I bought an Odroid-C2 which will be delivered in a week or two. It’s a pretty impressive piece of hardware for the price:
http://www.hardkernel.com/main/products/prdt_info.php
It’s very similar to the recently released raspberry pi 3:
I also ordered a USB-controlled relay board with the hope to build an automatic sprinkler system with solenoid valves to water my plants!
http://www.ebay.com/sch/i.html?_nkw=usb+relay+board
I’ve never dealt with electronics so this is quite exciting. I was surprised at how cheap the components are. I also never guessed that 240 volts could be controlled by a little USB connection.
I’m going to try to setup my Odroid-C2 as a ubuntu home server that will control my garden irrigation system solenoid valve using the usb-relay, which can hopefully be controlled by my ramnode VPS using a web page accessed by my phone. Apparently java 8 runs on the odroid and there’s a few java libs to control the USB signals. It’s going to be a fun project.
Something that’s interesting is how little power these little ARM computers use compared to desktops.
I was weighing up buying an ARM system-on-a-chip (SOC) Odroid-C2 which costs about AUD150 with a memory card, versus an old ordinary headless desktop which costs AUD80 such as this HP DC5800:
http://ssbb102.australiancomputertraders.com.au/HP-DC7800-Desktop-p/rdes004.htm
I was about to buy the desktop rather than the ARM SOC because the desktop would be easier to use and space wasn’t a problem. But when I compared the power usage, the ARM computers are so much cheaper to run.
Apparently the HP DC5800 desktop above with Core 2 Duo E8400 uses 100W on idle and 140W on load, both without the monitor or graphics card:
https://www.complang.tuwien.ac.at/anton/computer-power-consumption.html
While the Odroid-C2 ARM computer uses 1.8W on idle and 4.4W on load. But I’m not sure if this is using it’s GPU or other components:
http://forum.odroid.com/viewtopic.php?f=139&t=18902#p125371
I calculated the power consumption for a 1 Watt device using my power cost in Australia at AUD0.22 per kWh:
Input: Cost of electricity in dollars per kilo Watt hour: 0.22 $/kWh
Input: Power required by device in Watts: 1W
The number of mega joules per kilo Watt hour: 3.6 MJ/kWh
Cost of electricity in dollars per mega Watt: 0.061111111 $/MJ
Power required by device in mega Watts per hour: 0.0036 MJ/h
Cost of electricity to power device in dollars per hour : 0.00022 $/h
Cost of electricity to power device in dollars per day: 0.00528 $/day
Cost of electricity to power device in dollars per year : 1.9272 $/year
I think I’ve done the calculations right since they’re similar to this:
https://www.raspberrypi.org/forums/viewtopic.php?t=18043&p=182118
Therefore the Odroid C2 running at full load will cost about $8/year (=4.4W1.93$/yr). While the HP DC5800 desktop would cost about $269/year (=140W1.93$/yr).
That’s quite a big difference. I had no idea that a desktop computer costs so much to run continuously as a home server, especially considering that this annual cost is more than 3 times the price of the machine itself.
I’d be interested to hear your thoughts about power consumption and the ARM computers such as the Odroid-C2 or Raspberry pi 3 8) 
Cheers,
Keith