A limit switch is an electromechanical device that detects the presence, position or absence of a moving part and sends a signal to stop, start or reverse motion accordingly. They’re used across material handling and industrial automation to protect equipment, control travel and enforce safe operating limits.
On overhead cranes, gantry cranes and hoists, limit switches are typically fitted to define the end of travel on a runway, hoist or trolley, preventing overtravel and reducing wear on mechanical stops.
How does a limit switch work?
A limit switch works by physically or magnetically detecting contact from a moving part, such as a cam, roller or lever. When the actuator is triggered, internal contacts open or close, sending an electrical signal to the control circuit. That signal can stop a motor, trigger a warning light or feed data back to a PLC, depending on how the system is configured.
Most industrial limit switches are built for repeated mechanical operation and are rated to IP65 or higher, so they hold up in dusty, wet or otherwise demanding environments.
Types of limit switches
The right type depends on the application, the direction of travel being monitored and how precisely the switch needs to trigger.
Rotary limit switches
Rotary limit switches use a rotating cam mechanism to monitor multiple positions across a full range of travel, commonly on hoists, cranes and winches. Metreel’s range includes Top Rotary Limit Switches, Oscar Rotary Limit Switches, Fox Rotary Limit Switches, Base Rotary Limit Switches and Limitex Rotary & Cross Limit Switches.
Position limit switches
Position limit switches detect a single fixed point, typically the end of a linear travel path. They’re a common choice for defining safe travel limits on crane runways and conveyor systems. See Metreel’s Tango Position Limit Switches, 7551 & 7552 Position Limit Switches and X-FSC & X-FRZ Position Limit Switches.
Safety limit switches
Safety-rated limit switches are designed for use within a machine’s safety circuit, often with positive-mode opening contacts so the switch is guaranteed to signal a stop even if a contact welds shut. These are specified wherever a limit switch forms part of a risk assessment or safety function, rather than simply providing positional feedback.
Where are limit switches used?
- Crane and hoist travel limits, preventing overtravel on runways, trolleys and hook blocks
- Gantry and jib crane end stops
- Conveyor and automated handling systems, signalling product position
- Access doors and guarding, confirming a guard is closed before a machine can run
- General machine control, where a physical position needs to be fed back to a PLC or control panel
Choosing the right limit switch
Selecting a limit switch comes down to a handful of practical questions: how many positions need to be monitored, what actuator type suits the mechanism (roller, lever, plunger or rotary cam), what ingress protection the environment demands, and whether the application is safety-related. Getting this wrong typically shows up as premature switch failure or unreliable signalling, both of which are more costly to fix once the switch is installed and wired in.
Metreel’s range of limit switches
Metreel supplies the TER range of limit switches and wider electrical control equipment, including rotary, position and safety-rated switches alongside pendant controls, joystick controllers and radio remotes. Every switch is specified to suit the crane, hoist or handling system it’s controlling, rather than sold as a generic part.
Need help specifying a limit switch?
Metreel’s team can help you match the right limit switch to your application, from a single replacement part to a full electrical control specification.
Get in touch for free advice, or call 0115 647 0157 to speak to an expert.