4 ms·

Oh I only put the actual temperature sensor inside. Ran some thin wires out to the pi under the door gasket.

tzs 5y ago
I too have an RPi logging fridge/freezer temperature, but wirelessly. I use this wireless fridge/freezer thermometer [1]. The units that go in the fridge and freezer communicate with the display unit via 433 MHz RF. I have an RTL-SDR [2] on the RPi. I run rtl_433 [3] on the RPi. rtl_433 understands the protocols of a large number of wireless sensors, including the ones used by those AcuRite sensors. I've got it configured to output whatever sensor data it decodes in JSON format to a file, and a script that periodically parses new entries from that file and records in an sqlite DB the readings from the sensors I'm interested in. Rtl_433 is a fun program. It recognizes and decodes the transmissions of a lot of things. It is getting several neighbor's wireless thermometers and humidity sensors, a soil moisture sensor, several different car tire pressure sensors, a smoke detector, some kind of keypad (wireless lock?), a car remote, some kind of energy monitor, a rain gauge, and a wind speed/direction sensor. [1] https://www.amazon.com/gp/product/B004QJVU78/ https://www.amazon.com/gp/product/B004QJVU78/ [2] https://www.amazon.com/gp/product/B009U7WZCA/ https://www.amazon.com/gp/product/B009U7WZCA/ [3] https://github.com/merbanan/rtl_433 https://github.com/merbanan/rtl_433
- beervirus 5y ago
  Yikes. All unencrypted I assume?
  - genewitch 5y ago
    It's in an ISM band, I can't remember the rules, I think encryption is allowed (like, WPA) but for thermometers and stuff why bother? 99% of 433mhz (and 800/900 mhz) stuff is unidirectional (sensor to sensee), so where's the harm in some 100mW transmitter?
    - tzs 5y ago
      The only thing I've seen that appears to be encrypted is something rtl_433 identifies as a "Microchip-HCS200", which seems likely to be a device using this chip [1] for remote keyless entry systems. The encryption appears to be for authentication not secrecy. The button status is in an unencrypted portion of the message. Of course there may be plenty of sensors out there that fully encrypt in which case rtl_433 would probably not have decoders for them and so I would not see them at all. [1] https://www.microchip.com/en-us/product/HCS200 https://www.microchip.com/en-us/product/HCS200
      - genewitch 5y ago
        If you have an rtl anyhow and you want to see what is there that rtl_433 is missing is to use rtl_power on the command line, you can monitor specific chunks of bandwidth for as long as you want, and it saves as a CSV. btw if you try this and get a bunch of errors in the CSV (or NaN) your gain(s) are set incorrectly, and i'd try turning them down to start.

tzs 5y ago

I too have an RPi logging fridge/freezer temperature, but wirelessly. I use this wireless fridge/freezer thermometer [1]. The units that go in the fridge and freezer communicate with the display unit via 433 MHz RF. I have an RTL-SDR [2] on the RPi. I run rtl_433 [3] on the RPi. rtl_433 understands the protocols of a large number of wireless sensors, including the ones used by those AcuRite sensors. I've got it configured to output whatever sensor data it decodes in JSON format to a file, and a script that periodically parses new entries from that file and records in an sqlite DB the readings from the sensors I'm interested in. Rtl_433 is a fun program. It recognizes and decodes the transmissions of a lot of things. It is getting several neighbor's wireless thermometers and humidity sensors, a soil moisture sensor, several different car tire pressure sensors, a smoke detector, some kind of keypad (wireless lock?), a car remote, some kind of energy monitor, a rain gauge, and a wind speed/direction sensor. [1] https://www.amazon.com/gp/product/B004QJVU78/ https://www.amazon.com/gp/product/B004QJVU78/ [2] https://www.amazon.com/gp/product/B009U7WZCA/ https://www.amazon.com/gp/product/B009U7WZCA/ [3] https://github.com/merbanan/rtl_433 https://github.com/merbanan/rtl_433

beervirus 5y ago
Yikes. All unencrypted I assume?
- genewitch 5y ago
  It's in an ISM band, I can't remember the rules, I think encryption is allowed (like, WPA) but for thermometers and stuff why bother? 99% of 433mhz (and 800/900 mhz) stuff is unidirectional (sensor to sensee), so where's the harm in some 100mW transmitter?
  - tzs 5y ago
    The only thing I've seen that appears to be encrypted is something rtl_433 identifies as a "Microchip-HCS200", which seems likely to be a device using this chip [1] for remote keyless entry systems. The encryption appears to be for authentication not secrecy. The button status is in an unencrypted portion of the message. Of course there may be plenty of sensors out there that fully encrypt in which case rtl_433 would probably not have decoders for them and so I would not see them at all. [1] https://www.microchip.com/en-us/product/HCS200 https://www.microchip.com/en-us/product/HCS200
    - genewitch 5y ago
      If you have an rtl anyhow and you want to see what is there that rtl_433 is missing is to use rtl_power on the command line, you can monitor specific chunks of bandwidth for as long as you want, and it saves as a CSV. btw if you try this and get a bunch of errors in the CSV (or NaN) your gain(s) are set incorrectly, and i'd try turning them down to start.