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| Which display technology has the longest life? |
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| alank2:
Something like a Noritake vacuum fluorescent character display, or something like the HCMS-3916 smart LED displays? By longest life, I mean you can pick it up decades later and have a decent hope it will still work as opposed to being left on 24 hours a day everyday for years and years, but may be the answer is the same. |
| Gyro:
That's a difficult one. Unfortunately I don't think the "answer is the same". HD44780 interface LCD Character displays have been around and interchangeable for decades, and typically long life too. Unfortunately it would be rather optimistic to expect them to survive for decades more now. I wonder how backlit monochrome displays will fare against the competition in the years to come. VFDs seem to be rather more manufacturer specific, and are not physically long lived, as evidenced by the difficulty in finding replacements for displays in older (and even fairly recent) test equipment. Inteligent LEDs don't seem to have fared too well historically. Looking back, there have been many types of chip on board LEDs (HP, TI and others) but these have now reached the status of expensive 'lucky scores' on ebay. OLEDs are still evolving, and fairly short lived [EDIT: whether powered on or not] it's probably too early to predict which interface will prevail longer term. It's a shame you are looking for character displays (?), I'm sure dumb 7 segment LED ones will be available and reliable for decades to come. Unfortunately we seem to be at a juncture where inteligent displays, OLEDS, colour LCDs etc. have become cheap and plentiful but with a wide variety of interfaces. As dumb as possible might be the best starting point? |
| alank2:
Thanks for the reply Gyro! They do make 14 segment LED's as well, but it is hard to not have that 5x7 format where you can display characters cleanly. I've not had that great of luck with 7 segment displays, but it could be that I've bought cheap ones. Even the ones I get from Digikey/Mouser seem to have quality issues from time to time. I've had good luck with the intelligent displays (which you can still buy at Digikey/Mouser, but they are pricy). I've got some of these with date codes that are into the 90's that work perfectly. These are probably my idea of what has the most longevity - maybe they are designed for aerospace applications. I think VFD's are also pretty durable if you get a quality one (Noritake) and they claim 10+ years that can be 20 years real easily. |
| Gyro:
Yes, 14 segment starburst displays have always been less than aesthetically pleasing, I suspect that their day has passed. Depending on where you bought them you may well have had low quality LED displays, I wouldn't be surprised if a lot of ebay ones weren't parametric rejects even if they do light up. Pretty much any low quality outfit can mount a few LED dies on a PCB, match it up to a plastic moulding and pour some epoxy in. The brand name ones are better at stress relieving the whole thing so that the bond wires don't get pulled off. VFDs are also very variable, premium ones like Noritake are going to last much better. There are loads of variables, vacuum and seal quality, phosphor poisoning - no or absolute minimum Red phosphor area! (the Noritake rep told me that one), Filament coating etc. Getting the drive levels just right is also a major factor (esp. filament voltage). It's just a matter of rolling the dice and picking to most durable intelligent display interface standard. Of course Nixie and Panaplex displays still work after 50+ years storage in cold, damp, ex-military warehouses. They look pretty too. ;) P.S. Is this a one-off application or a product? If it's one-off then you could just buy some spares and be nice to them. If it's a product, then you would probably be better defining an 'intelligent display board interface' instead, and upgrading the display board design over time if you need to. |
| jmelson:
--- Quote from: Gyro on August 08, 2019, 04:30:09 pm --- HD44780 interface LCD Character displays have been around and interchangeable for decades, and typically long life too. Unfortunately it would be rather optimistic to expect them to survive for decades more now. I wonder how backlit monochrome displays will fare against the competition in the years to come. --- End quote --- I've got some 20-character LCDs with 44780 controller that have been running in my house 24/7 for almost 30 years. No sign of fade, patterns, etc. LEDs certainly should last a long time if run at reasonable current. VFDs definitely fade after long use, and develop patterns where always-on segments become dimmer. But, for any of these technologies, they should have a very long shelf life. LCDs from the 1970's - 1980's tended to go dark over time, even if not powered on, but I think the stuff made today seems to have much longer shelf life. Jon |
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