Livio wrote: ↑05 Jan 2020, 23:32
About those lil crypto MCUs are you able to use EEPROM to store some "calculated" data to avoid too much CPU usage like some guys do with thermistors readings?
I guess its possible to make array with "calibration data" and therefore ADC reading -> actual value would be mere 1 lookup, like result = cal_data[adc_sample].
The disadvantages would be:
- Need to perform calibration and flash its result.
- Fairly large table in flash/eeprom (assuming eeprom accessible like array or you're willing to reload that to RAM, wasting plenty of RAM).
And about that joule thief I've saw that a battery can be made of aluminum foil, paper with distilled water and graphite.
Guess distilled water isn't best choice, you likely want some salts or acids as electrolyte. Guess you had some residual salts or something on materials themselves so it did the trick.
I've tested a raw one I've made and has 0.7VDC and 700uA if shorted. It's ridiculous but maybe more cells like that together can power that blinker and seems it's able to recover fine from shorts giving back full power after a minute.
I can imagine blinker would start up from this "as is", 700mV should be ok, esp if you put capacitor parallel to battery. Say 2.2uF cercap holds enough power for few flashes in case of design I've mentioned, 1000uF would blink for a while without any battery at all. Though 2x of that sounds more adequate.
By the way aluminum-copper gives a bit more power but copper can release carbonate and stop conducting.
Aluminum should turn into harmful hydroxide and graphite probably will not change over time.
Sure, graphite is inert. So only one electrode would be spent. Just like zinc spent in more typical batteries while graphite used to conduct current. That also makes graphite quite useful for experiments with electrolisys, etc - unless I'm nut it wouldn't normally give byproducts, only some gases that make electrolyte (e.g. 2H2O -> 2H2 + O2).
Hard graphite is better since soft graphite can have some wax inside.
Actually factory made cells usually feature some graphite.
p.s. btw, what your wildest guess would be be about lowest startup voltage of joule-thief like designs?