Small motor control (Complete Novice)

I want to control a motor via a sensor of some type (Capacitance??). Currently, I am running a 5volt power supply and two rheostats to control 2 motor rmps. I want to introduce some type of sensor that will recognize that a piece of brass is in front of the sensor and stop one of the motors. When the brass leaves this station and is no longer seen by the sensor, I want the motor to make one revolution and deposit another piece of brass in front of the sensor. I have watched a couple videos on Arduino, and PLC.. I am less than a novice and not sure where to start. I would like some advice or guidance on how and where to start.
I am using the following products:

http://www.ebay.com/itm/13150113945...49&var=430874112790&ssPageName=STRK:MEBIDX:IT

http://www.ebay.com/itm/161359792728?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

http://www.ebay.com/itm/141856333969?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

I understand a proximity sensor will work. I do not know what should go between the sensor and the motor. The sensor does not have enough power to drive the motor.