5 ms·

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

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.

ForHackernews 7y ago
Do you really need to update every second? Plenty of clocks have only an hour and minute hand.
- lucb1e 7y ago
  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.
  - Mathnerd314 7y ago
    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.
    - lucb1e 7y ago
      I guess that's true, I didn't think of that while writing.
  - andoma 7y ago
    No, It's not just you.
- m-p-3 7y ago
  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.
- hanniabu 7y ago
  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.
  - icebraining 7y ago
    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.
thayne 7y ago
> 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.
- krzyk 7y ago
  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.
  - wlesieutre 7y ago
    I was under the impression that Amazfit used a transflective LCD
    - TMWNN 7y ago
      You are correct. (Pebble also used transflective LCD and also called it "e-paper".)
jrockway 7y ago
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 https://www.youtube.com/watch?v=MsbiO8EAsGw
- godelski 7y ago
  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.
  - jrockway 7y ago
    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.

ForHackernews 7y ago

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

lucb1e 7y ago
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.
- Mathnerd314 7y ago
  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.
  - lucb1e 7y ago
    I guess that's true, I didn't think of that while writing.
- andoma 7y ago
  No, It's not just you.
m-p-3 7y ago
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.
hanniabu 7y ago
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.
- icebraining 7y ago
  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.

thayne 7y ago

> 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.

krzyk 7y ago
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.
- wlesieutre 7y ago
  I was under the impression that Amazfit used a transflective LCD
  - TMWNN 7y ago
    You are correct. (Pebble also used transflective LCD and also called it "e-paper".)

jrockway 7y ago

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 https://www.youtube.com/watch?v=MsbiO8EAsGw

godelski 7y ago
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.
- jrockway 7y ago
  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.