Board Recommendation

I just discovered Arduino recently. I have been researching it the past couple days, and I am wowed at the potential in it! It's amazing that I didn't discover it sooner. I do have a couple years of experience with web development, so I know languages like PHP. Consequently, I don't think it will be too difficult for me to pick up a workable amount of the language I need for programming an Arduino (Java? C/C++?). Although my imagination is going crazy, the main thing I want to build is a weather station. I would like a board for this project that fulfills two main criteria:

  1. Functional in the cold. Being in the arctic, it could be measuring temperatures down to lower than -40°F/C. If I have to put it in a heated box, then I can work around that. But I would like to know if there is a board that would stand up to temperatures that cold occasionally.

  2. Expandable. Since my projects with the Arduino might get large, I want to get a board that will accommodate that potential. That doesn't mean I can't buy a second board if that does end up happening, but I would like to start off with the best one for me.

What's your recommendation?

Uno and a probe with long leads.

Oh, one more requirement I forgot to add: external power.

Could I get external power for the Uno? I doubt a battery would hold up in the winter.

The processor is advertised to work in:

Temperature Range:
-40°C to 85°C

I'm not so sure about the development board. It is really for prototyping, I don't know if the connectors (for example) would work properly in extreme cold. You might be better off developing on the board and then soldering together a finished product.

I have examples here:

Of course, you wouldn't use a breadboard either, but that page describes how you can set up a minimal system.

For example, a temperature sensor which I did solder together:

The processor with the most support is the Atmega328P, which is on the Uno board, and various smaller ones. By "most support" I mean you will find libraries that do what you want with the least effort.

As for expandable, personally I would go for a modular approach (eg. a couple of Unos or Atmega328P together) rather than trying to get a bigger board that does everything. Having said that though, various people have released boards which have more memory, etc. For example:

http://www.crossroadsfencing.com/BobuinoRev17/

You could link them together with I2C, SPI, or async serial, depending on distances, speed, and other factors like that.

You program in C++.

I want to build is a weather station

Google will be your friend here, as well as the link above I posted for my temperature/humidity/light logger. I designed mine to run on low power (3 x AA batteries) which may well be a consideration if you are leaving these things out "in the wild".

Uno with external max31865 chip and ptd1000 probe.

Only the probe goes outside.
atmega328p can take -40c.
Rest of board, who knows. See recent thread on frozen/expanding electrolytic caps..

I bit of research indicates you may find a Li-Ion battery that will work at -40C.

If it is going to get colder than that you may need to go with your "heated box" idea, at least to bring the temperature up a bit.

However I presume that this very issue confronts people in the Arctic and Antarctic, so there must be documentation about it around.

I found out that the DS18B20 sensor is used locally in a colder microclimate. I think I might go with that. I can't find the external max31865 chip you referenced, @CrossRoads. Is that how I would supply external power?

Nick, this actually will be close enough to a power receptacle that I think I can make it work. A battery would be nice, but I think it will be simpler just getting externally supplied power.

I appreciate all of the other info you both shared. I can inform you as I have more questions.

cyberstream:
Nick, this actually will be close enough to a power receptacle that I think I can make it work. A battery would be nice, but I think it will be simpler just getting externally supplied power.

Always the case, unless the power source is unreliable and you need battery backup to preserve data.

I'm looking at my power supply options now. I like the idea of having a power backup, but our power service is typically quite reliable. Furthermore, I'm concerned that the cold would wear down the battery, rendering it useless at the vital moment—when there is a power glitch. If I decide to just stick with power drawn from the grid, would this 9V power adapter do the job?

If I decide to go with a battery, I will probably look for some way to build a heated box. What I'm thinking of right now is building an insulated box with a thermostatically-controlled high-wattage incandescent light bulb in it. That would allow me to have a consistent battery backup so that I could have uninterrupted data logging. I could just use a sensor (like this) that could be placed away from the station just in case there is significant heat leakage. What do you think?

Also, do you know of power cables that can be plugged into a normal American outlet/extension cord and on the other can be plugged into the Arduino's USB port? I searched around the Internet a little bit without finding anything. I could just use USB power port that can be plugged into the outlet, and then I could plug the Arduino into the adapter via its USB cable. I don't like having that extra USB connection though. It's not very secure. I could tape it or maybe solder something, but I'm wondering if there is anything out there like this before I reinvent the wheel.