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Unread 12-02-2013, 10:33
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Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
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Rookie Year: 2002
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Re: Breaker Switches and Buttons to Motors

Quote:
Originally Posted by sthreet View Post
Not sure what you mean by three terminals...
A typical limit switch has three terminals seen here:



One is marked COM and the ground wire goes there.
Then you have a choice of two terminals for the signal wire that essentially give opposite answers.
  • NC is Normally Closed and completes the circuit only while the limit switch is not depressed
  • NO is Normally Open and completes the circuit only when the limit switch is depressed. The opposite of NC.
There are reasons to choose one over the other. For instance, we like Normally Closed if the switch is acting as a fail safe (if the switch fails, it's still safe). So, say the switch gets broken, then the mechanism is disabled by default, because NC acts like it's being depressed if it gets ripped off the robot.

Quote:
Originally Posted by sthreet View Post
But should I get rid of the not also?
Use of the -not- will depend on which terminal NC vs NO you wired up.
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Last edited by Mark McLeod : 12-02-2013 at 10:40.
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