oven 10 years, and its one which displays the time all day long, the display has run for nearly 100k hours. That's not a bad life for a low cost electron gun device.

It's a Sharp R-303CW, and I found the manual and schematic for it.  It is an LCD display, and appears to have an LED backlight - four LED's in series with an 82-ohm resistor to ground, controlled by one PNP transistor.

The display has 25 pins, composed of 22 SEG and 3 COM.  There's a big ribbon connector, but I think if that was the problem there would be some segments dimmer than others, or completely dark.  But mine is just uniformly dim.  So, it's a mystery.

Built in 2001.  Hell, it's barely broken in.

 

Offline Mr. Scram

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #23 on: December 04, 2017, 12:17:26 PM »
All things being equal, less or no multiplexing = better contrast.
More expensive meters typically have dual display, bargraph etc, that means a lot more segments, more commons, and more multiplexing required.
In this case it's a calculator with a graphic display, so I assume it does lots of multiplexing. Not too long ago this calculator would have been the duck's guts, now it's about as cheap as they come. In the case of the multimeter you're probably right, though!
 

Offline Mr. Scram

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Re: EEVblog #1044 - LCD Technology Tutorial
« Reply #24 on: December 04, 2017, 12:22:09 PM »
This discussion brings to mind the fact that the display on my Sharp Carousel microwave oven is getting dimmer with age.  It appears this is a common problem on a lot of such ovens.  Everything still works fine, but you just can't quite read the display anymore.  An odd form of planned obsolescence.

But on closer inspection, the segments are actually lit up, on a black background.  Does that mean it's really an LED display, not LCD?  Well, I guess the backlight could be amber.  There is a bit of polarizer darkening, but not total like my laptop display.  The Youtube videos on this problem refer to Sharp LCD display.  So is it likely there is a fix - short of replacement?
As a side note, I've noticed how people have shifted towards calling a lot of forms of wear or weaknesses in a design "planned obsolescence". In my mind there has to be a very intentional and deliberate act of shortening the lifespan of a product by the design choices made to call it that. Something that's run for over 15 years continuously and still works can, in my mind, not be called planned obsolescence by definition.
« Last Edit: December 04, 2017, 04:58:49 PM by Mr. Scram »
 
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