Hi Mike,

You will not be able to wire the proximity switches directly to this BOB unless they are 5V. They will not connect to your motor drivers either.

The simplest diagram I can find is here: http://www.cnczone.com/forums/gecko-...12349-cnc.html
It shows a 4 wire version but that is only because the sensor there is more advanced.

It will also help if you have a look at "Transistor" in wikipedia and such.

Can you point us in the direction of a datasheet for your sensors?