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Comment by afandian | Hacker News Reader

In Oxford city centre, and probably elsewhere, they replaced the live signage at bus stops. These tell you when the next bus is due, the time and date, etc.

They used to be amber LED matrixes. High contrast, high legibility, low resolution.

Now they are colour LCD panels. High resolution, high tech, probably high cost. Now they can show the logos of the bus operators, smooth scrolling text and any arbitrary images. None of which anyone really needs except perhaps the egos of the bus companies.

And they are completely illegible. The viewing angle is limited, the text is smaller, unnecessary stuff is there because the implementors can.

Careful what you ask for.

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Amber LED matrices are my favorite tech for signage. The individual LEDs are sunken into the black matrix to provide extra contrast from direct light exposure. There's nothing that comes close for public signage that needs to be placed outdoors. These are by far not cheap though.

Still, this article is about 7 segment displays. It's a quirky article, but I get the point: many people abuse 7-segment displays as an aesthetic choice where there wouldn't be no point in it.

7 and 16-segment displays can still be a superb choice in many scenarios. The contrast is still unmatched to other display techs. For bench instruments, 7-segment displays (especially the VFD ones) are much more readable than the alternatives IMHO. The second best choice IMHO is OLED, however glare in bright environments is still worse, and getting a large OLED gets expensive very quickly.

For big machinery, a large 7-segment display can be read across the room in any condition. A large readable display on a lathe is much better in terms of safety than an smaller OLED display, even considering the chance of a stuck segment.

The main airport in my country switched their digital signage to LCD screens with fancy animations.

And now they periodically show full screen ads instead of arrival / departure information.

It makes me miss the big red letter panel from the early 2000s.

This is really where OLED is the right answer, I think. On smaller devices it's more or less entirely replaced 7-segs and similar displays. High contrast, high legibility, high resolution, but high cost. But if you're considering the cost of a monochrome/limited-colour OLED vs an LCD against the rest of the cost of upgrading a bus stop signage display the differential won't be a huge factor - labour, metalwork, etc will be. I've also seen high-resolution signage-oriented LED/LCD displays used for this sort of thing successfully.

Oxford's travel signage has always been a bit crap, though (and not alone, of course, in this - lots of places in the UK and Europe (and I'm sure US) have crap signage following similar patterns).

The amber matrices were at least clearly readable, but the presentation of information left a lot to be desired. Even on legible displays, constant scrolling displays that alternate between scrolling directions for different text displays for no good reason, and other such madness make it so hard to actually get information about stops that I ended up writing my own wrappers around APIs/website scraping to make a legible display on my phone.

This sort of thing should really be considered in terms of accessibility - for able-bodied people with good eyesight and a quick mind these displays may be legible, but a good % of your users are disabled, elderly, etc - none of the moving display, low-viewing-angle, small-text displays will be usable, but partially sighted/elderly people will generally make do with big friendly text that doesn't change except when it needs to.

The cost of small (128x32) OLED displays with integrated drivers has absolutely plummeted in recent years. They are now cheaper than 7 segments unless you only have 2 digits to display. On top of that the oled display modules are typically 2 wire serial or something similarly economical, while 7 segments require more connections and external components. It's hard to imagine them coming back in small devices.

How long do new OLED displays hold up? (Honest question, I don't know). And how is the viewing angle? Do you need a glass panel to protect it, does that have issues with glare?

The viewing angle is good.

The burn-down is a real issue with OLEDs, though :(

MicroLED is the future for such use case. Sony's CREDIS is already deployed on some space like Apple Store. It's really wide view angle, bright, no burn-in, simple technology.

You're not thinking big picture, nor looking at things from a business perspective. The transit authority can sell ad space on those LCDs, thus increasing revenue as well as reducing TCO of the displays.

Telstra did a similar thing here in Australia - there are some old regulations that let them install payphones pretty much wherever they want which was probably good back in the day when payphones were essential, however they started installing new "payphones" in prominent advertising locations where the whole back of the phone was a massive advertising display.

https://www.itnews.com.au/news/telstra-wins-payphone-electro...

Colour LCD panels probably work out cheaper that LED matrixes.

An LED matrix has a great number of individual components, and is probably hand assembled due to low demand (compared to an LCD panel). Whereas an LCD panel are mass produced in every size and shape, with standard controllers you can pick up for pennies.

I'm not sure if/why they would be hand-assembled, as SMD pick & place machines exist for the lighting industry: https://youtu.be/Y45COU2LdXg

(Granted, these are not individually addressable, but that depends on the PCB.)

The biggest issue for LED matrix displays is not construction, but 1) density of the display and 2) size/power draw requirements.

You need to consider there's half a million of LEDs in a typical signage device. These consume and heat-up significantly compared to an OLED/LCD panel.

For a panel of the same size, OLED/LCD has higher density, which allows to pack more information (or have better quality signage in general).

It all depends on the usage scenario. In an indoor setting with fixed lighting, a larger LCD screen can be just as readable as OLED, can be very large nowdays (or tiled to achieve the same), and cost a fraction of a LED matrix.

OLED could definitely replace LCDs entirely, but it's still very expensive when it comes to larger panels, which is why it's just slowly replacing smaller displays at the moment.

For LCD panels, one thing a lot of people don't know if that there are several different types, and the cheapest is quite awful. As all the prices come down I'm seeing fewer and fewer of the TN panels, but they can still be found. Terrible for conference rooms.

There's also a cheap kind of panel family where they don't put every color on every pixel. That is, rather than RGB RGB RGB, they are RG GB RG GB RG GB. For most video is hard to tell the difference, but it trashes text. Someone put a TV that was both TN and this reduced color in a conference room.... took me a few months to get it swapped out, but enough people finally saw it and realized it was the TV and not the computer or their eyes that I was able to get it done.

Absolutely true. I wish TN didn't exist entirely, but I guess it works in some weird price/quality zone. When going rock-bottom, LCD panels can indeed get very bad.

A big problem stems from the fact that to most people "flat panels" are all the same (LCD-whatever, OLED, even plasma)..

A LED panel consumes a lot of power for a reason. It is damn bright, and remains readable in broad summer sunlight. Most LCDs are useless in this setting, except maybe transreflexive monochrome (usually black-on-olive or similar).

I almost forgot transreflexive even existed :(. It has been a long time since I've seen some, but I remember the contrast being acceptable even in direct sunlight. But always in very small form factors.

Are there new devices which make use of this display tech?

I can find a few parts offered with a quick search, all small screens.

Also Garmin makes navigators with such screens, e.g. Garmin Montana.

I had the same irritation when our desk phones were replaced by Voip around 15 years ago, I had a nice avaya 8434 phone with bright green LED display, you could see caller ID from across the room if you were away from your desk talking to a colleague.

The new voip phones had hard to read LCD displays and previous hard key features buried in menus - they made the office look more modern but sucked otherwise.

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