EEVblog #1297 - Turn an LCD into E-Paper! - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: March 31, 2020, 10:05:21 am
content: Dave's long term LCD DC bias experiment has turned a regular 7 segment LCD effectively into an E-Ink/E-Paper display!

author: capt bullshot
author_rank: Super Contributor
timestamp: March 31, 2020, 10:38:15 am
content: Can you make it display 1 4 2 0 2 0 in sequence (didn't watch the video)?

author: Brumby
author_rank: Unknown
timestamp: March 31, 2020, 10:41:01 am
content: It's driven by an Arduino - so when it is powered you could run any sequence you like.When unpowered, it will be in one, fixed state only.

author: Artlav
author_rank: Frequent Contributor
timestamp: March 31, 2020, 10:43:01 am
content: Just in case of brain farts, you did check that there are no residual charge in capacitors keeping it up?That is, would it stay lit up if pulled from the breadboard?

author: SeanB
author_rank: Super Contributor
timestamp: March 31, 2020, 10:58:40 am
content: I would guess there is a largish capacitor there holding a power rail at some voltage, and the brownout circuitry is keeping the microcontroller in reset, so the outputs are high impedance, allowing the stored charge on the LCD segments to stay in the state they are in. Allow the circuit to stay unpowered for around 5 minutes, and see if the display slowly goes back to translucent, as the stored charge decays odd of those high capacitance planes on the LCD glass.Also consider that Australia is a few hours ahead of the world, and Dave is kind of famous at this time of year to come out with some really outrageous and quite true items, though they are not always as they seem, but the physics are always true to the experimental world, and most established theories, even if they at first glance do not appear to be so.

author: hansibull
author_rank: Regular Contributor
timestamp: March 31, 2020, 11:00:43 am
content: QuoteThe really good ones are the ones that actually may be real. This is a good one

author: free_electron
author_rank: Super Contributor
timestamp: March 31, 2020, 03:40:39 pm
content: april 1'st effect

author: Fran_PSR
author_rank: Newbie
timestamp: March 31, 2020, 03:47:19 pm
content: I suppose the simplest explanation is the accumulation of static charges within it. I remember in my childhood disassembling digital clocks and calculators to play and experiment and on many occasions when you touch the LCD contacts with your fingers, strange characters would appear that would remain several minutes without any type of circuit connected. Perhaps the large segment size of that screen increases the internal electrostatic capabilities ... This is a simple idea ... I have no other arguments than those past experiences ... ;-)

author: typematrix
author_rank: Contributor
timestamp: March 31, 2020, 04:18:07 pm
content: That's an interesting development board , when i looked it up it costs 52 euros thou for the base kit.Anyone have it, is it useful.

author: SmokedComponent
author_rank: Regular Contributor
timestamp: March 31, 2020, 10:50:48 pm
content: What's with the extra wires that weren't there in the old video, eh?Show us the 9V battery below, sir.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 01, 2020, 03:22:02 pm
content: Quote from: typematrix on March 31, 2020, 04:18:07 pmI thought that looked good too. Not sure if they are shipping, in the middle of the pandemic!

author: Artlav
author_rank: Frequent Contributor
timestamp: April 02, 2020, 09:38:04 am
content: Sneaky time traveling Australians, he actually got me good this time.

author: SeanB
author_rank: Super Contributor
timestamp: April 02, 2020, 12:13:04 pm
content: Quote from: SmokedComponent on March 31, 2020, 10:50:48 pmNo need for a battery, just sneak in a supercapacitor of around 1F on the 5V power rail via a 100R current limiting resistor, and then a diode on the power input, along with a resistor connected to an input on the microcontroller that will hold the current count when low, and on a rising edge reset the MCU so the counter starts again from 0.

author: Zbig
author_rank: Frequent Contributor
timestamp: April 02, 2020, 09:17:07 pm
content: Either I'm getting dumber as I age faster than I realized or Dave is really raising the bar each yearPast years I was usually managing to figure this out by myself. Fun fact: as I was watching the unboxing bench thing on the second channel today, first I was like "yeah, sure, it's this time of year" but then again "hmm... it seems legit after all and the actual-TV-as-a-backdrop doesn't seem all that ridiculous..."