Remote Weather Station

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parkview
Guru Maker
Posts: 522
Joined: Tue Jun 24, 2014 8:25 pm
Location: Busselton
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Remote Weather Station

Post by parkview » Sat Oct 16, 2021 10:01 pm

What does the words: Remote Weather Station conjure up in your mind? In mine, it's a weather station way out off the main road on the Nullarbor desert.

This will be a many phased project - each phase building on the previous one as I learn and experiment along the way. Something like this:

Beta: just build a quick PCB to test out various sensor. Incorporate LOTs of test-points, and places/jumpers to measure voltage/current. Based on a STM32L151RE due to max programming space. Test this at home in the back yard. Allow for external sensors, but provide footprints for all on-board sensors too.

V1: The idea is that the first version would be setup in a remote farmers field. Will use LoRa tech to transmit the collected data back to me.

V2: The Second version would incorporate the Satellite data feed and be tested in a more remote place and be optimised for low power usage

I am initially imagining this to be the size of a 2L milk carton, and will be held up off the ground by maybe 10cm to 20cm on 4 legs. These legs might contain sensors to monitor soil temperature and moisture. I would like these to be as cheap and robust as possible, so I can place quite a few of them around WA.

All of the above will be powered from a LiFePO4 rechargeable battery. I haven't used these yet, but there are now four of these in transit for me to experiment with. I also have two different kinds of small 6V solar PV cells on their way too. There will be one mounted on each of the sun facing surfaces East-North-West. At the top there will be the a LUX and UV sensor, along with a GPS antenna and the LoRa/Satellite antenna.

Some of the data I would like to collect:
  • Air Temperature
  • Air Pressure
  • Air Humidity
  • sunlight LUX and UV index
  • Soil Moisture
  • Rain/Dew indicator
  • Lightning count
  • GPS (location/Datetime)
  • Accelerometer (is it still standing upright?)
A stretch goal later on might be to include rainfall, wind speed and direction.

When I start a project, I create a Project folder and a README.txt file where I write down my ideas, things to explore, tests to be run, things to purchase and a project journal. I might spend a day or two researching my ideas and making lists and notes etc. Next up is usually followed by designing up some test PCBs, as thats my thing, and I enjoy the process. This also might include some bread board tests and testing some software etc.

parkview
Guru Maker
Posts: 522
Joined: Tue Jun 24, 2014 8:25 pm
Location: Busselton
Contact:

Re: Remote Weather Station

Post by parkview » Sat Oct 16, 2021 10:28 pm

While I started designing up a 10cm x 10cm cheap Beta version with some weather station sensors and a STM32L151RE MCU, I quickly hit the silicon shortage snag and found that if you can find MCUs, prices have gone through the roof. A MCU I purchased back in 2019, is now five times the price. I now have to settle on a 64pin or 100 pin MCU for around $11 to $18. Luckily I have a few 48 pin MCU's in stock, but they don't have much Flash/SRAM and I would like a lot to start with, as I haven't done much programming on a STM32 platform. Etra Flash/SRAM allows me to write bloated code, that once I get working well enough, I can then explore the process of cleaning it up and shoehorning it into a smaller and cheaper MCU.

I did purchase some STM32L151 and STM32L433 development boards to experiment and test code out with my sensor boards. Generally the STM32L433 is way over blown, however it seems to use 1/2 the power of a STM32L151. Maybe my solar power budget might be enough to run the STM32L151 for a day of five on battery power - time will tell all when I run some battery and solar power tests.

In the mean time, I did research some solar PV to LiFePO4 batter charger IC's. Initially I was going to use the LTC4162 IC, which has built in Maximum Power Point Tracker (MPPT), but I could only find one project based on it, and it does cost around $13.26ea and in short supply! Stephen mentioned the open source https://hackaday.io/project/20909-lifepo4weredpi. A very nice project. I see that it (and some others), are using the CN3801 IC and also includes a built in MPPT. It didn't take long to whip up a small PCB for it:
solar-pcb.jpg
solar-pcb.jpg (44.57 KiB) Viewed 110 times
Note: the two solar/battery connectors and Inductor are not shown.

I placed an order for the IC's today - before they sell out. Now I can get started on some software testing - or rather learning how to write some STM32 code, or maybe STM32duino might be a quicker way to go ;-)

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