Normally Open Contact Switch

Push button switch momentary on contacts x2.

Normally open contact switch.

A light switch is generally a normally open contact which on actuation closes a circuit and thus allows the current to flow to the series connected light bulb see fig. Normally open contacts or switches with the normally open switching function are well known in daily life such as with light switches. 1a 250vac spst mini pushbutton switches normally open no black red cap 20pcs 4 5 out of 5 stars 156. That is the no and nc contacts are never simultaneously closed during the transition between states this is not always the case form c contacts follow this rule while the otherwise equivalent form.

4 6 out of 5 stars 16. Gardner bender gsw 22 electrical push button switch spst off mom on 6 a 120v ac screw terminal. Rarely are these familiar examples good for learning but a 3 way switch is an excellent example of using normally open and normally closed switches. When replacing an existing contact you also need to know if the contact being replaced was normally open or closed especially if more than one contact is wired into a zone.

If we had used a normally closed pushbutton switch instead the behavior would be exactly opposite. 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. Get it as soon as wed sep 30. Where a switch contains both normally open no and normally closed nc contacts the order in which they make and break may be significant.

Now let s go through a real world example of normally open and normally closed contacts that we are all familiar with. It is difficult and in some cases impossible to mix normally open and closed contacts on a single zone. 5sets magnetic reed switch magnetic door switch magnetic contact switch normally open closed nc no door alarm window security for dc 5v 12v 24v light. When buying contacts look for form c spdt single pole double.

The lamp would energize if the switch was left alone but it would turn off if anyone pressed the switch. In most cases the rule is break before make or b b m.