I am working on making a panic button device that is as small as possible for an elderly lady a few houses down from me. Im thinking of using a Nano and NRF24L01 packaged together in a small case with a button to send the signal to a high powered NRF24L01 that will not be limited by power restrictions of any sort that will relay the signal to my house. My concern is that I'm not sure if the panic device setup can run off of a 2032 coin cell and if so not sure for how long. I know I can put the chips in sleep and power down mode and they would only need to awaken upon interrupt from the button which hopefully never happens but when the need arises it HAS to work. Does anyone think this setup will work or is there a better way I can go about this? Thanks.
Have you seen Nick Gammon's energy saving tutorial?
I believe the nRF24 is very frugal when powered down, but I have never had a need for that so I have no personal experience. Have a look at the Nordic datasheet.
when the need arises it HAS to work
Nothing is 100% reliable but you could probably improve things (at the expense of battery life) if it sent a message at regular intervals. If your base station fails to receive a message it could alert you and give you an opportunity to investigate. Be sure to get a good quality switch with gold-plated contacts.
My mother had a thing like that - it made an emergency phone call when pressed. But she refused to carry it around with her.
...R
If you want this thing to be powered by a 2032 you can forget about the nano unless you remove leds regulator usb serial chip(ch340 ftdi) mm,
I would go with a attiny or a stripped pro mini.
With mcu and nrf24l01 sleeping all the time a 2032 should last years, if done right you should get down under 10uA when it sleeps.
But i would go with Robins idea and send a "all is well message" at intervals.
You should still get half a year+ out of a 2032 sending a message every 30 sec or something i would also let the mcu measure the battery voltage and send that so it can be monitored. As for the stronger relay station (i assume it will me mains powered) make sure it can reboot itself on semi power loss every time.
nrf can be a bit strange when it gets under 1.5v and then powering up again without loosing power completely,
it might need a complete power down to recover from that(might be because the nrf in question was a clone but as always really hard to tell when 90%+ are clones...)
Good luck.