Quoted from zizzlemeplease:not quite understanding why to not use the inexpensive banks of 8 optical relays available for arduino type stuff. they trigger with low current 3v, being optically isolated no need for flyback diodes if I'm not mistaken.
you are mistaken. 'optical relays' are not magic, they actually have scrs, bipolars or fets in them and require in the region of a million times more holding current than driving a mosfet directly cause you've got to power the internal led. A mosfet can easily be triggered by 3V too.
Also, because they have the same fet or whatever switching element, that could equally likely be destroyed without a flyback diode.
anyway, this is a quick and dirty build with bits to hand.