calculate current

[Kristian Hansen]

Hi,

I'm trying to do a rough calculation of current consumption for the nRF52840 chip.

The unit should sample 6 times an hour by using I2C to acquire samples from a gas sensor (with a microprocessor) for at least 30 days. I'm thinking I will use the RTC to keep track of date and time, storing 16 bits for date and time 6 times an hour.

I might also write to flash each time it samples (3 x 16 bits, 6 times an hour). I've also given ~100kB to work with at all times in RAM.

The nRF should be constantly ready to upload to the mobile, so the user can check in for new measurements at any time, and/or send notification when a certain level is hit. I used the online power profiler to get an estimate of the current consumption.

Here is what i have come up with so far:

I would appreciate it if anyone could point me in the right direction, thanks!

[Bjørn Kvaale]

Hi Kristian, I am a bit uncertain what your question is. I guess you are wondering if a coin cell battery would be enough to power the nrf52840 for >= 30 days? Is that correct? Considering coin cell batteries can have a capacity of roughly 225 mAh (see this great blogpost), one coin cell battery would last roughly 3214 hours before it would need to be switched out (i.e. 225 mAh/0.070 mA avg total consumption). That is more than the 720 hours in one month. So basically, if your consumption estimates are accurate, you should easily be able to use the nrf52840 for >= 30 days! Worst case, you could consider attaching a Li-Po battery to the nrf52840 (see infocenter).