Hello all,
It's been a while since I dabble on my Arduino but I'm itching to get something going.
I though about building a portable outdor weather station that could measure
temperature (and switch between C to F on the fly);
humidity;
heading (i.e. what's the direction of the wind) displayed both in a 360º scale and cardinal points (N, NW, W, SW, S, SE, E, NE);
altitude (and switch between m and ft on the fly);
atmosphere pressure (instant barometric in mmHg, bar, inHg or Pa and forecast trend based on how fast barometric pressure rises or falls).
OK, for temperature and humidity it's quite a simple matter of using a thermo higrometer sensor. No biggie.
For heading, I can usea GPS sensor.
For altitude, I can use both a GPS sensor or an altitude/pressure sensor;
For pressure, I will need an altitude/pressure sensor;
I haven't started programming yet, this is just a rough sketch but seems to be viable, right?
I plan to build this on an Arduino Uno I have somewhere as a prototype and use a clear lid waterproof box to see the information on a 16x2 LCD display.
OK, I foresee some issues, namely:
if I keep the thermo hygrometer inside the sealed box, temperature will get higher and higher (considering a small box). If I leave it outside I have to drill a hole on the box pass the signal cable and hot glue it so ensure water tightness.
to switch units, I'll need at least two water proof push buttons on the case (one to select the function the other to switch it);
heading (i.e. what's the direction of the wind) displayed both in a 360º scale and cardinal points
You can't get wind direction off a normal GPS sensor. GPS Sonde with special equipment for meteorology is used to get wind direction and speed.
Barometric pressure sensor reading changes with air humidity, unless you have Internet connection to get some reference value, you'll need GPS to calibrate in order to have correct altitude off barometric pressure sensors.
A single GPS receiver can identify location but NOT the direction in which the device is pointing.
For direction you need a compass - or a pair of GPS receivers sufficiently far apart that their relative positions can be used to determine the direction of the straight line between them.
You could possible get altitude from a sufficiently synced GPS but it's notoriously unreliable, and you need proper altitude to get the correct pressure.
Wind direction requires some sort of wind vane and a compass to compare the reading too. You can make yourself a basic wind vane any number of ways (google is your friend), you read the output into an ADC and depending on value you know which way it's pointing.
Both the pressure sensor and the humidity and temp sensors will need to not be sealed on a box. Both will need to be out of direct sunlight and the pressure sensor should be out of any wind.
When you say portable... how portable do you want this whole thing? A wind vane is going to restrict portability a little. If you want it battery powered then that's a whole different consideration