I wanted home assistant compatible plant watering solution that works on a solar panel and does not require being connected to the water line and is Zigbee compatible. Unfortunately, I could not find any. So I did a DIY solution: a big barrel which I manually fill with water, a 12V pump (usually sold for camper vans), some rechargeable batteries, 10W solar panel, a solar charging controller, and Tuya ZG-2002-RF switch.
An art student of mine once needed a way to electrically control precise small amounts of water. We solved that using:
1. Water tank and gravity
2. Medical IV flow regulator¹
3. Servo hooked up to that IV flow regulator via a 3D-printed part
It worked very well. In medical applications off must be really off, so it was also quite safe in that regard as well. Her 3D-printed part had a little bit too much flex in it, but in principle this works quite well. If it is really, really safety critical I would still recommend a mechanical fallback that protects in case of power loss or when the servo fails open (e.g. bending the hose with the force of a spring if electricity is gone).
Your suggestions should be fine for hardware failure but I'd be more concerned about software failure: what if a bug in your software makes it unresponsive and stuck in the state with the flow open? Maybe a watchdog or some other system running in parallel checking for a heartbeat or a max amount of time water can be flowing?
Exactly! I prefer the small power plugs that lets me control fans and other power systems as relays. Family has a habit if switching of light bulbs using light switches and i have not gotten the change approval to disable the physical switches in the house :)
For me the best solution was to use smart switches (mainly dimmers) and dumb lightbulbs. People can use the switches like any other if they want, but I can still have my automations and remote control.
I can recommend Shelly for light switches over smart bulbs. It's a relay that fits inside the wall switch with zigbee to sit between the light and the switch.
Disabling the physical light switch should usually only come after setting up a different way of controlling the light by hand, without a phone.
Most likely there is some sort of motion or presence sensor that turns on the lights which then turn themselves off after some time or no more presence is detected.
There are also small wireless switches that could be used in place of the actual wall switch.
I have done so in my apartment for example. Since the bedroom light switch is for some reason outside of the room I taped it down and put a wireless switch in a more reasonable spot.
Another example is the hallway light, which only turns on by motion sensing when the sun is starting to go down.
¹: see https://www.gvs.com/en/catalog/iv-flow-regulators
Your suggestions should be fine for hardware failure but I'd be more concerned about software failure: what if a bug in your software makes it unresponsive and stuck in the state with the flow open? Maybe a watchdog or some other system running in parallel checking for a heartbeat or a max amount of time water can be flowing?
Since many devices are also Zigbee router (it's a mesh network after all), maybe some additional lightbulb for exterior would suffice ?
Let's hope you don't have to get to the bathroom quickly late at night...
Most likely there is some sort of motion or presence sensor that turns on the lights which then turn themselves off after some time or no more presence is detected. There are also small wireless switches that could be used in place of the actual wall switch.
I have done so in my apartment for example. Since the bedroom light switch is for some reason outside of the room I taped it down and put a wireless switch in a more reasonable spot. Another example is the hallway light, which only turns on by motion sensing when the sun is starting to go down.