OH!! I didn't know that!!! Trouble is the schematics I were refering to were powered by USB hence I assumed it was only for power. As you probably know, am an amateur. An amateur and 500 pound pc dont mix hence I was reluctant to source power from usb! Ericgibbs, are you saying I need to wire my zener didodes to the gnd pin of the usb port?
Here's the schematic I was following
https://vusb.wdfiles.com/local--files/hardware/level-conversion-with-zener.gif.
So by not connecting to the gnd pin, I've effectively put a break in the circuit right? If so browney points to moffy and Mike.