Board Recommendation

Using Arduino Project Guidance
#1

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?

#2

Uno and a probe with long leads.

#3

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.

#4

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".

#5

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..

#6

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.

#7

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.

#8

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.

#9

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?

#10

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.

#11