anelok: more light

Werner Almesberger werner at almesberger.net
Sat Sep 28 11:44:53 EDT 2013


Last week, the sky was clear a few times and I tried to see how the
display did (at 7.5 V) in bright midday sunlight.

Exposed directly to the sun, you couldn't even tell whether it was
on. Providing a bit of shadow with a hand made it somewhat
readable. Then I tried the competition: two cell phones. They
didn't fare any better.

So, a clear 3:0 victory for the sun.

Since a password safe isn't really a standalone device, it's
probably okay if it's only as good as the rest of the field when
it comes to daylight use. In any case, I think it's sufficient for
a prototype.


Then, I had a second look at the article about the font:

http://guy.carpenter.id.au/gaugette/2012/11/11/font-support-for-ssd1306/

The logo on the PCB looks familiar. And indeed, here is the board:

http://www.adafruit.com/products/938

The technical specs of the panel are identical to ours. Their
circuit is slightly different, with the main difference being the
pixel current resistor. (According to the various data sheets,
what they have should fry their pixels, but other effects may
conspire to effectively make the current-control resistor
irrelevant, see below.)

They also use the charge pump and I really wonder whether their
panel (for which they say they don't have a data sheet) is really
electrically identical to the 0.96" panel, as they claim. A quick
search led me first here

http://www.panelook.com/UG-2864KSWLG01_WiseChip_1.3_OLED_overview_19667.html

then, a search for the data sheet,

http://www.gabotronics.com/download/datasheets/UG-2864KSWLG01.pdf

And this one looks like an older version of the data sheet I got
from EastRising, also with 12 V. So my guess would be that I'm not
the only one who's happy to operate a 12 V panel at 7.5 V :)

The makers of the UG-2864KSWLG01 themselves also list this display
in the "3.3V Supply for Embedded Charge Pump Function" category:

http://www.wisechip.com.tw/english/Products_01.asp

And of course, that charge pump delivers "only" 7.5 V.

WiseChip with their UG-2864KSWLG01 would also be a second source,
which is the most important result I take from all this.

- Werner



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