Question:
What are normally open and normally closed switches?
Answer:
Normally open (NO: normally open type) means SPST(Single Pole Single Throw)-NO specification.
Normally closed (NC: normally closed type) means SPST-NC specification.
The switchable type is a SPDT(Single Pole Double Throw) type, and can be switched from NC to NO or NO to NC.
Explanation:
There are three types of circuits (contact types) as shown in the figure below. The main type is SPST-NC, but many snap-action switches also use SPDT (switchable type).
Quick tips
The SPDT(switchable type) can be used to check the operation of the switch (for normal operation).
If the SPST-NO is for detection (or activation), the SPST-NO must be cut off at that time. By using this as a check circuit, it is possible to confirm that the switch has operated. Note that the load must be adjusted, for example, by incorporating a resistor in the check circuit.
Product category
Switches Basic Switches
Classification
Usage, Applications
Related keywords
Basic Switch
Normally Open
NO
Normally Close
NC
SPST-NO
SPST-NC
SPDT
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Switches | DigiKey Electronics
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