ESP8266 Community Forum

- Tue Dec 23, 2014 3:19 am #5501

Small note about your spreadsheet: you can either put batteries in parallel, doubling their capacity, or in series, doubling their voltage. I presume you want to do the latter, due to the ESP not working on 1.5V. If so, you can't assume double the capacity, so you'll be working with only 2500mAh in total.

Of Course, that was a mistake and not a small one, thx for pointing that out

I fixed that now.

- Tue Dec 23, 2014 3:54 am #5504

good work. how did you change sleep modes? 0.9.4 sdk says different sleep modes but i dont see

As mentioned (maybe not clear enough), i can't enable the sleep modes as of now but when they become available (well technically they are available if you write agains the SDK directly). My purpose with this sheet was to calculate whether I can run a sensor for a year on 2 x AA batteries and as it looks right now it's really hard.

The sensor i sketched in my sheet is a sensor that wake up by specified intervals and takes readings which means you can power most of the sensor down when it's not doing anything

The calculation get's much worse if you intend to make a sensor which wakes up on interrupts and the reason for this is that one can't go into Deep Sleep and can only go into Light Sleep so sensor can be waken up by GPIO interrupts and that consumes 0.5mA (Light Sleep) so if one let the sensor in this mode then on 2 x AA batteries you will run 2500mA/0.5mA/24h = 208days and that does not take into account events, let's say you have a door sensor and it opens at least once a day. The sensor will consume on each reading 0.1 mA (according to my sheet (70mA/3600)*5s) if ones want to read and send the value right away which i presume most would like to do in an event based sensor. So in total the hourly consumption (the event has be even out on 24h) is 0.5mA light sleep + (0.1mA/24h) = 0.5042mA so the days 2500mA/0.5042mA/24h = 207days so by using the sensor once a day it used one of the days.

I have added above example in the sheet as an example of an event based sensor (power consumption)

My point is, hard to make a low power sensor with ESP8266 unless there are other ways i don't know of.