As can be shown in the figure above, a proximity sensor was integrated with the conveyor belt. The proximity sensor is used as a detector. In the design, the bottles should be detected to stop the conveyor belt, for the filling process. A beam of infrared is emitted from the proximity sensor. When the beam is interfered with by an object, some of the beams get reflected back, which is detected by the sensor. Once detected, the sensor will send a signal to the PLC and the PLC acts depending on it.

As can be seen in the figure above, an object has been put on the conveyor belt, as the object interrupts the beam of the sensor, it will send an input to the PLC to send a command to the motor in order for the conveyor belt to stop. The conveyor belt is an output for the PLC that is connected to the PLC relay, depending on the PLC input signal it acts accordingly.