I am starting a project where I have two devices positioned about 100 meters apart. The secondary device will be controlling a solar charging array and relaying stats to the main device. The main device will display stats to the user and send control commands to the secondary device.
I plan on using a RS485 shield on each device.
Because I will be burrying the data cable(s) underground I am wondering what I need to consider when choosing a cable type to run the distance in a cost effective way.
I am out of my depth in terms of the cabling requirements, but have you looked into using fiber optics instead of copper wire? I recall that fiber can transmit data further and with less power than using conventional wires. I would imagine it is less dangerous to your electrical gear if you get ligntning strikes near where your cable trench is.
What you want is called "direct bury cable" - do a google search on that term, and you'll find Cat5e Direct Burial cable and other, which is probably what you want. Rent out a small trencher for a day, bury down about 18 inches (remember - call your local number for BLUE STAKE first!).
NickPyner:
Great idea, but I still think wireless might be a better bet, it surely involves a lot less digging.
I suspect it depends on many factors. If the Arduinos are battery powered, I could imagine the drain of doing wifi might drastically reduce the amount of time the batteries will last. You probably don't want wifi, which 802.11g is something like 95m best case for access points (according to wikipedia). I don't know if there are Arduino shields that do 803.11n instead of 803.11g which seems to give you more range.
I've buried cat3 phone wire just under the surface of the ground. No high voltage involved. You might try your inital test setup with the cable just laid on top of the ground.
NickPyner:
Great idea, but I still think wireless might be a better bet, it surely involves a lot less digging.
I suspect it depends on many factors. If the Arduinos are battery powered, I could imagine the drain of doing wifi might drastically reduce the amount of time the batteries will last. You probably don't want wifi, which 802.11g is something like 95m best case for access points (according to wikipedia). I don't know if there are Arduino shields that do 803.11n instead of 803.11g which seems to give you more range.
You can get some Ubiquity Nanostations (directional Wifi Radios) that will do 10km easy, assuming the two points are high enough off the ground.... Cost is about $50 per radio, you can probably find some used for less. You could also try 1 nanostation with an omnidirectional antenna, or a picostation. The ubiquiti gear is also power over ethernet, so you can power it remotely (and probably steal a little to power the arduinos too) or you can skip the POE injectors and run them off the solar panel's DC voltage.
Depends on the situation. Direct burial cable is pretty expensive, add in serial modules on each end, the time + cost of digging. If you live in a climate where you don't have the bury the cable very deep, you could probably get away with cheaper cable, or cheap cable + cheap conduit.