I would like to use a JeeNode outside for basic weather measurements but I am not sure how well it will do in cold temperatures. It frequently drops to -40C in the winter here and has been as low as -51C within the past 15 years. The resonator for instance is only rated to -20C and we've been below that already. I will however have AC power available so a battery will not be an issue. Will there be issues in this environment?
Cold temperature use(5 posts) (4 voices)
I have no experience whatsoever with such low temperatures, -10C is rare here, and -20C exceptional.
If you're concerned about this you could change the fuses so the ATmega runs at off its 8 MHz internal oscillator. This would get rid of the resonator issues, and brings the ATmega fully in spec - something which might be important at extreme temperatures, see http://news.jeelabs.org/2009/02/27/out-of-spec/
Haven't used JeeNodes outside yet (I want to get all the low-power battery / solar issues resolved first), but I'd be very interested to hear how it holds out in "real" weather conditions.
Since you have AC power - you could also put the whole thing in a big mitten along with a resistor, heating it up ever so slightly...
Just saw that the RFM12B operating temp range is "only" down to -40C (storage down to -55C).
An interesting topic!
What does AVR specs say about temperature? I've the feeling that the operating temperature of standard chips is usually above zero Celsius and some special design can run below it (like those used in cars etc.).
I think the standard solution is to have some kind of heated (and isolated) cabin or case for the electronic parts. Sensors can (must) reside outside of this artificial atmosphere. Heating of course takes more energy and should also be controllable to prevent overheating (thermostat). So I guess, battery powered solution is out of question. Batteries are drained in cold temperature very fast anyway.Posted 2009-12-29 ago #
I have been trying to use a JeeNode for a homemade weather station! It is now in beta testing. It has been outside for more than 2 weeks now!
Indeed we don't even get -10C that often here, with that already being extreme.
I had problems with the power saving stuff, as it had been discussed until a few months ago (didn't try the recent developments), which after pulling lots of hair, I attributed to the cold outside - The jeenode would hang after being put outside...that didn't happen if there was no power saving active, I think it had something to do indeed with the oscilators and watchdog timers...and it was even at not that low temperatures - about 10C.
I will try to report more on that one of these days. Now I only have the Arduino power saving and watchdog timers, and I am not using the radio timer as suggested.
But anyway, It has worked fine running from 3 AA batteries down to -5C at least! This is probably not very useful, since -5C is very far from -50C!
I will report on the station once it is completed!Posted 2009-12-29 ago #