Emergency Stop Input (E-Stop Input)
It is the safety input connected to the system through a normally closed contact that stops motion when the circuit opens. Thanks to the normally closed logic, the circuit opens not only when the button is pressed but also when the cable breaks or a terminal works loose, and the system moves to the safe side.
The basic principle of emergency stop design is that a fault falls to the safe side. If a normally open button were used, an emergency stop button with a broken cable would do nothing when pressed and the fault would go unnoticed. With a normally closed contact, motion stops the moment the break occurs and the fault reveals itself.
- Command interruption: only the command is cancelled through the driver's digital input; the power stage stays energised.
- Power interruption: the main contactor coil is placed on the emergency stop line; when the button is pressed the driver's supply voltage is cut completely. In applications where the load may remain suspended, this must be considered together with a mechanical brake.
The emergency stop button must be of the latching type released by twisting; a self-returning button is not an emergency stop. When you release the button the system must not move directly, it must wait for a new start command.
Electronic braking does not hold a load in the air; in heavy lifting applications the emergency stop is designed together with a spring-applied electromagnetic brake.
Context where this term is used: DC Motor Driver Selection Guide