Edge-Lit, Thin LCD TVs Are Having Early Heat Death Issues

August 15, 2024 by 60 Comments

Canadian consumer goods testing site RTINGS has been subjecting 100 TVs to an accelerated TV longevity test, subjecting them so far to over 10,000 hours of on-time, equaling about six years of regular use in a US household. This test has shown a range of interesting issues and defects already, including for the OLED-based TVs. But the most recent issue which they covered is that of uniformity issues with edge-lit TVs. This translates to uneven backlighting including striping and very bright spots, which teardowns revealed to be due to warped reflector sheets, cracked light guides, and burned-out LEDs.

Excluding the 18 OLED TVs, which are now badly burnt in, over a quarter of the remaining TVs in the test suffer from uniformity issues. But things get interesting when contrasting between full-array local dimming (FALD), direct-lit (DL) and edge-lit (EL) LCD TVs. Of the EL types, 7 out of 11 (64%) have uniformity issues, with one having outright failed and others in the process of doing so. Among the FALD and DL types the issue rate here is 14 out of 71 (20%), which is still not ideal after a simulated 6 years of use but far less dramatic.

Cracks in the Samsung AU8000's Light Guide Plate (Credit: RTINGS)
Cracks in the Samsung AU8000’s Light Guide Plate (Credit: RTINGS)

As part of the RTINGS longevity test, failures and issues are investigated and a teardown for analysis, and fixing, is performed when necessary. For these uniformity issues, the EL LCD teardowns revealed burned-out LEDs in the EL LED strips, with cracks in the light-guide plate (LGP) that distributes the light, as well as warped reflector sheets. The LGPs are offset slightly with plastic standoffs to not touch the very hot LEDs, but these standoffs can melt, followed by the LGP touching the hot LEDs. With the damaged LGP, obviously the LCD backlighting will be horribly uneven.

In the LG QNED80 (2022) TV, its edge lighting LEDs were measured with a thermocouple to be running at a searing 123 °C at the maximum brightness setting. As especially HDR (high-dynamic range) content requires high brightness levels, this would thus be a more common scenario in EL TVs than one might think. As for why EL LCDs still exist since they seem to require extreme heatsinking to keep the LEDs from melting straight through the LCD? RTINGS figures it’s because EL allows for LCD TVs to be thinner, allowing them to compete with OLEDs while selling at a premium compared to even FALD LCDs.

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Tiny Games Challenge: A Retro Racing Game On A 16×2 LCD

July 24, 2024 by 9 Comments

Sometimes, all it takes is a change in perspective to take something boring and make it fun. That’s true about 16×2 LCD; in its usual landscape format, it’s a quick and easy way to provide a character-based display for a project. But flip it 90 degrees and use a little imagination, and it can become a cool retro racing game that fits in the palm of your hand.

[arduinocelantano] has made it a habit to press the humble 16×2 character LCD into service in ways it clearly wasn’t intended to support, such as playing Space Invaders and streaming video on it. Both of these projects seem to inform the current work, which was one of the first entries in our current Tiny Games Challenge contest. The racing game requires multiple sprites to animate the roadway and the cars, using six “layers” of eight custom characters and rapidly switching between them to create the appearance of movement. The video below has a brief sample of gameplay.

Flipping the display on its side makes for a somewhat limited game — it’s all straightaway, all the time — but that could probably be fixed. [arduinocelentano] suggests scaling it up to a 16×4 to include curves, but we’d bet you could still simulate curves on the upper part of the game field while leaving the player’s car fixed on a straight section. Higher difficulties could be achieved by moving the curved section closer to the player’s position.

Sure, it’s limited, but that’s half the charm of games like these. If you’ve got an idea for our Tiny Games Challenge, head over to our contest page and let us know about it. We’re keen to see what you come up with.

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Responsive LCD Backlights With A Little Lateral Thinking

July 3, 2024 by 23 Comments

LCD televisions are a technological miracle, but if they have an annoying side it’s that some of them are a bit lacklustre when it comes to displaying black. [Mousa] has a solution, involving a small LCD and a bit of lateral thinking.

These screens work by the LCD panel being placed in front of a bright backlight, and only letting light through at bright parts of the picture. Since LCD isn’t a perfect attenuator, some of the light can make its way through, resulting in those less than perfect blacks. More recent screens replace the bright white backlight with an array of LEDs that light up with the image, but the electronics to make that happen are not exactly trivial.

The solution? Find a small LCD panel and feed it from the same HDMI source as a big panel. Then place an array of LDRs on the front of the small LCD, driving an array of white LEDs through transistor drivers to make a new responsive backlight. We’re not sure we’d go to all this trouble, but it certainly looks quite cool as you can see below the break.

This may be the first responsive backlight we’ve brought you, but more than one Ambilight clone has graced these pages.

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PCB Design Review: HDMI To LVDS Sony Vaio LCD Devboard

May 14, 2024 by 23 Comments

Today, we revisit another board from [Exentio] – a HDMI/DVI to LVDS transmitter for the Sony Vaio P display. This board is cool to review – it has a high-speed serial interface, a parallel interface, a healthy amount of power distribution that can be tricky to route, and many connectors to look over.

I’ve decided to show this review to you all because it demonstrates a PCB improvement concept we haven’t yet touched upon, that you should absolutely know about when doing board layout. Plus, I get a chance to talk about connector choice considerations!

The board is lovely. It integrates the DPI-LVDS circuit we’ve previously reviewed, but also a HDMI to parallel RGB chip from Texas Instruments, TFP401, a chip appreciated enough that even Adafruit has adapters with it. The fun thing about this chip is that it doesn’t even handle EDID like the usual HDMI to RGB/LVDS chips you get on cheap Aliexpress boards. So, there’s no firmware to take care of – it just receives a HDMI/DVI signal, converts it into parallel RGB, then converts that to LVDS, and off to the display it goes. The downside is that you have to provide your own EDID with an EEPROM, but that isn’t that tricky.

Again, this is a two-layer board, and, again, I like this – fitting tracks to the smallest possible space is a respectable and enjoyable challenge. This board has absolutely done well by this challenge. I do see how this board could be routed in an even better way, however, and it could be way way cleaner as a result. For a start, rotating the chip would improve the odds a whole lot.

The Chip Gets Rotated

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PCB Design Review: ESP32-S3 Round LCD Board

March 19, 2024 by 6 Comments

For our next installment, I have a lovely and daring PCB submitted by one of our readers, [Vas]. This is an ESP32-S3 board that also has an onboard round TFT display, very similar to the one we used on the Vectorscope badge. The badge is self-sufficient – it has an ESP32, it has a display, a programming connector, two different QWIIC ports you could surely use as GPIOs – what’s not to love?

This is a two-layer board, and I have to admit that I seriously enjoy such designs. Managing to put a whole lot of things into two layers is quite cool in my book, and I have great fun doing so whenever I get the opportunity. There’s nothing wrong with taking up more layers than needed – in fact, if you’re concerned about emitted/received noise or you have high-speed interfaces, four-layer is the way to go. But making complex boards with two layers is a nice challenge, and, it does tend to make these boards cheaper to manufacture as a very nice bonus.

Let’s improve upon it, and support [Vas]’s design. From what I can see looking at this board, we can help [Vas] a lot with ease of assembly, perhaps even help save a hefty amount of money if they go for third-party PCBA instead of sitting down with a stencil – which you could do with this board pretty easily, since all of the components on it, save for the display, are the ones you’d expect JLCPCB to stock.

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PCB Design Review: DPI-LVDS Sony Vaio LCD Devboard

March 12, 2024 by 12 Comments

Ordering a PCB with mistakes sucks. We should help each other avoid such mistakes – especially newcomers. One of the best ways to avoid these mistakes, especially if it’s your first one, is to get a few other people to look at it. You deserve to get a PCB that is as functional and as helpful as humanly possible, so that you can be happy with your project, and feel ever so slightly more confident in yourself in whatever you shall set out to do next.

At the end of last year, I put out a call for design review submissions, and we’ve received enough projects to make me feel overwhelmed for a bit. A design review has always felt like a personal thing, and here we are doing them in public. But in that sense, we hope that everyone can learn from them, and we hope to push forward a healthy review culture.

What’s more, these articles won’t just be design review. Every project I’m highlighting is worthy of a Hackaday feature just on its own, so tune in and learn more about them!

Today’s Contestant

For this example, I will be walking through a review I’ve already given someone with a pretty cool board, for a pretty cool project I’ve already shown you. Remember the Sony Vaio remake project? A fair bit of people have reached out to me afterwards, and one of them, [Exentio] also had the same Sony Vaio rebuild idea in mind. We started chatting, and he decided to tackle one of the project’s milestones, and perhaps the most crucial one – adapting the LCD.

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Oddball LCDs Reverse Engineered Thanks To Good Detective Work

December 12, 2023 by 5 Comments

Is there anything more discouraging to the reverse engineer than to see a black blob of epoxy applied directly to a PCB? We think not, because that formless shape provides no clue as to what chip lies beneath, and that means a lot of detective work if you’re going to figure out how to use this thing.

[Sudhir Chandra]’s detective story starts with a bunch of oddball LCDs, slim 1×32 character units rather than the more familiar 2×16 displays. Each bore the dreaded black COB blob on the back, as well as a handful of SMD components and not much else. Googling revealed no useful documentation, and the manufacturer wasn’t interested in fielding calls from a hobbyist. Reasoning that most manufacturers wouldn’t spin up a custom chip for every display, [Sudhir] assumed there was an ST7066, a common LCD driver chip, underneath the blob, especially given the arrangement of external components. But a jumper set was bodged together under this assumption didn’t get the display going.

Next up were more destructive methods, to decap the COB and see what kind of numbers might be on the chip. Sandpaper worked at first, but [Sudhir] eventually turned to the “Chips a la [Antoine]” method of decapping, which uses heat and brute force to get at the goods. This got down to the chip, but [Sudhir]’s microscope wasn’t up to the task of reading the die markings.

What eventually cracked the case was tracing out the voltages across the various external resistors and matching them up to other chips in the same family as the ST7066, plus the realization that the long, narrow epoxy blob probably covered a similarly shaped chip, which led to the culprit: an ST7070. This allowed [Sudhir] to build an adapter PCB for the displays, with plans for a custom Arduino library to talk to the displays.

This was a great piece of reverse engineering and a good detective story to boot. Hats off to [Sudhir] for sticking with it.