Normally Open And Normally Closed Switch Diagram. Figure 1b shows a single pole double throw spdt switch. For instance if we want to energize a load based on the inverse or not of a normally open contact we could do this.
The switch may be actuated by an electromagnetic coil making a reed relay or by bringing a permanent magnet near it. When it comes to electrical switches and contacts many people seem to be confused by the terms normally open no and normally closed nc the root of the problem seems to start with the fundamental concept of what it means to be open or closed this post attempts to clarify those concepts. We can tell this switch is a normally open no switch because it is drawn in an open position.
The ladder diagram contains contact rails on the left to the right of the diagram these contact rails are connected to the switching elements normally open normally closed contacts through the current path and the elements of the coil.
When relay no 1 coil is de energized it s normally closed contact is in it s normal state that is closed. Float switches that are configured to stay closed until liquid flips open the circuit are referred to as a normally closed float switch once liquid reaches a certain level it then forces the circuit open and activates the next step which could be a power shut off or alarm sound off. When it comes to electrical switches and contacts many people seem to be confused by the terms normally open no and normally closed nc the root of the problem seems to start with the fundamental concept of what it means to be open or closed this post attempts to clarify those concepts. If we wish to invert the output of any switch generated logic function we must use a relay with a normally closed contact.
