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DIY thermostat Tasmota - Shelly - ESP8266 + sensor + enclosure

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    DIY thermostat Tasmota - Shelly - ESP8266 + sensor + enclosure

    I designed and implemented HS based thermostats a while ago. They do work and even respond to voice commands over Google Home.

    Control is by WiFi enabled relays in the mechanical room driven by HS. Rooms temperature is taken by battery powered RF sensors a.k.a. Wireless Tags.
    The sensors are the problem as they churn batteries every 6 mo. or so. I'm fed up with it and I want line powered sensors.

    Design wise it is not a biggie as I can use Shelly1 (ESP8266 plus power supply in small format, fits in single gang wall box) plus BME280 sensor (temperature, humidity and barometric pressure). I even can throw-in a small I2C display module to display the sensor readings. All this was tested successfully at my test bench running under Tasmota flashed into Shelly 1.

    The enclosure is the problem. How to put everything together in a single gang box and yet have the sensor outside "breathing" the air and isolated from the internal heat that Shelly produces and yet looking nice.

    I can't afford some crappy outlook as far as it will be quite visible. I'm after quality enclosure 3 D print is o.k. Alternatively I'm willing to consider any ready made device that is line powered and connected. I'm using Big6 plug-in for communication so I'm pretty open to any protocol - MQTT, TCP, HTTP etc. RF devices with WiFi gateway are O.K. as well. The only thing that I steer away from is Z-Wave as it doesn't work well in larger areas like mine.

    Any thoughts or experience to share ?

    Thanks


    #2
    A means for airflow from bottom of the enclosure where the sensor is located through the top is needed to allow the sensor to function and heat to escape. A grid of small holes or slats is typically used. Most easily done if the unit extends a 1/2" of so from the wall. Isolation of the Shelly from the sensor will also help, but probably harder to design while still keeping airflow for cooling.

    In my outside sensor installations that have sun exposure, I use active cooling with a small squirrel cage fans that are enabled with bimetal temperature switch to improve the airflow. In these cases, they just needed to be functional, and ascetics are not important.

    Your essential problem is that you are using a WiFi device and a power supply design that is not optimized to minimize heat. Without the heat, then more options exist for the sensor location. Do you really need the sensors to be operational with a 100% duty cycle. Can't they sample and then go to sleep for a minute. Why generate heat for the 55 seconds when waiting for the next sample to be taken?

    Bluetooth technology is a good alternative with attractive packaging and very long battery life. Heat is not an issue in this case.

    Comment


      #3
      Originally posted by Michael McSharry View Post

      Your essential problem is that you are using a WiFi device and a power supply design that is not optimized to minimize heat. Without the heat, then more options exist for the sensor location. Do you really need the sensors to be operational with a 100% duty cycle. Can't they sample and then go to sleep for a minute. Why generate heat for the 55 seconds when waiting for the next sample to be taken?

      Bluetooth technology is a good alternative with attractive packaging and very long battery life. Heat is not an issue in this case.
      Michael McSharry Thanks for the response and thoughtful input.

      Yes, sampling in 5 minutes intervals is O.K. plus the transmitting of data takes less than 1 sec. leading to less than 1% duty cycle. I have no problem with that. However, not sure if Shelly1 can be put in "deep sleep" as I do not have access to GPIO16 that is normally used for that. I will play with it today and will post the result here. With this said, I don't get much relief as I still can't put the sensor inside the wall. Even with reduced heat from Shelly the air inside the wall is not representative of the air in the room. Hence I will still need some special enclosure that is hard to find.

      On the Bluetooth side, there are many BT sensors out there but they are all battery powered and batteries do not last long, which is my original problem. I do have battery powered sensors now that I want to escape from. I may consider battery sensor if batteries are confirmed to last at least 2 years like my Sonoff RF motion detectors.

      Comment


        #4
        Deep sleep can be programmed as a timer so no external access is needed for this function. An example of Bluetooth Temp and Humidity with "up to 3 years" battery life.

        Shelly BLU H&T - Shelly BLU H&T - All products - Shop - Shelly‚Äč

        If you are not within Bluetooth range, then any other Shelly Gen2 or Gen3 device can be used as Bluetooth to WiFi bridge.

        Comment


          #5
          Shelly blu h&t will work if battery life is 3 years as advertised. Unfortunately it is not available per their web site and not available at Amazon either.

          Comment


            #6
            Originally posted by Michael McSharry View Post

            If you are not within Bluetooth range, then any other Shelly Gen2 or Gen3 device can be used as Bluetooth to WiFi bridge.
            This is actually another problem on top of "device unavailable". I'm trying to keep the number of property-wide networks to a minimum. I do have WiFi of course and 433 Mhz RF network to support multiple Sonoff RF motion detectors. I like the long battery life of 433 Mhz RF devices and I'm using 2 Sonoff RF gateways to support it. I'm not using Zigbee or Z-wave or any other network for that matter. BT is natural on smart phones, computers and peripherals and that's normal. However to build a network of BT Gateways for the purpose of serving BT sensors is a bit of stretch for me.

            Meanwhile on related news I failed miserably to adopt BLE280 I2C sensors in Tasmota. Looks like Amazon is shipping some crap as other I2C devices were recognized properly on my Shelly/ESP8266. I have 0 out of 3 sensors working. Returning them all. Here is the item at Amazon to avoid.

            https://www.amazon.com/dp/B07KYJNFMD

            Furthermore the BT sensor maybe interesting from another prospective. Looks like it can act as BT beacon for presence detection. I have played twice with 2 years gap with espresense.com They have interesting development going on for presence detection using BT and smart phones. Last time I checked them was about 9 mo. ago and they were on version 13.xxx but still not ready for prime time IMHO.

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