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OLED first runtime result

A project log for Home environment monitor

Yet another wireless network of environmental sensors in a home

tundraTundra 12/20/2018 at 04:240 Comments

OLED display runtime was 52.3hrs to hitting the wall of not dropping voltage, and 54.3hrs till last serial data. I'm not sure if the significance of it, but the OLED was still displaying the last image (meaning it was running fine when the Feather ARM processor brownout detector halted operation). Also measured OLED module consumption at 8.6mA (not including the Feather in this measurement) during the test with DMM. 

Calculating average usage:

For cell capacity of 1200mAh, for the run with eInk, at 85 hrs, if I was able to pull all the available capacity out of the battery, it would be 1200/85 = 14.11mA average and for the OLED test at 54.3hrs it would be 1200/54.3 = 22.1mA average. I suspect my calculation is somewhat high as the OLED still displaying an image tells me there was still some untapped capacity remaining in the battery. The eInk displaying an image after the end of the test means nothing, as it will hold the same image with no power applied.

Difference between eInk calculated average draw of 14.11 and OLED calculated average draw of 22.1mA is within 10% of the measured OLED module draw of 8.6mA. To see 72hrs on the 1200mAh means getting the total draw under 16.6mA - I'm not sure if it's possible to reduce the OLED, meaning I'd have to drop the average Feather consumption approximately 50%. I'll need to research how the sleep modes work. Other options are a bigger battery, accepting the need to charge from a battery pack during power outage exceeding 2 days or getting power to the thermostat from a circuit powered by the generator. I would prefer to run off alkaline so that  replacement is trivial in extended power fail situations or supercapacitor so that cycle life of the battery isn't a factor. 

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