Newhaven Display Forum

Newhaven Products => OLEDs => Topic started by: markdpend on June 03, 2015, 05:04:28 AM

Title: NHD-0420CW-AG3 Pixel Test
Post by: markdpend on June 03, 2015, 05:04:28 AM
Hi, I built a few projects using the NHD-0420CW-AG3 OLED display a couple years ago and am now refurbishing them.  I want to see if the displays have any issues so I wrote a small routine to light up every pixel (sent 0xFF) in every position (all 80), as shown below.   It was on for less than a minute about 4-5 times.   I found a little burn-in and only 1 dead pixel in only 1 character (row 2, column 15).  You can't see the burn-in but you can see the dead pixel in the picture.  So far so good until I turned it on a couple minutes later (normal operation) and find a couple columns of pixels that now won't turn off.  Hoping it might be a saturation issue that would eventually subside, I waited about an hour but they were still there and that's when I took the pictures.  So I have some questions.  Did I damage the display turning everything on at once?  If so, is it repairable with either component(s) change (I'm handy with electronics) or maybe a software approach?  If I did damage it, is there a preferred way to test the pixels?  I've got 3 more old units I want to test but am reluctant to try this again.  Thanks.
Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: Paul_B on June 03, 2015, 08:33:47 AM

I have seen similar behavior before usually caused by ESD (Electrostatic Discharge) damage to the module / controller. Unfortunately in this case the damage is irreversible, generally devices with finer geometries are more susceptible to damage from ESD.

I always recommend working on a static-safe work bench and following the appropriate procedures to ensure your device is protected from ESD. This includes grounding enclosures, bezels, etc ...

Finally, can you please tell me what steps you took to ground your devices as a whole?


Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: markdpend on June 03, 2015, 03:11:57 PM
Thanks for the quick reply.  Sorry, I had the wrong part number.  It's the NHD-0420DZW-AG5, not the slim one.  The displays are mounted in a plastic box.  All power (VCC) and ground is via connector pins 2 and 1 respectively.  I don't have anything electrically/directly attached to the bezel itself.  The power design is robust (VCC, GND), i.e. thick traces, star distribution, etc.  There is no earth ground as it runs on a 2-prong AC/DC adapter.  I work on a grounded bench.  These displays, however, didn't come out when I worked on the project as they're permanently soldered to another PCB so they never get touched.  This was just a software exercise for the display.  I have a PIC inside a ZIF socket that comes out when I make firmware changes.  I'm grounded when I do that.

Any connection to lighting up all the pixels?  The problem showed up right after doing that and it's been in use and trouble free for a couple of years.
Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: markdpend on June 03, 2015, 06:21:30 PM
Well the problem went away as mysteriously as it showed up.  It's been sitting several hours unplugged since the first pictures were taken.  Pics below.  You can see some of the burn-in on this one.  So I ran the pixel test program on my other blockers and everything went fine.  If you have any more insight, I'll take it.  Thanks for the help once again.

So I have maybe a related question.  I have a plasma TV and it also suffers from burn-in.  Is that characteristic of "organic" technologies?  Is there another type of 4x20 character display technology with as good contrast as your OLED (character color-on-black background) that doesn't suffer burn-in, kind of like the way LCDs evolved?

And one more if I may.  How does one earn non-zero Karma?
Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: Paul_B on June 04, 2015, 08:39:08 AM

Burn-in (as in ghostly image) is a more susceptible to OLED displays, however it can still occur with standard LCD's.

The length of time required for noticeable screen burn to develop varies due to many factors. It can take as little as only a few weeks for noticeable ghosting to set in, especially if the screen displays a certain image (example: a menu bar at the top or bottom of the screen) constantly, and displays it continually over time.

Please note that screen burn-in can easily be avoided, you may want to think of a plan to reduce long-term display in the same place on the screen.

Below are a few simple steps you can take to prevent burn-in:

E.g. In your case maybe install a PIR sensor to turn off the display when no one is in proximity of the unit.

E.g. Enable the OLED's built-in scroll feature.

Finally, Karma points are given by members to other members for any reason, usually for answering or posting a helpful question  8)
Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: markdpend on June 04, 2015, 03:10:31 PM
Thanks for the reply.  That's a great idea on the PIR sensor.  I already incorporated an LDR sensor in the latest model to turn off the display at night but replacing it with a sensor that can turn it off when no one is around is much better and also gave me an idea of triggering some sort of moving text when nobody's around to show it's on/working to equally excite, on average, all the pixels to help improve wear uniformity.  I wasn't aware of the OLED's built-in scroll feature, will have to look into that. 

Back atcha on the Karma.   ;D
Title: Re: NHD-0420CW-AG3 Pixel Test
Post by: Paul_B on June 05, 2015, 07:39:57 AM
Not a problem, have a good one!