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Comment by xorcist | Hacker News Reader

Why isn't e-ink perfect here? A watch is perfectly usable in monochrome and is used in bright daylight which would favor high contrast and viewing angles. Plus battery life is good. Turns out there has been a few on the market but nobody really wanted them. Strange.

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E-ink has fairly low refresh rates, and even though it uses no power at rest, it takes a lot of energy to refresh. 'Battery life is good' has become a catechism, but it really depends on the use case.

I don't have hard numbers, but if you need to update as frequently as every second, I don't think you'd gain much over a low-brightness color display with a polarized window for sunlight viewing.

And battery life seems like the only major draw of e-ink, as long as they are limited to one or two colors and a full-screen refresh rate that your eyes can easily register.

People have tried to develop tricks to update faster and minimize how much of the display gets refreshed, but I'm not aware of many successes since a lot of it seems to require reverse engineering; the companies which produce the displays jealously guard any information about the refresh parameters and functionality as highly confidential IP, and the process appears to be heavily dependent on temperature.

Do you really need to update every second? Plenty of clocks have only an hour and minute hand.

As one data point, I frequently look at the second indicator on my phone or laptop (I configured both to show one at all times), but even nerdy colleagues tell me that's just me, so that's probably just me.

I think I'd be fine with having to tap my wristwatch to update the display. It would be cool if it could just show seconds without tapping, but if having to tap means the difference between a few days of battery life and months of battery life (I'm on a computer most of the day so it would wake only a few times a day), then sure.

Once you're fine with tapping to update the display, you might as well just use a non-E-ink display, keep it turned off most of the time, and turn it on to use it, since that's one tap.

I guess that's true, I didn't think of that while writing.

No, It's not just you.

I guess you would have to, if you want to have a playback indicator. You wouldn't have to refresh the whole screen to gradually fill up the bar, as the ghosting effect would be negligible.

Note that this is a smartwatch, not a digital watch. Using eInk would prevent the use of apps on the watch if the refresh rate is once every few seconds.

An eInk display can refresh much faster than that, it's just that you can't keep refreshing so fast if you want to spend less energy than an LCD would. But you could adjust dynamically depending on the current use.

> And battery life seems like the only major draw of e-ink

I also find e-ink easier on the eyes than any backlit display. At least for reading. For a watch it probably doesn't matter too much.

Amazfit Bip is a great watch and it has color e-ink display, works up to 45 days on a charge.

And the more sunlight the more readable it is.

I was under the impression that Amazfit used a transflective LCD

You are correct.

(Pebble also used transflective LCD and also called it "e-paper".)

I built an e-ink clock recently. E-ink has two downsides; the datasheet says that the display will be damaged if it's refreshed more than every 3 minutes (I ignore that and refresh it every minute, so we'll see if it lasts) and the black/white/black refresh cycle is very visually distracting. Having that thing in the field of view just doesn't work.

Both of these issues can be gotten around with a different refresh algorithm, but of course the datasheet doesn't include any of them. The vendors regard their refresh logic as proprietary and so you have to spend months trying to figure out what will work, like this: https://www.youtube.com/watch?v=MsbiO8EAsGw

I've been thinking about doing a similar project for fun. How long have you had the clock? I'd be really curious how hard that 1 minute refresh rate is on the screen. I have a Kindle and I definitely read more than a page a minute (especially on that small screen) and haven't noticed any problems. But a clock is more consistent and constant.

As for a watch, I could see getting notifications once a minute being fine.

A couple months. No side effects at all so far.

When developing this, it obviously refreshed much more than once a minute. Nothing ever led me to believe anything bad was happening. No burn in, no artifacts, no weird behavior at all.

I think the datasheet is being super ultra mega conservative, designed to cover the worst possible unit that they would let past QC being put in a product that would cost billions of dollars to recall. If you got an average unit and you're making one of these things.... you can probably refresh it in a loop for decades and never have a problem. I wouldn't bet billions on it, but I will bet $20 on it.

I use Garmin Instinct with monochrome display. It has so many features, even a simple navigation system, and it’s battery goes 2 weeks. I love it.

I can’t understand why people want to have color, fancy screens on a watch. Do we need colors to see the time? A calendar notification? Heart rate ?

A watch should serve information without distracting, and most importantly, I should be able to go out without thinking about battery life of my watch. It should be reliable enough to carry it in the arm.

To you it makes zero sense, to a ton of other people it does. I love the value having statuses conveyed to me in color, it allows me to quickly process information.

Right, changed my comment

Every time the topic of battery life on smart watches pops up, there's a debate: does a battery life of more than a day actually help?

Some argue that the daily habit of charging makes it easier to remember to do it, vs a less frequent schedule.

And people do use the Apple Watch for sleep tracking, charging it during showers and other preparations in the morning or at night, so the battery life is good enough for effectively 24 hours of use.

The problem is that you need a lot of headroom. If you are fully depleating the battery almost every day that will typically result in a 50% capacity drop over 2 years.

And suddenly even if your device had some headroom when new it still won't last a day.

I’m on hour 21 and I still have 30% remaining on my Series 4. Even if a 50% drop is true, and that hasn’t been my experience with any previous Watch, there’s a lot of headroom.

Good, but the question was whether any headroom mattered.

I’m on year 3 I think of having an Apple Watch. It’s a series 1 or 2. It’s at 30% right now after 13 hours. With almost no usage of the watch. And 8 hours of sleeping (with Watch on) and/or DND on. If I actively used it, I’m guessing it would be almost dead right now.

I love my Pebble Time, the availability of a basic color palette makes it easier to build a user-friendly UI.

I agree with the fancy screen, IMO this is not necessary but that's what users want apparently.

I bet you have clothes with pockets.

E-ink is not necessary for a long battery life - the Amazfit Bip, has a long one (up to 45 days).

An Amazfit Bip equivalent, with an open system would be a great product at least for a niche (Amazfit's interface and functionality is arguably poor).

edit: has this post been downvoted with information at hand? The statement above is technically correct: the Bip has an LCD (see specs), and it lasts very long; therefore, E-ink is not the only option for a display of a long-lasting device.

I googled it, and "Always-on reflective 1.28 inch color touch display" makes it sound like it's using Mirasol or some other color e-paper display.

^ Notably, that's very different tech from actual e-ink.

Google better :-P

From https://amazfitcentral.com/amazfit-bip-specifications:

> The watch has a color LCD display which shows info with a resolution of 176 x 176 pixels. It is a reflective panel which will allow you to save battery while it is in stand by, as it will still be able to show you what time is it.

Yeah, there is no need for low refresh rate eink. Lcd doesn't consume much power and is readable. I've had several lcd watches and their batteries lasted for years.

sigh that is what I loved about Pebble

The Pebble screen is hard to read in regular room light -- which, sadly, is the kind of light that most of us are in most of the time.

When Pebble went under I switched to a Samsung watch with an AMOLED screen and the difference in view-ability is stunning.

Did you have a Pebble Time or a Pebble Classic / Pebble 2?

I agree with you with regard to the Pebble Time, but the Pebble 2's screen is fantastic. I can see the time even in an abnormally dim room, without the built-in light. (The trade-off, of course, is that the Pebble 2's screen is black and white, but I think that's fine on a watch).

I had a classic and a Time.

And you found the Classic hard to read in dim rooms?

I’m just surprised. I’ve admittedly never owned a Classic (only a Time and P2), but I thought the Classic was supposed to be almost as good as a Pebble 2. And I find my P2 as easy to read as a normal watch.

The classic's display was pretty far from the surface of the watch and that hampered the display. Though it was easier to read than the Time.

I expect both the Steel and the P2 are much easier to read than the classic.

I've had a Pebble Steel (original), Pebble Time Round, and Pebble 2. The screens on all of them were very readable, IMHO.

So true. I'm sad to see so much resistance towards Pebble and e-ink in this thread.

I'm still using my Pebble Time, I love it. I adore only having to charge it once a week and still being able to see the time on it.

Just the fact that anyone can look at my wrist and see the time without shaking it or anything is worth much more than refresh rate and apps for me.

All I need a smartwatch for is to see messages and notifications from my phone.

Pebble is not eink though, it's transflective, marketed as "e-paper" but it's not at all like the screens of book readers

TIL. I've been going around calling it e-ink. Either way, it's better than a LED screen for battery time.

I worked on android wear when we were just deciding on hardware. We had an option for a color, low power, slow-refresh display. Andy vetoed it very quickly because "next to an OLED it looks like shit". Basically the logic was that consumers will read one review and get the pretty OLED watche instead.

It doesn't emit light, so you still have to pair it with a backlight. There are some pretty bad ghosting issues, so things that refresh frequently have readability issues. This also makes it bad for all the "smart" watch things - for a regular watch, e-ink would be acceptable, but could be replaced with a traditional watch face which draws even less power.

Aren't e-ink displays opaque, making backlights impractical? Ebooks readers like the kindle paperwhite have front lights LEDs below the screen and a light guide layer to disperse it.

Qualcomm IMOD was pretty cool. Looks like Apple gobbled it up. https://appleinsider.com/articles/15/12/15/apple-has-taken-o...

I am still using my pebble every day.

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