Polymer LED display issue

G

Gavin Melville

Guest
Hi,

I have an application that just suits a Polymer LED display perfectly.
I can get a 2 line 16 char display (such as a Delta PDC1602M), and all
looks good (power consumption, life, interface etc)

The only problem is that buried in the specs is the line that says "Do
not hold the same display picture over 1 min, because they will cause
none uniformity in the display screen."

Ignoring the bad english, I think this is some kind of burn in
phenomonon. Other makers mention a "differential burn in" issue, but
put no time limit on it, however most manufacturers do not even
mention this.

Trying it, so far, has produced no observable effects. I can see it
would be easy to solve this on a graphics display, but much harder on
a text display that never has quite enough characters anyway.

A web search has not prodiced any real useful info -- does anyone have
any real experience with PLED displays and this issue in particular ?

TIA,


--
Regards,
Gavin Melville
gavin.melville@acclipse.co.nz
 
Gavin Melville <gavin.melville@acclipse.co.nz> wrote:
Hi,

I have an application that just suits a Polymer LED display perfectly.
I can get a 2 line 16 char display (such as a Delta PDC1602M), and all
looks good (power consumption, life, interface etc)

The only problem is that buried in the specs is the line that says "Do
not hold the same display picture over 1 min, because they will cause
none uniformity in the display screen."

Ignoring the bad english, I think this is some kind of burn in
phenomonon. Other makers mention a "differential burn in" issue, but
put no time limit on it, however most manufacturers do not even
mention this.
Click to expand...
I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice
 
On 23 Aug 2005 12:34:22 GMT, the renowned Ian Stirling
<root@mauve.demon.co.uk> wrote:

Gavin Melville <gavin.melville@acclipse.co.nz> wrote:
Hi,

I have an application that just suits a Polymer LED display perfectly.
I can get a 2 line 16 char display (such as a Delta PDC1602M), and all
looks good (power consumption, life, interface etc)

The only problem is that buried in the specs is the line that says "Do
not hold the same display picture over 1 min, because they will cause
none uniformity in the display screen."

Ignoring the bad english, I think this is some kind of burn in
phenomonon. Other makers mention a "differential burn in" issue, but
put no time limit on it, however most manufacturers do not even
mention this.

I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice
Click to expand...
The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
On 23 Aug 2005 12:34:22 GMT, the renowned Ian Stirling
root@mauve.demon.co.uk> wrote:

Gavin Melville <gavin.melville@acclipse.co.nz> wrote:
Hi,

I have an application that just suits a Polymer LED display perfectly.
I can get a 2 line 16 char display (such as a Delta PDC1602M), and all
looks good (power consumption, life, interface etc)

The only problem is that buried in the specs is the line that says "Do
not hold the same display picture over 1 min, because they will cause
none uniformity in the display screen."

Ignoring the bad english, I think this is some kind of burn in
phenomonon. Other makers mention a "differential burn in" issue, but
put no time limit on it, however most manufacturers do not even
mention this.

I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice

The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.
Click to expand...
That too.
I think the pixels'd be more or less isothermal though.
 
On 23 Aug 2005 18:05:31 GMT, the renowned Ian Stirling
<root@mauve.demon.co.uk> wrote:

Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
On 23 Aug 2005 12:34:22 GMT, the renowned Ian Stirling
root@mauve.demon.co.uk> wrote:

Gavin Melville <gavin.melville@acclipse.co.nz> wrote:
Hi,

I have an application that just suits a Polymer LED display perfectly.
I can get a 2 line 16 char display (such as a Delta PDC1602M), and all
looks good (power consumption, life, interface etc)

The only problem is that buried in the specs is the line that says "Do
not hold the same display picture over 1 min, because they will cause
none uniformity in the display screen."

Ignoring the bad english, I think this is some kind of burn in
phenomonon. Other makers mention a "differential burn in" issue, but
put no time limit on it, however most manufacturers do not even
mention this.

I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice

The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.

That too.
I think the pixels'd be more or less isothermal though.
Click to expand...
Sure, but for a given set of display patterns, the difference in
brightness of pixels due to burn-in should increase much more quickly
(in relation to the expected life of product) at high temperatures.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice

The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.

That too.
I think the pixels'd be more or less isothermal though.

Sure, but for a given set of display patterns, the difference in
brightness of pixels due to burn-in should increase much more quickly
(in relation to the expected life of product) at high temperatures.
Click to expand...
I expect this to occur, but Delta indicate that it occurs over 1
minute, not 5000 hours, which in this use would be years.
--
Regards,
Gavin Melville
gavin.melville@acclipse.co.nz
 
On Wed, 24 Aug 2005 15:40:02 +1200, the renowned Gavin Melville
<gavin.melville@acclipse.co.nz> wrote:

I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice

The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.

That too.
I think the pixels'd be more or less isothermal though.

Sure, but for a given set of display patterns, the difference in
brightness of pixels due to burn-in should increase much more quickly
(in relation to the expected life of product) at high temperatures.

I expect this to occur, but Delta indicate that it occurs over 1
minute, not 5000 hours, which in this use would be years.
Click to expand...
The application note that I have says "a long time" not "1 minute",
which I would interpret as many hours (probably > 100 or >500). It
also says that the effect of temperature < 50°C on life is small. They
do go on at some length about automatically blanking the display,
scrolling or doing other annoying things.

What's the document number of what you are looking at?


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Hi Spehro,

http://www.delta-opto.com.tw/english/products/default.htm , click on
PDC1602M (a pdf file). Last page (22) , 15.4 says "(4) Do not hold
the same display picture over 1 min, because they will cause none
uniformity in the display screen."

Several other datasheets from Delta have similar warnings.

I have not found many other displays with reasonable power consumption
-- I can use either 16x2 text or 128 x 64 graphics.

On Wed, 24 Aug 2005 00:36:50 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 24 Aug 2005 15:40:02 +1200, the renowned Gavin Melville
gavin.melville@acclipse.co.nz> wrote:


I think it's poorly stated.
All OLEDs will decay due to use, being at (for eaxample) 50% light output
at 5000 hours illuminated.
After 5000 hours, if pixel A is always on, and pixel B is never on,
then when you want to light A and B, A will be 50% dimmer than B.

You need to think about this when designing displays, or live with the
fact that they will look blotchy.
light A and B together, you'll notice

The OLED/PLED degradation is apparently greatly accelerated by high
temperatures.

That too.
I think the pixels'd be more or less isothermal though.

Sure, but for a given set of display patterns, the difference in
brightness of pixels due to burn-in should increase much more quickly
(in relation to the expected life of product) at high temperatures.

I expect this to occur, but Delta indicate that it occurs over 1
minute, not 5000 hours, which in this use would be years.

The application note that I have says "a long time" not "1 minute",
which I would interpret as many hours (probably > 100 or >500). It
also says that the effect of temperature < 50°C on life is small. They
do go on at some length about automatically blanking the display,
scrolling or doing other annoying things.

What's the document number of what you are looking at?


Best regards,
Spehro Pefhany
Click to expand...
--
Regards,
Gavin Melville
gavin.melville@acclipse.co.nz
 
On Thu, 25 Aug 2005 10:06:06 +1200, the renowned Gavin Melville
<gavin.melville@acclipse.co.nz> wrote:

Hi Spehro,

snip
Click to expand...

Thanks for the link. I see what you mean. Life appears to be 5,000
hours to 50%, since it's measured with 50% duty cycle. Still looks
like it should be hundreds of hours to see a visible difference.

Have you talked to the office in Taiwan? (they'll probably refer it
back to the dudes in FL, but it can't hurt)


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Spehro Pefhany wrote:
Thanks for the link. I see what you mean. Life appears to be 5,000
hours to 50%, since it's measured with 50% duty cycle. Still looks
like it should be hundreds of hours to see a visible difference.

Have you talked to the office in Taiwan? (they'll probably refer it
back to the dudes in FL, but it can't hurt)
Click to expand...
The reply from Taiwan was a bit of a stunner.

"Due to the display uniformity in the display screen , we advise our
customer that don't hold the same display picture over 1 min.

Display skills :
1. Try to scrolling the pattern after 1 min. then return to the
original pattern
2. After 1 min. turn off the pattern , when you want to see the
pattern , try to contact some key button to start the pattern"

Back to the search for low power display, and don't go near Delta.......
 
<gavin.melville@acclipse.co.nz> wrote in message
news:1125138935.170242.171990@g14g2000cwa.googlegroups.com...

The reply from Taiwan was a bit of a stunner.
Click to expand...
Yeah, what kind of useless product is this?

Even a CRT takes many hours to get burn-in images.

Hard to tell from their English, but I wonder if they mean that a picture
would show up as an after-image if you change to an all-lit image?

Discrete LED brightness varies with temperature (brighter when colder), so
maybe the lit pixels get warmer than the unlit pixels. They would then
appear dimmer when the unlit pixels are turned on, at least until all pixels
warmed to the same temperature.

Plastic isn't as good a heat conductor as glass or inorganic LED material.

Back to the search for low power display, and don't go near Delta.......
Click to expand...
I heard OLED displays are not actually very low power, they are emitting
light energy rather than absorbing it as LCDs do.
 
On Sat, 27 Aug 2005 11:31:25 GMT, the renowned "Kryten"
<kryten_droid_obfusticator@ntlworld.com> wrote:

I heard OLED displays are not actually very low power, they are emitting
light energy rather than absorbing it as LCDs do.

They are lower power than an LCD + LED backlight.
Click to expand...


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
gavin.melville@acclipse.co.nz wrote:
Spehro Pefhany wrote:
Thanks for the link. I see what you mean. Life appears to be 5,000
hours to 50%, since it's measured with 50% duty cycle. Still looks
like it should be hundreds of hours to see a visible difference.

Have you talked to the office in Taiwan? (they'll probably refer it
back to the dudes in FL, but it can't hurt)

The reply from Taiwan was a bit of a stunner.

"Due to the display uniformity in the display screen , we advise our
customer that don't hold the same display picture over 1 min.
Click to expand...
I think this is just generic, and nothing specific to this OLED.
They are not saying that after 61s, there will be damage.
What they are trying to get across is that if you have the display
static for long periods, you'll notice nonuniformity eventually.
 
On 27 Aug 2005 18:26:21 GMT, the renowned Ian Stirling
<root@mauve.demon.co.uk> wrote:

gavin.melville@acclipse.co.nz wrote:
Spehro Pefhany wrote:
Thanks for the link. I see what you mean. Life appears to be 5,000
hours to 50%, since it's measured with 50% duty cycle. Still looks
like it should be hundreds of hours to see a visible difference.

Have you talked to the office in Taiwan? (they'll probably refer it
back to the dudes in FL, but it can't hurt)

The reply from Taiwan was a bit of a stunner.

"Due to the display uniformity in the display screen , we advise our
customer that don't hold the same display picture over 1 min.


I think this is just generic, and nothing specific to this OLED.
They are not saying that after 61s, there will be damage.
What they are trying to get across is that if you have the display
static for long periods, you'll notice nonuniformity eventually.
Click to expand...
Rather extreme CYA statement, though.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Spehro Pefhany <speffSNIP@interlogdotyou.knowwhat> wrote:
On 27 Aug 2005 18:26:21 GMT, the renowned Ian Stirling
root@mauve.demon.co.uk> wrote:

gavin.melville@acclipse.co.nz wrote:
Spehro Pefhany wrote:
Thanks for the link. I see what you mean. Life appears to be 5,000
hours to 50%, since it's measured with 50% duty cycle. Still looks
like it should be hundreds of hours to see a visible difference.

Have you talked to the office in Taiwan? (they'll probably refer it
back to the dudes in FL, but it can't hurt)

The reply from Taiwan was a bit of a stunner.

"Due to the display uniformity in the display screen , we advise our
customer that don't hold the same display picture over 1 min.


I think this is just generic, and nothing specific to this OLED.
They are not saying that after 61s, there will be damage.
What they are trying to get across is that if you have the display
static for long periods, you'll notice nonuniformity eventually.

Rather extreme CYA statement, though.
Click to expand...
I think it's possibly a case of the translator not fully understanding the
engineers.
 
Hi,

I have one on test now -- completed 8 hours without showing any sign of
degradation. Will keep the group informed.

Gavin Melville.
 
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