A limit switch is used to control electrical devices by breaking and completing electrical circuits. It has three terminals. The power input terminal is called the common terminal and is used to connect the switch to a power source. It is abbreviated "COM." The other terminals are the normally open ("NO") terminal and the normally closed ("NC") terminal. The NO terminal keeps the circuit incomplete by preventing electricity from flowing from the power supply to the electrical device until the limit switch's control arm is actuated. The NC terminal allows electricity to flow to the electrical device until the switch's control arm is actuated.
Mounting the Switch
Select a location that provides room for the switch's arm to fully actuate and is accessible for easy maintenance.
Drill a hole for each mounting screw. Ensure that the drill bit you use is small enough to allow a snug fit for the mounting screws.
Mount the switch. Hold the switch in one hand and install the mounting screws with the other. You can start the screws with a drill, but use a screwdriver for the final tightening to avoid stripping the holes.
Wiring the Switch
Remove 1/4 inch of insulation from the end of your power wire with diagonal pliers. The power wire connects to your power supply and carries energy to your electrical device.
Insert the exposed conductor of the power wire into the COM terminal and secure it by tightening the terminal retention screw with a screwdriver.
Remove 1/4 inch of insulation from the end of your control wire with diagonal pliers. The control wire connects to the electrical device that the limit switch is intended to control.
Insert the exposed conductor of the control wire into the NO or the NC terminal and secure it by tightening the terminal retention screw with a screwdriver.