FAQ02455 of Emergency Stop Switches FAQ

A general-purpose push button switch is used for controls, e.g., to start machine operation or to switch modes. An emergency stop push button switch is used as a safety measure to stop hazardous parts (loads).

An Emergency Stop Switch must be highly visible in color and shape, and must be easy to operate in emergency situations. The following requirements are specified in the European Standard EN 418 (International Standard: ISO13850).

1. A direct opening mechanism must be installed on the NC contact.

2. There must be a self-holding function.

3. The button must be a "mushroom" head design or something equally easy to use.

4. The button must be red and the background must be yellow.

In addition to the 4 points mentioned above, the emergency stop control circuit must have countermeasures for each category.

here is no difference between a general-purpose push button switch and an emergency push button switch regarding the function of the NO contact.

A general-purpose push button switch doesn't have a direct opening mechanism on the NC contact. If the contact welds, conduction will be maintained and the device cannot be stopped in a hazardous situation (load). If this occurs, the device may keep operating in the hazardous state. Therefore, use the NC contact of an emergency stop push button switch for safety applications.