These are good questions to ask as the longevity of your device in an outdoor environment will depend on how well you protect it.
First, I build and deploy sensors for outdoor use. I don't have to worry about 12V sensors like you but I have developed a carrier board that is open source. I employ a few different technologies on this board and you can see if any of them might be helpful for you. I could not have done it without the Particle community who gave me many of the solutions incorporated into the design. This board has protected my Borons very well in parks and recreation facilitates in the US and Canada.
There are a few different issues you have to think about with protection:
- Reverse polarity
- Over voltage
- Short circuit
- ESD or transients
Based on this project and some others I have worked on, here are some ideas:
- A simple and very robust way of protecting your. device is to use opto isolators. They can (before the current supply chain issues) be cheap and are easy to implement.
- Zener diodes are a good way to cap the voltage ( I use one on the carrier board as the Argon cannot take 12V while the Boron can) just make sure they can handle the power you need to dissipate if needed.
- Short circuits can cause high current drain. I use fuses as they are cheap and very versatile. Unfortunately, if they are blown, you need to replace them. For this reason, you might look at a PTC which will reset itself (not back to its former self but close) once the short is cleared.
- Coupling a varistor with a fuse can protect against both over current and over voltage.
- For higher speed GPIO lines - like i2c lines - you can take a look at the TVS diodes.
There is a lot here, and this community has a number of experts. Hopefully this list can get you started.
Thanks,
Chip