Weather Station Is A Tutorial in Low Power Design

Building your own weather station is a fun project in itself, but building it to be self-sufficient and off-grid adds another set of challenges to the mix. You’ll need a battery and a solar panel to power the station, which means adding at least a regulator and charge controller to your build. If the panel and battery are small, you’ll also need to make some power-saving tweaks to the code as well. (Google Translate from Italian) The tricks that [Danilo Larizza] uses in his build are useful for more than just weather stations though, they’ll be perfect for anyone trying to optimize their off-grid projects for battery and solar panel size.

When it comes to power conservation, the low-hanging fruit is plucked first. [Danilo] set the measurement intervals to as long as possible and put the microcontroller (a NodeMCU) to sleep in between. Removing the power from the sensors when the microcontroller was asleep was another easy step, but the device was still crashing overnight. Then he turned to a hardware solution and added a more efficient battery charger to the setup, which saved even more power. This is all the more impressive because the station communicates via WiFi which is notoriously difficult to run in low-power applications.

Besides the low power optimizations, the weather station itself is interesting for its relative simplicity. It could be built with things most of us have knocking around. Best of all, [Danilo] published the source code on his site, so most of the hard work has been done already. If you’re thinking he seems a little familiar, it’s because we’ve featured some of his projects before, like his cheap WiFi extender antenna and his homemade hybrid tube amplifier.

15 thoughts on “Weather Station Is A Tutorial in Low Power Design

  1. Seems more like a tutorial on how not to build a weather station. Even calling this a weather station is being overly generous, it’s just a bme280 after all that is placed in such a way that it measures solar heat gain more than anything else… I guess pressure when the wind isn’t blowing on the open hole is going to be the most accurate measurement…

    1. Agree, to get relevant measurement weather sensor must have proper radiation shield, and most weather station DIY projects just ignore that fact. Even some commercial solutions get that wrong. Radiation shields can be made for few bucks, one of popular and simple solutions is to stack white plastic bowls or plates. “DIY weather radiation shields” search gets few pretty cool and cheap solutions.

  2. I was expecting something smarter with low power design title. But I see a double conversion Vcc (3.7V -> 5V -> 3.3V) which is in best case a waste of 50% of energy from the battery. Really disappointing. At the same time there’s some management of the sensor power supply that consumes 3.6 µA @ 1 Hz humidity, pressure and temperature and 0.1 µA in sleep mode.
    I don’t want to see even the design of the box :)

  3. First thing to do is to change the AM1117-like LDO has these have very high idle power. Not easy as you still need high current capability due to WiFi.
    Second is to trow away nodeMCU, as speed is all when you want to cut off power use.
    Third is to use low power RF like Bluetooth LE or subGHz protocols.
    Final is sensor that can be powered for years on coin cells.

  4. Suggestion, wouldn’t it be better to use Zener diode to clamp solar panel voltage instead of using 3 regular diodes in series with panel? That way you can get some power out of solar panel even with indirect sunlight or on cloudy day, and you’re still protected when Sun is right above panel. Using 3 diodes lowers voltage for around 2 volts, rendering panel unusable at low-sunlight situations.

  5. Anyone know of a DIY solar powered weather station that uses SMS to broadcast weather data, send it upon request, send it at certain times on certain days (flying or launch days) or send it if weather parameters were outside specified limits? That sort of system would be handy for R/C and rocketry clubs with remote flying or launch sites to use to determine if a long drive to the site is worth making. Wind and rain are the only conditions that would deter one from making the drive.

    1. If its a permanent-ish spot, just toss a cell modem in there or get a Particle Photon/Electron to do the heavy lifting. Then attach a much larger panel/battery. A few 12V lead acids and a 50W panel ought to be plenty. Granted, it bumps up the cost, but you can do a lot with it.

      1. The Particle Electron is a fine way to go for easy cellular connectivity, but you can get the power usage down to something that can be supported by a much smaller panel. Run the sensors and data logging with a proper low-power microcontroller and buck converter, and only turn the Electron on every hour or so to listen for data requests. You should be able to get the average power consumption down to low double-digit milliwatts, which is manageable with a 1 or 2 W panel and one of those little 6V/4Ah lead-acids.

        This only works if you don’t need constantly up-to-date data or fast response to requests for it. Going to LTE Cat M1 may help with that, but I haven’t messed with those yet to see how much better the power consumption actually comes out.

        1. Of course you can always make it more efficient. But for quick and dirty and get it off the ground, bigger solar panels and more batteries are cheaper than the dev time and sleep modes. Especially if you already have a big open field.

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