PietroIbba:
a mean energy consumption of 37 mA (26 in sleep and 47 reading).
I doubt that your arduino is aquiring data 50% of the time.
You can reduce the consumption of the arduino into the 10s of µA when sleeping, so it shouldn't be a problem to achieve an average consumption of less than 1mA.
In that case, your station could be powered solely from your batteries for months, without any solar panel.
couka:
I doubt that your arduino is aquiring data 50% of the time.
Thank for pointing that out, i have corrected the previous post.
couka:
your station could be powered solely from your batteries for months, without any solar panel.
We already reduced the energy consumption to a minimal value for our configuration, so right now we are focusing on adding a solar panel suitable for our purpose with the consumption values mentioned above.
PietroIbba:
We already reduced the energy consumption to a minimal value for our configuration,
Out of curiosity, what's drawing so much current then? 26mA is quite a lot for doing nothing Status LEDs maybe?
To be on the safe side, I calculated with 50mA average draw, which results in a consumption of ~2,2kWh/year. As a rule of thumb, that means you need a solar panel with 2,2W peak power, depending on where you live.
That's under optimal conditions concerning placement of the panel and at least average weather.
Firstly you need to figure out the average cloudless solar radiation you'll get at midwinter, then derate that by
a factor of 20 or so to allow for fully overcast days. Your system uses 26mA on average, I'd expect you
need a panel capable of 2 to 4A or more to do this reliably at a guess, depending on lattitude. The worst
case is very very much worse than the best case.
You didn't say if the "several months" included winter though.
Your 2.4Ah battery will need derating as those capacity figures only hold for a brand new battery
fully charged at a particular temperature and discharge rate. However its good for several days anyway,
it only has to be good for 24 hours to work.
You should consider using a board designed for micro-power operation, since you can get the consumption
down to a few microamps if you do things right - the Uno has a USB-serial chip on it that doesn't have
a sleep mode, so its not designed for battery operation.
MarkT:
Your system uses 26mA on average, I'd expect you need a panel capable of 2 to 4A or more to do this reliably at a guess, depending on lattitude.
Could you explain in other words why i need a solar panel capable of 2 to 4A, i thought that a smaller one would have been enough (300 - 400 mA)
MarkT:
You didn't say if the "several months" included winter though.
No winter is not included, the period would be at least of 7/8 months, from late April to the end of October.
mauried:
Really need a bit more info about the weather station , ie what sort of sensors does it have?
Do any of the sensors draw current all the time ?
The equipped sensors are:
DHT22
BMP180
DS18B20
Thermistore 10k
Soil moisture sensor
Photoresistor LDR 20-50k
Every sensor is turned ON only when it needs to read.
couka:
Remove them then. Reducing the current consumption is a lot easier than using PV and it's cheaper, more reliable and more elegant as well.
We will certainly remove the LEDs, but i think that other than that we will only focus on a solar power supply for the existing wheater station and its current energy consumption.
Status LEDs maybe?