anelok: first light
sucotronic at gmail.com
Tue Sep 24 06:17:05 EDT 2013
Awesome!! From idea to some kind of prototype in less than 2 weeks!! I'm
your fan Werner xD
Btw, I don't how well will handle a cr2032 a current of almost 10ma; I know
the lcd only will be on for sort period of time (~2min?), but it'll
interesting to know what life battery cand we expect with this consumption.
Say for example, the screen is on 10 times a day for 2 minutes, with 210mah
from a cr2032, and a sleep consumption of 0.1 mA we can expect:
on time: 10*2 / (60*24) = 1.3% of time
sleep time: 98.6% of time
usable battery power: 210*0.7 = 147 mAh
147/ (0.013*10+0.986*0.1)= 643 hous = 26 days
It's a bit low, no?
On Mon, Sep 23, 2013 at 1:36 AM, Werner Almesberger
<werner at almesberger.net>wrote:
> I wrote:
> > - the wheel also seems to be fine. Debouncing needs some looking
> > into.
> Solved. The problem wasn't debouncing but that I forgot to set
> a pull-up on CLK / SCLK / WHEEL_B. CLK is the only signal that
> doesn't have a hard-wired pull-up in the Ben. By not setting the
> pull-up, the B signal (half of the rotary encoder) floated. So
> the state the Ben saw depended not only on the switch but also on
> flux, humidity, whether I touched that contact, and so on.
> Setting the pull-up removed all "ghost movements".
> > - voltage levels, especially the level of the high voltage (the OLED
> > has a DC-DC converter to generate ~12 V),
> Fun discovery: it's only ~7.4 V, which is actually what the
> controller chip is designed to provide. The display panel is
> rated at 12.0 +/- 0.5 V, so I'm quite below that. It does look
> good, though :)
> > - behaviour when turning on more than 50% of the pixels.
> Nothing untoward happens. I see a little bit of "shadowing"
> (lines with more pixels getting dimmer) but that's only when
> turning on a lot of pixels and even then it's barely visible.
> Seems that the total current is still within what the controller
> can supply. The controller's charge pump is rated at 6 mA while
> the display could draw up to 31 mA at 12 V. The 7.4 V operation
> seems to help :)
> I've then made some more systematic measurements:
> OLED voltage Default image All white Display off
> --------------- --------------- --------------- -----------
> 3.3 V + pump 9.98 mA 22.8 mA (1) 114 uA
> 7.5 V external 3.54 mA 11.7 mA 398 uA
> 12.0 V external 7.57 mA (2) 667 uA
> (1) decays from 22.9 mA
> (2) overcurrent event
> The first set is with all the power coming from the Ben, measuring
> the total current delivered by the Ben through VDD. I did drive all
> IO lines but WHELL_COM low for the "display off" measurement (since
> I'd otherwise have a negative current on VDD) but left them in their
> normal idle state otherwise.
> I then turned off the charge pump and supplied 7.5 V externally.
> The current measured is now what goes into the OLED's VCC and thus
> doesn't include the (usually negligible) consumption of the OLED's
> The two data sets suggest that the charge pump will be able to drive
> up to about 50% of the pixels without any problems.
> Then I increased the external supply to 12 V. Brightness increased
> noticeably and so did the current. Alas, something went wrong when
> trying the all white image: the display briefly flashed on, there
> was an angry beep from the overcurrent detection of my power supply
> (set to 50 mA), and the display went dark.
> After that, it wouldn't accept external power or output the charge
> pump voltage, so it seems the trace/wire got fried somwhere. It still
> runs fine on the charge pump, though, despite the connection to the
> external 2.2 uF buffer capacitor now being severed.
> I'll have to see how the display performs in bright daylight. If
> it's still readable when only powered by the charge pump (or if even
> running it at 12 V wouldn't help), then I'd prefer to stick with
> ~7.5 V. Otherwise, we'll need another and more complex boost
> - Werner
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