I picked up a couple of these super cheap Arduino UNO clones - What a PITA.

They use instead of an FTDI USB chip they use an infernal CHG340 chip yes there is a MAC driver for it

http://www.wch.cn/download/CH341SER_MAC_ZIP.html but the bastard driver produces a name like this

cu.wch ch341 USB=>RS232 fa210

The Arduino IDE doesnt like spaces and trys to write to the device at cu.wch which of course doenst exist. The only way I have managed to get the the things to work under OSX 10.10.5 is to create a symbolic link to the drive name.

sudo ln -s /dev/tty.wch\ ch341\ USB\=\>RS232\ 1450 /dev/tty.USB0

thanks to

http://arduino.stackexchange.com/questions/3700/rename-device-name-ch340-usb-to-serial-mac-os My recomendation is dont waste your money on this rubbish - stick to the real deal FTDI chips and saveyour self a world of pain. note the windows driver does appear to work