No fail-safe besides the limit of only running the pump for 10 seconds at a time. I will continue to keep an eye on the data being pumped to Home Assistant and look to add a condition if/when the sensor fails.
Part of the joy of process control is thinking about all of the ways that things can fail. Adding to your woes...
Relays can fail, and it's actually a common failure mode for them to get stuck in the "closed" position, meaning that your pump runs forever. I learned this the hard way controlling heaters.
Amusing anecdote: I wanted to set something up to water my tree while my family was on a trip, and I ended up with a large pail of water next to the tree and a siphon tube running between them. Totally passive.
Part of the joy of process control is thinking about all of the ways that things can fail. Adding to your woes...
Relays can fail, and it's actually a common failure mode for them to get stuck in the "closed" position, meaning that your pump runs forever. I learned this the hard way controlling heaters.
Amusing anecdote: I wanted to set something up to water my tree while my family was on a trip, and I ended up with a large pail of water next to the tree and a siphon tube running between them. Totally passive.