Very interesting !! Thanks for the idea !
@scalz : I missed your reply ! Interesting withe paper !
@Nca78 you can have brownout if the battery is near end of life and nothing has been designed to handle a bit the internal res. but with a fresh a coincell and some capa, you can do some chain tx but that's not the best for the battery life.
The only case where i had issue with brownout at startup, plus it was a fresh coincell was with a crappy ali coincell batt!! very bad quality! now I'm using only good quality coincell like duracell, varta, maxell.. and that's day and night
@carlierd If you're interested this doc explains very well the capacitor calc etc... http://www.ti.com.cn/cn/lit/wp/swra349/swra349.pdf
- capa ideally calculated/estimated (on mine I have 200uF, plus others for sensors, radio is 86uA etc..) and after multiple msg presentation on frsh coincell i don't fall under 2.85 (voltage starts 3.05V) because I can't recover voltage during this period.
Hopefully a transmit is not 1sec! More something like says 30+ ms (depending if signing is needed, ack, retries.. etc). To not break capa benefits, it's better to sleep between tx during chains..to recover voltage and optimize battery life. Sleeping 200ms can be enough
- For the capa leakage, it depends of capa. common good quality ceramic have not those leakage (few nano). Sure on this design it's not a ceramic.
- You're right at runtime 1Mhz consumes less than 8Mhz; mA vs thousands uA. But at 1Mhz everything is slower, comms too (I mean code execution). During deep sleep, there is no difference in power consumption. Oscillator is stopped so mhz does not mean. Note: at 8Mhz you can wake in few uA, at 1Mhz it's slower of course.
Some pictures of my scene controller inspired by this post ! I modified the original sketch to have two functions: keyboard for my alarm (from key 1 to 9) and scene controller (from key 10 to 16). Thanks @awi for the idea and the original sketch !
@Nca78 Like @mfalkvidd wrote, the expected life duration is greater than 2 years. But it's just theory. My first node (on 2*AA) was started several weeks ago and the battery level did not change. So I am confident
I measure the power consumption when working at 1 MHz and there was no difference between 1 or 8 MHz. As I have to decrease the transmission speed at 1 MHz, I got some issues. The main was probably with the signing feature.
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