Author Topic: Tech Question: Switch State  (Read 395 times)

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Offline WeatherHost

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Tech Question: Switch State
« on: May 30, 2018, 06:00:22 PM »
This concerns the configuration of a magnetic reed switch, the type used in alarms, etc.

>>  Out of the package, not installed with the magnet removed from the reed switch.  The switch is open, no contact is made across the leads, infinite ohms.

>>  Installed in everyday use.  The (door, window or other) portal is closed and the magnet is against the switch.  The switch is closed and contact is made, meaning '0' ohms and the circuit is completed.

Is this switch 'Normally Open' (NO), or 'Normally Closed' (NC)?

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Offline mcrossley

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Re: Tech Question: Switch State
« Reply #1 on: May 30, 2018, 06:11:10 PM »
NO
Mark

Offline SLOweather

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Re: Tech Question: Switch State
« Reply #2 on: May 30, 2018, 06:19:59 PM »

Offline WeatherHost

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Re: Tech Question: Switch State
« Reply #3 on: June 01, 2018, 05:16:33 PM »
Not how I was taught, nor how packages have been labeled on past purchases.

'Normal;' is the state in which the item is normally used.  In the case of the switch above, normal would be installed with the portal closed and the magnet engaged.  That creates a closed loop 'normally'.  In an alarm system, the protected loop is closed and the system is armed.  If the portal opens (magnet removed from switch), the switch opens, the protected circuit is broken and the alarm is triggered.

And I have two other packages of switches factory marked NC, Normally Closed that work the same way as these new ones I just got that were marked NO, Normally Open.

Perhaps it's all about the industry of intended use.



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