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Refresh rate for eInk Display
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Refresh rate for eInk Display

by garyvdg on Wed Jul 08, 2020 8:19 am

I am just getting started using one of the eInk displays (the 2.13 E-ink FeatherWing monochrome) and have a question about the warning in the Adafruit learning guide https://learn.adafruit.com/adafruit-eink-display-breakouts/usage-expectations that says,

you shouldn't refresh or change the display more than every 3 minutes (180 seconds)


Do not update more than once every 180 seconds or you may permanently damage the display


Is this refresh the same as doing the
Code: Select all | TOGGLE FULL SIZE
display.display()
function?

I ask because the example sketches provided with the display libraries download draw new stuff to the display every 15 seconds.

What is it that should not be done more than once every 180 seconds?

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Re: Refresh rate for eInk Display

by dastels on Wed Jul 08, 2020 12:47 pm

Yes,
Code: Select all | TOGGLE FULL SIZE
display.display();

is the refresh.

It's a little confused, and I don't know why the example is refreshing more often. eink displays are generally used in cases where you don't need real time display. Especially when the controller will sleep or even power down most of the time to conserve battery, waking occasionally to take readings and update the display. eInk has the advantage of not needing to consume power to retain the display.

I would stick with the 3 minute refresh limit. If you need more frequent updates, consider oled displays.

Dave

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Re: Refresh rate for eInk Display

by garyvdg on Wed Jul 08, 2020 12:56 pm

Dave,

Thanks for the response and recommendation.

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Re: Refresh rate for eInk Display

by sloot on Sun Nov 29, 2020 1:05 am

well, there goes my plan for a clock. Even one without a seconds display ....

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Re: Refresh rate for eInk Display

by dastels on Sun Nov 29, 2020 11:30 am

Yes, eink isn't generally good for realtime display. It's great for infrequent updated, always displayed, low power use since you can power down and have the display remain, waking occasionally to update.

Dave

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Re: Refresh rate for eInk Display

by sloot on Sun Nov 29, 2020 11:59 pm

Yeah, I wasn't going to display seconds, only minutes.

My plan was to use the magtag, and the demo slideshow code for that, is a refresh every 60 seconds.

I'm confused about this 3 minute refresh for e-ink displays and permanently damaging them. In another thread on the magtag e-ink display, you recommended running the GFX demo, but that would have a faster refresh rate than 3 minutes.

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Re: Refresh rate for eInk Display

by dastels on Mon Nov 30, 2020 11:24 am

I haven't measured the MagTag's update time, but it it likely on the order of 10 seconds. As I said, for general use you want a low refresh rate. I probably wouldn't choose eInk for a clock display.

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Re: Refresh rate for eInk Display

by scotch1 on Wed Feb 03, 2021 4:27 pm

Curious if we know the refresh rate of this adafruit eink displayhttps://learn.adafruit.com/adafruit-eink-display-breakouts/usage-expectations, in comparison to the pimorini pHAT which takes 15-20 seconds?

A couple of seconds is much better than 15-20 making the pimorini not useful for minute updates. THe advice is 180 second intervals, but tutorials https://blog.adafruit.com/2021/01/08/creating-a-home-education-school-clock-with-a-raspberry-pi-piday-raspberrypi-python-raspberry_pi-recantha-worlds6440/ are out there making it appear that minute intervals are ok, leading folks (me) to purchase incorrect tool for the job: Yes, should do more R+D and read more of these forums and adafruit input :)

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Re: Refresh rate for eInk Display

by s_p_e_x on Mon Mar 15, 2021 6:23 pm

Perhaps the examples should include a warning about the refresh rate as well. Or default to a 3 minute refresh?

It is awkward that the tutorial guides the users to the examples which refresh every second, with a big red banner saying "you'll hurt your device if you go faster than once per 3 minutes!"

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Re: Refresh rate for eInk Display

by jfinley on Fri May 28, 2021 12:24 am

I too was a bit surprised by the 3 minute update interval warning (surprised, because I didn't do enough research, my bad).

However, does anyone know where this limit is specified? I found what looks like the same panel (I have the 2.13" mono 250x122 breakout) at good-display dot com, and don't see any limits like that in their spec (not sure I'm looking at the right thing, the GDEH0213B73). There's a similar-looking waveshare hat that says the same thing (180s update interval) but no source material there either. Could it be one of those folklore things that has passed through generations of panels and no longer applies? Has anyone ever actually seen one of these newer little panels fail due to (possibly due to) too-fast refresh?

Three minutes just seems like a really really long time - update in a couple seconds, then... what the heck is going on with those little bubbles for three minutes?

I'm mostly just curious; I don't know what I want to use mine for in the first place. Wondering why kindles work and such :).

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Re: Refresh rate for eInk Display

by jfinley on Sat May 29, 2021 1:31 am

I ran across this: https://www.good-display.com/news/80.html

They indeed say don't do a full refresh more often than every 180 seconds, but imply you can do a partial refresh more often than that, and that there needs to be a full refresh after several partial refreshes to top off the pixels. So something like a clock would work if you updated the minutes with a partial refresh and did a full refresh every ten minutes, for example. The full refresh is so flashy-blinky though, that it would be pretty ugly as part of a nice ux. They don't say what the failure mode is if you full-update too often, or how many partial refreshes you can do before a full refresh is needed.

I am pretty sure the panel is a GDEH0213B72 (not a ...B73 like I said before). Their Arduino sample code for that one shows working partial refresh, anyway. The partial refresh is nice & clean.

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Please be positive and constructive with your questions and comments.