u/_maxt3r_

Hi! As an embedded software engineer making my own PCB is a pretty big milestone, and I have lots to learn! Please be severe but kind :)

The project is a Bluetooth Low Energy (BLE)-enabled magnetic switch sensor powered by a CR2450 button cell battery. Tested on a development board, now I need something "real" I might eventually develop as a real product (one can dream!).

My design requirements/constraints:

1. Small form factor, prioritize thinness over XY footprint
2. Long battery life: (hence, why I picked the Reed switch, rather than a hall effect sensor, and why the somewhat oversized CR2450 over the more standard CR2032).
   1. The device will deep sleep 98%+ of the time, wake up to capture a few edges, then go back to sleep. Daily or weekly data transfer to Home Assistant or Smartphone.
3. The expected reed switch switching frequency is very low: maximum ~10Hz in short bursts on occasional daily use.
4. Transmit power will be set as low as possible to maximise battery life, wireless range is not a priority on the application I have in mind (a few meters is fine).

Main worries:

1. Will it power up
2. EMC emissions
3. Battery life (is there anything that could cause leaks).

Notes:

The two capacitors were selected based on:

1. The chip vendor required one mandatory 10uF
2. Bursts of BLE transmission don't do well with button cell batteries due to their high internal resistance.

Given the somewhat simplicity of the device, I might be fooling myself in thinking I don't need any other components.

Thanks!!