Ray This is why I posted
Just a thought although all of the above is correct are we assuming that the sensor has a resistor built in of say about 10K If not would it be prudent to put a current limiting R in.. My sensors have 10K internal so not needed.
It truly is not that difficult just buy the switches and play with one of them not connected to the BOB and see it working. You need to mount them as has been said so that the target slides across the top and not head on so to speak. ..Clive