Temperature Sensor Configuration

  • I guess I should first build out my prototype then address this "concern." My setup will be a wireless sensor that will collect temperature and humidity. The goal is to have that sensor as small as possible. I plan on creating a few types that all have different size batteries. I from then will need to see which size gives me the most battery life for the most temperature readings. I from there will need to configure a controller to receive all that information. Here is my current idea:

    1. DHT22 temperature/RH sensor
    2. The DHT22 sensor will be attached to a PCS New Pro Mini Atmega328 3.3V
    3. The sensor will then be attached to a NRF24L01+ 2.4GHz
    4. The controller that will receive the information will be a Raspberry Pi 2.0 Model B 512MB.
    5. On the controller I am uncertain as to the software that will be placed on the controller.

    Do you think this configuration will provide me what Im looking for?
    Once I get this setup working i will test antennas on the configuration to test the length.

  • Admin

    As far as I know, the DHT22 is not a good candidate. Supply voltage needs to be above 3v, which means that you can't get the last juice out of your batteries.

    Look around for a sensor that can operate down to 1.8v, like si7021, both radio and atmega is capable of operating at that voltage level, so the sensor could operate for longer time on the same set of batteries.

    Also consider how frequent you will need to have the sensor data collected, as that also greatly affects battery life. There are other threads around the forum where there are calculations on theoretical battery life.

    I am building my sensors with si7021, and custom build pcb, to keep size down as well as battery life long.

  • Thanks for the advice. I will look at that option.

    What type of data polling frequency do you plan on using?

    What type of batteries have you looked at?

    I ideally would like to be able to change the polling frequency but so far I can think of maybe 1 minute to 10 minutes is what i would like to do.

  • Where did you pirchase your si7021?

  • Questions about the configuration and setup, sorry a bit new to this. I should be fine with just connecting the radio, atmega, and the si7021 together without having to worry about attaching a regulator because all are able to operate that the 3.3 correct? Or do I need to prepare the sensor to work down to 1.8v?

  • Admin


    at the moment I check temperature / humidity every 60 seconds. But only transmit if there are any changes since the last read. I use 2 x AA batteries for power.

    I purchased mine from mouser, and used it on my sensor board (http://forum.mysensors.org/topic/510/minimal-design-thoughts)

    No special things are needed in order to have the sensor operating down to 1.8V (it's operational supply range is 1.8 -> 3.6V, almost the same as the radio).

  • I too got mine from Mouser.

    I plan on trying multiple battery configurations. I will keep you updated on my results.

  • Wow, very impressed with your design and how you got the radio mounted directly on the sensor. This is ideally what Im trying to do and apply a battery that will have the smallest footprint possible.

    Ill take a closure look at all your steps provided.

    Do you foresee a setup that can mimic this using the atmega?

  • I apologize for the questions and how simple they may be, as Im new to this community but very intrigued with the creativity and endless possibilities.

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