Zigbee freezer sensor

Hardware
1

https://www.aliexpress.com/item/1005006128690857.html

I want to put a sensor in my freezer in the back patio to make sure it’s not failing due to power failure or something else. This sensor says it supports -10c, so it’s no good as the freezer goes to -32.

Everything seems to have similar specs and nothing below minus 10 in zigbee. This is a limitation of Zigbee?

I see something talking about Bluetooth items but I don’t have a Bluetooth gateway in my .HA

Any ideas?

2

Power plug that measures consumption?

1 Like
3

Hi,
There’s at least two reasons why internal freezer sensors are a bad idea:

  • A freezer is a large metal box - a great Faraday cage that blocks radio signals.
  • Batteries don’t like cold temperatures as the chemical reactions slow down.

I made a temperature monitoring system using several cabled DS18x20 sensors connected to a ESP8266 (Wemos D1 Mini clone) and a small OLED display. The software worked great with ESPhome showing temp graphs in HASS, and real-time temps on the screen.

The only issue was getting the sensors inside the freezer - the flexible door seal didn’t conform around the cable well enough leaving a small airgap. This was just enough for water to condense and freeze. A 3d-printed wedge-shaped shim to smooth out the surface might fix this. The easy alternative is to drill a hole, or use an existing port.

As has been suggested, an indirect measurement of current draw might be easier to monitor.

1 Like
4

I use an Aqara temperature and humidity sensor. My freezer runs at about -21 C. It works fine. The only issue I have is that the battery level reading is meaningless - it always says a low number. I just ignore this and check the battery if the device goes offline.

5

That’s a possibility but the freezer would be turning on and off for example I just plugged one in to see how it works and it’s drawing 0.
I guess I could have some stuff model of how long it goes between compression runs and if it goes for longer than that raise an alarm of some sort.

6

I have used those sensors that you linked to in freezers for months and they work just fine. Still on the same batteries for many months. I do have a smart plug that acts as a router nearby. 3 meters.

7

Yes but you can set up alerting based on how long it stays at 0. If you have a few days data you will quickly see the trends on how long it stays at 0 before it starts drawing power.