Next generation temperature sensor for MySensors



  • So my first ever MySensor was the temperature sensor. Unfortunately, it was a lot of hassle to get the example on the website to work. It turns out version 2 of the MySensors library doesn't want to work with external libraries anymore apparently, so I had to install and modify an old version of those libraries.

    Let's fix this. What would be a good 'default' temperature sensor nowadays, to put on the MySensors website?

    Requirements

    • Be accurate
    • Should not use too much power when sleeping, for battery powered use.
    • Be able to connect multiple temperature sensors to one node.

    The most promising to me seem to be:

    BME280 ($3,5)
    This sensor combines temperature, humidity and barometric pressure.
    It has performed really well in tests.
    It's relatively expensive, but you get three sensors.
    Communicates via the I2C bus. You can connect 2.
    Frugal when sleeping, power hungry when in use.

    The others aren't as awesome.

    • DS18B20. <$1. Temperature only. Cheap, good, and you can connect lots of them to one node. But it needs special libraries, which MySensors 2 doesn't support.
    • Si7021. $2. temperature and humidity. Precise (0.3 degrees), but hardcoded I2C ID's, so can't use more than one per sensor. Good long term stability. Slow first response. Also surprisingly bad review by Phil Moyer.
    • HTU21D(F). $2,5. Humidity sensor first, but good review by Phil Moyer. I can't tell if the F is a different verision..
    • SHT31. $4,5. Difficult to connect 2, and 3 is impossible. Good review.
    • SHT71. $15. Low power. Uses proprietary one-wire protocol. Too expensive.
    • DHT22/AM2302. $2,5. The old classic. Uses proprietary one-wire protocol. Many spikes in readings.

    Perhaps it might be a good idea to create two official temperature sensors:

    • The cheap Dallas for temperature sensor networks with lots of sensors.
    • The BME280 to measure temperature and more in your home.

    Sources
    http://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_many.html
    https://community.openenergymonitor.org/t/htu21d-si7021-temperature-and-humidity-sensor-possible-dht22-replacement/1106/23
    https://m.facebook.com/notes/phil-moyer/comparing-temperaturehumidity-sensors/10157468075605557

    What you do think?


  • Mod

    @alowhum said in Next generation temperature sensor for MySensors:

    It turns out version 2 of the MySensors library doesn't want to work with external libraries anymore apparently

    What do you mean? I'm using 2.x with tons of external libraries (e.g. Ds18b20) without issues.

    On the sensor topic: I have bad experience with si7021 too. Some seem to have very inaccurate humidity readings.
    Recently ordered a bme280. Seems very accurate so far!



  • I mean that the makers of MySensors want to avoid depending on external libraries for the 'official' sketches they provide on the website. It's why the temperature sensor code provided there doesn't really work out-of-the-box anymore.



  • "official" sketches that depends on external librairies : https://github.com/mysensors/MySensorsArduinoExamples


  • Mod

    @alowhum said in Next generation temperature sensor for MySensors:

    I mean that the makers of MySensors want to avoid depending on external libraries for the 'official' sketches they provide on the website. It's why the temperature sensor code provided there doesn't really work out-of-the-box anymore.

    This doesn't really have to do with depending on an external library. The problem is that the example sketch uses a modified version of the library. This is mentioned in the third post of the topic.

    An earlier discussion about temperature sensors is available at
    https://forum.mysensors.org/topic/3801/witch-temp-hum-sensor-is-best-to-use-for-battery-powered-sensors Maybe the information there can be useful for finding a replacement sensor.



  • Hi there, thanks for sharing this valuable information. I'm also looking for a temperature sensor. I live in Calgary. We live in a rental apartment and moved to this place a month back. I have heard that there is more chance of getting flooded here. So my husband and I are planning on installing a temperature and flood sensor in our home. The problem is I am not that much aware of these sensors as I have never used them before, but I do have some requirements. I am looking for a sensor with a PC programmable transmitter that has an output of about 20mA and it should be a fast response with reduced tip. What are the things that I should consider while selecting the temperature range? Please help with some suggestions.

    EDIT: Removed spam link



  • Hey Andrea, just to be sure: the sensors listed here are electronic components that can be used to create a DIY sensor network. This will involve some programming and perhaps soldering. It's quite a different proposition to commercial offerings.

    The MySensors network supports two types of transmitters. You can research how much output they provide.
    I don't know how to answer your question about 'reduced tip', or what you this temperature range you refer to is even about. You probably won't get many suggestions without being more precise.

    I would recommend starting a new thread on this forum where you explain your situation in some more detail.



  • @alowhum
    Thank you for your kind concern. How do I research the output provided by MySensors network? I would try making a new thread.


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