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 <[email protected]>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 > logic. > > 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 > converter. > > - Werner > > _______________________________________________ > Qi Hardware Discussion List > Mail to list (members only): [email protected] > Subscribe or Unsubscribe: > http://lists.en.qi-hardware.com/mailman/listinfo/discussion > -- Felix
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