2. Button mechanism
The emergency stop button, whether it is a normally closed contact or a normally open contact, will bounce back if not pressed in place (fully pressed), rendering the action ineffective.
When using normally open contacts, if the emergency stop button is not pressed properly, the emergency stop will not have any effect (because the normally open contacts are not closed); However, when using normally closed contacts, regardless of whether the emergency stop button is pressed properly or not, the emergency stop only works through the action of the contacts.
3. Control circuit
The most basic function of the emergency stop button is to stop the vehicle in case of an emergency, avoiding mechanical or personal accidents. However, due to the prolonged operation of the machine, especially in the emergency stop section of the circuit, there is a possibility of malfunction and circuit breakage.
At this point, if the emergency stop button uses normally open contacts, the circuit faults in the emergency stop section will not be detected. If the emergency stop button is used, it will be too late to detect them again. When using normally closed contacts, if there is a fault in the emergency stop circuit, it will only cause the machine to stop at most, with relatively less loss.
Therefore, when designing an electrical control system, it is best to use normally closed contacts for the emergency stop button.