Momentary and Latching Buttons
A momentary button makes contact only while it is held pressed and opens when released; a latching button locks on one press and is released on a second press. In the control of moving loads the momentary type is preferred for safety, because it makes the motion stop the moment the operator takes their hand off.
The choice directly determines the safety behaviour. A momentary button establishes hold-to-run logic: as soon as the operator releases the button the command is cut. A latching button, on the other hand, locks the command; the motion continues even if the operator walks away.
- Lifting, doors and barriers: Since a person may be under the load, a momentary button or a remote control with momentary commands is preferred.
- Continuously running process: In long-lasting motions such as a greenhouse curtain, a damper or a conveyor, start/stop logic is more practical. The KS250's separate start and stop inputs (IN1–IN4) let you set up exactly this behaviour with momentary buttons.
The advantage of establishing latching behaviour inside the driver is that after an emergency stop or a supply interruption the system does not restart by itself on a locked command. If you use a physical latching button, the contact is still closed when power returns and the motion can start without warning.
When choosing the button also look at the contact current rating; gold-plated contacts working at signal level are more reliable at low current.
The context in which this term is used: DC Motor Driver Selection Guide