Off-grid low power Home Assistant and WiFi?

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1

Hey Everyone,

I have a special use case for network and power regulation. We have a fully remote location that needs insulated pipes to not freeze (again). Our solution is to activate a small low-power heating lamp when the temperature approaches freezing and then turn it off when the temperature reaches a higher threshold. Our expectations are that the affected area would warm for about 10 minutes and then cool off over an hour or so and then repeat.

If I were at home, the solution would be simple:

  • Bluetooth LE thermometer monitors and reports the temperature
  • Home Assistant monitors the reported temperature
  • When the temperature is too cold, Home Assistant turn on the power plug to the heating bulb
  • When the temperature target is reached, Home Assistant turn off the power plug

However with this location completely off-grid, power and network become a challenge.

For this solution, we are considering the following:

Since the entirety of this instance of Home Assistant’s work will be monitoring one temperature sensor and turning on/off a single smart plug, I think a Pi Zero W should be fine for this case while using the least amount of power. The idle consumption of the smart plug should (I’m guessing) be on par or less than the Pi Zero. The thermometer is self-powered.

My concern is the Pi Zero WiFi. I’d like it to be as energy efficient as possible, but I’d also like to be able to connect to it to periodically check the results recorded by the Pi Zero Home Assistant and make any adjustments as needed. This means the WiFi needs to stay off, but turn on if my phone is around.

My thoughts on this is to create an automation that will turn the WiFi on if my phone Bluetooth beacon is detected and then turn it off when my phone Bluetooth beacon is gone. However, I keep finding conflicting information on if/when this is possible.

My questions:

  1. How can I configure Home Assistant running on a Pi Zero W to turn on/off its own Wifi based on my phone’s Bluetooth beacon?
  2. How can I configure the Pi Zero W network to open and allow my phone to directly connect to it over the internal Pi Zero WiFi?
  3. How can I make sure only my phone is allowed to connect and not some random person walking by?

Thank you for your help!!

2

I don’t know the specific answers. However, I would use a thermostat to turn the lamp on and off. Thermostats are much more reliable than all the other stuff (HASS, pi, Bluetooth sensor,etc) . I would use the other stuff to monitor what is going on. Simpler is better.

3

So don’t. For your use case all you need is a device you can really own like a esphome based hardware if you want to have it over-engineered. HA is absolute overkill for such a simple thermostat function. :thermometer:

Even one of the cheapest hygrometers which can be owned is capable to function as a thermostat and switching a load after you install your *ware of choice on it :point_down:

ESP01Relay

image

The ones that are soon forbidden in the US? :see_no_evil:

Jokes beside - many electrical space heaters actually have a thermostat integrated. :bulb:

4

One thing we wanted to do was track how much the heater is used and for how long, hence the desire to use Home Assistant. We may add more Bluetooth sensors to get a better idea of the temperature differentials in the area if power allows. But to start, the simple on/off will do.

Back to the original questions: Automation to turn on/off WiFi? Direct WiFi connection?

5

:point_down:

You can save energy on the plug you own and have duty cycle sensor as well to measure the on-time.

Just choose or build a device based on a esp32 so it can receive data from your bluetooth sensors.

Also if there is phone reception you might want to have your smart gear connected? :signal_strength:

Isn’t supported by HA.

6

There is a few things you need to take into consideration, like 500Wh battery sounds nice, but at the freezing point it might only deliver 300Wh and over time the battery will wear down and deliver even less.
Also be aware that the 500Wh might be what can be drawn out of the battery with a really unreal load, where the battery is drain totally.
Many devices have a minimum power required to even operate and you might reach that point well before the battery i drained totally.