Emergency Stop Button (normally open vs normally close)

E-stop Button is used to terminate the whole process of the machine. The main purpose of E-stop Button is for Safety.

View E-stop Button Image Here

During the installation process, both NO and NC connection of E-stop won’t matter, because that is the first time that the wires is connected to the circuit, it means that the connectivity is functioning well, and the E-stop button is functioning well also. But there are some situations that you might encounter in the future where NC connection is more important than NO when we are dealing with E-stop button.

We can’t prevent some malfunction that may occur in the future.

Reasons of E-stop malfunction

• Defective E-stop Button
• Open Wire (disadvantage when E-stop is normally open) – this might occur when there is some stress on the wire.
• Short circuit (disadvantage when E-stop is normally close) – this might occur when there is moisture.

Note: the chance that the wire will be shorted is lesser than wire will be open depending on the enclosure’s IP rating, even on our home appliances, we encounter a lot of open circuit problems that short circuit problems because of the stress on the wire.

Defective E-stop Button

We can’t do anything about the defective E-stop Button, we can perform the preventive maintenance to ensure that E-stop is Working Properly and to check if we need to replace it before it malfunctions.

Open Wire and Short Circuit

Like the Note above normally close E-stop Button has its advantage compare to normally open E-stop Button, because the stress on the wire that cause open connection is so difficult to see, while the moisture on the other hand is easier to see and chances to encounter short circuit is lesser than open wire.

Example:

Emergency Stop button is used to stop the machine if the there are some troubles that might cause accident.

When E-stop is Normally open, and the wire experience stress and it became open the circuit below will not work anymore it means the machine will not stop even if E-stop button is pressed and it is dangerous.

When E-stop is Normally Close, and the wire experience stress and it became open the machine will stop immediately, and it will become a down time, but safety is more important than anything else.