which colour LCD C-STN/TFT/TFD?

John Devereux <jdREMOVE@THISdevereux.me.uk> writes:
> Don McKenzie <look@mysig.com> writes:
> 
> > Ajab wrote:
> >>
> >> Why should I go for OLEDs? Are they better that TFT?
> >
> > yes:
> > http://www.dontronics.com/oled.html
> > Cheers Don...
> 
> Isn't there a problem with lifetime?

Depends on the color.  Based on OSRAM's specs, yellow seems to have
the longest lifetime, at 50k hours (that's 100% brightness, 100% of
the time, until it drops to 50% lumens).  Other colors are as low as
10k hours, or just over a year.  Note that this is a fundamental of
LEDs themselves, not just OLEDs, but you only really notice the
problem when it appears as "burn-in" on the display.

However, note that some oled manufacturers are dropping their display
lines.  A lot of their oled matrix displays are either already
obsolete, or will be out of production soon.  Check with the
manufacturer before designing them in.

OLEDs also cost more than LCDs; a 2.7" 128x64 monochrome (16 levels)
display is $37 (qty 1).

If cost isn't an issue, also check out VFDs.  They're even more
expensive ($165 for that size) but, like OLEDs, they're emissive vs
reflective (i.e. the elements themselves produce light, rather than
blocking a backlight like LCDs do) so "off" is *really* off, and on is
really on.  This comes in handy when the display will be used in a
dark room, as you don't get the "glowing grey rectangle" effect that a
backlit LCD has.

Er, of course my experience is with monochrome displays, not full
color.  Not sure if VFD is an option in full color.

DJ Delorie <dj@delorie.com> writes:

> John Devereux <jdREMOVE@THISdevereux.me.uk> writes:
>> Don McKenzie <look@mysig.com> writes:
>> 
>> > Ajab wrote:
>> >>
>> >> Why should I go for OLEDs? Are they better that TFT?
>> >
>> > yes:
>> > http://www.dontronics.com/oled.html
>> > Cheers Don...
>> 
>> Isn't there a problem with lifetime?
>
> Depends on the color.  Based on OSRAM's specs, yellow seems to have
> the longest lifetime, at 50k hours (that's 100% brightness, 100% of
> the time, until it drops to 50% lumens).  Other colors are as low as
> 10k hours, or just over a year.  Note that this is a fundamental of
> LEDs themselves, not just OLEDs, but you only really notice the
> problem when it appears as "burn-in" on the display.

50k hours is equivalent to most industrial CCFL LCD backlights -
although you can change those!

I think one of the OLED application notes I saw gave a lifetime
*assuming a certain percentage* "on" time - so you have to be careful
to read the small print.

> However, note that some oled manufacturers are dropping their display
> lines.  A lot of their oled matrix displays are either already
> obsolete, or will be out of production soon.  Check with the
> manufacturer before designing them in.

It does seem like they are still very much niche products. Still much
more expensive than LCD when I last looked (a few months ago).

> OLEDs also cost more than LCDs; a 2.7" 128x64 monochrome (16 levels)
> display is $37 (qty 1).
>
> If cost isn't an issue, also check out VFDs.  They're even more
> expensive ($165 for that size) but, like OLEDs, they're emissive vs
> reflective (i.e. the elements themselves produce light, rather than
> blocking a backlight like LCDs do) so "off" is *really* off, and on is
> really on.  This comes in handy when the display will be used in a
> dark room, as you don't get the "glowing grey rectangle" effect that a
> backlit LCD has.

I quite like VFD - the last time I had one was ~25 years ago in one of
the early pocket calculators. Much nicer than the later LED and LCD
displays. Funny they still have a role to play, considering the
revolution in display technology since then.

-- 

John Devereux

John Devereux <jdREMOVE@THISdevereux.me.uk> writes:
> 50k hours is equivalent to most industrial CCFL LCD backlights -
> although you can change those!

Well, you can change an OLED too, I suppose.

> I think one of the OLED application notes I saw gave a lifetime
> *assuming a certain percentage* "on" time - so you have to be careful
> to read the small print.

IIRC mine spec'd 100% on, 100% duty cycle.  So my app is careful to
use the minimum lumens required for the task, since the display *will*
be on 100% of the time.

Plus, the app note suggested moving the image around over time, to
even out the wear and avoid burn-in.

> It does seem like they are still very much niche products. Still much
> more expensive than LCD when I last looked (a few months ago).

Yeah, too bad.  I have a niche requirement that they fit just
perfectly.  Good thing I only need a few :-)

> I quite like VFD - the last time I had one was ~25 years ago in one of
> the early pocket calculators. Much nicer than the later LED and LCD
> displays. Funny they still have a role to play, considering the
> revolution in display technology since then.

Noritake has a line of VFDs that are drop-in replacements for standard
LCD panels, now.  www.noritake-elec.com

So perhaps it's just that the demand *in general* is so high, that
niche products become profitable?

Ajab wrote:
> I don't know much about LCDs.

We noticed ;-)

> I just need to choose a colour LCD which is clearly visible from 10mm
> glass.

I'll assume you mean _through_ 10 mm of glass.  Well, that's a bit more 
than usual to put in front of an LCD panel, but no particular burden.

> Cost is not a problem. What else criteria I need to tell?

Let's see: size, resolution, op./non-op. thermal range, mechanical 
ruggedness, long-time stability, ambient brightness, update speed, 
available power --- and I'm quite sure I missed some important criteria.

In article <fb9qf0$baa$00$1@news.t-online.com>, HBBroeker@t-online.de 
says...
> Ajab wrote:
> > I don't know much about LCDs.
> 
> We noticed ;-)
> 
> > I just need to choose a colour LCD which is clearly visible from 10mm
> > glass.
> 
> I'll assume you mean _through_ 10 mm of glass.  Well, that's a bit more 
> than usual to put in front of an LCD panel, but no particular burden.
> 
> > Cost is not a problem. What else criteria I need to tell?
> 
> Let's see: size, resolution, op./non-op. thermal range, mechanical 
> ruggedness, long-time stability, ambient brightness, update speed, 
> available power --- and I'm quite sure I missed some important criteria.

If it's behind 10 mm of glass, I'd bet it's going into a hazardous area 
enclosure.  Make sure it isn't too far behind the glass, or you can have 
parallax problems and glare.  Make sure to try viewing the display under 
direct sun, and with polarized glasses on.  I've come across some POS 
terminals that got the polarization "wrong", so the display is 
completely black with my shades on; I would have to bend my neck 90 
degrees to read it.

--Gene